Table of contents

Optical wide-field surveys with a high cadence are expected to create a new field of astronomy, so-called "movie astronomy," in the near future. The amount of data from the observations will be huge, and hence efficient data compression will be indispensable. Here we propose a low-rank matrix approximation with sparse matrix decomposition as a promising solution to reduce the data size effectively while preserving sufficient scientific information. We apply one of the methods to the movie data obtained with the prototype model of the Tomo-e Gozen mounted on the 1.0 m Schmidt telescope of Kiso Observatory. Once full-scale observation with the Tomo-e Gozen commences, it will generate ∼30 TB of data per night. We demonstrate that the data are compressed by a factor of about 10 in size without losing transient events like optical short transient point sources and meteors. The intensity of point sources can be recovered from the compressed data. The processing runs sufficiently fast, compared with the expected data-acquisition rate in the actual observing runs.

Observations reveal a uniform Kolmogorov turbulence throughout the diffuse ionized interstellar medium (ISM) and supersonic turbulence preferentially located in the Galactic plane. Correspondingly, we consider the Galactic distribution of electron density fluctuations consisting of not only a Kolmogorov density spectrum but also a short-wave-dominated density spectrum with the density structure formed at small scales due to shocks. The resulting dependence of the scatter broadening time on the dispersion measure (DM) naturally interprets the existing observational data for both low- and high-DM pulsars. According to the criteria that we derive for a quantitative determination of scattering regimes over wide ranges of DMs and frequencies ν, we find that the pulsars with low DMs are primarily scattered by the Kolmogorov turbulence, while those at low Galactic latitudes with high DMs undergo more enhanced scattering dominated by the supersonic turbulence, where the corresponding density spectrum has a spectral index of $\approx 2.6$. Furthermore, by considering a volume filling factor of the density structures with the dependence on ν as $\propto {\nu }^{1.4}$ in the supersonic turbulence, our model can also explain the observed shallower ν scaling of the scattering time than the Kolmogorov scaling for the pulsars with relatively large DMs. The comparison between our analytical results and the scattering measurements of pulsars in turn makes a useful probe of the properties of the large-scale ISM turbulence, e.g., an injection scale of ∼100 pc, and also characteristics of small-scale density structures.

We present APEX 218 GHz observations of molecular emission in a complete sample of embedded protostars in the Ophiuchus star-forming region. To study the physical properties of the cores, we calculate H₂CO and c-C₃H₂ rotational temperatures, both of which are good tracers of the kinetic temperature of the molecular gas. We find that the H₂CO temperatures range between 16 K and 124 K, with the highest H₂CO temperatures toward the hot corino source IRAS 16293-2422 (69–124 K) and the sources in the ρ Oph A cloud (23–49 K) located close to the luminous Herbig Be star S1, which externally irradiates the ρ Oph A cores. On the other hand, the c-C₃H₂ rotational temperature is consistently low (7–17 K) in all sources. Our results indicate that the c-C₃H₂ emission is primarily tracing more shielded parts of the envelope whereas the H₂CO emission (at the angular scale of the APEX beam; 3600 au in Ophiuchus) mainly traces the outer irradiated envelopes, apart from in IRAS 16293-2422, where the hot corino emission dominates. In some sources, a secondary velocity component is also seen, possibly tracing the molecular outflow.

A millisecond pulsar is a neutron star that has been substantially spun up by accretion from a binary companion. A previously unrecognized factor governing the spin evolution of such pulsars is the crucial effect of nonsteady or transient accretion. We numerically compute the evolution of accreting neutron stars through a series of outburst and quiescent phases, considering the drastic variation of the accretion rate and the standard disk–magnetosphere interaction. We find that, for the same long-term average accretion rate, X-ray transients can spin up pulsars to rates several times higher than can persistent accretors, even when the spin-down due to electromagnetic radiation during quiescence is included. We also compute an analytical expression for the equilibrium spin frequency in transients, by taking spin equilibrium to mean that no net angular momentum is transferred to the neutron star in each outburst cycle. We find that the equilibrium spin rate for transients, which depends on the peak accretion rate during outbursts, can be much higher than that for persistent sources. This explains our numerical finding. This finding implies that any meaningful study of neutron star spin and magnetic field distributions requires the inclusion of the transient accretion effect, since most accreting neutron star sources are transients. Our finding also implies the existence of a submillisecond pulsar population, which is not observed. This may point to the need for a competing spin-down mechanism for the fastest-rotating accreting pulsars, such as gravitational radiation.

SDSS J2222+2745 is a galaxy cluster at z = 0.49, strongly lensing a quasar at z = 2.805 into six widely separated images. In recent Hubble Space Telescope imaging of the field, we identify additional multiply lensed galaxies and confirm the sixth quasar image that was identified by Dahle et al. We used the Gemini-North telescope to measure a spectroscopic redshift of z = 4.56 of one of the lensed galaxies. These data are used to refine the lens model of SDSS J2222+2745, compute the time delay and magnifications of the lensed quasar images, and reconstruct the source image of the quasar host and a lensed galaxy at z = 2.3. This galaxy also appears in absorption in our Gemini spectra of the lensed quasar, at a projected distance of 34 kpc. Our model is in agreement with the recent time delay measurements of Dahle et al., who found τ_AB = 47.7 ± 6.0 days and τ_AC = −722 ± 24 days. We use the observed time delays to further constrain the model, and find that the model-predicted time delays of the three faint images of the quasar are τ_AD = 502 ± 68 days, τ_AE = 611 ± 75 days, and τ_AF = 415 ± 72 days. We have initiated a follow-up campaign to measure these time delays with Gemini North. Finally, we present initial results from an X-ray monitoring program with Swift, indicating the presence of hard X-ray emission from the lensed quasar, as well as extended X-ray emission from the cluster itself, which is consistent with the lensing mass measurement and the cluster velocity dispersion.

We present observations of the occulted active region AR 12222 during the third Nuclear Spectroscopic Telescope ARray (NuSTAR) solar campaign on 2014 December 11, with concurrent Solar Dynamics Observatory (SDO)/AIA and FOXSI-2 sounding rocket observations. The active region produced a medium-size solar flare 1 day before the observations, at ∼18 UT on 2014 December 10, with the post-flare loops still visible at the time of NuSTAR observations. The time evolution of the source emission in the SDO/AIA 335 Å channel reveals the characteristics of an extreme-ultraviolet late-phase event, caused by the continuous formation of new post-flare loops that arch higher and higher in the solar corona. The spectral fitting of NuSTAR observations yields an isothermal source, with temperature 3.8–4.6 MK, emission measure (0.3–1.8) × 10⁴⁶ cm⁻³, and density estimated at (2.5–6.0) × 10⁸ cm⁻³. The observed AIA fluxes are consistent with the derived NuSTAR temperature range, favoring temperature values in the range of 4.0–4.3 MK. By examining the post-flare loops' cooling times and energy content, we estimate that at least 12 sets of post-flare loops were formed and subsequently cooled between the onset of the flare and NuSTAR observations, with their total thermal energy content an order of magnitude larger than the energy content at flare peak time. This indicates that the standard approach of using only the flare peak time to derive the total thermal energy content of a flare can lead to a large underestimation of its value.

