Table of contents

We report the discovery of 10 kpc [C ii] 158 μm halos surrounding star-forming galaxies in the early universe. We choose deep Atacama Large Millimeter/submillimeter Array data for 18 galaxies, each with a star formation rate of ≃10–70 M_⊙ with no signature of an active galactic nucleus whose [C ii] lines are individually detected at z = 5.153–7.142, and we conduct stacking of the [C ii] lines and dust continuum in the uv-visibility plane. The radial profiles of the surface brightnesses show a 10 kpc scale [C ii] halo at the 9.2σ level, significantly more extended than the Hubble Space Telescope stellar continuum data by a factor of ∼5 on the exponential-profile basis, as well as the dust continuum. We compare the radial profiles of [C ii] and Lyα halos universally found in star-forming galaxies at this epoch, and we find that the scale lengths agree within the 1σ level. While two independent hydrodynamic zoom-in simulations match the dust and stellar continuum properties, the simulations cannot reproduce the extended [C ii] line emission. The existence of the extended [C ii] halo is evidence of outflow remnants in the early galaxies and suggests that the outflows may be dominated by cold-mode outflows expelling the neutral gas.

Similar to their low-mass counterparts, massive stars likely form via the collapse of prestellar molecular cores. Recent observations suggest that most massive cores are subvirial (i.e., not supported by turbulence) and therefore are likely unstable to gravitational collapse. Here we perform radiation-hydrodynamic simulations to follow the collapse of turbulent massive prestellar cores with subvirial and virialized initial conditions to explore how their dynamic state affects the formation of massive stars and core fragmentation into companion stars. We find that subvirial cores undergo rapid monolithic collapse, resulting in higher accretion rates at early times as compared to the collapse of virialized cores that have the same physical properties. In contrast, we find that virialized cores undergo a slower, gradual collapse and significant turbulent fragmentation at early times, resulting in numerous companion stars. In the absence of strong magnetic fields and protostellar outflows, we find that the faster growth rate of massive stars that are born out of subvirial cores leads to an increase in the radiative heating of the core, thereby further suppressing fragmentation at early times when turbulent fragmentation occurs for virialized cores. Regardless of initial condition, we find that the massive accretion disks that form around massive stars dominant the accretion flow onto the star at late times and eventually become gravitationally unstable and fragment to form companion stars at late times.

We report our spectroscopic monitoring of the detached, grazing, and slightly eccentric 12 day double-lined eclipsing binary EPIC 219568666 in the old nearby open cluster Ruprecht 147. This is the second eclipsing system to be analyzed in this cluster, following our earlier study of EPIC 219394517. Our analysis of the radial velocities combined with the light curve from the K2 mission yields absolute masses and radii for EPIC 219568666 of M₁ = 1.121 ± 0.013 M_☉ and R₁ = 1.1779 ± 0.0070 R_☉ for the F8 primary and M₂ = 0.7334 ± 0.0050 M_☉ and R₂ = 0.640 ± 0.017 R_☉ for the faint secondary. Comparison with current stellar evolution models calculated for the known metallicity of the cluster points to a primary star that is oversized, as is often seen in active M dwarfs, but this seems rather unlikely for a star of its mass and with a low level of activity. Instead, we suspect a subtle bias in the radius ratio inferred from the photometry, despite our best efforts to avoid it, which may be related to the presence of spots on one or both stars. The radius sum for the binary, which bypasses this possible problem, indicates an age of 2.76 ± 0.61 Gyr, which is in good agreement with a similar estimate from the binary in our earlier study.

We study the influence of density-dependent symmetry energy at high densities in simulations of core-collapse supernovae, black hole formation, and proto–neutron star cooling by extending the relativistic mean field (RMF) theory used for the Shen equation-of-state (EOS) table. We adopt the extended RMF theory to examine the density dependence of the symmetry energy with a small value of the slope parameter L, while the original properties of the symmetric nuclear matter are unchanged. In order to assess matter effects at high densities, we perform numerical simulations of gravitational collapse of massive stars adopting the EOS table at high densities beyond 10¹⁴ g cm⁻³ with the small L value, which is in accord with the experimental and observational constraints, and compare them with the results obtained by using the Shen EOS. Numerical results for 11.2 and 15 M_⊙ stars exhibit minor effects around the core bounce and in the following evolution for 200 ms. Numerical results for 40 and 50 M_⊙ stars reveal a shorter duration toward the black hole formation with a smaller maximum mass for the small-L case. Numerical simulations of proto–neutron star cooling over 10 s through neutrino emissions demonstrate increasing effects of the symmetry energy at high densities. Neutrino cooling drastically proceeds in a relatively long timescale with high luminosities and average energies with the small symmetry energy. Evolution toward the cold neutron star is affected because of the different behavior of neutron-rich matter, while supernova dynamics around core bounce remains similar in less neutron-rich environments.

We developed methods for mapping spatial variations of the spatial power spectrum (SPS) and structure function slopes, with the goal of connecting the statistical properties of neutral hydrogen (H i) with the turbulent drivers. The new methods were applied to the H i observations of the Small and Large Magellanic Clouds (SMC and LMC). In the case of the SMC, we find highly uniform turbulent properties of H i, with no evidence for local enhancements of turbulence due to stellar feedback. These properties could be caused by a significant turbulent driving on large scales. Alternatively, the significant line-of-sight depth of the SMC could be masking out localized regions with a steeper SPS slope caused by stellar feedback. In contrast to the SMC, the LMC H i shows a large diversity in terms of its turbulent properties. Across most of the LMC, the small-scale SPS slope is steeper than the large-scale slope due to the presence of the H i disk. On small spatial scales, we find several areas of localized steepening of the SPS slope around major H ii regions, with the 30 Doradus region being the most prominent. This is in agreement with predictions from numerical simulations, which suggest a steepening of the SPS slope due to stellar feedback that erodes and destroys interstellar clouds. We also find a localized steepening of the large-scale SPS slope in the outskirts of the LMC. This is likely caused by the flaring of the H i disk, or alternatively, by ram-pressure stripping of the LMC disk due to the interactions with the surrounding halo gas.

We derive the recent star formation histories (SFHs) of 23 active dwarf galaxies using Hubble Space Telescope observations from the Legacy Extragalactic UV Survey. We apply a color–magnitude diagram (CMD) fitting technique using two independent sets of stellar models, PARSEC-COLIBRI and MIST. Despite the nonnegligible recent activity, none of the 23 star-forming dwarfs show enhancements in the last 100 Myr larger than three times the 100 Myr average. The unweighted mean of the individual SFHs in the last 100 Myr is also consistent with a rather constant activity, irrespective of the atomic gas fraction. We confirm previous results that for dwarf galaxies, the CMD-based average star formation rates (SFRs) are generally higher than the FUV-based SFRs. For half of the sample, the 60 Myr average CMD-based SFR is more than two times the FUV SFR. In contrast, we find remarkable agreement between the 10 Myr average CMD-based SFR and the Hα-based SFR. Finally, using core helium-burning stars of intermediate mass, we study the pattern of star formation spatial progression over the past 60 Myr and speculate on the possible triggers and connections of the star formation activity with the environment in which these galaxies live. Approximately half of our galaxies show spatial progression of star formation in the last 60 Myr and/or very recent diffuse and off-center activity compared to RGB stars.

We present a size analysis of a sample of ∼49,000 galaxies from the Cosmic Assembly Near-infrared Deep Extragalactic Survey GOODS North and South fields, using redshift-independent relative surface-brightness metrics to determine an unbiased measure of the differential size evolution of galaxies at 1 ≤ z ≤ 7. We introduce a novel method of removing foreground objects from distant galaxy (z > 3) images that makes use of the Lyman break at 912 Å, in what we call "2D Lyman-break imaging." The images used are in the rest-frame optical at z < 3 and progressively bluer bands at z > 3. They are therefore subject to K-correction and cosmological dimming effects, which are tested and corrected for. We separately consider a mass-selected sample (with masses in the range 10⁹M_⊙ ≤ M_* ≤ 10^10.5M_⊙) and a number-density-selected sample (using a constant number density of n = 1 × 10⁻⁴Mpc⁻³). Instead of utilizing the commonly used, but potentially biased, effective radii for size measurements, we measure the redshift-independent Petrosian radius, defined by the parameter η, for each galaxy for three values of η, and use this as a proxy for size. The evolution of the measured radii can be described by a power law of the form R_Petr = α(1+z)^β kpc where β < 0. We find that the outer radius increases more rapidly, suggesting that as a galaxy grows, mass is added to its outer regions via an inside-out growth. This growth is stronger for the number-density-selected sample, with a growth rate of nearly three in the outer radii compared to the inner. We test and confirm these results using a series of image simulations.

The metallicity structure of the Milky Way disk stems from the chemodynamical evolutionary history of the Galaxy. We use the National Radio Astronomy Observatory Karl G. Jansky Very Large Array to observe ∼8–10 GHz hydrogen radio recombination line and radio-continuum emission toward 82 Galactic H ii regions. We use these data to derive the electron temperatures and metallicities for these nebulae. Since collisionally excited lines from metals (e.g., oxygen, nitrogen) are the dominant cooling mechanism in H ii regions, the nebular metallicity can be inferred from the electron temperature. Including previous single-dish studies, there are now 167 nebulae with radio-determined electron temperature and either parallax or kinematic distance determinations. The interferometric electron temperatures are systematically 10% larger than those found in previous single-dish studies, likely due to incorrect data analysis strategies, optical depth effects, and/or the observation of different gas by the interferometer. By combining the interferometer and single-dish samples, we find an oxygen abundance gradient across the Milky Way disk with a slope of −0.052 ± 0.004 dex kpc⁻¹. We also find significant azimuthal structure in the metallicity distribution. The slope of the oxygen gradient varies by a factor of ∼2 when Galactocentric azimuths near ∼30° are compared with those near ∼100°. This azimuthal structure is consistent with simulations of Galactic chemodynamical evolution influenced by spiral arms.

We report spectroscopic measurements of stars in the recently discovered young stellar association Price-Whelan 1 (PW 1), which was found in the vicinity of the Leading Arm (LA) of the Magellanic Stream (MS). We obtained Magellan+MIKE high-resolution spectra of the 28 brightest stars in PW 1  and used The Cannon to determine their stellar parameters. We find that the mean metallicity of PW 1  is [Fe/H] = −1.23 with a small scatter of 0.06 dex and the mean RV is ${V}_{\mathrm{hel}}$  = 276.7 $\mathrm{km}\,{{\rm{s}}}^{-1}\,$ with a dispersion of $11.0$$\mathrm{km}\,{{\rm{s}}}^{-1}$. Our results are consistent in ${\text{}}{T}_{\mathrm{eff}}$, $\mathrm{log}g$, and [Fe/H] with the young and metal-poor characteristics (116 Myr and [Fe/H] = −1.1) determined for PW 1  from our discovery paper. We find a strong correlation between the spatial pattern of the PW 1  stars and the LA II  gas with an offset of −1015 in ${L}_{\mathrm{MS}}$  and +155 in ${B}_{\mathrm{MS}}$. The similarity in metallicity, velocity, and spatial patterns indicates that PW 1  likely originated in LA II. We find that the spatial and kinematic separation between LA II  and PW 1  can be explained by ram pressure from Milky Way (MW) gas. Using orbit integrations that account for the LMC and MW halo and outer disk gas, we constrain the halo gas density at the orbital pericenter of PW 1  to be ${{\boldsymbol{n}}}_{\mathrm{halo}}(17\,\mathrm{kpc})={2.7}_{-2.0}^{+3.4}\times {10}^{-3}\,\mathrm{atoms}\,{\mathrm{cm}}^{-3}$ and the disk gas density at the midplane at $20\,\mathrm{kpc}$ to be ${{\boldsymbol{n}}}_{\mathrm{disk}}(20\,\mathrm{kpc},0)={6.0}_{-2.0}^{+1.5}\times {10}^{-2}\,\mathrm{atoms}\,{\mathrm{cm}}^{-3}$. We, therefore, conclude that PW 1  formed from the LA II  of the MS, making it a powerful constraint on the MW–Magellanic interaction.

Voyager 1 observed Kolmogorov-like (k^−5/3) compressible turbulence just upwind of the heliopause. Subsequent measurements by Voyager 1 further from the heliopause revealed that the observed fluctuations were now fully incompressible, with a k^−5/3 spectrum that was essentially identical to that of the earlier compressible spectrum. Zank et al. showed that only compressible fast magnetosonic modes could be transmitted from the inner heliosheath into the very local interstellar medium (VLISM), and could exhibit a k^−5/3 spectrum. We show here that the small plasma beta VLISM admits three-wave interactions between a fast magnetosonic mode, a zero-frequency mode, and an Alfvén wave. The fast magnetosonic mode is converted to an incompressible Alfvén (or zero-frequency) mode with wavenumber almost identical to that of the initial compressible fast mode. The initial compressible and generated incompressible spectra are essentially identical. For the wavelength range observed by Voyager 1, we estimate that compressible fast modes are fully mode-converted to incompressible fluctuations within ∼10 au of the heliopause. We suggest that the VLISM magnetic field spectrum is a superposition of a higher amplitude ∼k^−5/3 spectrum of heliospheric origin with an estimated correlation length ∼30 au, having a minimum wavenumber ∼(100)⁻¹ (au)⁻¹, and a lower amplitude (possibly local) ISM k^−5/3 spectrum, the latter possessing an outer scale ≥2 pc. We suggest that the transmission of compressible turbulence from an inner asterosheath into the local circumstellar interstellar medium surrounding a star, and the subsequent mode conversion to incompressible turbulence, may be a general mechanism by which stars drive turbulence in the interstellar medium.

This paper considers the concept of wave-particle thermodynamic equilibrium in order to improve our understanding of the role of turbulent heating in the solar wind proton plasma. The thermodynamic equilibrium in plasmas requires the energy of a plasmon—the quantum of plasma fundamental oscillation—to be balanced by the proton-magnetized plasma energy, that is, the magnetic field and proton kinetic/thermal energy. This equilibrium has already been confirmed in several prior analyses, but also in this paper, by analyzing (i) multi-spacecraft data sets along the radial profile of the inner heliosphere, and (ii) representative data sets of a variety of 27 different space and astrophysical plasmas. Recently, it was shown that the slow mode of the near-Earth solar wind plasma is characterized by a missing energy source that is necessary for keeping the energy balance in the plasmon–proton-magnetized plasma. Here we show strong evidence that this missing energy is the turbulent energy heating the solar wind. In particular, we derive and compare the radial and velocity profiles of this missing energy and the turbulent energy in the inner heliosphere, also considering other minor contributions, such as the temperature of pickup protons. The connection of the missing plasmon–proton energy with the turbulent energy provides a new method for estimating and cross-examining the turbulent energy in space and astrophysical plasmas, while it confirms the universality of the involved new Planck-type constant that implies a large-scale quantization.

We study the early evolution of a hot-channel-like magnetic flux rope (MFR) toward eruption. Combining with imaging observation and magnetic field extrapolation, we find that the hot channel possibly originated from a preexisting seed MFR with a hyperbolic flux tube (HFT). In the precursor phase, three-dimensional tether-cutting reconnection at the HFT is most likely resulting in the heating and buildup of the hot channel. In this process, the forming hot channel was rapidly enlarged at its spatial size and slipped its feet to two remote positions. Afterward, it instantly erupted outwards with an exponential acceleration, leaving two core dimmings near its feet. We suggest that preflare reconnection at the HFT played a crucial role in enlarging the seed MFR and facilitating the onset of its final solar eruption. Moreover, a recently predicted drifting of MFR's footpoints was detected at both core dimmings. In particular, we find that MFR's west footpoint drift was induced by a new reconnection geometry among the erupting MFR's leg and thereby inclined arcades. As MFR's west footpoints gradually drifted to a new position, a set of newborn atypical flare loops connected into the west core dimming, causing a rapid decrease of dimmed area inside this core dimming and also generating a secondary flare ribbon at their remote feet. This reveals that core dimmings may suffer a pronounced diminishment due to the eruptive MFR's footpoint drift, implying that mapping the real footpoints of the erupting MFR down to the Sun's surface is more difficult than previously thought.

It has been reported that some broad-absorption lines (BALs) in quasar spectra can be decomposed into multiple narrow-absorption lines (NALs), which we define as "Type N BALs." In this paper, using the spectra of 2005 BAL quasars from the Sloan Digital Sky Survey (SDSS), we have visually identified a total of 6764 C ivλλ1548 and 1551 NAL systems with 1.4186 ≤ z_abs ≤ 3.8005, including 4174 C iv NAL systems within BAL troughs from 1349 quasars and 2590 outside BAL troughs from 1319 quasars. About two-thirds of the BAL quasars in the total sample contain Type N BALs, indicating the ubiquity of Type N BALs, which serve as a new perspective for studying outflows in the context of the NAL complex. Moreover, we find that, for both samples of C iv NAL systems within and outside BAL troughs, the distributions of velocity separation among distinct C iv NAL systems in the same quasar show significant excesses at the positions of C iv and Si iv doublet splittings, which offers statistical evidence for the idea that radiative forces play a significant role in driving both BAL and NAL outflows in BAL quasars.

As computational resolution of modern cosmological simulations come closer to resolving individual star-forming clumps in a galaxy, the need for "resolution-appropriate" physics for a galaxy-scale simulation has never been greater. To this end, we introduce a self-consistent numerical framework that includes explicit treatments of feedback from star-forming molecular clouds (SFMCs) and massive black holes (MBHs). In addition to the thermal supernovae feedback from SFMC particles, photoionizing radiation from both SFMCs and MBHs is tracked through full three-dimensional ray tracing. A mechanical feedback channel from MBHs is also considered. Using our framework, we perform a state-of-the-art cosmological simulation of a quasar-host galaxy at z ∼ 7.5 for ∼25 Myr with all relevant galactic components, such as dark matter, gas, SFMCs, and an embedded MBH seed of ≳10⁶M_⊙. We find that feedback from SFMCs and an accreting MBH suppresses runaway star formation locally in the galactic core region. Newly included radiation feedback from SFMCs, combined with feedback from the MBH, helps the MBH grow faster by retaining gas that eventually accretes on to the MBH. Our experiment demonstrates that previously undiscussed types of interplay between gas, SFMCs, and a MBH may hold important clues about the growth and feedback of quasars and their host galaxies in the high-redshift universe.

A generalized ion-sound speed for space and astrophysical plasmas in the regions of near- and far-from-thermal equilibrium is derived in the context of the new formulated invariant Kappa distribution. Inspired by the recent studies on the origin of polytropic behavior in space plasmas, it has been shown that the sound speed is connected to the extended polytropic index of Kappa distributed particles, which itself depends on the invariant Kappa index and the potential degrees of freedom. Generally, the ion-sound speed is a function of the polytropic index of Kappa distributed particles, which varies between two asymptotic regions of equilibrium and anti-equilibrium states. It is found that the ion-sound speed takes its maximum value in an equilibrium plasma and it reduces by approaching to the anti-equilibrium states. Furthermore, dispersion relation of the ion-acoustic waves in our formulism confirms, correspondingly, the recent study on the generalized formulation of Debye shielding in space plasmas. Finally, the classical and generalized relations between the ion-sound speed, the Debye length and the ion oscillation frequency have been discussed.

We have performed a spectroscopic observation over the south polar coronal hole (PCH) with the Hinode Extreme-ultraviolet (EUV) Imaging Spectrometer (EIS) during an on-orbit partial solar eclipse. In this partial eclipse, the Moon passed through the EIS observing area that was set in the south PCH at the height of 0.9–1.4 solar radii. Using the lunar occultation, we have corrected for the scattered light contamination from bright regions of the Sun that is present in the dark PCH emission line profiles. The nonthermal width of the corrected emission line profile in the PCH increases from the limb toward the high-altitude corona. It has also been confirmed that the nonthermal width tends to decrease beyond ∼1.2 solar radii. These results are consistent with the model in which outward-propagating Alfvén waves start being dissipated at ∼1.2 solar radii, as previously reported. The reduced energy within ∼1.4 solar radii contributes to atmospheric heating and the initial acceleration for the solar wind in the low corona. The remaining energy flux at 1.4 solar radii may be dissipated in the distant corona and is sufficient to provide the additional acceleration required to drive the fast solar wind.

We investigate the internal dynamics of anisotropic, rotating globular clusters with a multimass stellar population by performing new direct N-body simulations. In addition to the well-known radial mass segregation effect, where heavy stars and stellar remnants sink toward the center of the cluster, we find a mass segregation in the distribution of orbital inclinations as well. This newly discovered anisotropic mass segregation leads to the formation of a disk-like structure of massive objects near the equatorial plane of a rotating cluster. This result has important implications on the expected spatial distribution of black holes in globular clusters.

So far, most studies on the structure of coronal mass ejections (CMEs) are conducted through white-light coronagraphs, demonstrating that about one third of CMEs exhibit the typical three-part structure in the high corona (e.g., beyond 2 ${R}_{\odot }$), i.e., the bright front, the dark cavity, and the bright core. In this paper, we address the CME structure in the low corona (e.g., below 1.3 ${R}_{\odot }$) through extreme-ultraviolet (EUV) passbands and find that the three-part CMEs in the white-light images can possess a similar three-part appearance in the EUV images, i.e., a leading edge, a low-density zone, and a filament or hot channel. The analyses identify that the leading edge and the filament or hot channel in the EUV passbands evolve into the front and the core later within several solar radii in the white-light passbands, respectively. What is more, we find that the CMEs without an obvious cavity in the white-light images can also exhibit the clear three-part appearance in the EUV images, which means that the low-density zone in the EUV images (observed as the cavity in white-light images) can be compressed and/or transformed gradually by the expansion of the bright core and/or the reconnection of the magnetic field surrounding the core during the CME propagation outward. Our study suggests that more CMEs can possess the clear three-part structure in their early eruption stage. The nature of the low-density zone between the leading edge and the filament or hot channel is discussed.

The tomographic Alcock–Paczynski (AP) method utilizes the redshift evolution of the AP distortion to place constraints on cosmological parameters. In previous works, it was performed via the anisotropic two-point correlation function statistic. In this work we consider the feasibility of conducting the analysis in the Fourier domain. We use the integrated galaxy power spectrum as a function of direction, ${\hat{P}}_{{\rm{\Delta }}k}(\mu )$, to quantify the magnitude of anisotropy in the large-scale structure clustering, and use its redshift variation to do the AP test. The method is tested on the large, high-resolution Big-MultiDark Planck simulation at redshifts z = 0–1. Testing the redshift evolution of ${\hat{P}}_{{\rm{\Delta }}k}(\mu )$ in the true cosmology and cosmologies deviating from the truth with δΩ_m = 0.1, δw = 0.3, we find that the redshift evolution of the AP distortion overwhelms the redshift space distortions effects by a factor of ∼1.7–3.6. The method works well throughout the range of k ∈ (0.2, 1.8) h Mpc⁻¹. We tune the halo mass within the range 2 × 10¹³–10¹⁴M_⊙, and find that the change of halo bias results in ≲5% change in ${\hat{P}}_{{\rm{\Delta }}k}(\mu )$, which is less significant compared with the cosmological effect. Our work shows that it is feasible to conduct the tomographic AP analysis in the Fourier space.