Zhang proposed a type of GRB-less X-ray transient associated with double neutron star (NS–NS) mergers under the conjecture of a rapidly spinning magnetar merger product with the line of sight off the short gamma-ray burst (GRB) jet. We investigate possible light curves of these transients by considering different observers' viewing angles. We perform Monte Carlo simulations to calculate the peak luminosity function (LF) and event rate density of these X-ray transients. By considering that a fraction of massive neutron stars may be supra-massive and later collapse into black holes after spinning down, we investigate how the predicted LF depends on the equation of state (EoS) of the central object and the geometry of the system. In general, the LF can be fit by two log-normal distributions peaking around ${10}^{46.4}$ and ${10}^{49.6}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$, corresponding to the trapped and free zones, respectively. For the majority of the EoS models, the current non-detection is consistent with having a free zone solid angle, at most a few times the solid angle of the short GRB jet. The event rate density of these X-ray transients is around a few tens of ${\mathrm{Gpc}}^{-3}\,{\mathrm{yr}}^{-1}$ for luminosity above 10⁴⁵$\mathrm{erg}\,{{\rm{s}}}^{-1}$. We predict that future X-ray telescopes (such as Einstein Probe) with sensitivity $\sim {10}^{-11}\,\mathrm{erg}\,{{\rm{s}}}^{-1}\,{\mathrm{cm}}^{-2}$ would detect as many as several tens of such transients per year per steradian. Within 200 Mpc, the aLIGO average range for NS–NS mergers, the estimated event rate of these transients is about 1 transient per year all sky.

The theory of binary star formation predicts that close binaries (a < 100 au) will experience periodic pulsed accretion events as streams of material form at the inner edge of a circumbinary disk (CBD), cross a dynamically cleared gap, and feed circumstellar disks or accrete directly onto the stars. The archetype for the pulsed accretion theory is the eccentric, short-period, classical T Tauri binary DQ Tau. Low-cadence (∼daily) broadband photometry has shown brightening events near most periastron passages, just as numerical simulations would predict for an eccentric binary. Magnetic reconnection events (flares) during the collision of stellar magnetospheres near periastron could, however, produce the same periodic, broadband behavior when observed at a one-day cadence. To reveal the dominant physical mechanism seen in DQ Tau's low-cadence observations, we have obtained continuous, moderate-cadence, multiband photometry over 10 orbital periods, supplemented with 27 nights of minute-cadence photometry centered on four separate periastron passages. While both accretion and stellar flares are present, the dominant timescale and morphology of brightening events are characteristic of accretion. On average, the mass accretion rate increases by a factor of five near periastron, in good agreement with recent models. Large variability is observed in the morphology and amplitude of accretion events from orbit to orbit. We argue that this is due to the absence of stable circumstellar disks around each star, compounded by inhomogeneities at the inner edge of the CBD and within the accretion streams themselves. Quasiperiodic apastron accretion events are also observed, which are not predicted by binary accretion theory.

The main object of the paper is to present the condition of the nondiffusive part of the Reynolds stress for driving the double-cell structure of the solar meridional circulation, which has been revealed by recent helioseismic observations. By conducting a set of mean-field hydrodynamic simulations, we confirm for the first time that double-cell meridional circulation can be achieved along with the solar-like differential rotation when the Reynolds stress transports the angular momentum upward in the lower part and downward in the upper part of the convection zone. It is concluded that in a stationary state, the accumulated angular momentum via the Reynolds stress in the middle layer is advected to both the upper and lower parts of the convection zone by each of the two meridional circulation cells, respectively.

Alfvén waves are believed to play an important role in the heating and acceleration of the fast solar wind emanating from coronal holes. Nonlinear interactions between the dominant ${{\boldsymbol{z}}}_{+}$ waves and minority ${{\boldsymbol{z}}}_{-}$ waves have the potential to transfer wave energy either to smaller perpendicular scales ("direct cascade") or to larger scales ("inverse cascade"). In this paper we use reduced magnetohydrodynamic (RMHD) simulations to investigate how the cascade rates ${\epsilon }_{\pm }$ depend on perpendicular wavenumber and radial distance from the Sun center. For models with a smooth background atmosphere, we find that an inverse cascade (${\epsilon }_{+}\lt 0$) occurs for the dominant waves at radii between 1.4 and $2.5\,{R}_{\odot }$ and dimensionless wavenumbers in the inertial range ($15\lt {a}_{\perp }\lt 44$), and a direct cascade (${\epsilon }_{+}\gt 0$) occurs elsewhere. For a model with density fluctuations, there are multiple regions with an inverse cascade. In both cases, the cascade rate ${\epsilon }_{+}$ varies significantly with perpendicular wavenumber, indicating that the cacsade is a highly nonlocal process. As a result of the inverse cascades, the energy dissipation rates are much lower than expected from a phenomenological model and are insufficient to maintain the temperature of the background atmosphere. We conclude that RMHD models are unable to reproduce the observed properties of the fast solar wind.

Astronomical radio signals are subjected to phase dispersion while traveling through the interstellar medium. To optimally detect a short-duration signal within a frequency band, we have to precisely compensate for the unknown pulse dispersion, which is a computationally demanding task. We present the "fast dispersion measure transform" algorithm for optimal detection of such signals. Our algorithm has a low theoretical complexity of $2{N}_{f}{N}_{t}+{N}_{t}{N}_{{\rm{\Delta }}}{\mathrm{log}}_{2}({N}_{f})$, where N_f, N_t, and N_Δ are the numbers of frequency bins, time bins, and dispersion measure bins, respectively. Unlike previously suggested fast algorithms, our algorithm conserves the sensitivity of brute-force dedispersion. Our tests indicate that this algorithm, running on a standard desktop computer and implemented in a high-level programming language, is already faster than the state-of-the-art dedispersion codes running on graphical processing units (GPUs). We also present a variant of the algorithm that can be efficiently implemented on GPUs. The latter algorithm's computation and data-transport requirements are similar to those of a two-dimensional fast Fourier transform, indicating that incoherent dedispersion can now be considered a nonissue while planning future surveys. We further present a fast algorithm for sensitive detection of pulses shorter than the dispersive smearing limits of incoherent dedispersion. In typical cases, this algorithm is orders of magnitude faster than enumerating dispersion measures and coherently dedispersing by convolution. We analyze the computational complexity of pulsed signal searches by radio interferometers. We conclude that, using our suggested algorithms, maximally sensitive blind searches for dispersed pulses are feasible using existing facilities. We provide an implementation of these algorithms in Python and MATLAB.