Because follow–up observations of quadruple gravitational lens systems are of extraordinary importance for astrophysics and cosmology, we present single-epoch optical spectra and r-band light curves of PS J0147+4630. This recently discovered system mainly consists of four images ABCD of a background quasar around a foreground galaxy G that acts as a gravitational lens. First, we use long-slit spectroscopic data in the Gemini Observatory Archive and a multi-component fitting to accurately resolve the spectra of A, D, and G. The spectral profile of G resembles that of an early-type galaxy at a redshift of 0.678 ± 0.001, which is about 20% higher than the previous estimate. Additionally, the stellar velocity dispersion is measured to ∼5% precision. Second, our early r-band monitoring with the Liverpool Telescope leads to accurate light curves of the four quasar images. Adopting time delays predicted by the lens model, the new lens redshift, and a standard cosmology, we report the detection of microlensing variations in C and D as large as ∼0.1 mag on timescales of a few hundred days. We also estimate an actual delay between A and B of a few days (B is leading), which demonstrates the big potential of optical monitoring campaigns of PS J0147+4630.

Type II supernovae (SNe) stem from the core collapse of massive (>8 M_⊙) stars. Due to their short lifespan, we expect a very low rate of such events in elliptical hosts, where the star formation rate is low, and which are mostly comprised of an old stellar population. SN 2016hil (iPTF16hil) is an SN II located in the extreme outskirts of an elliptical galaxy at z = 0.0608 (projected distance 27.2 kpc). It was detected near peak (M_r ∼ −17 mag) 9 days after the last non-detection. The event has some potentially peculiar properties: it presented an apparently double-peaked light curve, and its spectra suggest low metallicity content (Z < 0.4 Z_⊙). We place a tentative upper limit on the mass of a potential faint host at $\mathrm{log}\tfrac{M}{{M}_{\odot }}={7.27}_{-0.24}^{+0.43}$ using deep optical imaging from Keck/LRIS. In light of this, we discuss the possibility of the progenitor forming locally and other more exotic formation scenarios such as a merger or common-envelope evolution causing a time-delayed explosion. Further observations of the explosion site in the UV are needed in order to distinguish between the cases. Regardless of the origin of the transient, observing a population of such seemingly hostless SNe II could have many uses, including an estimate the amount of faint galaxies in a given volume, and tests of the prediction of a time-delayed population of core-collapse SNe in locations otherwise unfavorable for the detection of such events.

We present the ensemble expectation values for the translation-invariant, rank-2 Minkowski tensors in three dimensions, for a linearly redshift-space-distorted Gaussian random field. The Minkowski tensors ${W}_{1}^{0,2}$, ${W}_{2}^{0,2}$ are sensitive to global anisotropic signals present within a field, and by extracting these statistics from the low-redshift matter density one can place constraints on the redshift-space distortion parameter β = f/b. We begin by reviewing the calculation of the ensemble expectation values $\langle {W}_{1}^{0,2}\rangle$, $\langle {W}_{2}^{0,2}\rangle$ for isotropic, Gaussian random fields, then consider how these results are modified by the presence of a linearly anisotropic signal. Under the assumption that all fields remain Gaussian, we calculate the anisotropic correction due to redshift-space distortion in a coordinate system aligned with the line of sight, finding inequality between the diagonal elements of $\langle {W}_{1}^{0,2}\rangle$, $\langle {W}_{2}^{0,2}\rangle$. The ratio of diagonal elements of these matrices provides a set of statistics that are sensitive only to the redshift-space distortion parameter β. We estimate the Fisher information that can be extracted from the Minkowski tensors, and find ${W}_{1}^{0,2}$ is more sensitive to β than ${W}_{2}^{0,2}$, and a measurement of ${W}_{1}^{0,2}$ accurate to ∼1% can yield a $\sim 4 \%$ constraint on β. Finally, we discuss the difference between using the matrix elements of the Minkowski tensors directly against measuring the eigenvalues. For the purposes of cosmological parameter estimation we advocate the use of the matrix elements, to avoid spurious anisotropic signals that can be generated by the eigenvalue decomposition.

The G-band bright points (GBPs) are driven by the granular convection flow, and appear with different morphologies in the quiet Sun, such as points, elongated chains, and knees. A point-like GBP represents a single slender flux tube, while the others represent the interaction of several slender flux tubes. This paper presents a deep-learning method, GBPs Mask Region-based Convolutional Neural Networks (GBP-MRCNN) for morphological classification of GBPs. A training set including 10,404 samples and a validation set including 2057 samples have been built. A total of 906 images as a testing set have been detected, segmented, and classified. They consist of 74,973 points (88.3%), 8660 elongated chains (10.2%), and 1239 knees (1.5%). GBP-MRCNN has achieved an efficient classification of GBPs with a mean average precision of 0.93. For points, elongated chains, and knees, the quiet Sun fractional area average values are 0.47%, 0.14%, and 0.03%, respectively. Correspondingly, the mean areas are (2.02 ± 0.69) × 10⁴, (6.17 ± 1.71) × 10⁴ and (6.99 ± 1.74) × 10⁴ km², respectively. The maximum intensity contrasts are 1.05 ± 0.12, 1.18 ± 0.17, and 1.36 ± 0.17, respectively. The mean eccentricities of points and elongated chains are 0.48 ± 0.23 and 0.89 ± 0.01, respectively. We adopt constituent points to describe how many points constitute a nonpoint-like GBP. The mean constituent points of elongated chains and knees are estimated as 2.77 ± 0.57 and 3.06 ± 0.65, respectively. The maximum length of the elongated chains can extend to over 1000 km, which corresponds to over eight single slender flux tubes. The characteristics of GBPs with different morphologies can be explained by the interaction between magnetic flux tubes and photospheric convection, and then help to build improved magnetic flux tube models.

In this paper, we study in detail the evolution of a mini-sigmiod originating in a cross-equatorial coronal hole, where the magnetic field is mostly open and seriously distinct from the closed background field above active-region sigmoids. The source region first appeared as a bipole, which subsequently experienced a rapid emergence followed by a long-term decay. Correspondingly, the coronal structure initially appeared as arc-like loops, then gradually sheared and transformed into continuously sigmoidal loops, mainly owing to flux cancellation near the polarity inversion line. The temperature of J-shaped and sigmoidal loops is estimated to be about 2.0 × 10⁶ K, greater than that of the background coronal hole. Using the flux-rope insertion method, we further reconstruct the nonlinear force-free fields that well reproduces the transformation of the potential field into a sigmoidal field. The fact that the sheared and sigmoidal loops are mainly concentrated at around the high-Q region implies that the reconnection most likely takes place there to form the sigmoidal field and heat the plasma. Moreover, the twist of sigmoidal field lines is estimated to be around 0.8, less than the values derived for the sigmoids from active regions. However, the sigmoidal flux may quickly enter an unstable regime at the very low corona (<10 Mm) due to the open background field. The results suggest that the mini-sigmoid, at least the one in our study, has the same formation and eruption process as the large-scale one, but is significantly influenced by the overlying flux.

The unusually narrow X-ray source imaged with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) during an impulsive spike lasting for ∼10 s during the Geostationary Operational Environmental Satellite C7.9 flare on 2011 September 25 (SOL2011-09-25T03:32) was only ∼2'' wide and ∼10'' long. Comparison with Helioseismsic and Magnetic Imager magnetograms and Atmospheric Imaging Assembly images at 1700 Å shows that the X-ray emission was primarily from a long ribbon in the region of positive polarity with little if any emission from the negative polarity ribbon. However, a thermal plasma source density of ∼10¹² cm⁻³ estimated from the RHESSI-derived emission measure and source area showed that this could best be interpreted as a coronal hard X-ray source in which the accelerated electrons with energies less than ∼50 keV were stopped by Coulomb collisions in the corona, thus explaining the lack of the more usual bright X-ray footpoints. Analysis of RHESSI spectra shows greater consistency with a multi-temperature distribution and a low-energy cutoff to the accelerated electron spectrum of 22 keV compared to 12 keV if a single-temperature distribution is assumed. This leads to a change in the lower limit on the total energy in electrons by an order of magnitude, given the steepness of the best-fit electron spectrum with a power-law index of ∼6.

Galactic cosmic-ray (GCR) helium and heavier ions are important sources of space radiation, and their elemental spectra and composition can help us better understand the transport in both the galaxy and the heliosphere. A model based on the numerical solution of Parker's transport equation is used to study the modulation of GCR helium and heavier ions in the inner heliosphere. The model incorporates a modified Parker heliospheric magnetic field, time-dependent diffusion and drift model, time-delayed heliosphere, and randomly determined solar magnetic polarity during solar maximum. We set the outer boundary of modulation at 85 au, and the reference unmodulated GCR energy spectra for GCR helium and heavier ions, which are assumed to have a general form, are determined by fitting the numerical results to the selected GCR measurements, e.g., BESS, ACE/CRIS, HEAO-3-C2, etc. In addition, we use the Sun's polar magnetic field data from NSO/NISP to determine the possibility of A > 0 during the recent solar maximum, and it gives an improved numerical result during the period 2013–2015. Finally, the fitted unmodulated GCR energy spectra are used to study the long-term modulation of GCRs of helium and heavier ions, and the computed results show good agreement with various GCR measurements.

Mildly relativistic shocks that are embedded in colliding magnetohydrodynamic flows are prime sites for relativistic particle acceleration and the production of strongly variable, polarized multi-wavelength emission from relativistic jet sources such as blazars and gamma-ray bursts. The principal energization mechanisms at these shocks are diffusive shock acceleration and shock drift acceleration. In recent work, we had self-consistently coupled shock acceleration and radiation transfer simulations in blazar jets in a basic one-zone scenario. These one-zone models revealed that the observed spectral energy distributions (SEDs) of blazars strongly constrain the nature of the hydromagnetic turbulence in the shock layer. In this paper, we expand our previous work by including full time dependence and treating two zones, one being the site of acceleration and the other a larger emission zone. This construction is applied to multi-wavelength flares of the flat-spectrum radio quasar (FSRQ) 3C 279, fitting snapshot SEDs and generating light curves that are consistent with observed variability timescales. We also present a generic study for the typical flaring behavior of the BL Lac object Mrk 501. The model predicts correlated variability across all wavebands, but cross-band time lags depending on the type of blazar (FSRQ versus BL Lac), as well as distinctive spectral hysteresis patterns in all wavelength bands, from millimeter radio waves to gamma-rays. These evolutionary signatures serve to provide diagnostics on the competition between acceleration and radiative cooling.

The recently published fourth Fermi Large Area Telescope source catalog (4FGL) reports 5065 gamma-ray sources in terms of direct observational gamma-ray properties. Among the sources, the largest population is the active galactic nuclei (AGNs), which consists of 3137 blazars, 42 radio galaxies, and 28 other AGNs. The blazar sample comprises 694 flat-spectrum radio quasars (FSRQs), 1131 BL Lac- type objects (BL Lacs), and 1312 blazar candidates of an unknown type (BCUs). The classification of blazars is difficult using optical spectroscopy given the limited knowledge with respect to their intrinsic properties, and the limited availability of astronomical observations. To overcome these challenges, machine-learning algorithms are being investigated as alternative approaches. Using the 4FGL catalog, a sample of 3137 Fermi blazars with 23 parameters is systematically selected. Three established supervised machine-learning algorithms (random forests (RFs), support vector machines (SVMs), artificial neural networks (ANNs)) are employed to general predictive models to classify the BCUs. We analyze the results for all of the different combinations of parameters. Interestingly, a previously reported trend the use of more parameters leading to higher accuracy is not found. Considering the least number of parameters used, combinations of eight, 12 or 10 parameters in the SVM, ANN, or RF generated models achieve the highest accuracy (Accuracy ≃91.8%, or ≃92.9%). Using the combined classification results from the optimal combinations of parameters, 724 BL Lac type candidates and 332 FSRQ type candidates are predicted; however, 256  remain without a clear prediction.

We developed a spectroscopic monitoring project to investigate the kinematics of the broad-line region (BLR) in active galactic nuclei (AGNs) with ultrafast outflows (UFOs). Mrk 79 is a radio-quiet AGN with UFOs and warm absorbers and has been monitored by three reverberation mapping (RM) campaigns, but its BLR kinematics are not yet understood. In this paper, we report the results from a new RM campaign of Mrk 79, which was undertaken with the Lijiang 2.4 m telescope. Mrk 79 appears to come out the faint state, with the mean flux approximately a magnitude fainter than the historical record. We successfully measured the lags of the broad emission lines including Hβ λ4861, Hγ λ4340, He ii λ4686, and He i λ5876 with respect to the varying AGN continuum. Based on the broad Hβ λ4861 line, we measured a black hole mass of ${M}_{\bullet }={5.13}_{-1.55}^{+1.57}\times {10}^{7}{M}_{\odot }$, and an estimated accretion rate of ${\dot{M}}_{\bullet }=(0.05\pm 0.02)\,{L}_{\mathrm{Edd}}\,{c}^{-2}$, indicating that Mrk 79 is a sub-Eddington accretor. We found that Mrk 79 deviates from the canonical Radius−Luminosity relationship. The marginal blueshift of the broad He ii λ4686 line detected from the rms spectrum indicates outflow of high-ionization gas. The velocity-resolved lag profiles of the broad Hγ λ4340, Hβ λ4861, and He i λ5876 lines show similar signatures such that the largest lag occurs in the red wing of the lines and then the lag decreases to both sides. These signatures may suggest that the BLR of Keplerian motion probably exists as outflow gas motion. All findings including UFOs, warm absorbers, and the kinematics of high- and low-ionization BLR, may provide indirect evidence that the BLR of Mrk 79 probably originates from a disk wind.

Recent analyses of 21 cm neutral hydrogen (H i) emission have demonstrated that H i gas is organized into linear filamentary structures that are preferentially aligned with the local magnetic field, and that the coherence of these structures in velocity space traces line-of-sight magnetic field tangling. On this basis, we introduce a paradigm for modeling the properties of magnetized, dusty regions of the interstellar medium (ISM), using the orientation of H i structure at different velocities to map "magnetically coherent" regions of space. We construct three-dimensional (position–position–velocity) Stokes parameter maps using H i4PI full-sky spectroscopic H i data. We compare these maps, integrated over the velocity dimension, to Planck maps of the polarized dust emission at 353 GHz. Without any free parameters governing the relation between H i intensity and dust emission, we find that our Q and U maps are highly correlated (r > 0.75) with the 353 GHz Q and U maps of polarized dust emission observed by Planck and reproduce many of its large-scale features. The E/B ratio of the dust emission maps agrees well with the H i-derived maps at large angular scales (ℓ ≲ 120), supporting the interpretation that this asymmetry arises from the coupling of linear density structures to the Galactic magnetic field. We demonstrate that our 3D Stokes parameter maps constrain the 3D structure of the Galactic ISM and the orientation of the interstellar magnetic field.

Using multiwavelength imaging observations from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory on 2012 May 3, we present a novel physical scenario for the formation of a temporary X-point in the solar corona, where plasma dynamics are forced externally by a moving prominence. Natural diffusion was not predominant; however, a prominence driven inflow occurred first, forming a thin current sheet, thereafter enabling a forced magnetic reconnection at a considerably high rate. Observations in relation to the numerical model reveal that forced reconnection may rapidly and efficiently occur at higher rates in the solar corona. This physical process may also heat the corona locally even without establishing a significant and self-consistent diffusion region. Using a parametric numerical study, we demonstrate that the implementation of the external driver increases the rate of the reconnection even when the resistivity required for creating normal diffusion region decreases at the X-point. We conjecture that the appropriate external forcing can bring the oppositely directed field lines into the temporarily created diffusion region first via the plasma inflows as seen in the observations. The reconnection and related plasma outflows may occur thereafter at considerably larger rates.

The observation of radio, X-ray, and H_α emission from substellar objects indicates the presence of plasma regions and associated high-energy processes in their surrounding envelopes. This paper numerically simulates and characterizes critical velocity ionization (CVI), a potential ionization process, that can efficiently generate plasma as a result of neutral gas flows interacting with seed magnetized plasmas. By coupling a gas–magnetohydrodynamic (MHD) interactions code (to simulate the ionization mechanism) with a substellar global circulation model (to provide the required gas flows), we quantify the spatial extent of the resulting plasma regions, their degree of ionization, and their lifetime for a typical substellar atmosphere. It is found that the typical average ionization fraction reached at equilibrium (where the ionization and recombination rates are equal and opposite) ranges from 10⁻⁵ to 10⁻⁸, at pressures between 10⁻¹ and 10⁻³ bar, with a trend of increasing ionization fraction with decreasing atmospheric pressure. The ionization fractions reached as a result of CVI are sufficient to allow magnetic fields to couple to gas flows in the atmosphere.

A fraction of dwarf galaxies in the Virgo Cluster contain disk features like bars and spiral arms. Using N-body simulations, we investigate the effects of tidal forces on the formation of such disk features in disk dwarf galaxies resembling VCC 856. We consider eight cluster–galaxy models in which disk dwarf galaxies with differing pericenter distance and spin orientation experience the tidal gravitational force of a Virgo-like Navarro–Frenk–White halo, as well as an additional eight galaxy–galaxy models in which two dwarf galaxies undergo tidal interactions with different strength. We find that the cluster tidal effect is moderate owing to the small galaxy size, making the bars form earlier by ∼1–1.5 Gyr compared to the cases in isolation. While the galactic halos significantly lose their mass within the virial radius due to the cluster tidal force, the mass of the stellar disks is nearly unchanged, suggesting that the inner regions of a disk–halo system are secured from the tidal force. The tidal forcing from either the cluster potential or a companion galaxy triggers the formation of two-armed spirals at early time before a bar develops. The tidally driven arms decay and wind with time, suggesting that they are kinematic density waves. In terms of the strength and pitch angle, the faint arms in VCC 856 are best matched with the arms in a marginally unstable galaxy produced by a distant tidal encounter with its neighbor ∼0.85 Gyr ago.

Magnetic reconnection occurs when new flux emerges into the corona and becomes incorporated into the existing coronal field. A new active region (AR) emerging in the vicinity of an existing AR provides a convenient laboratory in which reconnection of this kind can be quantified. We use high time-cadence 171 Å data from Solar Dynamics Observatory (SDO)/AIA, focused on new/old active region pair 11147/11149, to quantify reconnection. We identify new loops as brightenings within a strip of pixels between the regions. This strategy is premised on the assumption that the energy responsible for brightening a loop originates in magnetic reconnection. We catalog 301 loops observed in the 48 hr time period beginning with the emergence of AR 11149. The rate at which these loops appear between the two ARs is used to calculate the reconnection rate between them. We then fit these loops with magnetic field, solving for each loop's field strength, geometry, and twist (via its proxy, coronal α). We find the rate of newly brightened flux overestimates the flux that could be undergoing reconnection. This excess can be explained by our finding that the interconnecting region is not at its lowest energy (constant-α) state; the extrapolations exhibit loop-to-loop variation in α. This flux overestimate may result from the slow emergence of AR 11149, which allows time for Taylor relaxation internal to the domain of the reconnected flux to bring the α distribution toward a single value, providing another mechanism for brightening loops after they are first created.

The compact configuration of Phase II of the Murchison Widefield Array (MWA) consists of both a redundant subarray and pseudo-random baselines, offering unique opportunities to perform sky-model and redundant interferometric calibration. The highly redundant hexagonal cores give improved power spectrum sensitivity. In this paper, we present the analysis of nearly 40 hr of data targeting one of the MWA's epoch of reionization (EoR) fields observed in 2016. We use both improved analysis techniques presented in Barry et al. and several additional techniques developed for this work, including data quality control methods and interferometric calibration approaches. We show the EoR power spectrum limits at redshift 6.5, 6.8, and 7.1 based on our deep analysis on this 40 hr data set. These limits span a range in k-space of 0.18 h Mpc⁻¹ < k < 1.6 h Mpc⁻¹, with a lowest measurement of Δ² ≤ 2.39 × 10³ mK² at k = 0.59 h Mpc⁻¹ and z = 6.5.

Line intensity mapping (LIM) is a promising approach to study star formation and the interstellar medium (ISM) in galaxies by measuring the aggregate line emission from the entire galaxy population. In this work, we develop a simple yet physically motivated framework for modeling the line emission as would be observed in LIM experiments. It is done by building on analytic models of the cosmic infrared background that connect total infrared luminosity of galaxies to their host dark matter halos. We present models of the ${\rm{H}}\,{\rm{i}}$ 21 cm, CO (1−0), [${\rm{C}}\,{\rm{ii}}$] 158 μm, and [${\rm{N}}\,{\rm{ii}}$] 122 and 205 μm lines consistent with current observational constraints. With four case studies of various combinations of these lines that probe different ISM phases, we demonstrate the potential for reliably extracting physical properties of the ISM, and the evolution of these properties with cosmic time, from auto- and cross-correlation analysis of these lines as measured by future LIM experiments.

We present [C i] $\left({}^{3}{{P}}_{1}\to {}^{3}{{P}}_{0}\right)$, ¹²CO, ¹³CO, and C¹⁸O ($J=2\to 1$) observations of the central region (radius 1 kpc) of the starburst galaxy NGC 1808 at 30–50 pc resolution conducted with the Atacama Large Millimeter/submillimeter Array. Radiative transfer analysis of multiline data indicates warm (${T}_{{\rm{k}}}\sim 40\mbox{--}80$ K) and dense (${n}_{{{\rm{H}}}_{2}}\sim {10}^{3\mbox{--}4}$ cm⁻³) molecular gas with high column density of atomic carbon (${N}_{{\rm{C}}{\rm{I}}}\sim 3\times {10}^{18}$ cm⁻²) in the circumnuclear disk (central 100 pc). The C i/H₂ abundance in the central 1 kpc is $\sim 3\mbox{--}7\times {10}^{-5}$, consistent with the values in luminous infrared galaxies. The intensity ratios of [C i]/CO (1–0) and [C i]/CO (3–2), respectively, decrease and increase with radius in the central 1 kpc, whereas [C i]/CO (2–1) is uniform within statistical errors. The result can be explained by excitation and optical depth effects, since the effective critical density of CO (2–1) is comparable to that of [C i]. The distribution of [C i] is similar to that of ¹³CO (2–1), and the ratios of [C i] to ¹³CO (2–1) and C¹⁸O (2–1) are uniform within $\sim 30 \%$ in the central $\lt 400$ pc starburst disk. The results suggest that [C i] $\left({}^{3}{{P}}_{1}\to {}^{3}{{P}}_{0}\right)$ luminosity can be used as a CO-equivalent tracer of molecular gas mass, although caution is needed when applied in resolved starburst nuclei (e.g., circumnuclear disk), where the [C i]/CO (1–0) luminosity ratio is enhanced owing to high excitation and atomic carbon abundance. The [C i]/CO (1–0) intensity ratio toward the base of the starburst-driven outflow is $\lesssim 0.15$, and the upper limits of the mass and kinetic energy of the atomic carbon outflow are $\sim 1\times {10}^{4}\,{M}_{\odot }$ and $\sim 3\times {10}^{51}\,\mathrm{erg}$, respectively.

We report Atacama Large Millimeter Array (ALMA) observations of four high-redshift dusty star-forming galaxy candidates selected from far-infrared (FIR)/submillimeter observations in the COSMOS field. We securely detect all galaxies in the continuum and spectroscopically confirm them at z = 3.62–5.85 using ALMA 3 mm line scans, detecting multiple CO and/or [C i] transitions. This includes the most distant dusty galaxy currently known in the COSMOS field, ID85001929 at z = 5.847. These redshifts are lower than we had expected, as these galaxies have substantially colder dust temperatures (i.e., their spectral energy distributions peak at longer rest-frame wavelengths) than most literature sources at z > 4. The observed cold dust temperatures are best understood as evidence for optically thick dust continuum in the FIR, rather than the result of low star formation efficiency with rapid metal enrichment. We provide direct evidence that, given their cold spectral energy distributions, cosmic microwave background (CMB) plays a significant role in biasing their observed Rayleigh–Jeans (RJ) slopes to unlikely steep values and, possibly, reducing their CO fluxes by a factor of two. We recover standard RJ slopes when the CMB contribution is taken into account. High-resolution ALMA imaging shows compact morphology and evidence for mergers. This work reveals a population of cold dusty star-forming galaxies that were underrepresented in current surveys and are even colder than typical main-sequence galaxies at the same redshift. High FIR dust optical depth might be a widespread feature of compact starbursts at any redshift.

We study optical phenomena in generic regular, magnetically charged, spherically symmetric black hole spacetimes arising from coupling of the Einstein gravity and nonlinear electrodynamics (NED) with the Maxwellian weak-field limit, where photons follow null geodesics of an effective geometry, directly reflecting the electromagnetic nonlinearity. We compare the motion of photons with that of massless neutrinos, which are not affected directly by nonlinearities of the non-Maxwellian electromagnetic field and follow null geodesics of the background spacetime. We determine shadows of such black holes, compare the time delays of photons and neutrinos moving in their field, and construct images of the Keplerian disks. We demonstrate that in the case of the "Maxwellian" NED black holes the optical phenomena give relevant signatures of the NED effects detectable by GRAVITY or the Event Horizon Telescope, but they are not strong enough to be excluded by recent observations as in the case of regular Bardeen black holes.

Active regions (ARs) are a candidate source of the slow solar wind (SW), the origins of which are a topic of ongoing research. We present a case study that examines the processes by which SW is modulated in the presence of an AR in the vicinity of the SW source. We compare properties of SW associated with a coronal hole (CH)–quiet Sun boundary to SW associated with the same CH but one Carrington rotation later, when this region bordered the newly emerged NOAA AR 12532. Differences found in a range of in situ parameters are compared between these rotations in the context of source region mapping and remote sensing observations. Marked changes exist in the structure and composition of the SW, which we attribute to the influence of the AR on SW production from the CH boundary. These unique observations suggest that the features that emerge in the AR-associated wind are consistent with an increased occurrence of interchange reconnection during SW production, compared with the initial quiet Sun case.

We study the kinematics of the M87 jet using the first-year data of the KVN and VERA Array (KaVA) large program, which has densely monitored the jet at 22 and 43 GHz since 2016. We find that the apparent jet speeds generally increase from ≈0.3c at ≈0.5 mas from the jet base to ≈2.7c at ≈20 mas, indicating that the jet is accelerated from subluminal to superluminal speeds on these scales. We perform a complementary jet kinematic analysis by using archival Very Long Baseline Array monitoring data observed in 2005–2009 at 1.7 GHz and find that the jet is moving at relativistic speeds up to ≈5.8c at distances of 200–410 mas. We combine the two kinematic results and find that the jet is gradually accelerated over a broad distance range that coincides with the jet collimation zone, implying that conversion of Poynting flux to kinetic energy flux takes place. If the jet emission consists of a single streamline, the observed trend of jet acceleration (Γ ∝ z^0.16±0.01) is relatively slow compared to models of a highly magnetized jet. This indicates that Poynting flux conversion through the differential collimation of poloidal magnetic fields may be less efficient than expected. However, we find a nonnegligible dispersion in the observed speeds for a given jet distance, making it difficult to describe the jet velocity field with a single power-law acceleration function. We discuss the possibility that the jet emission consists of multiple streamlines following different acceleration profiles, resulting in jet velocity stratification.

As the remnants of stars with initial masses ≲8 M_⊙, white dwarfs contain valuable information on the formation histories of stellar populations. In this paper, we use deep, high-quality, u-band photometry from the Canada–France Imaging Survey, griz photometry from Pan-STARRS1, as well as proper motions from Gaia DR2, to select 25,156 white dwarf candidates over ∼4500 deg² using a reduced proper motion diagram. We develop a new white dwarf population synthesis code that returns mock observations of the Galactic field white dwarf population for a given star formation history, while simultaneously taking into account the geometry of the Milky Way (MW), survey parameters, and selection effects. We use this model to derive the star formation histories of the thin disk, thick disk, and stellar halo. Our results show that the MW disk began forming stars (11.3 ± 0.5) Gyr ago, with a peak rate of (8.8 ± 1.4) M_⊙ yr ⁻¹ at (9.8 ± 0.4) Gyr, before a slow decline to a constant rate until the present day—consistent with recent results suggesting a merging event with a satellite galaxy. Studying the residuals between the data and best-fit model shows evidence for a slight increase in star formation over the past 3 Gyr. We fit the local fraction of helium-atmosphere white dwarfs to be (21 ± 3)%. Incorporating this methodology with data from future wide-field surveys such as the Large Synoptic Survey Telescope, Euclid, The Cosmological Advanced Survey Telescope for Optical and ultraviolet Research, and the Wide Field Infrared Survey Telescope should provide an unprecedented view into the formation of the MW at its earliest epoch through its white dwarfs.

We analyze Chandra observations of the hot atmospheres of 40 early spiral and elliptical galaxies. Using new temperature, density, cooling time, and mass profiles, we explore relationships between their hot atmospheres and cold molecular gas. Molecular gas mass correlates with atmospheric gas mass and density over four decades from central galaxies in clusters to normal giant ellipticals and early spirals. The mass and density relations follow power laws: ${M}_{\mathrm{mol}}\propto {M}_{{\rm{X}}}^{1.4\pm 0.1}$ and ${M}_{\mathrm{mol}}\propto {n}_{{\rm{e}}}^{1.8\pm 0.3}$, respectively, at 10 kpc. The ratio of molecular gas to atmospheric gas within a 10 kpc radius lies between 3% and 10% for early-type galaxies and between 3% and 50% for central galaxies in clusters. Early-type galaxies have detectable levels of molecular gas when their atmospheric cooling times fall below ∼1 Gyr at a radius of 10 kpc. A similar trend is found in central cluster galaxies. We find no relationship between the ratio of the cooling time to free-fall time, t_c/t_ff, and the presence or absence of molecular clouds in early-type galaxies. The data are consistent with much of the molecular gas in early-type galaxies having condensed from their hot atmospheres.

Previous research has shown that the deflection of coronal mass ejections (CMEs) in interplanetary space, especially fast CMEs, is a common phenomenon. The deflection caused by the interaction with background solar wind is an important factor to determine whether CMEs could hit Earth or not. As the Sun rotates, there will be interactions between solar wind flows with different speeds. When faster solar wind runs into slower solar wind ahead, it will form a compressive area corotating with the Sun, which is called a corotating interaction region (CIR). These compression regions always have a higher density than the common background solar wind. When interacting with CME, will this make a difference in the deflection process of CME? In this research, first, a three-dimensional (3D) flux-rope CME initialization model is established based on the graduated cylindrical shell (GCS) model. Then this CME model is introduced into the background solar wind, which is obtained using a 3D IN (INterplanetary) -TVD-MHD model. The Carrington Rotation (CR) 2154 is selected as an example to simulate the propagation and deflection of fast CME when it interacts with background solar wind, especially with the CIR structure. The simulation results show that: (1) the fast CME will deflect eastward when it propagates into the background solar wind without the CIR; (2) when the fast CME hits the CIR on its west side, it will also deflect eastward, and the deflection angle will increase compared with the situation without CIR.

It has been known for some time that compact stars containing quark matter can masquerade as neutron stars in the range of measured mass and radius, making it difficult to draw firm conclusions on the phases of matter present inside the star. Using the vector-enhanced Bag model (vBag), we examine mass–radius and mass–compactness relations with Maxwell and Gibbs construction for hybrid stars with transitions from nuclear matter to two- or three-flavor quark matter, including sequential transitions. Not only can stable hybrid stars with either two- or three-flavor quark matter mimic neutron stars (the traditional masquerade), it also appears difficult to distinguish two-flavor from three-flavor quark matter, even in cases where a phase transition can be said to have occurred, such as in the presence of a distinct kink in the mass–radius relation. Furthermore, allowing for sequential flavor transitions, we find that the transition into an unstable branch can be caused by either a transition from nuclear to unstable quark matter or the sequential transition from nuclear to stable but "masquerading" two-flavor to unstable three-flavor quark matter. Addressing chiral restoration as well as quark deconfinement in a model of the phase transition, as the vBag does, adds further flexibility to the high-density equation of state, motivating caution in using even high-precision M–R data to draw firm conclusions on the nature of phases and phase transitions in neutron stars.

Circumplanetary disks (CPDs) may be essential to the formation of planets, regulating their spin and accretion evolution. We perform a series of 3D hydrodynamics simulations in both the isothermal and adiabatic limits to systematically measure the rotation rates, sizes, and masses of CPDs as functions of ${q}_{\mathrm{thermal}}$, the ratio of the planet mass to the disk thermal mass. Our ${q}_{\mathrm{thermal}}$ ranges from 0.1 to 4; for our various disk temperatures, this corresponds to planet masses between one Earth mass and four Jupiter masses. Within this parameter space, we find that isothermal CPDs are disky and bound within ∼10% of the planet's Bondi radius ${r}_{{\rm{B}}}$, with the innermost $\sim 0.05\,{r}_{{\rm{B}}}$ in full rotational support. Adiabatic CPDs are spherical (and therefore not actually "disks"), bound within $\sim 0.2\,{r}_{{\rm{B}}}$, and mainly pressure-supported, with rotation rates scaling linearly with ${q}_{\mathrm{thermal}};$ extrapolation suggests full rotational support of adiabatic envelopes at $\sim 10\,{q}_{\mathrm{thermal}}$. Fast rotation and 3D supersonic flow render isothermal CPDs significantly different in structure from—and orders of magnitude less massive than—their 1D isothermal hydrostatic counterparts. Inside a minimum-mass solar nebula, even a maximally cooled, isothermal CPD around a 10 Earth-mass core may have less than one Earth mass, suggesting that gas giant formation may hinge on angular momentum transport processes in CPDs. Our CPD sizes and masses appear consistent with the regular satellites orbiting solar system giants.

We investigate constraints on some key cosmological parameters by confronting metastable dark energy (DE) models with different combinations of the most recent cosmological observations. Along with the standard ΛCDM model, two phenomenological metastable DE models are considered: (i) DE decays exponentially, (ii) DE decays into dark matter. We find that: (1) when considering the most recent supernovae and BAO data, and assuming a fiducial ΛCDM model, the inconsistency in the estimated value of the ${{\rm{\Omega }}}_{{\rm{m}},0}{h}^{2}$ parameter obtained by either including or excluding Planck cosmic microwave background (CMB) data becomes very much substantial and points to a clear tension; (2) although the two metastable DE models that we study provide greater flexibility in fitting the data, and they indeed fit the supernovae (SNe) Ia+BAO data substantially better than ΛCDM, they are not able to alleviate this tension significantly when CMB data are included; (3) while local measurements of the Hubble constant are significantly higher relative to the estimated value of H₀ in our models (obtained by fitting to SNe Ia and BAO data), the situation seems to be rather complicated with hints of inconsistency among different observational data sets (CMB, SNe Ia+BAO, and local H₀ measurements). Our results indicate that we might not be able to remove the current tensions among different cosmological observations by considering simple modifications of the standard model or by introducing minimal DE models. A complicated form of expansion history, different systematics in different data and/or a nonconventional model of the early universe might be responsible for these tensions.

We present a comprehensive study of a series of recurrent jets that occurred at the periphery of the NOAA active region 12114 on 2014 July 7. These jets were found to share the same source region and exhibited rotational motions as they propagated outward. The multiwavelength imaging observations made by the AIA and IRIS telescopes reveal that some of the jets contain cool plasma only, while some others contain not only cool but also hot plasma. The Doppler velocities calculated from the IRIS spectra show a continuous evolution from blue- to redshifts as the jet motions change from upward to downward. Additionally, some jets exhibit opposite Doppler shifts on both their sides, indicative of rotating motions along their axes. The inclination angle and three-dimensional velocity of the largest jet were inferred from the imaging and spectroscopic observations, which show high consistency with those derived from the stereoscopic analysis using dual-perspective observations by SDO/AIA and STEREO-B/EUVI. By relating the jets to the local UV/EUV and full-disk GOES X-ray emission enhancements, we found that the previous five small-scale jets were triggered by five bright points while the last/largest one was triggered by a C1.6 solar flare. Together with a number of type III radio bursts generated during the jet eruptions as well as a weak CME that was observed in association with the last jet, our observations provide evidence in support of multiscale magnetic reconnection processes being responsible for the production of jet events.

With MUSE, Chandra, VLA, ALMA, and UVIT data from the GASP program, we study the multiphase baryonic components in a jellyfish galaxy (JW100) with a stellar mass 3.2 × 10¹¹M_⊙ hosting an active galactic nucleus (AGN). We present its spectacular extraplanar tails of ionized and molecular gas, UV stellar light, and X-ray and radio continuum emission. This galaxy represents an excellent laboratory to study the interplay between different gas phases and star formation and the influence of gas stripping, gas heating, and AGNs. We analyze the physical origin of the emission at different wavelengths in the tail, in particular in situ star formation (related to Hα, CO, and UV emission), synchrotron emission from relativistic electrons (producing the radio continuum), and heating of the stripped interstellar medium (ISM; responsible for the X-ray emission). We show the similarities and differences of the spatial distributions of ionized gas, molecular gas, and UV light and argue that the mismatch on small scales (1 kpc) is due to different stages of the star formation process. We present the relation Hα–X-ray surface brightness, which is steeper for star-forming regions than for diffuse ionized gas regions with a high [O i]/Hα ratio. We propose that ISM heating due to interaction with the intracluster medium (either for mixing, thermal conduction, or shocks) is responsible for the X-ray tail, observed [O i] excess, and lack of star formation in the northern part of the tail. We also report the tentative discovery in the tail of the most distant (and among the brightest) currently known ULX, a pointlike ultraluminous X-ray source commonly originating in a binary stellar system powered by either an intermediate-mass black hole or a magnetized neutron star.

EX Lup is the prototype of a class of pre-main-sequence eruptive stars defined by their repetitive outbursts lasting several months. In 2008 January–September EX Lup underwent its historically largest outburst, brightening by about 4 mag in visual light. In previous studies we discovered ongoing silicate crystal formation in the inner disk during the outburst, but also noticed that the measured crystallinity fraction started decreasing after the source returned to the quiescent phase. Here we present new observations of the 10 μm silicate feature, obtained with the MIDI and VISIR instruments at Paranal Observatory. The observations demonstrate that within five years practically all crystalline forsterite disappeared from the surface of the inner disk. We reconstruct this process by presenting a series of parametric axisymmetric radiative transfer models of an expanding dust cloud that transports the crystals from the terrestrial zone to outer disk regions where comets are supposed to form. It is possible the early Sun also experienced similar flare-ups, and the forming planetesimals might have incorporated crystalline silicate material produced by such outbursts. Finally, we discuss how far the location of the dust cloud could be constrained by future James Webb Space Telescope observations.

The collection of planetary system properties derived from large surveys such as Kepler provides critical constraints on planet formation and evolution. These constraints can only be applied to planet formation models, however, if the observational biases and selection effects are properly accounted for. Here we show how epos, the Exoplanet Population Observation Simulator, can be used to constrain planet formation models by comparing the Bern planet population synthesis models to the Kepler exoplanetary systems. We compile a series of diagnostics, based on occurrence rates of different classes of planets and the architectures of multiplanet systems within 1 au, that can be used as benchmarks for future and current modeling efforts. Overall, we find that a model with 100-seed planetary cores per protoplanetary disk provides a reasonable match to most diagnostics. Based on these diagnostics we identify physical properties and processes that would result in the Bern model more closely matching the known planetary systems. These are as follows: moving the planet trap at the inner disk edge outward; increasing the formation efficiency of mini-Neptunes; and reducing the fraction of stars that form observable planets. We conclude with an outlook on the composition of planets in the habitable zone, and highlight that the majority of simulated planets smaller than 1.7 Earth radii in this zone are predicted to have substantial hydrogen atmospheres. The software used in this paper is available online for public scrutiny at  https://github.com/GijsMulders/epos.

We present and discuss results from the first spatially resolved kinematic study of ram-pressure stripping of a massive late-type galaxy at intermediate redshifts. Our target, the spectacular "jellyfish" galaxy, A1758N_JFG1, was previously identified as a fast-moving member of the equal-mass merger A1758N (z = 0.28), with a star formation rate of 48 M_☉ yr⁻¹, far above the galaxy main sequence. Integral field unit (IFU) data obtained by us unambiguously confirm ram-pressure stripping as the physical mechanism driving the optical morphology and high star formation rate of this system by revealing extended [O ii]λ3727 Å emission up to 40 kpc (in projection) downstream, as well as an ordered radial-velocity field generated by (a) conservation of angular momentum of the interstellar gas stripped from the edge of the galactic disk and (b) drag forces exerted by the intracluster medium on the "tentacles" of stripped material. We find no evidence of significant nuclear activity in A1758N_JFG1, although an AGN might, at this early stage of the stripping process, be obscured by high column densities of gas and dust near the galactic core. Finally, our exploration of possible trajectories of A1758N_JFG1 found solutions consistent with the notions (a) that the A1758N merger proceeds along an axis that is substantially inclined with respect to the plane of the sky and (b) that A1758N_JFG1 participated in the merger, rather than having been accreted independently from the field.

It is well known that aligned, aspherical dust grains emit polarized radiation and that the degree of polarization depends on the angle ψ between the interstellar magnetic field and the line of sight (LOS). However, anisotropy of the dust absorption cross sections also modulates the total intensity of the radiation as the viewing geometry changes. We report a detection of this effect in the high Galactic latitude Planck data, finding that the 353 GHz dust intensity per N_H i is smaller when the Galactic magnetic field is mostly in the plane of the sky and larger when the field is mostly along the LOS. These variations are of opposite sign and roughly equal magnitude as the changes in polarized intensity per N_H i with ψ, as predicted. In principle, the variation in intensity can be used in conjunction with the dust polarization angle to constrain the full 3D orientation of the Galactic magnetic field.

The properties of Alfvénic solar wind turbulence have been studied for decades using spacecraft measurements. In particular, the observation of spectral anisotropy of magnetic fluctuations has stimulated the development of several phenomenological models, one of the most popular being critical balance. However, the experimental validation of these models is intrinsically difficult because of the one-dimensional nature of the measurements provided by spacecraft instrumentation. In this work, a thorough search is performed in the Wind spacecraft database to extract samples of field-aligned fast solar wind, which allow the precise estimation of the parallel spectral properties of the magnetic fluctuations, and of their intermittency. Hilbert spectral analysis is used, in order to eliminate the possible role of nonstationarity and large-scale structures. Our results indicate that the spectral anisotropy predicted by the critical balance theory is not observed in the selected database, thus questioning the validity of the critical balance in the solar wind turbulence. A stochastic process characterized by a −5/3 spectral scaling, which is not necessarily attributed to usual turbulence, as indicated by the absence of intermittency, is indeed observed in the analyzed data samples.

Outflows are a pervasive feature of mechanical feedback from super star clusters (SSCs) in starburst galaxies, playing a fundamental role in galaxy evolution. Observations are now starting to confirm that outflows can undergo catastrophic cooling, suppressing adiabatic superwinds. Here we present a suite of one-dimensional, hydrodynamic simulations that study the ionization structure of these outflows and the resulting line emission generated by the cooling gas. We use the non-equilibrium atomic chemistry package within MAIHEM, our modified version of FLASH, which evolves the ionization state of the gas and computes the total cooling rate on an ion-by-ion basis. We find that catastrophically cooling models produce strong nebular line emission compared to adiabatic outflows. We also show that such models exhibit non-equilibrium conditions, thereby generating more highly ionized states than equivalent equilibrium models. When including photoionization from the parent SSC, catastrophically cooling models show strong C ivλ1549 and O viλ1037 emission. For density-bounded photoionization, He iiλ1640, λ4686, C iii] λ1908, Si ivλ1206, and Si iiiλ1400 are also strongly enhanced. These lines are seen in extreme starbursts where catastrophic cooling is likely to occur, suggesting that they may serve as diagnostics of such conditions. The higher ionization generated by these flows may help to explain line emission that cannot be attributed to SSC photoionization alone.

We present numerical calculations of spectra and structure of accretion disk models appropriate for near-Eddington luminosity black hole X-ray binaries. Our work incorporates nonzero torque at the ISCO as well as several dissipation profiles based on first-principles three-dimensional disk interior simulations. We found that significant dissipation near the photosphere can produce steep power-law-like spectra for models with moderate viewing angles spanning a range of black hole spins while including inner torque pushes the spectral peak to higher energies. Consistent with previous studies, we also conclude that disks with stresses at the inner edge remain viable models for high-frequency quasi-periodic oscillations, especially given that increasing dissipation near the photospheres actually resulted in QPO power spectra with higher quality factors compared to those found in recent work.

In this paper, we present a scheme to investigate the opacity of the universe in a cosmological-model-independent way, with the combination of current and future measurements of an SN Ia sample and galactic-scale strong gravitational lensing systems with SNe Ia acting as background sources. The observational data include the current newly compiled SNe Ia data (Pantheon sample) and a simulated sample of SNe Ia observed by the forthcoming Large Synoptic Survey Telescope (LSST), which are taken for luminosity distances (D_L) possibly affected by the cosmic opacity, as well as strongly lensed SNe Ia observed by the LSST, which are responsible for providing the observed time-delay distance unaffected by the cosmic opacity. Focusing on only one specific type of standard cosmological probe, this provides an original method to measure cosmic opacity at high precision. Working on the simulated sample of strongly lensed SNe Ia observed by the LSST in the 10 yr z-band search, our results show that, with the combination of the current newly compiled SNe Ia data (Pantheon sample), there is no significant deviation from the transparency of the universe at the current observational data level. Moreover, strongly lensed SNe Ia in a 10 yr LSST z-band search would produce more robust constraints on the validity of cosmic transparency, with a larger sample of unlensed SNe Ia detected in the future LSST survey. We have also discussed the ways in which our methodology could be improved, with the combination of current and future available data in the gravitational wave and electromagnetic domain.