Polarimetric observations of T Tauri and Herbig Ae/Be stars are a powerful way to image protoplanetary disks. However, interpretation of these images is difficult because the degree of polarization is highly sensitive to the angle of scattering of stellar light off the disk surface. We examine how disks with and without gaps created by planets appear in scattered polarized light as a function of inclination angle. Isophotes of inclined disks without gaps are distorted in polarized light, giving the appearance that the disks are more eccentric or more highly inclined than they truly are. Apparent gap locations are unaffected by polarization, but the gap contrast changes. In face-on disks with gaps, we find that the brightened far edge of the gap scatters less polarized light than the rest of the disk, resulting in slightly decreased contrast between the gap trough and the brightened far edge. In inclined disks, gaps can take on the appearance of being localized "holes" in brightness rather than full axisymmetric structures. Photocenter offsets along the minor axis of the disk in both total intensity and polarized intensity images can be readily explained by the finite thickness of the disk. Alone, polarized scattered light images of disks do not necessarily reveal intrinsic disk structure. However, when combined with total intensity images, the orientation of the disk can be deduced and much can be learned about disk structure and dust properties.

Nebular-phase observations and spectral models of Type Ic superluminous supernovae (SLSNe) are presented. LSQ14an and SN 2015bn both display late-time spectra similar to galaxy-subtracted spectra of SN 2007bi, and the class shows strong similarity with broad-lined SNe Ic such as SN 1998bw. Near-infrared observations of SN 2015bn show a strong Ca ii triplet, O i 9263, O i 1.13 μm, and Mg i 1.50 μm, but no distinct He, Si, or S emission. The high Ca ii NIR/[Ca ii] 7291, 7323 ratio of ∼2 indicates a high electron density of ${n}_{e}\gtrsim {10}^{8}$ cm⁻³. Spectral models of oxygen-zone emission are investigated to put constraints on the emitting region. Models require $M({\rm{O}} \mbox{-} \mathrm{zone})\gtrsim 10$M_⊙ to produce enough [O i] 6300, 6364 luminosity, irrespective of the powering situation and the density. The high oxygen-zone mass, supported by high estimated magnesium masses, points to explosions of massive CO cores, requiring ${M}_{\mathrm{ZAMS}}\gtrsim 40\,{M}_{\odot }$. Collisions of pair-instability pulsations do not provide enough mass to account for the emission. [O ii] and [O iii] lines emerge naturally in many models, which strengthens the identification of broad [O ii] 7320, 7330, [O iii] 4363, and [O iii] 4959, 5007 in some spectra. A small filling factor $f\lesssim 0.01$ for the O/Mg zone is needed to produce enough luminosity in Mg i] 4571, Mg i 1.504 μm, and O i recombination lines, which shows that the ejecta is clumped. We review the constraints from the nebular spectral modeling in the context of the various scenarios proposed for SLSNe.

Using many observations obtained during 2007 with the Spectro-Polarimeter of the HinodeSolar Optical Telescope, we explore the angular distribution of magnetic fields in the quiet internetwork regions of the solar photosphere. Our work follows from the insight of Stenflo, who examined only linear polarization signals in photospheric lines, thereby avoiding complications of the analysis arising from the differing responses to linear and circular polarization. We identify and isolate regions of a strong polarization signal that occupy only a few percent of the observed quiet Sun area yet contribute most to the net linear polarization signal. The center-to-limb variation of the orientation of linear polarization in these strong signal regions indicates that the associated magnetic fields have a dominant vertical orientation. In contrast, the great majority of the solar disk is occupied by much weaker linear polarization signals. The orientation of the linear polarization in these regions demonstrates that the field orientation is dominantly horizontal throughout the photosphere. We also apply our analysis to Stokes profiles synthesized from the numerical MHD simulations of Rempel as viewed at various oblique angles. The analysis of the synthetic data closely follows that of the observations, lending confidence to using the simulations as a guide for understanding the physical origins of the center-to-limb variation of linear polarization in the quiet Sun area.

We present two-dimensional hydrodynamical simulations for the evolution of early-type galaxies containing central massive black holes (MBHs), starting at an age of $\simeq 2\,\mathrm{Gyr}$. The code contains accurate and physically consistent radiative and mechanical active galactic nucleus (AGN) wind feedback, with parsec-scale central resolution. Mass input comes from stellar evolution; energy input includes Type Ia (SNIa) and II supernovae and stellar heating; star formation (SF) is included. Realistic, axisymmetric dynamical galaxy models are built solving the Jeans' equations. The lowest mass models (${M}_{\star }=8\ {10}^{10}\,{M}_{\odot }$) develop global outflows sustained by SNIa heating, ending with a lower amount of hot gas and new stars. In more massive models, nuclear outbursts last to the present epoch, with large and frequent fluctuations in nuclear emission and from the gas (${L}_{{\rm{X}}}$). Each burst lasts $\sim {10}^{7.5}$ years, during which cold, inflowing, and hot, outflowing gas phases coexist. The ${L}_{{\rm{X}}}\mbox{--}{T}_{{\rm{X}}}$ relation for the gas matches that of local galaxies. AGN activity causes positive feedback for SF. Roughly half of the total mass loss is recycled into new stars (${\rm{\Delta }}{M}_{\star }$), just ≃3% of it is accreted on the MBH, the remainder being ejected from the galaxy. The ratio between the mass of gas expelled to that in new stars, the load factor, is $\simeq 0.6$. Rounder galaxy shapes lead to larger final MBH masses, ${\rm{\Delta }}{M}_{\star }$, and ${L}_{{\rm{X}}}$. Almost all of the time is spent at very low nuclear luminosities, yet one quarter of the total energy is emitted at an Eddington ratio $\gt 0.1$. The duty-cycle of AGN activity is approximately 4%.

Astrometric data from the recent Gaia Data Release 1 have been matched against the sample of stars from Kepler with known rotation periods. A total of 1299 bright rotating stars were recovered from the subset of Gaia sources with good astrometric solutions, most with temperatures above 5000 K. From these sources, 894 were selected as lying near the main sequence using their absolute G-band magnitudes. These main-sequence stars show a bimodality in their rotation period distribution, centered roughly around a 600 Myr rotation isochrone. This feature matches the bimodal period distribution found in cooler stars with Kepler, but was previously undetected for solar-type stars due to sample contamination by subgiants. A tenuous connection between the rotation period and total proper motion is found, suggesting that the period bimodality is due to the age distribution of stars within ∼300 pc of the Sun, rather than a phase of rapid angular momentum loss. This work emphasizes the unique power for understanding stellar populations that is created by combining temporal monitoring from Kepler with astrometric data from Gaia.