Over the past half-century, X-ray and radio observations of accreting neutron stars and stellar-mass black holes have yielded a rich observational picture, with common features including state transitions and jet formation, but also sharp differences. While black hole X-ray binaries overwhelmingly suppress jets in so-called soft states, accreting neutron stars are less restrictive, with a soft state wind observed in some sources to coexist with a jet. We propose an explanation for these differences that leads to a generalization of a foundational element, the hardness–intensity diagram of Fender et al. The inverse relation between jets and winds fits into a picture that connects to prograde accretion, while the possibility of counterrotation between accretion disk and compact object accounts for observed differences in accreting neutron stars. This picture comes with a surprising twist, which is that neutron stars embody the small-scale analog of FRII quasars, an idea that allows us to complete the scale-invariant picture for the jet–disk connection.

We present the first plasma simulations obtained with the code dHybridR, a hybrid particle-in-cell code with fluid electrons and both thermal and energetic ions that retain relativistic dynamics. dHybridR is constructed to study astrophysical and space-physics problems where a few energetic nonthermal particles (i.e., cosmic rays, CRs) affect the overall dynamics of a nonrelativistic plasma, such as CR-driven instabilities, collisionless shocks, magnetic reconnection, turbulence, etc. In this method paper we provide some applications to linear (resonant/nonresonant CR streaming instability) and strongly nonlinear (parallel shocks) problems that show the capabilities of the code. In particular, we provide the first self-consistent hybrid runs that show the acceleration of relativistic ions at nonrelativistic shocks; CRs develop a power law in momentum, which translates into a broken power law in energy that exhibits a steepening around the ion rest mass, as predicted by the theory of diffusive shock acceleration. We present examples of 2D dHybridR runs relevant for fast shocks in radio supernovae, whose evolution can be followed in real time, and 3D runs of low-Mach-number heliospheric shocks, which can be compared with in situ spacecraft observations.

Giant exoplanets located >1 au away from their parent stars have atmospheric environments cold enough for water or ammonia clouds. We have developed a new equilibrium cloud and reflected-light spectrum model, ExoREL, for widely separated giant exoplanets. The model includes the dissolution of ammonia in liquid-water cloud droplets, an effect studied for the first time for exoplanets. While preserving the causal relationship between temperature and cloud condensation, ExoREL is simple and fast to enable efficient exploration of parameter space. Using the model, we find that the mixing ratio of methane and the cloud top pressure of a giant exoplanet can be uniquely determined from a single observation of its reflected-light spectrum at wavelengths less than 1 μm if it has a cloud deck deeper than ∼0.3 bar. This measurement is enabled by the weak and strong bands of methane and requires a signal-to-noise ratio of 20. The cloud pressure, once derived, provides information about the internal heat flux of the planet. Importantly, we find that for a low, Uranus-like internal heat flux, the planet can have a deep liquid-water cloud, which will sequester ammonia and prevent the formation of the ammonia cloud that would otherwise be the uppermost cloud layer. This newly identified phenomenon causes a strong sensitivity of the cloud top pressure to the internal heat flux. Reflected-light spectroscopy from future direct-imaging missions should therefore not only measure the atmospheric abundances but also characterize the thermal evolution of giant exoplanets.

Magnetically arrested disks (MADs) appear when accretion flows are supplied with a sufficient amount of magnetic flux. In this work, we use results of magnetohydrodynamic simulations to set the configuration of the magnetic field and investigate the dynamics and radiative properties of the resulting accretion flow (i.e., without that of the jet) of MADs. The method developed here is applied to both the MAD and the standard and normal evolution (SANE) accretion flow with or without large-scale magnetic fields. For the radiative processes, we include synchrotron, bremsstrahlung, and Compton scattering. We find that, in general, accretion flows of MADs have similar spectra to those of the SANE, which complicates the task of distinguishing MADs from SANEs. At the same accretion rates, MADs are systematically brighter than SANEs. However, the critical accretion rate above which the hot solution ceases to exist is lower in MADs. Consequently, the maximum luminosity an MAD can reach is comparable to but slightly lower than that of SANE, and the dependence on the magnetic flux is weak. We then discuss the implications of our results for active galactic nuclei and accreting black hole binaries.

We present Keck/MOSFIRE (Multi-Object Spectrometer for InfraRed Exploration) and Keck/LRIS (Low Resolution Imaging Spectrometer) spectroscopy of A1689-217, a lensed (magnification ∼7.9), star-forming (SFR ∼ 16 M_☉ yr⁻¹), dwarf (log(M_*/M_☉) = 8.07–8.59) Lyα emitter (EW₀ ∼ 138 Å) at z = 2.5918. Dwarf galaxies similar to A1689-217 are common at high redshift and likely responsible for reionization, yet few have been studied with detailed spectroscopy. We report a 4.2σ detection of the electron-temperature-sensitive [O iii] λ4363 emission line and use this line to directly measure an oxygen abundance of 12 + log(O/H) = 8.06 ± 0.12 (∼1/4 Z_☉). A1689-217 is the lowest-mass galaxy at z > 2 with an [O iii] λ4363 detection. Using the rest-optical emission lines, we measure A1689-217's other nebular conditions, including electron temperature (T_e([O iii]) ∼ 14,000 K), electron density (n_e ∼ 220 cm⁻³), and reddening ($E(B-V)$ ∼ 0.39). We study relations between strong-line ratios and direct metallicities with A1689-217 and other galaxies with [O iii] λ4363 detections at z ∼ 0–3.1, showing that the locally calibrated, oxygen-based, strong-line relations are consistent from z ∼ 0 to 3.1. We also show additional evidence that the O₃₂ versus R₂₃ excitation diagram can be utilized as a redshift-invariant, direct-metallicity-based, oxygen abundance diagnostic out to z ∼ 3.1. From this excitation diagram and the strong-line ratio–metallicity plots, we observe that the ionization parameter at fixed O/H is consistent with no redshift evolution. Although A1689-217 is metal-rich for its M_* and star formation rate, we find it to be consistent within the large scatter of the low-mass end of the fundamental metallicity relation.

We present detailed observations of ZTF18abukavn (SN2018gep), discovered in high-cadence data from the Zwicky Transient Facility as a rapidly rising (1.4 ± 0.1 mag hr⁻¹) and luminous (${M}_{g,\mathrm{peak}}=-20$ mag) transient. It is spectroscopically classified as a broad-lined stripped-envelope supernova (Ic-BL SN). The high peak luminosity (${L}_{\mathrm{bol}}\gtrsim 3\times {10}^{44}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$), the short rise time (${t}_{\mathrm{rise}}=3\,\mathrm{days}$ in g band), and the blue colors at peak ($g\mbox{--}r\sim -0.4$) all resemble the high-redshift Ic-BL iPTF16asu, as well as several other unclassified fast transients. The early discovery of SN2018gep (within an hour of shock breakout) enabled an intensive spectroscopic campaign, including the highest-temperature (${T}_{\mathrm{eff}}\gtrsim {\rm{40,000}}\,{\rm{K}}$) spectra of a stripped-envelope SN. A retrospective search revealed luminous (${M}_{g}\sim {M}_{r}\approx -14$ mag) emission in the days to weeks before explosion, the first definitive detection of precursor emission for a Ic-BL. We find a limit on the isotropic gamma-ray energy release ${E}_{\gamma ,\mathrm{iso}}\lt 4.9\times {10}^{48}\,\mathrm{erg}$, a limit on X-ray emission ${L}_{{\rm{X}}}\lt {10}^{40}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$, and a limit on radio emission $\nu {L}_{\nu }\lesssim {10}^{37}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$. Taken together, we find that the early ($\lt 10\,\mathrm{days}$) data are best explained by shock breakout in a massive shell of dense circumstellar material (0.02 ${M}_{\odot }$) at large radii ($3\times {10}^{14}\,\mathrm{cm}$) that was ejected in eruptive pre-explosion mass-loss episodes. The late-time ($\gt 10\,\mathrm{days}$) light curve requires an additional energy source, which could be the radioactive decay of Ni-56.

We determine the observability in transmission of inhomogeneous cloud cover on the limbs of hot Jupiters through post-processing a general circulation model to include cloud distributions computed using a cloud microphysics model. We find that both the east and west limbs often form clouds, but that the different properties of these clouds enhance the limb-to-limb differences compared to the clear case. Using the James Webb Space Telescope, it should be possible to detect the presence of cloud inhomogeneities by comparing the shape of the transit light curve at multiple wavelengths because inhomogeneous clouds impart a characteristic, wavelength-dependent signature. This method is statistically robust even with limited wavelength coverage, uncertainty on limb-darkening coefficients, and imprecise transit times. We predict that the short-wavelength slope varies strongly with temperature. The hot limbs of the hottest planets form higher-altitude clouds composed of smaller particles, leading to a strong Rayleigh slope. The near-infrared spectral features of clouds are almost always detectable, even when no spectral slope is visible in the optical. In some of our models a spectral window between 5 and 9 μm can be used to probe through the clouds and detect chemical spectral features. Our cloud particle size distributions are not lognormal and differ from species to species. Using the area- or mass-weighted particle size significantly alters the relative strength of the cloud spectral features compared to using the predicted size distribution. Finally, the cloud content of a given planet is sensitive to a species' desorption energy and contact angle, two parameters that could be constrained experimentally in the future.

Quasars at early redshifts (z > 6) with companion galaxies offer unique insights into the growth and evolution of the first supermassive black holes. Here, we report on a 150 ks Chandra observation of PSO J308.0416−21.2339, a z = 6.23 quasar with a merging companion galaxy identified in [C ii] and rest-frame UV emission. With ${72.3}_{-8.6}^{+9.6}$ net counts, we find that PSO J308.0416−21.2339 is powerful (${L}_{X}={2.31}_{-0.76}^{+1.14}\times {10}^{45}\ \mathrm{erg}\,{{\rm{s}}}^{-1}\,{\mathrm{cm}}^{-2}$ in rest-frame 2.0–10.0 keV) yet soft (spectral power-law index ${\rm{\Gamma }}={2.39}_{-0.36}^{+0.37}$ and optical-to-X-ray slope α_OX = −1.41 ± 0.11). In addition, we detect three hard-energy photons 20 to the west of the main quasar, cospatial with the brightest UV emission of the merging companion. As no soft-energy photons are detected in the same area, this is potentially indicative of a highly obscured source. With conservative assumptions, and accounting for both background fluctuations and the extended wings of the quasar's emission, these photons only have a probability P = 0.021 of happening by chance. If confirmed by deeper observations, this system is the first high-redshift quasar and companion individually detected in X-rays and is likely a dual active galactic nucleus.

We present CO (J = 1−0) and/or CO (J = 2−1) spectroscopy for 31 galaxies selected from the ongoing Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, obtained with multiple telescopes. This sample is combined with CO observations from the literature to study the correlation of the CO luminosities (${L}_{\mathrm{CO}(1-0)}$) with the mid-infrared luminosities at 12 (${L}_{12\mu {\rm{m}}}$) and 22 μm (${L}_{22\mu {\rm{m}}}$), as well as the dependence of the residuals on a variety of galaxy properties. The correlation with ${L}_{12\mu {\rm{m}}}$ is tighter and more linear, but galaxies with relatively low stellar masses (${M}_{* }\lesssim {10}^{10}$M_⊙) and blue colors ($g-r\lesssim 0.5$ and/or NUV − r ≲ 3) fall significantly below the mean ${L}_{\mathrm{CO}(1-0)}$–${L}_{12\mu {\rm{m}}}$ relation. We propose a new estimator of the CO (1−0) luminosity (and thus the total molecular gas mass M_mol) that is a linear combination of three parameters: ${L}_{12\mu {\rm{m}}}$, ${M}_{* }$, and g − r. We show that, with a scatter of only 0.18 dex in log $({L}_{\mathrm{CO}(1-0)})$, this estimator provides unbiased estimates for galaxies of different properties and types. An immediate application of this estimator to a compiled sample of galaxies with only CO (J = 2−1) observations yields a distribution of the CO (J = 2−1) to CO (J = 1−0) luminosity ratios (R21) that agrees well with the distribution of real observations, in terms of both the median and the shape. Application of our estimator to the current MaNGA sample reveals a gas-poor population of galaxies that are predominantly early-type and show no correlation between molecular gas-to-stellar mass ratio and star formation rate, in contrast to gas-rich galaxies. We also provide alternative estimators with similar scatters, based on r- and/or z-band luminosities instead of ${M}_{* }$. These estimators serve as cheap and convenient M_mol proxies to be potentially applied to large samples of galaxies, thus allowing statistical studies of gas-related processes of galaxies.

We present the analysis of Chandra and NuSTAR spectra of NGC 4968, a local (D ∼ 44 Mpc) 12 μm selected Seyfert 2 galaxy, enshrouded within Compton-thick layers of obscuring gas. We find no evidence of variability between the Chandra and NuSTAR observations (separated by 2 yr), nor between the two NuSTAR observations (separated by 10 months). Using self-consistent X-ray models, we rule out the scenario where the obscuring medium is nearly spherical and uniform, contradicting the results implied by the <10 keV Chandra spectrum. The line-of-sight column density, from intervening matter between the source and observer that intercepts the intrinsic active galactic nucleus (AGN) X-ray emission, is well within the Compton-thick regime, with a minimum column density of 2 × 10²⁴ cm⁻². The average global column density is high (>3 × 10²³ cm⁻²), with both Compton-thick and Compton-thin solutions permitted, depending on the X-ray spectral model. The spectral models provide a range of intrinsic AGN continuum parameters and implied 2–10 keV luminosities (L_{2–10 keV,intrinsic}), where the higher end of L_{2–10 keV,intrinsic} is consistent with expectations from the 12 μm luminosity (L_{2–10 keV,intrinisc} ∼ 7 × 10⁴² erg s⁻¹). Compared with Compton-thick AGN previously observed by NuSTAR, NGC 4968 is among the most intrinsically X-ray luminous. However, despite its close proximity and relatively high intrinsic X-ray luminosity, it is undetected by the 105 month Swift-Burst Alert Telescope survey, underscoring the importance of multiwavelength selection for obtaining the most complete census of the most hidden black holes.

The presence of supermassive black holes (SMBHs) with masses up to M_• ∼ 10⁹${M}_{\odot }$ at redshifts z ≃ 7.5 suggests that their seeds may have started to grow long before the reionization in ambient medium with pristine chemical composition. During their latest 500 Myr episode of growing from z ≥ 10 to z ∼ 7, the black holes shone as luminous as 10¹¹–10¹²L_⊙, with a cumulative spectrum consisting of the intrinsic continuum from the hot accretion disk, nebular hydrogen, and helium spectral lines, and the free–free continuum from the gas of host halos. Here we address the question of whether such a plain spectrum would allow us to trace the evolution of these growing SMBHs. In our calculations we assume that host galaxies have stellar populations with masses smaller than the masses of their central black holes—the so-called obese black hole galaxies. Within this model we show that for a sufficiently high mass of gas in a host galaxy—not smaller than the mass of a growing black hole, the cumulative spectrum in the far-infrared reveals a sharp transition from a quasi-blackbody Rayleigh–Jeans spectrum of the black hole ∝λ⁻² to a flat free–free nebular continuum λ^0.118 on a longer wavelength limit. Once such a transition in the spectrum is resolved, the black hole mass can be inferred as a combination of the observed wavelength at the transition λ_k and the corresponding spectral luminosity. The possible observability of this effect in spectra of growing high-z SMBHs and determination of their mass with the upcoming James Webb Space Telescope and the planned space project Spektr-M is briefly discussed.

We explore the large to moderate scale anisotropy in distant radio sources using the TIFR GMRT Sky Survey (TGSS) ADR1 catalog. We use different measures, i.e., number counts, sky brightness, and flux per source, for this study. In agreement with earlier results, we report a significant excess of clustering signal above the angular scale of roughly 10° (i.e., l ⪅ 20–30). We find that some survey areas have a systematically low/high flux and argue this may be the cause of the observed signal of excess power at low multipoles. With mocks we demonstrate the effect of such large-scale flux systematics and recover a TGSS-like excess clustering signal by assuming 20% flux uncertainties over ∼10° × 10° sized patches. We argue that that TGSS at this stage, i.e., TGSS ADR1, is not suitable for large-scale clustering measurements. We find that the measure, flux per source, shows evidence of isotropy for all multipoles l > 2 despite the presence of systematics in the data.

We used resolved star counts from Hubble Space Telescope (HST) images to determine the center of gravity and the projected density profiles of six old globular clusters (GCs) in the Large Magellanic Cloud (LMC), namely NGC 1466, NGC 1841, NGC 1898, NGC 2210, NGC 2257, and Hodge 11. For each system, the LMC field contribution was properly taken into account by making use, when needed, of parallel HST observations. The derived values of the center of gravity may differ by several arcseconds (corresponding to more dal 1 pc at the distance of the LMC) from previous determinations. The cluster density profiles are all well fit by King models, with structural parameters that may differ from the literature ones by even factors of two. Similar to what was observed for Galactic GCs, the ratio between the effective and the core radius has been found to anticorrelate with the cluster dynamical age.

From a reduced chemical model of the Martian dayside ionosphere we derive an expression that can be used to estimate the electron temperature as a function of the ambient number densities of CO₂, O, ${{{\rm{O}}}_{2}}^{+}$, ${{\mathrm{CO}}_{2}}^{+}$, O⁺, and NO⁺ and the total ion number density. The model is tested in the sunlit ionosphere with Mars Atmosphere and Volatile EvolutioN/Neutral Gas Ion Mass Spectrometer (MAVEN/NGIMS) data from the Deep Dip campaigns DD2 (2015 April) and DD8 (2017 October). Around an altitude of ∼130–140 km the calculated electron temperatures along the DD2 orbits are in many cases compatible with the neutral temperatures derived from the CO₂ density profiles and downward integration of the hydrostatic balance equation, indicating efficient cooling of the electron population. For altitudes below 170 km the electron temperature (constructed from median density profiles) are higher for DD8 than for DD2 which we link to atmospheric solar cycle modulation. Median electron temperatures derived for DD2 and DD8 are roughly similar when inspecting similar CO₂ number densities and a simple power law is proposed to relate the electron temperature to the CO₂ number density. Calculated electron temperatures of approximately 1000 K around an altitude of 180–200 km appear not to conflict with published data from MAVEN Langmuir Probe Wave (LPW) measurements. At greater depths the LPW-derived electron temperatures have been reported as biased high and so a detailed comparison with results from the present work is merely proposed as a dedicated follow-up study.

We report the kinematic shift of the C iv broad absorption line (BAL) in quasar SDSS J120819.29+035559.4 (hereafter J1208+0355). This quasar shows two BAL systems, including a blue component of system A at ∼23,500 km s⁻¹ that shows a kinematic shift of 1166 ± 65 km s⁻¹, and a red component of system B at ∼7000 km s⁻¹ that can be decomposed into several narrow absorption lines (NALs). First, we confirm that the most likely cause for the equivalent width variations of the absorption lines (at least for system B) in J1208+0355 is the ionization change scenario as a response to the changes in the ionization continuum according to the following observational factors: (1) coordinated multiple absorption lines strengthening; (2) the continuum flux shows an obvious weakening. Second, we find line-locking phenomena from the blended NALs within system B, indicating that these outflow clouds are driven by a radiative force caused by resonance lines. The above two research aspects convincingly reveal that the BAL outflows of J1208+0355 are affected by the background radiation energy. Therefore, we infer that the kinematic shift shown in system A may be produced by actual line-of-sight acceleration of the outflow clouds, which is driven by radiation pressure from the background light source.

Star-forming regions presenting a density gradient experience a higher star formation rate than if they were of uniform density. We refer to the ratio between the star formation rate of a spherical centrally concentrated gas clump and the star formation rate that this clump would experience if it were of uniform density as the magnification factor ζ. We map ζ as a function of clump mass, radius, initial volume-density profile, and star formation timespan. For clumps with a steep density profile (i.e., a power-law slope ranging from −3 to −4, as observed in some high-density regions of Galactic molecular clouds), we find their star formation rate to be at least an order of magnitude higher than their top-hat equivalent. This implies that such clumps experience faster and more efficient star formation than expected based on their mean freefall time. This also implies that measurements of the star formation efficiency per freefall time of clumps based on their global properties, namely, mass, mean volume density, and star formation rate, present wide fluctuations. These reflect the diversity in the density profile of star-forming clumps, not necessarily variations in the physics of star formation. Steep density profiles inside star-cluster progenitors may be instrumental in the formation of multiple stellar populations, such as those routinely observed in old globular clusters.

A new class of faint, spectroscopically peculiar transients has emerged in the last decade. We term these events "calcium-strong transients" (CaSTs) because of their atypically high calcium-to-oxygen nebular line ratios. Previous studies have struggled to deduce the identity of their progenitors, due to a combination of their extremely extended radial distributions with respect to their host galaxies and their relatively high rate of occurrence. In this work, we find that the CaST radial distribution is consistent with the radial distribution of two populations of stars: old (ages >5 Gyr), low-metallicity (Z/Z_⊙ < 0.3) stars, and globular clusters. While no obvious progenitor scenario arises from considering old, metal-poor stars, the alternative production site of globular clusters leads us to narrow down the list of possible candidates to three binary scenarios: mergers of helium and oxygen/neon white dwarfs; tidal disruptions of helium white dwarfs by neutron stars; and stable accretion from low-mass helium-burning stars onto white dwarfs. While rare in the field, these binary systems can be formed dynamically at much higher rates in globular clusters. Subsequent binary hardening both increases their interaction rate and ejects them from their parent globular clusters prior to mass transfer contact. Their production in, and ejection from, globular clusters may explain their radial distribution and the absence of globular clusters at their explosion site. This model predicts a currently undiscovered high rate of CaSTs in nuclear star clusters. Alternatively, an undetermined progenitor scenario involving old, low-metallicity stars may instead hold the key to understanding CaSTs.