We present Atacama Large Millimeter/submillimeter Array observations of the GQ Lup system, a young Sun-like star with a substellar-mass companion in a wide-separation orbit. These observations of 870 μm continuum and CO J = 3–2 line emission with beam size ∼03 (∼45 au) resolve the disk of dust and gas surrounding the primary star, GQ Lup A, and provide deep limits on any circumplanetary disk surrounding the companion, GQ Lup b. The circumprimary dust disk is compact with an FWHM of 59 ± 12 au, while the gas has a larger extent with a characteristic radius of 46.5 ± 1.8 au. By forward-modeling the velocity field of the circumprimary disk based on the CO emission, we constrain the mass of GQ Lup A to be M_* = (1.03 ± 0.05) ∗ (d/156 pc) M_⊙, where d is a known distance, and determine that we view the disk at an inclination angle of 605 ± 05 and a position angle of 346° ± 1°. The 3σ upper limit on the 870 μm flux density of any circumplanetary disk associated with GQ Lup b of <0.15 mJy implies an upper limit on the dust disk mass of <0.04 M_⊕ for standard assumptions about optically thin emission. We discuss proposed mechanisms for the formation of wide-separation substellar companions given the non-detection of circumplanetary disks around GQ Lup b and other similar systems.

The roles of the Rossby wave instability (RWI) have been significantly developed in some important processes, such as planet formation and angular momentum transport through thin accretion disks. However, their development on accretion flows with advection is insignificant. In this paper, we investigate the effect of advection in the occurrence of RWI through accretion flows around black holes (BHs). In the absence of advection, the occurrence of RWI is extremely low because of high viscosity in the accretion flows around BHs. The results of this paper show that there is a significant chance for the occurrence of RWI in some wavelengths if we consider advection even in low amounts. Therefore, the RWI can be a suitable candidate for angular momentum transport in the accretion flows around BHs. Also, the results show that the advection parameter and the ratio of heat capacity, which are special characters of advection flows, play important roles in the occurrence of RWI.

The Fornax Cluster is the nearest ($\leqslant 20$ Mpc) galaxy cluster in the southern sky. NGC 1404 is a bright elliptical galaxy falling through the intracluster medium (ICM) of the Fornax Cluster. The sharp leading edge of NGC 1404 forms a classical "cold front" that separates 0.6 keV dense interstellar medium and 1.5 keV diffuse ICM. We measure the angular pressure variation along the cold front using a very deep (670 ks) Chandra X-ray observation. We are taking the classical approach—using stagnation pressure to determine a substructure's speed—to the next level by not only deriving a general speed but also directionality, which yields the complete velocity field as well as the distance of the substructure directly from the pressure distribution. We find a hydrodynamic model consistent with the pressure jump along NGC 1404's atmosphere measured in multiple directions. The best-fit model gives an inclination of 33° and a Mach number of 1.3 for the infall of NGC 1404, in agreement with complementary measurements of the motion of NGC 1404. Our study demonstrates the successful treatment of a highly ionized ICM as ideal fluid flow, in support of the hypothesis that magnetic pressure is not dynamically important over most of the virial region of galaxy clusters.

Strong X-ray emission from large scale jets of radio loud quasars still remains an open problem. Models based on inverse Compton scattering off cosmic microwave background photons by relativistically beamed jets have recently been ruled out, since Fermi LAT observations for 3C 273 and PKS 0637–752 give the upper limit far below the model prediction. Synchrotron emission from a separate electron population with multi-hundred TeV energies remains a possibility although its origin is not well known. We examine a photo-hadronic origin of such high energy electrons/positrons, assuming that protons are accelerated up to 10¹⁹ eV and produce electrons/positrons through a Bethe–Heitler process and photo-pion production. These secondary electrons/positrons are injected at sufficiently high energies and produce X-rays and γ-rays by synchrotron radiation without conflicting with the Fermi LAT upper limits. We find that the resultant spectrum well reproduces the X-ray observations from PKS 0637-752, if the proton power is at least ${10}^{49}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$, which is highly super-Eddington. It is noted that the X-ray emission originates primarily from leptons through a Bethe–Heitler process, while leptons from photo-pion origin lose energy directly through synchrotron emission of multi-TeV photons rather than cascading. To avoid the overproduction of the optical flux, optical emission is primarily due to synchrotron emission of secondary leptons rather than primary electrons, or a mild degree of beaming of the jet is needed if it is owing to the primary electrons. Proton synchrotron luminosity is a few orders of magnitude smaller.

In this paper, we propose a new framework for treating the angular information in the pulsar timing array (PTA) response to a gravitational wave (GW) background based on standard cosmic microwave background techniques. We calculate the angular power spectrum of the all-sky gravitational redshift pattern induced at the Earth for both a single bright source of gravitational radiation and a statistically isotropic, unpolarized Gaussian random GW background. The angular power spectrum is the harmonic transform of the Hellings & Downs curve. We use the power spectrum to examine the expected variance in the Hellings & Downs curve in both cases. Finally, we discuss the extent to which PTAs are sensitive to the angular power spectrum and find that the power spectrum sensitivity is dominated by the quadrupole anisotropy of the gravitational redshift map.

We study the significance of mergers in the quenching of star formation in galaxies at $z\sim 1$ by examining their color–mass distributions for different morphology types. We perform two-dimensional light profile fits to GOODS iz images of ∼5000 galaxies and X-ray selected active galactic nucleus (AGN) hosts in the CANDELS/GOODS-north and south fields in the redshift range $0.7\lt z\lt 1.3$. Distinguishing between bulge-dominated and disk-dominated morphologies, we find that disks and spheroids have distinct color–mass distributions, in agreement with studies at $z\sim 0$. The smooth distribution across colors for the disk galaxies corresponds to a slow exhaustion of gas, with no fast quenching event. Meanwhile, blue spheroids most likely come from major mergers of star-forming disk galaxies, and the dearth of spheroids at intermediate green colors is suggestive of rapid quenching. The distribution of moderate luminosity X-ray AGN hosts is even across colors, in contrast, and we find similar numbers and distributions among the two morphology types with no apparent dependence on Eddington ratio. The high fraction of bulge-dominated galaxies that host an AGN in the blue cloud and green valley is consistent with the scenario in which the AGN is triggered after a major merger, and the host galaxy then quickly evolves into the green valley. This suggests AGN feedback may play a role in the quenching of star formation in the minority of galaxies that undergo major mergers.

The heaviest metals found in stars in most ultra-faint dwarf (UFD) galaxies in the Milky Way halo are generally underabundant by an order of magnitude or more when compared with stars in the halo field. Among the heavy elements produced by n-capture reactions, only Sr and Ba can be detected in red giant stars in most UFD galaxies. This limited chemical information is unable to identify the nucleosynthesis process(es) responsible for producing the heavy elements in UFD galaxies. Similar [Sr/Ba] and [Ba/Fe] ratios are found in three bright halo field stars, BD−18°5550, CS 22185–007, and CS 22891–200. Previous studies of high-quality spectra of these stars report detections of additional n-capture elements, including Eu. The [Eu/Ba] ratios in these stars span +0.41 to +0.86. These ratios and others among elements in the rare Earth domain indicate an r-process origin. These stars have some of the lowest levels of r-process enhancement known, with [Eu/H] spanning −3.95 to −3.32, and they may be considered nearby proxies for faint stars in UFD galaxies. Direct confirmation, however, must await future observations of additional heavy elements in stars in the UFD galaxies themselves.

Outflows in active galactic nuclei (AGNs) are crucial to understand in investigating the co-evolution of supermassive black holes (SMBHs) and their host galaxies since outflows may play an important role as an AGN feedback mechanism. Based on archival UV spectra obtained with the Hubble Space Telescope and IUE, we investigate outflows in the broad-line region (BLR) in low-redshift AGNs (z < 0.4) through detailed analysis of the velocity profile of the C iv emission line. We find a dependence of the outflow strength on the Eddington ratio and the BLR metallicity in our low-redshift AGN sample, which is consistent with earlier results obtained for high-redshift quasars. These results suggest that BLR outflows, gas accretion onto SMBHs, and past star formation activity in host galaxies are physically related in low-redshift AGNs as in powerful high-redshift quasars.

The most commonly used index of stellar magnetic activity is the instrumental flux scale of singly ionized calcium H & K line core emission, S, developed by the Mount Wilson Observatory (MWO) HK Project, or the derivative index ${R}_{\mathrm{HK}}^{\prime }$. Accurately placing the Sun on the S scale is important for comparing solar activity to that of the Sun-like stars. We present previously unpublished measurements of the reflected sunlight from the Moon using the second-generation MWO HK photometer during solar cycle 23 and determine cycle minimum ${S}_{23,\min }=0.1634\pm 0.0008$, amplitude ${\rm{\Delta }}{S}_{23}=0.0143\pm 0.0012$, and mean $\langle {S}_{23}\rangle =0.1701\pm 0.0005$. By establishing a proxy relationship with the closely related National Solar Observatory Sacramento Peak calcium K emission index, itself well correlated with the Kodaikanal Observatory plage index, we extend the MWO S time series to cover cycles 15–24 and find on average $\langle {S}_{\min }\rangle =0.1621\pm 0.0008$, $\langle {\rm{\Delta }}{S}_{\mathrm{cyc}}\rangle =0.0145\pm 0.0012$, $\langle {S}_{\mathrm{cyc}}\rangle =0.1694\pm 0.0005$. Our measurements represent an improvement over previous estimates that relied on stellar measurements or solar proxies with non-overlapping time series. We find good agreement from these results with measurements by the Solar-Stellar Spectrograph at Lowell Observatory, an independently calibrated instrument, which gives us additional confidence that we have accurately placed the Sun on the S-index flux scale.

We compile an updated list of 38 measurements of the Hubble parameter H(z) between redshifts 0.07 ≤ z ≤ 2.36 and use them to place constraints on model parameters of constant and time-varying dark energy cosmological models, both spatially flat and curved. We use five models to measure the redshift of the cosmological deceleration–acceleration transition, z_da, from these H(z) data. Within the error bars, the measured z_da are insensitive to the model used, depending only on the value assumed for the Hubble constant H₀. The weighted mean of our measurements is z_da = 0.72 ± 0.05 (0.84 ± 0.03) for H₀ = 68 ± 2.8 (73.24 ± 1.74) km s⁻¹ Mpc⁻¹ and should provide a reasonably model-independent estimate of this cosmological parameter. The H(z) data are consistent with the standard spatially flat ΛCDM cosmological model but do not rule out nonflat models or dynamical dark energy models.

We present results from the MOSFIRE Deep Evolution Field (MOSDEF) survey on the identification, selection biases, and host galaxy properties of 55 X-ray, IR, and optically selected active galactic nuclei (AGNs) at $1.4\lt z\lt 3.8$. We obtain rest-frame optical spectra of galaxies and AGNs and use the BPT diagram to identify optical AGNs. We examine the uniqueness and overlap of the AGNs identified at different wavelengths. There is a strong bias against identifying AGNs at any wavelength in low-mass galaxies, and an additional bias against identifying IR AGNs in the most massive galaxies. AGN hosts span a wide range of star formation rates (SFRs), similar to inactive galaxies once stellar mass selection effects are accounted for. However, we find (at ∼2–3σ significance) that IR AGNs are in less dusty galaxies with relatively higher SFR and optical AGNs in dusty galaxies with relatively lower SFR. X-ray AGN selection does not display a bias with host galaxy SFR. These results are consistent with those from larger studies at lower redshifts. Within star-forming galaxies, once selection biases are accounted for, we find AGNs in galaxies with similar physical properties as inactive galaxies, with no evidence for AGN activity in particular types of galaxies. This is consistent with AGNs being fueled stochastically in any star-forming host galaxy. We do not detect a significant correlation between SFR and AGN luminosity for individual AGN hosts, which may indicate the timescale difference between the growth of galaxies and their supermassive black holes.

We present a revised Tip of the Red Giant Branch (TRGB) calibration, accurate to 2.7% of distance. A modified TRGB magnitude corrected for its color dependence, the QT magnitude, is introduced for better measurement of the TRGB. We determine the color–magnitude relation of the TRGB from photometry of deep images of HST/ACS fields around eight nearby galaxies. The zero-point of the TRGB at the fiducial metallicity ([Fe/H] = −1.6 (${(V-I)}_{0,\mathrm{TRGB}}=1.5$)) is obtained from photometry of two distance anchors, NGC 4258 (M106) and the Large Magellanic Cloud (LMC), to which precise geometric distances are known: M_QT,TRGB = −4.023 ± 0.073 mag from NGC 4258 and M_QT,TRGB = −4.004 ± 0.096 mag from the LMC. A weighted mean of the two zero-points is M_QT,TRGB = −4.016 ± 0.058 mag. Quoted uncertainty is ∼2× smaller than those of previous calibrations. We compare the empirical TRGB calibration derived in this study with theoretical stellar models, finding that there are significant discrepancies, especially for red color (${({\rm{F}}606{\rm{W}}-{\rm{F}}814{\rm{W}})}_{0}\gtrsim 2.5$). We provide the revised TRGB calibration in several magnitude systems for future studies.

We present a new model for the distribution of free electrons in the Galaxy, the Magellanic Clouds, and the intergalactic medium (IGM) that can be used to estimate distances to real or simulated pulsars and fast radio bursts (FRBs) based on their dispersion measure (DM). The Galactic model has an extended thick disk representing the so-called warm interstellar medium, a thin disk representing the Galactic molecular ring, spiral arms based on a recent fit to Galactic H ii regions, a Galactic Center disk, and seven local features including the Gum Nebula, Galactic Loop I, and the Local Bubble. An offset of the Sun from the Galactic plane and a warp of the outer Galactic disk are included in the model. Parameters of the Galactic model are determined by fitting to 189 pulsars with independently determined distances and DMs. Simple models are used for the Magellanic Clouds and the IGM. Galactic model distances are within the uncertainty range for 86 of the 189 independently determined distances and within 20% of the nearest limit for a further 38 pulsars. We estimate that 95% of predicted Galactic pulsar distances will have a relative error of less than a factor of 0.9. The predictions of YMW16 are compared to those of the TC93 and NE2001 models showing that YMW16 performs significantly better on all measures. Timescales for pulse broadening due to interstellar scattering are estimated for (real or simulated) Galactic and Magellanic Cloud pulsars and FRBs.