We demonstrate that the exact solution for the spectrum of synchrotron radiation from an isotropic population of monoenergetic electrons in a turbulent magnetic field with a Gaussian distribution of local field strengths can be expressed in the simple analytic form: ${\left(\tfrac{d\dot{N}}{d\omega }\right)}_{t}=\tfrac{\alpha }{3}\tfrac{1}{{\gamma }^{2}}\left(1+\tfrac{1}{{x}^{2/3}}\right)\exp \left(-2{x}^{2/3}\right)$, where $x=\tfrac{\omega }{{\omega }_{0}};{\omega }_{0}=\tfrac{4}{3}{\gamma }^{2}\tfrac{{{eB}}_{0}}{{m}_{e}c}.$ We use this expression to find the approximate synchrotron spectra for power-law electron distributions with $\propto \exp \left(-{\left[\gamma /{\gamma }_{0}\right]}^{\beta }\right)$-type high-energy cutoff; the resulting synchrotron spectrum has the exponential cutoff factor with a frequency raised to the 2β/(3β + 4) power in the exponent. For the power-law electron distribution without a high-energy cutoff, we find the coefficient a_m as a function of the power-law index, which results in the exact expression for the synchrotron spectrum when using the monochromatic (i.e., each electron radiates at the frequency ${\omega }_{m}={a}_{m}{\gamma }^{2}\,\tfrac{{{eB}}_{0}}{{m}_{e}c}$) approximation.

Shocks, turbulence, and winds all influence the electron velocity distribution in hot plasmas, exciting lower-energy electrons and generating a high-energy (typically power-law) tail. This effect, typically described as a κ distribution can affect both the line and continuum X-ray spectra emitted by the plasma. Hahn & Savin proposed a "Maxwellian decomposition" to generate the rate coefficients of κ distributions. Using their method and the AtomDB atomic database, we have developed a general model to calculate the emission from a plasma with a κ distribution. We compare our κ results for the charge state distribution and spectra of oxygen with those from KAPPA package with the ion data available within the CHIANTI atomic database. Sufficiently energetic electrons, created either in a κ distribution or merely a very hot Maxwellian plasma, can also emit via electron–electron (e–e) bremsstrahlung, a process not previously included in AtomDB. We have added this process to AtomDB and apply it to calculate the temperature gradients, as well as the total spectra from the post-shock regions of an accreting magnetic cataclysmic variable. We find the contribution of e–e bremsstrahlung to the total spectra exceeds 10% at KT ∼ 100 keV, with the total emissivity in the post-shock accretion stream differing by more than 10% at energies above 60 keV.

We present ALMA Band 6 (ν = 233 GHz, λ = 1.3 mm) continuum observations toward 68 "normal" star-forming galaxies within two Coma-like progenitor structures at z = 2.10 and 2.47, from which ISM masses are derived, providing the largest census of molecular gas mass in overdense environments at these redshifts. Our sample comprises galaxies with a stellar mass range of 1 × 10⁹M_⊙–4 × 10¹¹M_⊙ with a mean M_⋆ ≈ 6 × 10¹⁰M_⊙. Combining these measurements with multiwavelength observations and spectral energy distribution modeling, we characterize the gas mass fraction and the star formation efficiency, and infer the impact of the environment on galaxies' evolution. Most of our detected galaxies (≳70%) have star formation efficiencies and gas fractions similar to those found for coeval field galaxies and in agreement with the field scaling relations. However, we do find that the protoclusters contain an increased fraction of massive, gas-poor galaxies, with low gas fractions (f_gas ≲ 6%–10%) and red rest-frame ultraviolet/optical colors typical of post-starburst and passive galaxies. The relatively high abundance of passive galaxies suggests an accelerated evolution of massive galaxies in protocluster environments. The large fraction of quenched galaxies in these overdense structures also implies that environmental quenching takes place during the early phases of cluster assembly, even before virialization. From our data, we derive a quenching efficiency of _q ≈ 0.45 and an upper limit on the quenching timescale of τ_q < 1 Gyr.

We present three simultaneous/quasi-simultaneous NuSTAR and Swift data sets of the black hole (BH) GRS 1716-249 in its hard intermediate state. The accretion disk in this state may have reached the innermost stable circular orbit, and the NuSTAR spectra show a broad relativistic iron line and a strong Compton hump. To measure the BH spin, we construct a joint model consisting of a relativistic disk model kerrbb and a reflection model relxill, to fit the continuum and the reflection components, respectively. By applying this model to each data set independently, a consistent result is obtained on the BH spin and the disk inclination. The BH spin is a* ≳ 0.92, and the inclination angle (i) is around 40°–50°, based on the measurements of all data sets. In the third data set, a high BH mass (M_BH) is strongly disfavored by the spectral fits. By unfreezing the BH mass, we find a* > 0.92, $i={49.9}_{-1.3}^{+1.0\,\circ }$, and M_BH < 8.0 M_⊙, at a 90% confidence level. Considering the lower limit derived from a previous optical constraint, M_BH is in a range of 4.9–8.0 M_⊙.

We performed a long-term optical (B, V, R bands), infrared (J and K bands), and radio band (15, 22, 37 GHz band) study of the flat spectrum radio quasar, 3C 454.3, using data collected over a period of more than 8 yr (MJD 54500–57500). The temporal variability, spectral properties, and interwaveband correlations were studied by dividing the available data into smaller segments with more regular sampling. This helped us constrain the size and the relative locations of the emission regions for different wavebands. Spectral analysis of the source revealed the interplay between the accretion disk and jet emission. The source predominantly showed a redder-when-brighter trend, though we observed a bluer-when-brighter trend at high flux levels, which could be a signature of particle acceleration and radiative cooling. Significant correlations with near-zero lag were seen between various optical and infrared bands, indicating that these emission regions are cospatial. Correlations with a time lag of about 10–100 days are seen between the optical/infrared and radio bands indicating these emissions arise from different regions. We also observe the DCF peak lag change from year to year. We try to explain these differences using a curved jet model where the different emission regions have different viewing angles resulting in a frequency-dependent Doppler factor. This variable Doppler factor model explains the variability timescales and the variation in DCF peak lag between the radio and optical emissions in different segments. Lags of 6–180 days are seen between emissions in various radio bands, indicating a core-shift effect.

Using a population of large-scale filaments extracted from an AREPO simulation of a Milky Way–like galaxy, we seek to understand the extent to which observed large-scale filament properties (with lengths ≳100 pc) can be explained by galactic dynamics alone. From an observer's perspective in the disk of the galaxy, we identify filaments forming purely due to galactic dynamics, without the effects of feedback or local self-gravity. We find that large-scale galactic filaments are intrinsically rare, and we estimate that at maximum approximately one filament per kpc² should be identified in projection, when viewed from the direction of our Sun in the Milky Way. In this idealized scenario, we find filaments in both the arm and interarm regions and hypothesize that the former may be due to gas compression in the spiral potential wells, with the latter due to differential rotation. Using the same analysis pipeline applied previously to observations, we analyze the physical properties of large-scale galactic filaments and quantify their sensitivity to projection effects and galactic environment (i.e., whether they lie in the arm or interarm regions). We find that observed "Giant Molecular Filaments" are consistent with being non-self-gravitating structures dominated by galactic dynamics. Straighter, narrower, and denser "Bone-like" filaments, like the paradigmatic Nessie filament, have similar column densities, velocity gradients, and galactic plane heights (z ≈ 0 pc) to those in our simple model, but additional physical effects (such as feedback and self-gravity) must be invoked to explain their lengths and widths.

We report a new mechanism for the s-process in rotating massive metal-poor stars. Our models show that above a critical rotation speed, such stars evolve in a quasi-chemically homogeneous fashion, which gives rise to a prolific s-process. Rotation-induced mixing results in primary production of ¹³C, which subsequently makes neutrons via ${}^{13}{\rm{C}}{(\alpha ,{\rm{n}})}^{16}{\rm{O}}$ during core He burning. Neutron capture can last up to $\sim {10}^{13}\,{\rm{s}}$ (∼3 × 10⁵ yr) with the peak central neutron density ranging from ∼10⁷ to 10⁸${\mathrm{cm}}^{-3}$. Depending on the rotation speed and the mass loss rate, a strong s-process can occur with production of elements up to Bi for progenitors with initial metallicities of [Z] ≲ −1.5. This result suggests that rapidly rotating massive metal-poor stars are likely the first sites of the main s-process. We find that these stars can potentially explain the early onset of the s-process and some of the carbon-enhanced metal-poor (CEMP-s and CEMP-r/s) stars with strong enrichment attributed to the s-process or a mixture of the r-process and the s-process.

The creation of "hybrid" white dwarfs, made of a C–O core within an O–Ne shell has been proposed, and studies indicate that ignition in the C-rich central region makes these viable progenitors for thermonuclear (type Ia) supernovae. Recent work found that the C–O core is mixed with the surrounding O–Ne as the white dwarf cools prior to accretion, which results in lower central C fractions in the massive progenitor than previously assumed. To further investigate the efficacy of hybrid white dwarfs as progenitors of thermonuclear supernovae, we performed simulations of thermonuclear supernovae from a new series of hybrid progenitors that include the effects of mixing during cooling. The progenitor white dwarf model was constructed with the one-dimensional stellar evolution code Modules for Experiments in Stellar Astrophysics (MESA) and represented a star evolved through the phase of unstable interior mixing followed by accretion until it reached conditions for the ignition of carbon burning. This MESA model was then mapped to a two-dimensional initial condition for explosions simulated with FLASH. For comparison, similar simulations were performed for a traditional C–O progenitor white dwarf. By comparing the yields of the explosions, we find that, as with earlier studies, the lower C abundance in the hybrid progenitor compared to the traditional C–O progenitor leads to a lower average yield of ${}^{56}\mathrm{Ni}$. Although the unmixed hybrid white dwarf showed a similar decrement also in total iron-group yield, the mixed case does not and produces a smaller fraction of iron-group elements in the form of ${}^{56}\mathrm{Ni}$. We attribute this to the higher central density required for ignition and the location, center or off-center, of deflagration ignition.

Relative cross sections for m-fold photoionization (m = 1,..., 5) of Fe³⁺ by single-photon absorption were measured employing the photon-ion merged-beams setup PIPE at the PETRA III synchrotron light source operated at DESY in Hamburg, Germany. The photon energies used spanned the range of 680–950 eV, covering both the photoexcitation resonances from the 2p and 2s shells, as well as the direct ionization from both shells. Multiconfiguration Dirac–Hartree–Fock (MCDHF) calculations were performed to simulate the total photoexcitation spectra. Good agreement was found with the experimental results. These computations helped to assign several strong resonance features to specific transitions. We also carried out Hartree–Fock calculations with relativistic extensions taking into account both photoexcitation and photoionization. Furthermore, we performed extensive MCDHF calculations of the Auger cascades that result when an electron is removed from the 2p and 2s shells of Fe³⁺. Our theoretically predicted charge-state fractions are in good agreement with the experimental results, representing a substantial improvement over previous theoretical calculations. The main reason for the disagreement with the previous calculations is their lack of inclusion of slow Auger decays of several configurations that can only proceed when accompanied by de-excitation of two electrons. In such cases, this additional shake-down transition of a (sub)valence electron is required to gain the necessary energy for the release of the Auger electron.

The scattering of electrons by heat-flux-driven whistler waves is explored with a particle-in-cell simulation relevant to the transport of energetic electrons in flares. This simulation is initiated with a large heat flux produced by using a kappa distribution of electrons with positive velocity and a cold return current beam. This system represents energetic electrons escaping from a reconnection-driven energy-release site. This heat-flux system drives large-amplitude oblique whistler waves propagating both along and against the heat flux, as well as electron acoustic waves. While the waves are dominantly driven by the low-energy electrons, including the cold return current beam, the energetic electrons resonate with and are scattered by the whistlers on timescales of the order of a hundred electron cyclotron times. Peak whistler amplitudes of $\tilde{B}/{B}_{0}\sim 0.125$ and angles of ∼60° with respect to the background magnetic field are observed. Electron perpendicular energy is increased, while the field-aligned electron heat flux is suppressed. The resulting scattering mean-free-paths of energetic electrons are small compared with the typical scale size of energy-release sites in flares, which might lead to the effective confinement of energetic electrons required for the production of very energetic particles.

We design a novel, exact energy-conserving implicit nonsymplectic integration method for an eight-dimensional Hamiltonian system with four degrees of freedom. In our algorithm, each partial derivative of the Hamiltonian with respect to one of the phase-space variables is discretized by the average of eight Hamiltonian difference terms. Such a discretization form is a second-order approximation to the Hamiltonian gradient. It is shown numerically via simulations of a Fermi–Pasta–Ulam-β system and a post-Newtonian conservative system of compact binaries with one body spinning that the newly proposed method has extremely good energy-conserving performance, compared to the Runge–Kutta; an implicit midpoint symplectic method, and extended phase-space explicit symplectic-like integrators. The new method is advantageous over very long times and for large time steps compared to the state-of-the-art Runge–Kutta method in the accuracy of numerical solutions. Although such an energy-conserving integrator exhibits a higher computational cost than any one of the other three algorithms, the superior results justify its use for satisfying some specific purposes on the preservation of energies in numerical simulations with much longer times, e.g., obtaining a high enough accuracy of the semimajor axis in a Keplerian problem in the solar system or accurately grasping the frequency of a gravitational wave from a circular orbit in a post-Newtonian system of compact binaries. The new integrator will be potentially applied to model time-varying external electromagnetic fields or time-dependent spacetimes.

We study magnetic features on the solar surface that exist for several rotations during solar cycle 24. To identify them, we average synoptic maps over a range in latitude and stack the resulting longitudinal strips in time. We use synoptic maps of magnetograms obtained with the NSO/Synoptic Optical Long-term Investigations of the Sun instrument and create synoptic maps of the kinetic helicity of subsurface flows integrated over 2.0–7.1 Mm based on Solar Dynamics Observatory/Helioseismic and Magnetic Imager Dopplergrams. To distinguish between active and quiet regions, we sort the grid points of the synoptic maps by their activity level and divide the data into four subsets with 25% of activity each and into two subsets with the highest or lowest 12.5% of activity values. The kinetic helicity of these six subsets follows the hemispheric helicity rule with, on average, positive values in the southern and negative values in the northern hemisphere. However, the helicity of the subset with the highest activity is about four times higher than that of the other subsets, and the mid-quartile subsets show the weakest hemispheric helicity rule. We define the lifetime of complexes in each subset and find that for the high-activity subset, the amplitude of magnetic activity and kinetic helicity increases almost linearly with the lifetime of complexes. The distribution of flares closely resembles that of the high-activity subset. The flare-productive locations in long-lived complexes produce, on average, the same number of flares as those of short-lived complexes. However, long-lived complexes have a higher fractional number of these locations than the short-lived complexes and thus produce more flares not just because they live longer.

Since Gaia DR2 was released, many velocity structures in the disk have been revealed, such as large-scale ridge-like patterns in phase space. Both kinematic information and stellar elemental abundances are needed to reveal their evolution history. We have used labels from the APOGEE survey to predict elemental abundances for a huge amount of low-resolution spectra from the Large Sky Area Multi-Object Fibre Spectroscopic Telescope survey. Deep learning with artificial neural networks can automatically draw on physically sensible features in the spectrum for their predictions. Abundances of 12 individual elements, [C/Fe], [N/Fe], [O/Fe], [Mg/Fe], [Al/Fe], [Si/Fe], [S/Fe], [Cl/Fe], [Ca/Fe], [Ti/Fe], [Mn/Fe], and [Ni/Fe], along with basic stellar labels T_eff, log g, metallicity ([M/H] and [Fe/H]), and [α/M] for 1,063,386 stars have been estimated. Then, those stars were cross-matched with Gaia DR2 data to obtain kinematic parameters. We present distributions of chemical abundances in the V_ϕ versus R coordinate. Our results extend the chemical characterization of the ridges in the (R, V_ϕ) plane to about R = 13 kpc toward the anticenter direction. In addition, radial elemental abundance gradients for disk stars with abs(z) < 0.5 kpc are investigated, and we fitted a line for median abundance values of bins of stars with galactocentric distance between R > 7.84 kpc and R < 15.84 kpc. The radial metallicity gradients for disk stars are, respectively, −0.0475 ± 0.0015 for R ≥ 13.09 kpc and −0.0173 ± 0.0028 for R < 13.09 kpc. Gradients for other elemental abundances are also obtained for disk stars: the [α/M] gradient is 0.0030 ± 0.0002; the [Al/Fe] gradient is 0.0030 ± 0.0002; and the [Mn/Fe] gradient is −0.0078 ± 0.0005.

The TRAPPIST-1 system, consisting of an ultracool host star having seven known Earth-sized planets, will be a prime target for atmospheric characterization with the James Webb Space Telescope (JWST). However, the detectability of atmospheric molecular species may be severely impacted by the presence of clouds and/or hazes. In this work, we perform 3D general circulation model (GCM) simulations with the LMD-G model supplemented by 1D photochemistry simulations at the terminator with the Atmos model to simulate several possible atmospheres for TRAPPIST-1e, 1f, and 1g: (1) modern Earth, (2) Archean Earth, and (3) CO₂-rich atmospheres. The JWST synthetic transit spectra were computed using the GSFC Planetary Spectrum Generator. We find that the TRAPPIST-1e, 1f, and 1g atmospheres, with clouds and/or hazes, could be detected using JWST's NIRSpec Prism from the CO₂ absorption line at 4.3 μm in less than 15 transits at 3σ or less than 35 transits at 5σ. However, our analysis suggests that other gases would require hundreds (or thousands) of transits to be detectable. We also find that H₂O, mostly confined in the lower atmosphere, is very challenging to detect for these planets or similar systems if the planets' atmospheres are not in a moist greenhouse state. This result demonstrates that the use of GCMs, self-consistently taking into account the effect of clouds and subsaturation, is crucial to evaluate the detectability of atmospheric molecules of interest, as well as for interpreting future detections in a more global (and thus robust and relevant) approach.

Holm 15A, the brightest cluster galaxy of the galaxy cluster Abell 85, has an ultradiffuse central region, $\sim 2\,\mathrm{mag}$ fainter than the faintest depleted core of any early-type galaxy (ETG) that has been dynamically modeled in detail. We use orbit-based, axisymmetric Schwarzschild models to analyze the stellar kinematics of Holm 15A from new high-resolution, wide-field spectral observations obtained with the Multi-Unit Spectroscopic Explorer at the Very Large Telescope. We find a supermassive black hole with a mass of $(4.0\pm 0.80)\times {10}^{10}\ {M}_{\odot }$ at the center of Holm 15A. This is the most massive black hole with a direct dynamical detection in the local universe. We find that the distribution of stellar orbits is increasingly biased toward tangential motions inside the core. However, the tangential bias is less than that in other cored elliptical galaxies. We compare Holm 15A with N-body simulations of mergers between galaxies with black holes and find that the observed amount of tangential anisotropy and the shape of the light profile are consistent with a formation scenario where Holm 15A is the remnant of a merger between two ETGs with pre-existing depleted cores. We find that black hole masses in cored galaxies, including Holm 15A, scale inversely with the central stellar surface brightness and mass density. These correlations are independent of a specific parameterization of the light profile.

The discovery of quasars a few hundred megayears after the Big Bang represents a major challenge to our understanding of black holes as well as galaxy formation and evolution. Quasars' luminosity is produced by extreme gas accretion onto black holes, which have already reached masses of M_BH > 10⁹M_⊙ by z ∼ 6. Simultaneously, their host galaxies form hundreds of stars per year, using up gas in the process. To understand which environments are able to sustain the rapid formation of these extreme sources, we started a Very Large Telescope/Multi-Unit Spectroscopic Explorer (MUSE) effort aimed at characterizing the surroundings of a sample of 5.7 < z < 6.6 quasars, which we have dubbed the Reionization Epoch QUasar InvEstigation with MUSE (REQUIEM) survey. We here present results of our searches for extended Lyα halos around the first 31 targets observed as part of this program. Reaching 5σ surface brightness limits of 0.1–1.1 × 10⁻¹⁷ erg s⁻¹ cm⁻² arcsec⁻² over a 1 arcsec² aperture, we were able to unveil the presence of 12 Lyα nebulae, eight of which are newly discovered. The detected nebulae show a variety of emission properties and morphologies with luminosities ranging from 8 × 10⁴² to 2 × 10⁴⁴ erg s⁻¹, FWHMs between 300 and 1700 km s⁻¹, sizes <30 pkpc, and redshifts consistent with those of the quasar host galaxies. As the first statistical and homogeneous investigation of the circumgalactic medium of massive galaxies at the end of the reionization epoch, the REQUIEM survey enables the study of the evolution of the cool gas surrounding quasars in the first 3 Gyr of the universe. A comparison with the extended Lyα emission observed around bright (${M}_{1450}$ ≲ −25 mag) quasars at intermediate redshift indicates little variations on the properties of the cool gas from z ∼ 6 to z ∼ 3, followed by a decline in the average surface brightness down to z ∼ 2.

The habitable fraction of a planet's surface is important for the detectability of surface biosignatures. The extent and distribution of habitable areas are influenced by external parameters that control the planet's climate, atmospheric circulation, and hydrological cycle. We explore these issues using the ROCKE-3D general circulation model, focusing on terrestrial water fluxes and thus the potential for the existence of complex life on land. Habitability is examined as a function of insolation and planet rotation for an Earth-like world with zero obliquity and eccentricity orbiting the Sun. We assess fractional habitability using an aridity index that measures the net supply of water to the land. Earth-like planets become "superhabitable" (a larger habitable surface area than Earth) as insolation and day-length increase because their climates become more equable, reminiscent of past warm periods on Earth when complex life was abundant and widespread. The most slowly rotating, most highly irradiated planets, though, occupy a hydrological regime unlike any on Earth, with extremely warm, humid conditions at high latitudes but little rain and subsurface water storage. Clouds increasingly obscure the surface as insolation increases, but visibility improves for modest increases in rotation period. Thus, moderately slowly rotating rocky planets with insolation near or somewhat greater than modern Earth's appear to be promising targets for surface characterization by a future direct imaging mission.

By means of 3D hydrodynamical simulations, we evaluate here the impact that supernova (SN) explosions occurring within wind-driven bubbles have on the survival or destruction of dust grains. We consider both the dust generated within the ejecta and the dust initially present in the ambient gas and later locked up in the surrounding wind-driven shell (WDS). The collision of the SN blast wave with the WDS leads to a transmitted shock that moves into the shell and a reflected shock that moves into the ejecta. The transmitted shock is capable of destroying large amounts of the dust locked in the shell, but only if the mass of the WDS is small, less than a few tens the ejected mass. Conversely, massive WDSs, with several times the ejected mass, lead upon the interaction to strong radiative cooling, which inhibits the Sedov–Taylor phase and weakens the transmitted shock, making it unable to traverse the WDS. In such a case, the destruction/disruption of the ambient dust is largely inhibited. On the other hand, the SN remnants grow rapidly in the very tenuous region excavated by the stellar winds, and thus a large fraction of the dust generated within the ejecta is not efficiently destroyed by the SN reverse shock, nor by the reflected shock. Our calculations favor a scenario in which core-collapse SNe within sufficiently massive WDSs supply more dust to the interstellar medium than they are able to destroy.