We report on the search for gamma-ray emission from 20 magnetars using six years of Fermi Large Area Telescope observations. No significant evidence for gamma-ray emission from any of the currently known magnetars is found. We derived the most stringent upper limits to date on the 0.1–10 GeV emission of Galactic magnetars, which are estimated between ∼10⁻¹² and 10⁻¹¹ erg s⁻¹ cm⁻². We searched gamma-ray pulsations for the four magnetars having reliable ephemerides over the observing period, but detected none. We also report updated morphologies and spectral properties of seven spatially extended gamma-ray sources, which are most likely attributed to supernova remnants associated with or adjacent to the magnetars.

Ground-based interferometers are not perfect all-sky instruments, and it is important to account for their behavior when considering the distribution of detected events. In particular, the LIGO detectors are most sensitive to sources above North America and the Indian Ocean, and as the Earth rotates, the sensitive regions are swept across the sky. However, because the detectors do not acquire data uniformly over time, there is a net bias on detectable sources' right ascensions. Both LIGO detectors preferentially collect data during their local night; it is more than twice as likely to be local midnight than noon when both detectors are operating. We discuss these selection effects and how they impact LIGO's observations and electromagnetic (EM) follow-up. Beyond galactic foregrounds associated with seasonal variations, we find that equatorial observatories can access over 80% of the localization probability, while mid-latitudes will access closer to 70%. Facilities located near the two LIGO sites can observe sources closer to their zenith than their analogs in the south, but the average observation will still be no closer than 44° from zenith. We also find that observatories in Africa or the South Atlantic will wait systematically longer before they can begin observing compared to the rest of the world; though, there is a preference for longitudes near the LIGOs. These effects, along with knowledge of the LIGO antenna pattern, can inform EM follow-up activities and optimization, including the possibility of directing observations even before gravitational-wave events occur.

We study feedback during massive star formation using semi-analytic methods, considering the effects of disk winds, radiation pressure, photoevaporation, and stellar winds, while following protostellar evolution in collapsing massive gas cores. We find that disk winds are the dominant feedback mechanism setting star formation efficiencies (SFEs) from initial cores of ∼0.3–0.5. However, radiation pressure is also significant to widen the outflow cavity causing reductions of SFE compared to the disk-wind only case, especially for $\gt 100\,{M}_{\odot }$ star formation at clump mass surface densities ${{\rm{\Sigma }}}_{\mathrm{cl}}\lesssim 0.3\ {\rm{g}}\ {\mathrm{cm}}^{-2}$. Photoevaporation is of relatively minor importance due to dust attenuation of ionizing photons. Stellar winds have even smaller effects during the accretion stage. For core masses ${M}_{c}\simeq 10$–$1000\ {M}_{\odot }$ and ${{\rm{\Sigma }}}_{\mathrm{cl}}\simeq 0.1$–$3\ {\rm{g}}\ {\mathrm{cm}}^{-2}$, we find the overall SFE to be ${\bar{\varepsilon }}_{* f}=0.31{({R}_{c}/0.1\mathrm{pc})}^{-0.39}$, potentially a useful sub-grid star formation model in simulations that can resolve pre-stellar core radii, ${R}_{c}=0.057{({M}_{c}/60{M}_{\odot })}^{1/2}{({{\rm{\Sigma }}}_{\mathrm{cl}}/{\rm{g}}{\mathrm{cm}}^{-2})}^{-1/2}\ \mathrm{pc}$. The decline of SFE with M_c is gradual with no evidence for a maximum stellar-mass set by feedback processes up to stellar masses of ${m}_{* }\sim 300\ {M}_{\odot }$. We thus conclude that the observed truncation of the high-mass end of the IMF is shaped mostly by the pre-stellar core mass function or internal stellar processes. To form massive stars with the observed maximum masses of ∼150–$300{M}_{\odot }$, initial core masses need to be $\gtrsim 500$–$1000\ {M}_{\odot }$. We also apply our feedback model to zero-metallicity primordial star formation, showing that, in the absence of dust, photoevaporation staunches accretion at $\sim 50\ {M}_{\odot }$. Our model implies radiative feedback is most significant at metallicities $\sim {10}^{-2}{Z}_{\odot }$, since both radiation pressure and photoevaporation are effective in this regime.

In this work, we employ the dark matter equations of state (DMEOSs) obtained from the rotational curves of galaxies as well as the fermionic DMEOS with $m=1.0\,\mathrm{GeV}$ to study the structure of dark-matter admixed neutron stars (DMANSs). Applying the equation of state in the Skyrme framework for the neutron matter (NM), we calculate the mass–radius relation for different DMANSs with various DMEOSs and central pressure of dark matter (DM) to NM ratios. Our results show that for some DMEOSs, the mass–radius relations are in agreement with new observations, e.g., EXO 1745-248, 4U 1608-52, and 4U 1820-30, which are inconsistent with normal neutron stars. We conclude that both DMEOSs and central pressure ratios of DM to NM affect the slope of the mass–radius relation of DMANSs. This is because of the interaction between DM and NM, which leads to gravitationally or self-bound DMANSs. We study the radius of the NM sphere as well as the radius of the DM halo for different DMANSs. The results confirm that, in some cases, a NM sphere with a small radius is surrounded by a halo of DM with a larger radius. Our calculations verify that, due to the different degrees of DM domination in DMANSs, with a value of the visible radius of a star two possible DMANSs with different masses can exist. The gravitational redshift is also calculated for DMANSs with different DMEOSs and central pressure ratios. The results explain that the existence of DM in a DMANS leads to higher values of gravitational redshift of the star.

Diffusive shock acceleration by the shockwaves in supernova remnants (SNRs) is widely accepted as the dominant source for Galactic cosmic rays. However, it is unknown what determines the maximum energy of accelerated particles. The surrounding environment could be one of the key parameters. The SNR RCW 86 shows both thermal and nonthermal X-ray emission with different spatial morphologies. These emission originate from the shock-heated plasma and accelerated electrons respectively, and their intensities reflect their density distributions. Thus, the remnant provides a suitable laboratory to test possible association between the acceleration efficiency and the environment. In this paper, we present results of spatially resolved spectroscopy of the entire remnant with Suzaku. The spacially resolved spectra are well reproduced with a combination of a power-law for synchrotron emission and a two-component optically thin thermal plasma, corresponding to the shocked interstellar medium (ISM) with kT of 0.3–0.6 keV and Fe-dominated ejecta. It is discovered that the photon index of the nonthermal component becomes smaller when decreasing the emission measure of the shocked ISM, where the shock speed has remained high. This result implies that the maximum energy of accelerated electrons in RCW 86 is higher in the low-density and higher shock speed regions.

We report a strong minifilament eruption associated with Geostationary Operational Environmental Satellite C1.6 flare and WIND type-III radio burst. The minifilament, which lies at the periphery of active region 12259, is detected by Hα images from the New Vacuum Solar Telescope. The minifilament undergoes a partial and then a full eruption. Simultaneously, two co-spatial jets are successively observed in extreme ultraviolet images from the Solar Dynamic Observatory. The first jet exhibits a typical fan-spine geometry, suggesting that the co-spatial minifilament is possibly embedded in magnetic fields with a fan-spine structure. However, the second jet displays blowout morphology when the entire minifilament erupts upward, leaving behind a hard X-ray emission source in the base. Differential emission measure analyses show that the eruptive region is heated up to about 4 MK during the fan-spine jet, while up to about 7 MK during the blowout jet. In particular, the blowout jet is accompanied by an interplanetary type-III radio burst observed by WIND/WAVES in the frequency range from above 10 to 0.1 MHz. Hence, the minifilament eruption is correlated with the interplanetary type-III radio burst for the first time. These results not only suggest that coronal jets can result from magnetic reconnection initiated by erupting minifilaments with open fields, but also shed light on the potential influence of minifilament eruption on interplanetary space.

We present measurements of the clustering properties of a sample of infrared (IR) bright dust-obscured galaxies (DOGs). Combining 125 deg² of wide and deep optical images obtained with the Hyper Suprime-Cam on the Subaru Telescope and all-sky mid-IR images taken with Wide-Field Infrared Survey Explorer, we have discovered 4367 IR-bright DOGs with ${(i-[22])}_{\mathrm{AB}}\gt 7.0$ and flux density at 22 $\mu {\rm{m}}\gt 1.0$ mJy. We calculate the angular autocorrelation function (ACF) for a uniform subsample of 1411 DOGs with 3.0 mJy < flux (22 $\mu {\rm{m}}$) < 5.0 mJy and ${i}_{\mathrm{AB}}$ < 24.0. The ACF of our DOG subsample is well-fit with a single power law, $\omega (\theta )$ = (0.010 ± 0.003) ${\theta }^{-0.9}$, where θ is in degrees. The correlation amplitude of IR-bright DOGs is larger than that of IR-faint DOGs, which reflects a flux dependence of the DOG clustering, as suggested by Brodwin et al. We assume that the redshift distribution for our DOG sample is Gaussian, and consider two cases: (1) the redshift distribution is the same as IR-faint DOGs with flux at 22 $\mu {\rm{m}}$ < 1.0 mJy, mean and sigma z = 1.99 ± 0.45, and (2) z = 1.19 ± 0.30, as inferred from their photometric redshifts. The inferred correlation length of IR-bright DOGs is r₀ = 12.0 ± 2.0 and 10.3 ± 1.7 ${h}^{-1}$ Mpc, respectively. IR-bright DOGs reside in massive dark matter halos with a mass of $\mathrm{log}[\langle {M}_{{\rm{h}}}\rangle /({h}^{-1}\,{M}_{\odot })]={13.57}_{-0.55}^{+0.50}$ and ${13.65}_{-0.52}^{+0.45}$ in the two cases, respectively.

We provide a holistic view of galaxy evolution at high redshifts z ≳ 4, which incorporates the constraints from various astrophysical/cosmological probes, including the estimate of the cosmic star formation rate (SFR) density from UV/IR surveys and long gamma-ray burst (GRBs) rates, the cosmic reionization history following the latest Planck measurements, and the missing satellites issue. We achieve this goal in a model-independent way by exploiting the SFR functions derived by Mancuso et al. on the basis of an educated extrapolation of the latest UV/far-IR data from HST/Herschel, and already tested against a number of independent observables. Our SFR functions integrated down to a UV magnitude limit M_UV ≲ −13 (or SFR limit around 10⁻²M_⊙ yr⁻¹) produce a cosmic SFR density in excellent agreement with recent determinations from IR surveys and, taking into account a metallicity ceiling Z ≲ Z_⊙/2, with the estimates from long GRB rates. They also yield a cosmic reionization history consistent with that implied by the recent measurements of the Planck mission of the electron scattering optical depth τ_es ≈ 0.058; remarkably, this result is obtained under a conceivable assumption regarding the average value f_esc ≈ 0.1 of the escape fraction for ionizing photons. We demonstrate via the abundance-matching technique that the above constraints concurrently imply galaxy formation becoming inefficient within dark matter halos of mass below a few 10⁸M_⊙; pleasingly, such a limit is also required so as not to run into the missing satellites issue. Finally, we predict a downturn of the Galaxy luminosity function faintward of M_UV ≲ −12, and stress that its detailed shape, to be plausibly probed in the near future by the JWST, will be extremely informative on the astrophysics of galaxy formation in small halos, or even on the microscopic nature of the dark matter.

Recently, high angular resolution imaging instruments such as SPHERE and GPI have discovered many spiral-arm-like features in near-infrared scattered-light images of protoplanetary disks. Theory and simulations have suggested that these arms are most likely excited by planets forming in the disks; however, a quantitative relation between the arm-to-disk brightness contrast and planet mass is still missing. Using 3D hydrodynamics and radiative transfer simulations, we examine the morphology and contrast of planet-induced arms in disks. We find a power-law relation for the face-on arm contrast (δ_max) as a function of planet mass (${M}_{{\rm{p}}}$) and disk aspect ratio (h/r): ${\delta }_{\max }\approx {({({M}_{{\rm{p}}}/{M}_{{\rm{J}}})/(h/r)}^{1.38})}^{0.22}$. With current observational capabilities, at a 30 au separation, the minimum planet mass for driving detectable arms in a disk around a 1 Myr, 1 ${M}_{\odot }$ star at 140 pc at low inclinations is around Saturn mass. For planets more massive than Neptune masses, they typically drive multiple arms. Therefore, in observed disks with spirals, it is unlikely that each spiral arm originates from a different planet. We also find that only massive perturbers with at least multi-Jupiter masses are capable of driving bright arms with ${\delta }_{\max }\gtrsim 2$ as found in SAO 206462, MWC 758, and LkHα 330, and these arms do not follow linear wave propagation theory. Additionally, we find that the morphology and contrast of the primary and secondary arms are largely unaffected by a modest level of viscosity with $\alpha \lesssim 0.01$. Finally, the contrast of the arms in the SAO 206462 disk suggests that the perturber SAO 206462 b at ∼100 au is about $5\mbox{--}10\,{M}_{{\rm{J}}}$ in mass.