The extended main-sequence turn offs (eMSTOs) of several young to intermediate age clusters are examined in the Magellanic Clouds and the Milky Way. We explore the effects of extended star formation (eSF) and a range of stellar rotation rates on the behavior of the color–magnitude diagram, paying particular attention to the MSTO. We create synthetic stellar populations based on MESA stellar models to simulate observed Hubble Space Telescope and Gaia star cluster data. We model the effect of rotation as a nonparametric distribution, allowing for maximum flexibility. In our models the slow rotators comprise the blueward, and fast rotators the redward portion of the eMSTO. We simulate data under three scenarios: nonrotating eSF, a range of rotation rates with a single age, and a combination of age and rotation effects. We find that two of the five clusters (the youngest and oldest) favor an age spread, but these also achieve the overall worst fits of all clusters. The other three clusters show comparable statistical evidence between rotation and an age spread. In all five cases, a rotation-rate distribution alone is capable of qualitatively matching the observed eMSTO structure. In future work, we aim to compare our predicted $V\sin i$ with observations in order to better constrain the physics related to stellar rotation.

We present optical SuperNova Integral Field Spectrograph integral field spectroscopy, Hubble Space Telescope optical imaging, Chandra X-ray imaging, and Very Large Array radio interferometry of the merging galaxy 2MASX J04234080+0408017, which hosts a Seyfert 2 active galactic nucleus (AGN) at z = 0.046. Our observations reveal that radiatively driven, ionized gas outflows are successful to distances >10 kpc due to the low mass of the host system, encompassing the entirety of the observed optical emission. We also find that at large radii, where observed velocities cannot be reproduced by radiative driving models, high-velocity kinematics are likely due to mechanical driving from AGN winds impacting high-density host material. This impacting deposits sufficient energy to shock the host material, producing thermal X-ray emission and cosmic rays, which in turn promote the formation of in situ radio structure in a pseudo-jet morphology along the high-density lanes.

The neutron star (NS) low-mass X-ray binary 2A 1822−371 has an orbital period of 5.57 hr. Mass transfer in such short-period binaries is thought to be driven by magnetic braking with orbital shrinking. However, 2A 1822−371 shows a very rapid orbital expansion, implying that mass transfer occurs rapidly in this system. The accretion rate of the NS is observationally estimated to be higher than the Eddington limit, which is also hard to explain by the standard magnetic braking mechanism. In this work, we construct a model to account for the peculiar properties of 2A 1822−371. We assume that the donor star possesses a relatively strong magnetic field, which is coupled with the stellar winds excited by the X-ray radiation from the NS. This would generate efficient angular momentum loss, leading to a high mass transfer rate and hence orbital expansion. We provide possible evolutionary tracks of 2A 1822−371 and study how the input parameters affect the results. The observational implications of the irradiation-driven mass loss are also briefly discussed in the context of evolution of low-mass X-ray binaries and millisecond pulsars.

Four significant events of rapid ¹⁴C increase have taken place within the past several thousand years. The physical origin of these rapid increases is still a mystery but must be associated with extremely energetic cosmic processes. Pulsars are highly magnetized neutron stars that emit a beam of electromagnetic radiations. Any sudden release of the energy stored in the magnetic multipole field will trigger outbursts similar to the giant flares of magnetars. Here we show that the relativistic outflow from the outbursts of a nearby pulsar interacting with the interstellar medium generates a shock, which accelerates electrons to trillions of electron volts. The high-energy photons from synchrotron emission of the shock interact with Earth's atmosphere, producing the cosmogenic nuclide ¹⁴C, which can cause the rapid ¹⁴C increases discovered in tree rings. These same relativistic electrons can account for a significant fraction of the cosmic electron spectrum in the trillion electron volts energy range, as observed by space-borne satellites. Since these outburst events can significantly affect our environment, monitoring nearby pulsars for such outbursts may be important in the future.

Stars between two and three solar masses rotate rapidly on the main sequence, and the detection of slow core and surface rotation in the core-helium burning phase for these stars places strong constraints on their angular momentum transport and loss. From a detailed asteroseismic study of the mixed-dipole mode pattern in a carefully selected, representative sample of stars, we find that slow core rotation rates in the range reported by prior studies are a general phenomenon and not a selection effect. We show that the core rotation rates of these stars decline strongly with decreasing surface gravity during the core He-burning phase. We argue that this is a model-independent indication of significant rapid angular momentum transport between the cores and envelopes of these stars. We see a significant range in core rotation rates at all surface gravities, with little evidence for a convergence toward a uniform value. We demonstrate using evolutionary models that measured surface rotation periods are a biased tracer of the true surface rotation distribution, and we argue for using stellar models for interpreting the contrast between core and surface rotation rates. The core rotation rates we measure do not have a strong mass or metallicity dependence. We argue that the emerging data strongly favor a model where angular momentum transport is much more efficient during the core He-burning phase than in the shell-burning phases that precede and follow it.

Studying the internal processes of individual galaxies at kilo-parsec scales is crucial in enhancing our understanding of galaxy formation and evolution processes. In this work, we investigate the distribution of star formation rate (SFR), specific SFR (sSFR), and dust attenuation across individual galaxies for a sample of 32 galaxies selected from the MUSE-Wide Survey at 0.1 < z < 0.42 with a dynamic range in stellar masses between 10^7.7 and 10^10.3M_⊙. We take advantage of the high spatial resolution of the MUSE integral field spectrograph and measure reliable spatially resolved Hα and Hβ emission-line maps for individual galaxies. We also derive resolved stellar mass, SFR and dust maps using pixel-by-pixel spectral energy distribution (SED) fitting on high-resolution multiband Hubble Space Telescope (HST)/Advanced Camera for Surveys and HST/Wide Field Camera 3 data from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey survey. By combining these, we analyze the radial profile of various physical parameters across these galaxies. We observe a radial dependence in both stellar and nebular color excess profiles peaking at the inner regions of galaxies. We also find the color excess profiles to most strongly correlate with the integrated sSFRs of galaxies. The median sSFR_Hα radial profiles of galaxies in our sample show a 0.8 dex increase from the central regions outward. This increase compared with the almost flat median radial profile of sSFR_SED, which traces longer timescales of star formation, is in favor of the inside-out quenching of star formation. We bring further evidence for this quenching scenario from the locus of different subregions of galaxies on the SFR–M_* and sSFR–M_* relations.

We present a new method to infer parameters of the temperature–density relation in the intergalactic medium in the post-reionization epoch at z ∼ 2–4. This method is based on the analysis of the distribution of Lyα absorbers over column densities and Doppler parameters by the model joint probability density function. This approach allows us to measure the power-law index γ of the temperature–density relation and a certain combination of the temperature at the mean density T₀ and hydrogen photoionization rate Γ. To estimate T₀ and Γ separately, we employ measurements of the Lyα forest effective opacity and the model gas probability density function. We show that γ tends to be lower than 1.6 and reaches 1.3 at redshift ∼3. The inferred temperatures at the mean density are ∼(2 ± 0.5) × 10⁴ K in the studied redshift range. Both these estimates favor He II reionization at z ≳ 3. We find that the hydrogen photoionization rate is ∼0.6 × 10⁻¹² s⁻¹, which is consistent with previous measurements.

We report the results of an extensive radio-continuum observing campaign of host galaxies of short gamma-ray bursts (GRBs). The goal of this survey was to search for optically obscured star formation, possibly indicative of a population of young short-GRB progenitors. Our sample comprises the hosts and host-galaxy candidates of 16 short-GRBs from 2005 to 2015, corresponding to roughly one-third of the presently known ensemble of well-localized short bursts. Eight GRB fields were observed with ATCA (at 5.5 and 9.0 GHz), and eight fields with the VLA (mostly at 5.5 GHz). The observations typically achieved a 1σ_rms of 5–8 μJy. In most cases, they were performed years after the corresponding burst. No new short-GRB host with optically obscured star formation was found. Only one host galaxy was detected: that of GRB 100206A at z = 0.407. However, its starburst nature was already known from optical/IR data. Its measured radio flux can be interpreted as being due to a star formation rate of about 60 M_⊙ yr⁻¹. This is in good agreement with earlier expectations based on the observed broad-band spectral energy distribution of this galaxy. The 15 nondetections constrain the SFRs of the suspected host galaxies and provide upper limits on late-time luminosities of the associated radio afterglows and predicted kilonova radio flares. The nondetection of radio emission from GRB explosion sites confirms the intrinsically low luminosity of short-GRB afterglows and places significant constraints on the parameter space of magnetar-powered radio flares. Luminous radio flares from fiducial massive magnetars have not been found.

The study of the extragalactic background light (EBL) in the optical and near-infrared has received a lot of attention in the last decade, especially near the wavelength λ ≈ 3.4 μm, with remaining tension among different techniques for estimating the background. In this paper we present a measurement of the contribution of galaxies to the EBL at 3.4 μm that is based on the measurement of the luminosity function (LF) in Lake et al. and the mean spectral energy distribution of galaxies in Lake & Wright. The mean and standard deviation of our most reliable Bayesian posterior chain gives a 3.4 μm background of I_ν = 9.0 ± 0.5 kJy sr⁻¹ (νI_ν = 8.0 ± 0.4 nW m⁻² sr⁻¹e-fold⁻¹), with systematic uncertainties unlikely to be greater than 2 kJy sr⁻¹. This result is higher than most previous efforts to measure the contribution of galaxies to the 3.4 μm EBL, but is consistent with the upper limits placed by blazars and the most recent direct measurements of the total 3.4 μm EBL.

The mechanism of heating for hot, dilute, and turbulent plasmas represents a long-standing problem in space physics, whose implications concern both near-Earth environments and astrophysical systems. In order to explore the possible role of interparticle collisions, simulations of plasma turbulence—in both collisionless and weakly collisional regimes—have been compared by adopting Eulerian Hybrid Boltzmann–Maxwell simulations, being proton–proton collisions explicitly introduced through the nonlinear Dougherty operator. Although collisions do not significantly influence the statistical characteristics of the turbulence, they dissipate nonthermal features in the proton distribution function and suppress the enstrophy/entropy cascade in the velocity space, damping the spectral transfer toward large Hermite modes. This enstrophy dissipation is particularly effective in regions where the plasma distribution function is strongly distorted, suggesting that collisional effects are enhanced by fine velocity–space structures. A qualitative connection between the turbulent energy cascade in fluids and the enstrophy cascade in plasmas has been established, opening a new path to the understanding of astrophysical plasma turbulence.

We have observed the submillimeter continuum condensations SMM2, SMM4, SMM9, and SMM11 in the star-forming cluster Serpens Main using the Atacama Large Millimeter/submillimeter Array during Cycle 3 in the 1.3 mm continuum, ¹²CO J = 2 − 1, SO J_N = 6₅ − 5₄, and C¹⁸O J = 2 − 1 lines at an angular resolution of ∼055 (240 au). Sixteen sources have been detected in the 1.3 mm continuum, which can be classified into three groups. Group 1 consists of six sources showing extended continuum emission and bipolar/monopolar ¹²CO outflows. Although all the Group 1 members are classified as Class 0 protostars, our observations suggest evolutionary trends among them in terms of ¹²CO outflow dynamical time, SO emission distribution, C¹⁸O fractional abundance, and continuum morphology. Group 2 consists of four sources associated with a continuum filamentary structure and no ¹²CO outflows. Central densities estimated from the 1.3 mm continuum intensity suggest that they are prestellar sources in a marginally Jeans unstable state. Group 3 consists of six Spitzer sources showing point-like 1.3 mm continuum emission and clumpy ¹²CO outflows. These features of Group 3 suggest envelope dissipation, preventing disk growth from the present size, r ≲ 60 au. The Group 3 members are protostars that may be precursors to the T Tauri stars associated with small disks at radii, of tens of astronomical units, identified in recent surveys.

Recent theoretical studies suggest that stellar-mass binary black holes (BBHs) would merge more efficiently due to the Kozai–Lidov (K–L) mechanism if these binaries form in the vicinity of supermassive black holes (SMBHs). Since SMBHs are likely rotating rapidly, we continue our earlier study on the generalization of the K–L formalism to include the spin of the SMBH and study the evolution of a nearby BBH. We find that the eccentricity and orbital inclination of the BBH are significantly affected, because the spin (i) forces the orbital plane of the center-of-mass of the BBH around the SMBH to precess (the Lense–Thirring effect) and (ii) imposes an additional gravitomagnetic force on the BBH. As a result, the merger time of the BBH could be significantly different. We calculate the waveform from the BBH in one representative example and study its detectability with a milli-Hertz gravitational-wave detector, such as the Laser Interferometer Space Antenna (LISA). We find that the signal is distinguishable from that in the case without spin. Our results imply that the BBHs in the LISA band could potentially be used to probe the spin of the SMBHs in galaxy centers.

The giant impact hypothesis for Moon formation successfully explains the dynamic properties of the Earth–Moon system but remains challenged by the similarity of isotopic fingerprints of the terrestrial and lunar mantles. Moreover, recent geochemical evidence suggests that the Earth's mantle preserves ancient (or "primordial") heterogeneity that pre-dates the Moon-forming giant impact. Using a new hydrodynamical method, we here show that Moon-forming giant impacts lead to a stratified starting condition for the evolution of the terrestrial mantle. The upper layer of the Earth is compositionally similar to the disk, out of which the Moon evolves, whereas the lower layer preserves proto-Earth characteristics. As long as this predicted compositional stratification can at least partially be preserved over the subsequent billions of years of Earth mantle convection, a compositional similarity between the Moon and the accessible Earth's mantle is a natural outcome of realistic and high-probability Moon-forming impact scenarios. The preservation of primordial heterogeneity in the modern Earth not only reconciles geochemical constraints but is also consistent with recent geophysical observations. Furthermore, for significant preservation of a proto-Earth reservoir, the bulk major-element composition of the Earth–Moon system may be systematically shifted toward chondritic values.

We present MAESTROeX, a massively parallel solver for low Mach number astrophysical flows. The underlying low Mach number equation set allows for efficient, long-time integration for highly subsonic flows compared to compressible approaches. MAESTROeX is suitable for modeling full spherical stars as well as well as planar simulations of dynamics within localized regions of a star, and can robustly handle several orders of magnitude of density and pressure stratification. Previously, we have described the development of the predecessor of MAESTROeX, called MAESTRO, in a series of papers. Here, we present a new, greatly simplified temporal integration scheme that retains the same order of accuracy as our previous approaches. We also explore the use of alternative spatial mapping of the one-dimensional base state onto the full Cartesian grid. The code leverages the new AMReX software framework for block-structured adaptive mesh refinement (AMR) applications, allowing for scalability to large fractions of leadership-class machines. Using our previous studies on the convective phase of single-degenerate progenitor models of SNe Ia as a guide, we characterize the performance of the code and validate the new algorithmic features. Like MAESTRO, MAESTROeX is fully open source.

Short-lived radionuclides (SLRs) with mean lives τ of a few to hundreds of Myr provide unique opportunities to probe recent nucleosynthesis events in the interstellar medium and the physical conditions in which the Sun formed. Here we quantify the uncertainty in the predicted evolution of SLRs within a parcel of interstellar gas given the stochastic nature of stellar enrichment events. We assume that an enrichment progenitor is formed at every time interval γ. For each progenitor, we randomly sample the delay time between its formation and its enrichment event, based on several delay-time distribution (DTD) functions that cover a wide range of astrophysical sites. For each set of τ, γ, and DTD functions, we follow the abundances of SLRs for 15 Gyr and repeat this process thousands of times to derive their probability distributions. For τ/γ ≳ 2, the distributions depend on the DTD function, and we provide tabulated values and analytical expressions to quantify the spread. The relative abundance uncertainty reaches a maximum of ∼60% for τ/γ = 1. For τ/γ ≲ 1, we provide the probability for the SLR abundance to carry the signature of only one enrichment event, which is greater than 50% when τ/γ ≲ 0.3. For 0.3 ≲ τ/γ ≲ 2, a small number of events contributed to the SLR abundance. This case needs to be investigated with a separate statistical method. We find that an isolation time for the birth of the Sun of roughly 9–13 Myr is consistent with the observed abundances of ⁶⁰Fe, ¹⁰⁷Pd, and ¹⁸²Hf in the early solar system when assuming τ/γ ∼ 3 for these isotopes.

We perform a stacking analysis of Planck, AKARI, Infrared Astronomical Satellite, Wide-field Infrared Survey Explorer, and Herschel images of the largest number of (candidate) protoclusters at z ∼ 3.8 selected from the Hyper Suprime-Cam Subaru Strategic Program. Stacking the images of the 179 candidate protoclusters, the combined infrared (IR) emission of the protocluster galaxies in the observed 12–850 μm wavelength range is successfully detected with >5σ significance (at Planck). This is the first time that the average IR spectral energy distribution (SED) of a protocluster has been constrained at z ∼ 4. The observed IR SEDs of the protoclusters exhibit significant excess emission in the mid-IR compared to that expected from typical star-forming galaxies (SFGs). They are reproduced well using SED models of intense starburst galaxies with warm/hot dust heated by young stars, or by a population of active galactic nucleus (AGN)/SFG composites. For the pure star-forming model, a total IR (from 8–1000 μm) luminosity of ${19.3}_{-4.2}^{+0.6}\times {10}^{13}\,{L}_{\odot }$ and a star formation rate of ${16.3}_{-7.8}^{+1.0}\times {10}^{3}\,{M}_{\odot }$ yr⁻¹ are found, whereas for the AGN/SFG composite model, ${5.1}_{-2.5}^{+2.5}\times {10}^{13}\,{L}_{\odot }$ and ${2.1}_{-1.7}^{+6.3}\times {10}^{3}\,{M}_{\odot }$ yr⁻¹ are found. Uncertainty remains in the total SFRs; however, the IR luminosities of the most massive protoclusters are likely to continue increasing up to z ∼ 4. Meanwhile, no significant IR flux excess is observed around optically selected QSOs at similar redshifts, which confirms previous results. Our results suggest that the z ∼ 4 protoclusters trace dense, intensely star-forming environments that may also host obscured AGNs missed by the selection in the optical.

We present a nonlinear mean-field model of the solar interior dynamics and dynamo, which reproduces the observed cyclic variations of the global magnetic field of the Sun, as well as the differential rotation and meridional circulation. Using this model, we explain, for the first time, the extended 22 yr pattern of the solar torsional oscillations, observed as propagation of zonal variations of the angular velocity from high latitudes to the equator during the time equal to the full dynamo cycle. In the literature, this effect is usually attributed to the so-called "extended solar cycle." In agreement with the commonly accepted idea, our model shows that the torsional oscillations can be driven by a combination of magnetic field effects acting on turbulent angular momentum transport and the large-scale Lorentz force. We find that the 22 yr pattern of the torsional oscillations can result from a combined effect of an overlap of subsequent magnetic cycles and magnetic quenching of the convective heat transport. The latter effect results in cyclic variations of the meridional circulation in the sunspot formation zone, in agreement with helioseismology results. The variations of the meridional circulation, together with other drivers of the torsional oscillations, maintain their migration to the equator during the 22 yr magnetic cycle, resulting in the observed extended pattern of the torsional oscillations.

Being able to image active regions (ARs) on the Sun's far side is useful for modeling the global-scale magnetic field around the Sun and for predicting the arrival of major ARs that rotate around the limb onto the near side. Helioseismic methods have already been developed to image the Sun's far-side ARs using near-side high-cadence Doppler-velocity observations; however, the existing methods primarily explore the 3-, 4-, and 5-skip helioseismic waves, leaving room for further improvement in the imaging quality by including waves with more multiskip waves. Taking advantage of the fact that 6-skip waves have the same target-annuli geometry as 3- and 4-skip waves and that 8-skip waves have the same target-annuli geometry as 4-skip waves, we further develop a time–distance helioseismic code to include a total of 14 sets of measurement schemes. We then apply the new code on the Solar Dynamics Observatory/Helioseismic and Magnetic Imager observed Dopplergrams and find that the new code provides substantial improvements over the existing codes in mapping newly emerged ARs and ARs near both far-side limbs. Comparing 3 months of far-side helioseismic images with the Solar TErrestrial RElations Observatory/Extreme UltraViolet Imager observed 304 Å images, we find that 97.3% of the helioseismically detected far-side ARs that are larger than a certain size correspond to an observed region with strong EUV brightening. The high reliability of the new imaging tool will potentially allow us to further calibrate the far-side helioseismic images into maps of magnetic flux.

As the Sun moves through the local interstellar medium (LISM), neutral atoms travel through the heliosphere and can be detected by IBEX. We consider interstellar neutral (ISN) hydrogen atoms with a drifting Maxwellian distribution function in the LISM that travel on almost hyperbolic trajectories to the inner heliosphere. They are subject to solar gravity and radiation pressure, as well as ionization processes. For ISN H, the radiation pressure, which exerts an effective force comparable to gravitation, decelerates individual atoms and shifts the longitude of their observed peak relative to that of ISN He. We used the peak longitude of the observed flux in the lowest energy channel of IBEX-Lo to investigate how radiation pressure shifts the ISN H signal over almost an entire solar cycle (2009–2018). Thus, we have created a new methodology to determine the Lyα effective radiation pressure from IBEX ISN H data. The resulting effective ratio of the solar radiation pressure and gravitation (μ_eff = 1.074 ± 0.038), averaged over cycle 24, appears to agree within the uncertainties with simulations based on total irradiance observations⁷ while being higher by ∼21%. Our analysis indicates an increase of μ_eff with solar activity, albeit with substantial uncertainties. Further study of IBEX H response functions and future Interstellar Mapping and Acceleration Probe data should provide significant reduction of the uncertainties and improvements in our understanding of the effects of radiation pressure on ISN atoms.

We present light curves and spectra of the tidal disruption event (TDE) ASASSN-18pg/AT 2018dyb spanning a period of one year. The event shows a plethora of strong emission lines, including the Balmer series, He ii, He i, and metal lines of O iiiλ3760 and N iiiλλ4100, 4640 (blended with He ii). The latter lines are consistent with originating from the Bowen fluorescence mechanism. By analyzing literature spectra of past events, we conclude that these lines are common in TDEs. The spectral diversity of optical TDEs is thus larger than previously thought and includes N-rich events besides H- and He-rich events. We study how the spectral lines evolve with time, by means of their width, relative strength, and velocity offsets. The velocity width of the lines starts at ∼13,000 km s⁻¹ and decreases with time. The ratio of He ii to N iii increases with time. The same is true for ASASSN-14li, which has a very similar spectrum to AT 2018dyb but its lines are narrower by a factor of >2. We estimate a black hole mass of M_BH = ${3.3}_{-2.0}^{+5.0}\times {10}^{6}$M_⊙ by using the M–σ relation. This is consistent with the black hole mass derived using the MOSFiT transient fitting code. The detection of strong Bowen lines in the optical spectrum is an indirect proof for extreme ultraviolet and (reprocessed) X-ray radiation and favors an accretion origin for the TDE optical luminosity. A model where photons escape after multiple scatterings through a super-Eddington thick disk and its optically thick wind, viewed at an angle close to the disk plane, is consistent with the observations.

The observed properties of long gamma-ray burst (GRB) host galaxies show them to often be of a rather low metallicity and/or of high specific star formation rate (SFR). It is not clear which of these properties is a dominant factor in determining if a galaxy will host a GRB or not. In fact there are indications, at least in the local universe, that the two may be anticorrelated and that the metallicity is the deciding parameter. Here, we consider GRB production models dependent on both quantities and show that when compared to the best available data, the respective star formation fractions appear indistinguishable out to a redshift of z ∼ 4. However, the fraction of galaxies hosting a GRB, as determined by the specific SFR, is less at tension with the observed host galaxy fraction than the corresponding metallicity determined fraction, but this conclusion is model dependent. Well established galaxy stellar mass and star formation rate functions at high redshift are crucial in breaking the apparent degeneracy between the specific rate and metallicity in GRB production probability.

Using high spatial and temporal data from the New Vacuum Solar Telescope and the Solar Dynamics Observatory, we present unambiguous observations of recurrent two-sided loop jets caused by magnetic reconnection between erupting minifilaments and a nearby large filament. The observations demonstrate that three two-sided loop jets, which ejected along the large filament in opposite directions, were similar in appearance and originated from the same region. We find that a minifilament erupted and drove the first jet. It reformed at the same neutral line later, and then underwent partial and total eruptions, driving the second and third jets, respectively. In the course of the jets, cool plasma was injected into the large filament. Furthermore, persistent magnetic flux cancellation occurred at the neutral line under the minifilament before its eruption and continued until the end of the observation. We infer that magnetic flux cancellation may account for building and then triggering the minifilament to erupt to produce the two-sided loop jets. This observation not only indicates that two-sided loop jets can be driven by minifilament eruptions, but also sheds new light on our understanding of the recurrent mechanism of two-sided loop jets.

Loops are one of the fundamental structures that trace the geometry of the magnetic field in the solar atmosphere. Their evolution and dynamics provide a crucial proxy for studying how the magnetized structures are formed and heated in the solar atmosphere. Here, we report on spectroscopic observations of a set of transition-region loops taken by the Interface Region Imaging Spectrograph (IRIS) at Si iv 1394 Å in the sit-and-stare mode. The loops are corresponding to the flux emergence at its very late phase when the emerged magnetic features in the photosphere have fully developed. We find the transition-region loops are still expanding and moving upward with a velocity of a few kilometers per second (≲10 km s⁻¹) at this stage. The expansion of the loops leads to interactions between the loops themselves and with the ambient field, which can drive magnetic reconnection evidenced by multiple intense brightenings, including transition-region explosive events and IRIS bombs in the footpoint region associated with the moving polarity. A set of quasi-periodic brightenings with a period of about 130 s is found at the loop apex, from which the Si iv 1394 Å profiles are significantly non-Gaussian with enhancements at both blue and red wings at Doppler velocities of about 50 km s⁻¹. We suggest that the transition-region loops in the very late phase of flux emergence can be powered by heating events generated by the interactions between the expanding loops and the ambient fields and also by (quasi-)periodic processes, such as oscillation-modulated braiding reconnection.

Solar energetic particles (SEPs), accelerated during solar eruptions, propagate in turbulent solar wind before being observed with in situ instruments. In order to interpret their origin through comparison with remote sensing observations of the solar eruption, we thus must deconvolve the transport effects due to the turbulent magnetic fields from the SEP observations. Recent research suggests that the SEP propagation is guided by the turbulent meandering of the magnetic fieldlines across the mean magnetic field. However, the lengthening of the distance the SEPs travel, due to the fieldline meandering, has so far not been included in SEP event analysis. This omission can cause significant errors in estimation of the release times of SEPs at the Sun. We investigate the distance traveled by the SEPs by considering them to propagate along fieldlines that meander around closed magnetic islands that are inherent in turbulent plasma. We introduce a fieldline random walk model which takes into account the physical scales associated to the magnetic islands. Our method remedies the problem of the diffusion equation resulting in unrealistically short pathlengths, and the fractal dependence of the pathlength of random walk on the length of the random-walk step. We find that the pathlength from the Sun to 1 au can be below the nominal Parker spiral length for SEP events taking place at solar longitudes 45E to 60W, whereas the western and behind-the-limb particles can experience pathlengths longer than 2 au due to fieldline meandering.

Interstellar neutral atoms provide a remote diagnostic of plasma in the outer heliosheath and the very local interstellar medium via charge exchange collisions that convert ions into atoms and vice versa. So far, most studies of interstellar atoms assumed that daughter hydrogen atoms directly inherit the kinetic properties of parent protons. This assumption neglects angular scattering of the interacting particles. However, for low relative velocities, as expected for charge exchanges in the outer heliosheath, this scattering is significant. In this study, we present how the parameters of daughter populations depend on the relative velocity and temperatures of parent populations. For this purpose, we numerically compute collision terms with and without this scattering. We find that the secondary population of interstellar hydrogen atoms, for the parent populations with the relative bulk velocity of 20 km s⁻¹ and equal temperatures of 7500 K, has ∼2 km s⁻¹ higher bulk velocity if the scattering is taken into account. Additionally, temperatures are higher by ∼2400 K and ∼1200 K in parallel and perpendicular directions to the relative motion of parent populations, respectively. Moreover, a significant departure of secondary atoms from the Maxwell–Boltzmann distribution is expected for high relative velocities of parent populations. This process affects the distribution and density of interstellar atoms in the heliosphere and production of pickup ions. Thus, we show that angular scattering in charge exchange collisions is important to include in analyses of interstellar neutral atoms and pickup ions observed at 1 au and in the outer heliosphere.

Disentangling the different stages of the star formation process, in particular in the high-mass regime, is a challenge in astrophysics. Chemical clocks could help alleviate this problem, but their evolution strongly depends on many parameters, leading to degeneracy in the interpretation of the observational data. One of these uncertainties is the degree of CO depletion. We present here the first self-consistent magneto-hydrodynamic simulations of high-mass, star-forming regions at different scales, fully coupled with a nonequilibrium chemical network, which includes C–N–O bearing molecules. Depletion and desorption processes are treated time dependently. The results show that full CO depletion (i.e., all gas-phase CO frozen-out on the surface of dust grains) can be reached very quickly, in one-third or even smaller fractions of the freefall time, whether the collapse proceeds on slow or fast timescales. This leads to a high level of deuteration in a short time, both for typical tracers like N₂H⁺, as well as for the main ion ${{\rm{H}}}_{3}^{+}$, the latter being in general larger and more extended. N₂ depletion is slightly less efficient, and no direct effects on N-bearing molecules and deuterium fractionation are observed. We show that CO depletion is not the only driver of deuteration, and that there is a strong impact on D_frac when changing the grain size. We finally apply a two-dimensional Gaussian point-spread function to our results to mimic observations with single-dish and interferometers. Our findings suggest that the low-values observed in high-mass star-forming clumps are in reality masking a full-depletion stage in the inner 0.1 pc region.

This paper presents the solar soft X-ray irradiance (0.3–3.0 nm) obtained from the mission-long full-Sun X-ray images observed with the Soft X-ray Telescope (SXT) of the Yohkoh mission (1991–2001). The irradiance was calculated using filter-ratio temperatures and emission measures (EMs) from the full-Sun integrated X-ray signals employing a coronal spectrum synthesized with CHIANTI atomic database version 8.0. Dependence of the results on the assumption of elemental abundances is investigated. The SXT irradiance for a shorter wavelength range was also calculated and compared with the low energy flux (0.1–0.8 nm) of the X-Ray Sensor on board the GOES satellite. To incorporate the spatial information of the observed corona, we tried the alternative method to derive irradiance by applying the filter-ratio method to the images of northern hemispheric corona instead of spatially integrated signals from there. The EM weighted average of the spatially resolved temperatures turned out to be generally 20%–30% lower than those derived from the integrated signals, while the total of spatially resolved EMs are accordingly 1.5–2 times higher. This trend is enhanced when solar activity is the lowest in early 1996. The irradiance obtained from the alternative method does not significantly vary from the result from the integrated signals. This provides some validation for the simpler full-Sun integrated method. The temporal variation of the EMs of cool (<1.5 MK), medium, and hot (>2.5 MK) components indicates that the ratio of the hot component relative to the medium component is higher in the ascending phase (mid 1998–2001) than in the descending phase (1992–1995) of the solar activity cycle.

Terrestrial planets are believed to be formed via giant impacts of Mars-sized protoplanets. Planets formed via giant impacts have highly eccentric orbits. A swarm of planetesimals around the planets may lead to eccentricity damping for the planets via the equipartition of random energies (dynamical friction). However, dynamical friction increases eccentricities of planetesimals, resulting in high velocity collisions between planetesimals. The collisional cascade grinds planetesimals to dust until dust grains are blown out due to radiation pressure. Therefore, the total mass of planetesimals decreases due to collisional fragmentation, which weakens dynamical friction. We investigate the orbital evolution of protoplanets in a planetesimal disk, taking into account collisional fragmentation of planetesimals. For 100 km sized or smaller planetesimals, dynamical friction is insignificant for eccentricity damping of planets because of collisional fragmentation. On the other hand, giant impacts eject collisional fragments. Although the total mass of giant impact ejecta is 0.1–0.3 Earth masses, the largest impact ejecta are ∼1000 km in size. We also investigate the orbital evolution of single planets with initial eccentricities of 0.1 in a swarm of such giant impact ejecta. Although the total mass of giant impact ejecta decreases by a factor of 3 in 30 Myr, eccentricities of planets are damped down to the Earth level (∼0.01) due to interaction with giant impact ejecta. Therefore, giant impact ejecta play an important role for determination of terrestrial planet orbits.

The black hole spacetime is described by general relativity and characterized by two quantities: the black hole mass and spin. Black hole spin measurement requires information from the vicinity of the event horizon, which is spatially resolved for the Galactic center Sagittarius A* (Sgr A*) and the nearby radio galaxy M87 by means of very long baseline interferometry observations with the Event Horizon Telescope (EHT). In this paper, we simulate EHT observations for a gas cloud intermittently falling onto a black hole and construct a method for spin measurement based on its relativistic flux variation. The light curve of the infalling gas cloud is composed of peaks formed by photons which directly reach a distant observer and by secondary ones reaching the observer after more than one rotation around the black hole. The time interval between the peaks is determined by a period of photon rotation near the photon circular orbit which uniquely depends on the spin. We perform synthetic EHT observations for Sgr A* under the more realistic situation where a number of gas clouds intermittently fall toward the black hole with various initial parameters. Even for this case, the black hole spin dependence is detectable in correlated flux densities which are accurately calibrated by baselines between sites with redundant stations. The synthetic observations indicate that our methodology can be applied to EHT observations of Sgr A* from 2017 April.

We revisit the problem of the thermal bulge of asynchronous hot Jupiters using HD 209458 b as a fiducial study. We improve upon previous works by using a double-gray atmosphere model and interior structure from MESA as the background state and then solve for the thermal bulge in response to the semidiurnal component of stellar insolation. The atmosphere model is based on the radiative transfer with Eddington's two-stream approximation. Two opacity cases are considered: the first introduces a greenhouse effect, and the second exhibits a strong temperature inversion. We find that for the predominant thermal bulges excited by g-modes of lower orders, our results are qualitatively similar to the adiabatic results from Arras & Socrates. It arises because the perturbed heating due to self-absorption of thermal emissions can be significant (i.e., greenhouse effect) against Newtonian damping, thereby leading to almost undamped thermal bulges. We also find that the contribution to the thermal bulge from the evanescent waves in the convective zone is not negligible, implying that the thermal bulge is not merely confined in the atmosphere and radiative envelope. Assuming the torque balance between the thermal and gravitational bulges, we estimate the tidal quality factor of the planet for gravitational tides to match the observed radius. The limitations of our model are also briefly discussed.

It has been asserted that the primary star in the HD 189733 system steadily accretes evaporated exospheric gases from its "hot Jupiter" companion, rather like a T Tauri star accreting from a disk. We conduct statistical and periodogram analyses of the photometric time series of the primary, as acquired by the automated photoelectric telescope, Microvariability and Oscillations of Stars, and Wise Observatory, to investigate this claim with the goal of revealing the presence of accretion shocks or photospheric accretion hotspots as are found in T Tauri systems such as AA Tau. None of the anticipated features were found. We re-analyze existing radio, optical, ultraviolet, and X-ray data within the framework of accreting T Tauri systems to determine physical quantities such as plasma density and temperature, accretion rate, and flare lengths. We find that with an accretion rate of $\dot{M}\sim {10}^{9}$–10¹¹ g s⁻¹, the star is more similar to a system that intermittently absorbs gas from sungrazing comets in outburst than classical T Tauri systems, which have accretion rates at least two orders of magnitude larger. If such accretion exists, it would result in undetectably low activity at all wavelengths. Alternatively, all of the emission properties observed thus far are in agreement with stellar activity from a magnetically active star.

Chondrules are approximately millimeter-sized beads of crystallized silicate melt. They formed mainly in the first ∼3 Ma of the Sun's protoplanetary disk and are the main constituents of chondritic asteroids. Here we report on the size–frequency distributions (2D and 3D) of chondrules in the brecciated ordinary chondrite (OC) Northwest Africa (NWA) 5205. We investigated three large (centimeter- to decimeter-sized) chondritic lithic clasts of a particular textural type ("cluster chondrite") with eye-catching different chondrule sizes. One clast shows the largest mean chondrule size (∼1.5 mm) ever measured in a chondrite. As in the other OCs, we find a positive correlation between the minimum and mean chondrule size, which we consider as an argument for chondrule size sorting. Chondrule size–frequency distributions in the clasts are distinctly more symmetric than the about log-normal distributions in other OCs. Furthermore, we find a co-enrichment of chondrule types with a priori small mean sizes (type I, porphyritic) in clasts with overall small mean chondrule sizes. We consider this as the fingerprint of an additional/second size-sorting process, which acted later on these chondrule populations. This process possibly subdivided a typical LL-type chondrule population into several subpopulations with different mean chondrule sizes. We speculate that this second sorting occurred in a unidirectional gas stream or headwind, e.g., by settling of chondrules through an asteroidal atmosphere or interaction with an expanding impact plume. Possibly, fine-grained matrix was almost completely removed by this, and the size-sorted chondrule subpopulations accreted in a hot state separately in different regions of the asteroid.

Despite surface liquid water's importance to habitability, observationally diagnosing its presence or absence on exoplanets is still an open problem. Inspired within the solar system by the differing sulfur cycles on Venus and Earth, we investigate thick sulfate (H₂SO₄–H₂O) aerosol haze and high trace mixing ratios of SO₂ gas as observable atmospheric features whose sustained existence is linked to the near absence of surface liquid water. We examine the fundamentals of the sulfur cycle on a rocky planet with an ocean and an atmosphere in which the dominant forms of sulfur are SO₂ gas and H₂SO₄–H₂O aerosols (as on Earth and Venus). We build a simple but robust model of the wet, oxidized sulfur cycle to determine the critical amounts of sulfur in the atmosphere–ocean system required for detectable levels of SO₂ and a detectable haze layer. We demonstrate that for physically realistic ocean pH values (pH ≳ 6) and conservative assumptions on volcanic outgassing, chemistry, and aerosol microphysics, surface liquid water reservoirs with greater than 10⁻³ Earth oceans are incompatible with a sustained observable H₂SO₄–H₂O haze layer and sustained observable levels of SO₂. Thus, we propose the observational detection of an H₂SO₄–H₂O haze layer and of SO₂ gas as two new remote indicators that a planet does not host significant surface liquid water.

Stars rarely form in isolation. Nearly half of the stars in the Milky Way have a companion, and this fraction increases in star-forming regions. However, why some dense cores and filaments form bound pairs while others form single stars remains unclear. We present a set of three-dimensional, gravo-magnetohydrodynamic simulations of turbulent star-forming clouds, aimed at understanding the formation and evolution of multiple-star systems formed through large-scale (≳10³ au) turbulent fragmentation. We investigate three global magnetic field strengths, with global mass-to-flux ratios of μ_ϕ = 2, 8, and 32. The initial separations of protostars in multiples depend on the global magnetic field strength, with stronger magnetic fields (e.g., μ_ϕ = 2) suppressing fragmentation on smaller scales. The overall multiplicity fraction (MF) is between 0.4 and 0.6 for our strong and intermediate magnetic field strengths, which is in agreement with observations. The weak field case has a lower fraction. The MF is relatively constant throughout the simulations, even though stellar densities increase as collapse continues. While the MF rarely exceeds 60% in all three simulations, over 80% of all protostars are part of a binary system at some point. We additionally find that the distribution of binary spin misalignment angles is consistent with a randomized distribution. In all three simulations, several binaries originate with wide separations and dynamically evolve to ≲10² au separations. We show that a simple model of mass accretion and dynamical friction with the gas can explain this orbital evolution.

We present a 142 ks Chandra observation of the enigmatic combination supernova remnant G310.6–1.6 consisting of a bright pulsar-wind nebula driven by an energetic pulsar, surrounded by a highly circular, very faint shell with a featureless, probably synchrotron, spectrum. Comparison with an observation 6 yr earlier shows no measurable expansion of the shell, though some features in the pulsar-wind nebula have moved. We find an expansion age of at least 2500 yr, implying a current shock velocity less than about 1000 km s⁻¹. We place severe upper limits on thermal emission from the shell; if the shell locates the blast wave, a Sedov interpretation would require the remnant to be very young, about 1000 yr, and to have resulted from a dramatically sub-energetic supernova, ejecting ≪0.02M_⊙ with energy E ≲ 3 × 10⁴⁷ erg. Even a merger-induced collapse of a white dwarf to a neutron star, with a low-energy explosion, is unlikely to produce such an event. Other explanations seem equally unlikely.

Wave–particle instabilities driven by departures from local thermodynamic equilibrium have been conjectured to play a role in governing solar wind dynamics. We calculate the statistical variation of linear stability over a large subset of Helios I and II observations of the fast solar wind using a numerical evaluation of the Nyquist stability criterion, accounting for multiple sources of free energy associated with protons and helium including temperature anisotropies and relative drifts. We find that 88% of the surveyed intervals are linearly unstable. The median growth rate of the unstable modes is within an order of magnitude of the turbulent transfer rate, fast enough to potentially impact the turbulent scale-to-scale energy transfer. This rate does not significantly change with radial distance, though the nature of the unstable modes, and which ion components are responsible for driving the instabilities, does vary. The effect of ion–ion collisions on stability is found to be significant; collisionally young wind is much more unstable than collisionally old wind, with very different kinds of instabilities present in the two kinds of wind.

We present new measurements of the cosmic cold molecular gas evolution out to redshift 6 based on systematic mining of the Atacama Large Millimeter/submillimeter Array (ALMA) public archive in the COSMOS deep field (A³COSMOS). Our A³COSMOS data set contains ∼700 galaxies (0.3 ≲ z ≲ 6) with high-confidence ALMA detections in the (sub)millimeter continuum and multiwavelength spectral energy distributions. Multiple gas mass calibration methods are compared, and biases in band conversions (from observed ALMA wavelength to rest-frame Rayleigh–Jeans tail continuum) have been tested. Combining our A³COSMOS sample with ∼1000 CO-observed galaxies at 0 ≲ z ≲ 4 (75% at z < 0.1), we parameterize galaxies' molecular gas depletion time (${\tau }_{\mathrm{depl}}$) and molecular gas to stellar mass ratio (${\mu }_{\mathrm{molgas}}$) each as a function of the stellar mass (${M}_{\star }$), offset from the star-forming main sequence (${\rm{\Delta }}\mathrm{MS}$) and cosmic age (or redshift). Our proposed functional form provides a statistically better fit to current data (than functional forms in the literature) and implies a "downsizing" effect (i.e., more-massive galaxies evolve earlier than less-massive ones) and "mass quenching" (gas consumption slows down with cosmic time for massive galaxies but speeds up for low-mass ones). Adopting galaxy stellar mass functions and applying our ${\mu }_{\mathrm{molgas}}$ function for gas mass calculation, we for the first time infer the cosmic cold molecular gas density evolution out to redshift 6 and find agreement with CO blind surveys as well as semianalytic modeling. These together provide a coherent picture of cold molecular gas, star formation rate, and stellar mass evolution in galaxies across cosmic time.

We present the kinematical properties of the UV and optical Fe ii emission gas based on the velocity shift and line width measurements of a sample of 223 Type 1 active galactic nuclei (AGNs) at 0.4 < z < 0.8. We find a strong correlation between the line widths of the UV and optical Fe ii emission lines, indicating that both Fe ii emission features arise from similar distances in the broad-line region (BLR). However, in detail we find differing trends, depending on the width of Fe ii. While the velocity shifts and dispersions of the UV Fe ii (Fe ii_uv) and optical Fe ii (Fe ii_opt) emission lines are comparable to each other for AGNs with relatively narrow Fe ii_opt line widths (i.e., FWHM < 3200 km s⁻¹; Group A), Fe ii_opt is broader than Fe ii_uv for AGNs with relatively broad Fe ii_opt (i.e., FWHM > 3200 km s⁻¹; Group B). Fe ii emission lines are on average narrower than Hβ and Mg ii for Group A, indicating the Fe ii emission region is further out in the BLR, while for Group B AGNs Fe ii_opt is comparable to Hβ and broader than Mg ii. While Fe ii emission lines are on average redshifted (40 ± 141 km s⁻¹ and 182 ± 95 respectively for Fe ii_uv and Fe ii_opt), indicating inflow, the sample as a whole shows a large range of velocity shifts, suggesting the complex nature of the gas kinematics.

The Galactic stellar halo is predicted to have formed at least partially from the tidal disruption of accreted dwarf galaxies. This assembly history should be detectable in the orbital and chemical properties of stars. The H3 Survey is obtaining spectra for 200,000 stars and, when combined with Gaia data, is providing detailed orbital and chemical properties of Galactic halo stars. Unlike previous surveys of the halo, the H3 target selection is based solely on magnitude and Gaia parallax; the survey therefore provides a nearly unbiased view of the entire stellar halo at high latitudes. In this paper we present the distribution of stellar metallicities as a function of Galactocentric distance and orbital properties for a sample of 4232 kinematically selected halo giants to 100 kpc. The stellar halo is relatively metal-rich, $\langle [\mathrm{Fe}/{\rm{H}}]\rangle =-1.2$, and there is no discernible metallicity gradient over the range 6 < R_gal < 100 kpc. However, the halo metallicity distribution is highly structured, including distinct metal-rich and metal-poor components at R_gal < 10 kpc and R_gal > 30 kpc, respectively. The Sagittarius stream dominates the metallicity distribution at 20–40 kpc for stars on prograde orbits. The Gaia–Enceladus merger remnant dominates the metallicity distribution for radial orbits to ≈30 kpc. Metal-poor stars with [Fe/H] < −2 are a small population of the halo at all distances and orbital categories. We associate the "in situ" stellar halo with stars displaying thick disk chemistry on halo-like orbits; such stars are confined to $| z| \lt 10\,\mathrm{kpc}$. The majority of the stellar halo is resolved into discrete features in chemical–orbital space, suggesting that the bulk of the stellar halo formed from the accretion and tidal disruption of dwarf galaxies. The relatively high metallicity of the halo derived in this work is a consequence of the unbiased selection function of halo stars and, in combination with the recent upward revision of the total stellar halo mass, implies a Galactic halo metallicity that is typical for its mass.

We develop an approach for fitting the results of modeling a wriggling radial large-scale iron pattern along the Galactic disk, derived over young (high-mass) Cepheids, with the metallicity distribution obtained using low-mass long-living dwarf stars in the close solar vicinity. For this purpose, during the step at which the theoretical abundance distribution over low-mass stars in the solar vicinity is computed, we propose the redefinition of the initial mass function so that the resulting theoretical stellar distribution over masses would be close to the distribution in the observed sample. By means of the above algorithm and subsequent corrections of the theoretical metallicity distribution function (MDF), as described in the literature, we have achieved fairly good agreement between the theoretical and observed MDFs for low-mass stars in the local solar vicinity.

With high spatial and temporal resolution, Hα data from the New Vacuum Solar Telescope, X-ray images from the X-ray telescope on board Hinode and simultaneous observations from the Solar Dynamics Observatory, we present multiwavelength observations of the interaction between a mini-filament (MF) and its overlying large-scale active-region loops (ARLs) that occurred in AR 12497 on 2016 February 13. The MF was activated by the convergence and cancellation of the magnetic flux under it. Brightenings first appeared at the junction of the MF and its overlying large-scale ARLs. A blowout jet with some plasma blobs was observed to move along the newly formed large-scale ARLs, and caused the oscillations of these loops. The blowout jet exhibited a counterclockwise rotation due to the untwisting motion of the MF, suggesting that the twist is transferred from the MF to the ARLs. The transferred twist was measured to be about 0.34–0.52 turn. During the interaction progress, a group of hot loops formed in the high-temperature wavelength (94 Å). These hot loops connected the west footpoints of the original ARLs and the east footpoints of the MF. The differential emission measure analysis demonstrated that these hot loops contained a high-temperature component (∼8 MK). Meanwhile the footpoints of the ARLs were finally shifted to the west footpoint of the MF. These observations suggest that magnetic reconnection takes place between the MF and its overlying large-scale ARLs and results in a confined untwisting blowout jet.

We present observations and magnetic field models of an intermediate filament present on the Sun in 2012 August, associated with a polarity inversion line that extends from AR 11541 in the east into the quiet Sun at its western end. A combination of Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly, SDO/Helioseismic and Magnetic Imager (HMI), and Global Oscillation Network Group Hα data allow us to analyze the structure and evolution of the filament from 2012 August 4 23:00 UT to 2012 August 6 08:00 UT when the filament was in equilibrium. By applying the flux rope insertion method, nonlinear force-free field models of the filament are constructed using SDO/HMI line-of-sight magnetograms as the boundary condition at the two times given above. Guided by observed filament barbs, both modeled flux ropes are split into three sections each with a different value of axial flux to represent the nonuniform photospheric field distribution. The flux in the eastern section of the rope increases by 4 × 10²⁰ Mx between the two models, which is in good agreement with the amount of flux canceled along the internal PIL of AR 11541, calculated to be 3.2 × 10²⁰ Mx. This suggests that flux cancellation builds flux into the filament's magnetic structure. Additionally, the number of field line dips increases between the two models in the locations where flux cancellation, the formation of new filament threads, and growth of the filament is observed. This suggests that flux cancellation associated with magnetic reconnection forms concave-up magnetic field that lifts plasma into the filament. During this time, the free magnetic energy in the models increases by 0.2 × 10³¹ ergs.

In optical bands, the spectra of M giants often overlap with those of M dwarfs due to their similarities, especially for low or moderate resolution spectra. Traditionally, several feature indices, such as Na i, CaH, TiO5, and K i, are used to distinguish between M giants and M dwarfs. However, these features are selected by experience based on a small amount of standard spectra. Hence, it is not clear if these features are the most effective ones to detect M giants. In this paper, we use a machine-learning method, eXtreme Gradient Boosting (XGBoost), to discern M giants from M dwarfs for spectroscopic surveys. The important feature bands for distinguishing between M giants and M dwarfs are accurately identified by the XGBoost method through evaluating and quantifying the importance of each feature in spectra, including Na i, B1, and Ca ii, which are consistent with previous studies. Moreover, we find that a blend feature around 6564 Å (named B2) is sensitive to luminosity and that the feature combinations of both B1 versus CaH and B2 versus CaH, based on the average spectral flux, are important in distinguishing M giants from M dwarfs. Furthermore, our XGBoost prediction model achieves 99.79% overall accuracy and 96.87% recognition precision for M giants, outperforming the other three popular machine-learning algorithms (i.e., SVM, random forests, and ELM). Using such a prediction model, we detected 28,714 M-giant spectra from LAMOST DR5 and thus provided a larger amount of M giants for related scientific research.

Cold atomic hydrogen clouds are the precursors of molecular clouds. Due to self-absorption, the opacity of cold atomic hydrogen may be high, and this gas may constitute an important mass component of the interstellar medium. Atomic hydrogen gas can be cooled to temperatures much lower than found in the cold neutral medium through collisions with molecular hydrogen. In this paper, we search for H i narrow self-absorption (HINSA) features in the Large Magellanic Cloud (LMC) as an indicator of such cold H i clouds, and use the results to quantify atomic masses and atomic-to-molecular gas ratio. Our search for HINSA features was conducted toward molecular clouds in the LMC using the ATCA+Parkes H i survey and the MAGMA CO survey. HINSA features are prevalent in the surveyed sightlines. This is the first detection of HINSA in an external galaxy. The HINSA-H i/${{\rm{H}}}_{2}$ ratio in the LMC varies from 0.5 × 10⁻³ to 3.4 × 10⁻³ (68% interval), with a mean value of (1.31 ± 0.03) × 10⁻³, after correcting for the effect of foreground H i gas. This is similar to the Milky Way value and indicates that similar fractions of cold gas exist in the LMC and the Milky Way, despite their differing metallicities, dust content and radiation fields. The low ratio also confirms that, as with the Milky Way, the formation timescale of molecular clouds is short. The ratio shows no radial gradient, unlike the case for stellar metallicity. No correlation is found between our results and those from previous H i absorption studies of the LMC.

To deepen our understanding of the chemical properties of the Planck Galactic Cold Clump (PGCC) G168.72-15.48, we performed observations of nine molecular species, namely, c-C₃H, H₂CO, HC₅N, HC₇N, SO, CCH, N₂H⁺, CH₃OH, and CH₃CCH, toward two dense cores in PGCC G168.72-15.48 using the Tianma Radio Telescope and Purple Mountain Observatory Telescope. We detected c-C₃H, H₂CO, HC₅N, N₂H⁺, CCH, and CH₃OH in both G168-H1 and G168-H2 cores, whereas HC₇N and CH₃CCH were detected only in G168-H1 and SO was detected only in G168-H2. Mapping observations reveal that the CCH, N₂H⁺, CH₃OH, and CH₃CCH emissions are well coupled with the dust emission in G168-H1. Additionally, N₂H⁺ exhibits an exceptionally weak emission in the denser and more evolved G168-H2 core, which may be attributed to the N₂H⁺ depletion. We suggest that the N₂H⁺ depletion in G168-H2 is dominated by N₂ depletion, rather than the destruction by CO. The local thermodynamic equilibrium calculations indicate that the carbon-chain molecules of CCH, HC₅N, HC₇N, and CH₃CCH are more abundant in the younger G168-H1 core. We found that starless core G168-H1 may have the properties of cold dark clouds based on its abundances of carbon-chain molecules. While, the prestellar core G168-H2 exhibits lower carbon-chain molecular abundances than the general cold dark clouds. With our gas-grain astrochemical model calculations, we attribute the observed chemical differences between G168-H1 and G168-H2 to their different gas densities and different evolutionary stages.

We model the ALMA and Very Large Array (VLA) millimeter radial profiles of the disk around HL Tau to constrain the properties of the dust grains. We adopt the disk evolutionary models of Lynden-Bell & Pringle and calculate their temperature and density structure and emission. These disks are heated by the internal viscosity and irradiated by the central star and a warm envelope. We consider a dust size distribution n(a) da ∝ a^−3.5da, and vary the maximum grain size in the atmosphere and the midplane, a_max = 100 μm, 1 mm, and 1 cm. We also include dust settling and vary the dust-to-gas mass ratio from 1 to 9 times the ISM value. We find that the models that can fit the observed level of emission along the profiles at all wavelengths have an atmosphere with a maximum grain size a_max = 100 μm, and a midplane with a_max = 1 cm. The disk substructure, with a deficit of emission in the gaps, can be due to dust properties in these regions that are different from those in the rings. We test an opacity effect (different a_max) and a dust mass deficit (smaller dust-to-gas mass ratio) in the gaps. We find that the emission profiles are better reproduced by models with a dust deficit in the gaps, although a combined effect is also possible. These models have a global dust-to-gas mass ratio twice the ISM value, needed to reach the level of emission of the 7.8 mm VLA profile.

We present a new relationship between central black hole (BH) mass and host galaxy stellar bulge mass extending to the lowest BH masses known in dwarf galaxies (M_BH ≲ 10⁵M_⊙; M_⋆ ∼ 10⁹M_⊙). We have obtained visible and near-infrared Hubble Space Telescope imaging of seven dwarf galaxies with optically selected broad-line active galactic nuclei (AGNs) and BH mass estimates from single-epoch spectroscopy. We perform 2D photometric modeling with GALFIT to decompose the structure of these galaxies and find that the majority have an inner bulge/pseudo-bulge component with an exponential disk that dominates the total stellar mass. Using the modeling results and color-dependent mass-to-light ratios, we determine the stellar mass of each photometric component in each galaxy. We determine the M_BH–M_bulge relation using a total of 12 dwarf galaxies hosting broad-line AGNs, along with a comparison sample of 88 galaxies with dynamical BH masses and 37 reverberation-mapped AGNs. We find a strong correlation between BH mass and bulge mass with $\mathrm{log}({M}_{\mathrm{BH}}/{M}_{\odot })=(1.24\pm 0.08)$$\mathrm{log}({M}_{\mathrm{bulge}}/{10}^{11}{M}_{\odot })+(8.80\pm 0.09)$. The near-linear slope and normalization are in good agreement with correlations found previously when only considering higher-mass systems. This work has quadrupled the number of dwarf galaxies on the BH–bulge mass relation, with implications for BH seeding and predictions for gravitational wave detections of merging BHs at higher redshifts with LISA.

We present a detailed analysis of a confined filament eruption and jet associated with a C1.5 class solar flare. Multi-wavelength observations from the Global Oscillations Network Group and Solar Dynamics Observatory reveal the filament forming over several days following the emergence and then partial cancellation of a minority polarity spot within a decaying bipolar active region. The emergence is also associated with the formation of a 3D null point separatrix that surrounds the minority polarity. The filament eruption occurs concurrently with brightenings adjacent to and below the filament, suggestive of breakout and flare reconnection, respectively. The erupting filament material becomes partially transferred into a strong outflow jet (∼60 km s⁻¹) along coronal loops, becoming guided back toward the surface. Utilizing high-resolution Hα observations from the Swedish Solar Telescope/CRisp Imaging SpectroPolarimeter, we construct velocity maps of the outflows, demonstrating their highly structured but broadly helical nature. We contrast the observations with a 3D magnetohydrodynamic simulation of a breakout jet in a closed-field background and find close qualitative agreement. We conclude that the suggested model provides an intuitive mechanism for transferring twist/helicity in confined filament eruptions, thus validating the applicability of the breakout model not only to jets and coronal mass ejections but also to confined eruptions and flares.

The Interstellar Boundary Explorer (IBEX) mission discovered the presence of a global structure in energetic neutral atom emissions from the outer heliosphere not predicted by any model—the IBEX "ribbon." In the search for possible explanations, observations have pointed to a likely source from neutral atoms produced through charge exchange with the outflowing solar wind, the secondary solar wind, which then undergoes charge exchange again beyond the heliopause within the very local interstellar medium. Here we study the plasma structure beyond the heliopause created from a range of secondary neutral atom sources: (1) solar wind atoms, (2) pickup atoms inside the termination shock, and (3) suprathermal atoms from the inner heliosheath, between the termination shock and heliopause. All of these particle sources populate the plasma environment beyond the heliopause. At the high end of the observational energy range of IBEX (3.1–6.0 keV FWHM), the significantly broadened and positionally shifted energetic neutral atom signature of the ribbon suggests plasma structure associated primarily with secondary suprathermal atoms from the inner heliosheath. The population created from this suprathermal population extends well above 6 keV (the top of the IBEX energy range) and provides a source for an extremely broad (>60° in angular) width shifted southward (>10°) in latitude from the direction centered on the local interstellar magnetic field. Thus, the extension of plasma structure to energies above IBEX provides a unified explanation of the ribbon created primarily from secondary solar wind atoms to a broadened and shifted structure (the broad ribbon or belt) created primarily from secondary suprathermal atoms in the heliosheath.

The major components of chondrites are chondrules and matrix. Measurements of volatile abundance in Semarkona chondrules suggest that chondrules formed in a dense clump that had a higher solid density than the gas density in the solar nebula. We investigate collisions between chondrules and matrix in the surface region of dense clumps using fluffy aggregate growth models. Our simulations show that the collisional growth of aggregates composed of chondrules and matrix takes place in the clumps well before they experience gravitational collapse. The internal structure of chondrite parent bodies (CPBs) can be thereby determined by aggregate growth. We find that the aggregate growth generates two scales within CPBs. The first scale is involved with the small-scale distribution of chondrules and determined by the early growth stage, where chondrules accrete aggregates composed of matrix grains. This accretion can reproduce the thickness of the matrix layer around chondrules found in chondrites. The other scale is related to the large-scale distribution of chondrules. Its properties (e.g., the abundance of chondrules and the overall size) depend on the gas motion within the clump, which is parameterized in this work. Our work thus suggests that the internal structure of CPBs may provide important clues about their formation conditions and mechanisms.

We perform a series of two-dimensional radiation-hydrodynamic simulations of the collision between supernova ejecta and circumstellar media (CSMs). The hydrodynamic interaction of a fast flow and the surrounding media efficiently dissipates the kinetic energy of the fast flow and is considered as a dominant energy source for a specific class of core-collapse supernovae. Despite some observational evidence for aspherical ejecta and/or CSM structure, multidimensional effects in the ejecta–CSM interaction are relatively unexplored. Our numerical simulations equipped with an adaptive mesh refinement technique successfully reproduce hydrodynamic instabilities developing around the ejecta–CSM interface. We also investigate effects of disklike CSMs on the dynamical evolution of supernova ejecta and bolometric light curves. We find that emission powered by ejecta–disk interaction exhibits significant viewing angle dependence. For a line of sight close to the symmetry axis, the observer directly sees the supernova ejecta, leading to a short brightening timescale. For an observer seeing the emission through the CSM disk, thermal photons diffuse throughout the CSM, and thus the light curve is severely smeared out.

Cosmic rays (CRs) in the Galaxy are an important dynamical component of the interstellar medium (ISM) that interact with the other major components (interstellar gas and magnetic and radiation fields) to produce broadband interstellar emissions that span the electromagnetic spectrum. The standard modeling of CR propagation and production of the associated emissions is based on a steady-state assumption, where the CR source spatial density is described using a smoothly varying function of position that does not evolve with time. While this is a convenient approximation, reality is otherwise, where primary CRs are produced in and about highly localized regions, e.g., supernova remnants, which have finite lifetimes. In this paper, we use the latest version of the GALPROP CR propagation code to model time-dependent CR injection and propagation through the ISM from a realistic 3D discretized CR source density distribution, together with full 3D models for the other major ISM components, and make predictions of the associated broadband nonthermal emissions. We compare the predictions for the discretized and equivalent steady-state model, finding that the former predicts novel features in the broadband nonthermal emissions that are absent for the steady-state case. Some of the features predicted by the discretized model may be observable in all-sky observations made by WMAP and Planck, the recently launched eROSITA, the Fermi-LAT, and ground-based observations by HESS, HAWC, and the forthcoming CTA. The nonthermal emissions predicted by the discretized model may also provide explanations of puzzling anomalies in high-energy γ-ray data, such as the Fermi-LAT north/south asymmetry and residuals like the so-called "Fermi bubbles."

We present Very Large Telescope SINFONI near-infrared (NIR) integral field spectroscopy of six z ∼ 0.2 Lyman break galaxy "analogs" (LBAs) from which we detect H i, He i, and [Fe ii] recombination lines and multiple H₂ rovibrational lines in emission. The Paα kinematics reveal high velocity dispersions and low rotational velocities relative to random motions ($\langle {V}_{\mathrm{rot}}/\sigma \rangle =1.2\pm 0.8$). Matched-aperture comparisons of Hβ, Hα, and Paα reveal that the nebular color excesses are lower relative to the continuum color excesses than is the case for typical local star-forming systems. We compare observed He i/H i recombination line ratios to photoionization models to gauge the effective temperatures (T_eff) of massive ionizing stars, finding that the properties of at least one LBA are consistent with extra heating from an active galactic nucleus (AGN) and/or an overabundance of massive stars. We use H₂ 1−0 S(·) rovibrational spectra to determine a rotational excitation temperature T_ex ∼ 2000 K for warm molecular gas, which we attribute to UV heating in dense photon-dominated regions. Spatially resolved NIR line ratios favor excitation by massive young stars, rather than supernova or AGN feedback. Our results suggest that the local analogs of Lyman break galaxies are primarily subject to strong feedback from recent star formation, with evidence for AGNs and outflows in some cases.

Some short gamma-ray bursts (SGRBs) are thought to be caused by the mergers of binary neutron stars which may sometimes produce massive neutron star remnants capable of producing extragalactic fast radio bursts (FRBs). We conducted a deep search for FRBs from the sites of six low-redshift SGRBs. We collected high time- and frequency-resolution data from each of the sites for 10 hr using the 2 GHz receiver of the Green Bank Telescope (GBT). Two of the SGRB sites we targeted were visible with the Arecibo Radio Telescope with which we conducted an additional 10 hr of 1.4 GHz observations for each. We searched our data for FRBs using the GPU-optimized dedispersion algorithm heimdall and the machine-learning-based package Fast Extragalactic Transient Candidate Hunter. We did not discover any FRBs, but would have detected any with peak flux densities in excess of 87 mJy at the GBT or 21 mJy at Arecibo with a signal-to-noise ratio of at least 10. The isotropic-equivalent energy of any FRBs emitted from these sites in our bands during our observations must not have exceeded a few times 10³⁸ erg, comparable to some of the lowest energy bursts yet seen from the first known repeating FRB 121102.

We computed a grid of theoretical models to fit the δ Scuti frequencies of CoRoT 100866999 detected earlier from the CoRoT time serials. The pulsating primary star is determined to be a main-sequence star with a rotation period of ${4.1}_{-0.5}^{+0.6}$ days, rotating slower than the orbital motion. The fundamental parameters of the primary star are determined to be $M={1.71}_{-0.04}^{+0.13}\,{M}_{\odot }$, $Z={0.012}_{-0.000}^{+0.004}$, ${f}_{\mathrm{ov}}={0.02}_{-0.02}^{+0.00}$, ${T}_{\mathrm{eff}}={8024}_{-297}^{+249}$ K, $L={11.898}_{-1.847}^{+2.156}\,{L}_{\odot }$, $\mathrm{log}g={4.166}_{-0.002}^{+0.013}$, $R={1.787}_{-0.016}^{+0.040}\,{R}_{\odot }$, and ${X}_{{\rm{c}}}={0.488}_{-0.020}^{+0.011}$, matching those obtained from the eclipsing light-curve analysis. Based on the model fittings, p₁ and p₅ are suggested to be two dipole modes, and p₃, p₄, p₆, and p₇ are suggested to be four quadrupole modes. In particular, p₄ and p₇ are identified as two components of one quintuplet. Based on the best-fitting model, we find that p₁ is a g mode and the other nonradial modes have pronounced mixed characters, which give strong constraints on the convective core. Finally, the relative size of the convective core of CoRoT 100866999 is determined to ${R}_{\mathrm{conv}}/R={0.0931}_{-0.0013}^{+0.0003}$.

The early optical emission of gamma-ray bursts (GRBs) gives an opportunity to understand the central engine and first stages of these events. About 30% of GRBs present flares whose origin is still a subject of discussion. We present optical photometry of GRB 180620A with the COATLI telescope and RATIR instrument. COATLI started to observe from the end of prompt emission at T + 39.3 s and RATIR from T + 121.4 s. We supplement the optical data with the X-ray light curve from Swift/XRT. We observe an optical flare from T + 110 s to T + 550 s, with a temporal index decay α_O,decay = 1.32 ± 0.01, and Δt/t = 1.63, which we interpret as the signature of a reverse shock component. After the initial normal decay the light curves show a long plateau from T + 500 s to T + 7800 s in both X-rays and the optical before decaying again after an achromatic jet break at T + 7800 s. Fluctuations are seen during the plateau phase in the optical. Adding to the complexity of GRB afterglows, the plateau phase (typically associated with the coasting phase of the jet) is seen in this object after the "normal" decay phase (associated with the deceleration phase of the jet), and the jet break phase occurs directly after the plateau. We suggest that this sequence of events can be explained by a rapid deceleration of the jet with t_d ≲ 40 s due to the high density of the environment (≈100 cm⁻³) followed by reactivation of the central engine, which causes the flare and powers the plateau phase.

We present results from modeling the broadband X-ray spectrum of the Type 1 active galactic nucleus (AGN) 2MASX J193013.80+341049.5 using NuSTAR, Swift, and archival XMM-Newton observations. We find this source to be highly X-ray obscured, with column densities exceeding 10²³ cm⁻² across all epochs of X-ray observations, spanning an 8 yr period. However, the source exhibits prominent broad optical emission lines, consistent with an unobscured Type 1 AGN classification. We fit the X-ray spectra with both phenomenological reflection models and physically motivated torus models to model the X-ray absorption. We examine the spectral energy distribution of this source and investigate some possible scenarios to explain the mismatch between X-ray and optical classifications. We compare the ratio of reddening to X-ray absorbing column density (${E}_{B-V}$/${N}_{{\rm{H}}}$) and find that 2MASX J193013.80+341049.5 likely has a much lower dust-to-gas ratio relative to the Galactic interstellar medium, suggesting that the broad line region itself could provide the source of extra X-ray obscuration, being composed of low-ionization, dust-free gas.