We develop a three-dimensional kinematic self-sustaining model of the solar dynamo in which the poloidal field generation is from tilted bipolar sunspot pairs placed on the solar surface above regions of strong toroidal field by using the SpotMaker algorithm, and then the transport of this poloidal field to the tachocline is primarily caused by turbulent diffusion. We obtain a dipolar solution within a certain range of parameters. We use this model to study the build-up of the polar magnetic field and show that some insights obtained from surface flux transport models have to be revised. We present results obtained by putting a single bipolar sunspot pair in a hemisphere and two symmetrical sunspot pairs in two hemispheres. We find that the polar fields produced by them disappear due to the upward advection of poloidal flux at low latitudes, which emerges as oppositely signed radial flux and which is then advected poleward by the meridional flow. We also study the effect that a large sunspot pair, violating Hale's polarity law, would have on the polar field. We find that there would be some effect—especially if the anti-Hale pair appears at high latitudes in the mid-phase of the cycle—though the effect is not very dramatic.

We present the exact solutions for the collapse of a spherically symmetric cold (i.e., pressureless) cloud under its own self-gravity, valid for arbitrary initial density profiles and not restricted to the realm of self-similarity. These solutions exhibit a number of remarkable features, including the self-consistent formation of and subsequent accretion onto a central point mass. A number of specific examples are provided, and we show that Penston's solution of pressureless self-similar collapse is recovered for polytropic density profiles; importantly, however, we demonstrate that the time over which this solution holds is fleetingly short, implying that much of the collapse proceeds non-self-similarly. We show that our solutions can naturally incorporate turbulent pressure support, and we investigate the evolution of overdensities—potentially generated by such turbulence—as the collapse proceeds. Finally, we analyze the evolution of the angular velocity and magnetic fields in the limit that their dynamical influence is small, and we recover exact solutions for these quantities. Our results may provide important constraints on numerical models that attempt to elucidate the details of protostellar collapse when the initial conditions are far less idealized.

Strong Alfvénic turbulence develops eddy-like motions perpendicular to the local direction of magnetic fields. This local alignment induces velocity gradients perpendicular to the local direction of the magnetic field. We use this fact to propose a new technique of studying the direction of magnetic fields from observations, which we call the velocity gradient technique. We test our idea by employing the synthetic observations obtained via 3D magnetohydrodynamical (MHD) numerical simulations for different sonic and Alfvén Mach numbers. We calculate the velocity gradient, ${\boldsymbol{\Omega }}$, using the velocity centroids. We find that ${\boldsymbol{\Omega }}$ traces the projected magnetic field best for the synthetic maps obtained with sub-Alfvénic simulations and provides good point-wise correspondence between the magnetic field direction and the direction of ${\boldsymbol{\Omega }}$. The reported alignment is much better than the alignment between the density gradients and the magnetic field, and we demonstrate that it can be used to find the magnetic field strength with an analog of the Chandrasekhar–Fermi method. This new technique does not require dust polarimetry, and our study opens up a new way of studying magnetic fields using spectroscopic data.

We report the detection of a GeV γ-ray source that spatially overlaps and is thus very likely associated with the unidentified very high energy (VHE) γ-ray source HESS J1427−608 with the Pass 8 data recorded by the Fermi Large Area Telescope. The photon spectrum of this source is best described by a power law with an index of 1.85 ± 0.17 in the energy range of 3–500 GeV, and the measured flux connects smoothly with that of HESS J1427−608 at a few hundred gigaelectronvolts. This source shows no significant extension and time variation. The broadband GeV to TeV emission over four decades of energies can be well fitted by a single power-law function with an index of 2.0, without obvious indication of spectral cutoff toward high energies. Such a result implies that HESS J1427−608 may be a PeV particle accelerator. We discuss the possible nature of HESS J1427−608 according to the multiwavelength spectral fittings. Given the relatively large errors, either a leptonic or a hadronic model can explain the multiwavelength data from radio to VHE γ-rays. The inferred magnetic field strength is a few micro-Gauss, which is smaller than the typical values of supernova remnants (SNRs) and is consistent with some pulsar wind nebulae (PWNe). On the other hand, the flat γ-ray spectrum is slightly different from typical PWNe but is similar to that of some known SNRs.

For the X1.7 class flare on 2013 May 13 (SOL2013-05-13T01:53), its initiation process was well observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory and the Extreme UltraViolet Imager (EUVI) on board STEREO-B. The initiation process incorporates the following phenomena: an X-ray precursor that started ∼9 minutes before flare onset, two hot magnetic loops (as seen with AIA hot channels) forming a sigmoidal core magnetic structure (as seen with the EUVI), a rapidly formed magnetic flux rope (MFR) that expands outward, and a flare loop that contracts inward. The two hot magnetic loops were activated after the occurrence of the X-ray precursor. After activation, magnetic reconnection occurred between the two hot magnetic loops (inside the sigmoid structure), which produced the expanding MFR and the contracting flare loop (CFL). The MFR and CFL can only be seen with AIA hot and cool channels, respectively. For this flare, the real initiation time can be regarded as being from the starting time of the precursor, and its impulsive phase started when the MFR began its fast expansion. In addition, the CFL and the growing postflare magnetic loops are different loop systems, and the CFL was the product of magnetic reconnection between sheared magnetic fields that also produced the MFR.

A multiply lensed galaxy, MACS0647-JD, with a probable photometric redshift of $z\simeq {10.7}_{-0.4}^{+0.6}$ is claimed to constitute one of the very earliest known galaxies, formed well before reionization was completed. However, spectral evidence that MACS0647-JD lies at high redshift has proven infeasible and so here we seek an independent-lensing-based "geometric redshift" derived from the angles between the three lensed images of MACS0647-JD, using our free-form mass model (WSLAP+) for the lensing cluster MACSJ0647.7+7015 (at z = 0.591). Our lens model uses the nine sets of multiple images, including those of MACS0647-JD, identified by the CLASH survey toward this cluster. We convincingly exclude the low-redshift regime of z < 3, for which convoluted critical curves are generated by our method, as the solution bends to accommodate the wide angles of MACS0647-JD for this low redshift. Instead, a best fit to all sets of lensed galaxy positions and redshifts provides a geometric redshift of $z\simeq {10.8}_{-0.4}^{+0.3}$ for MACS0647-JD, strongly supporting the higher photometric redshift solution. Importantly, we find a tight linear relation between the relative brightnesses of all nine sets of multiply lensed images and their relative magnifications as predicted by our model. This agreement provides a benchmark for the quality of the lens model, and establishes the robustness of our free-form lensing method for measuring model-independent geometric source distances and for deriving objective central cluster mass distributions. After correcting for its magnification the luminosity of MACS0647-JD remains relatively high at M_UV = −19.4, which is within a factor of a few in flux of some surprisingly luminous z ≃ 10–11 candidates discovered recently in Hubble blank field surveys.

The recent discovery of a diffuse cosmic neutrino flux extending up to PeV energies raises the question of which astrophysical sources generate this signal. Blazars are one class of extragalactic sources which may produce such high-energy neutrinos. We present a likelihood analysis searching for cumulative neutrino emission from blazars in the 2nd Fermi-LAT AGN catalog (2LAC) using IceCube neutrino data set 2009-12, which was optimized for the detection of individual sources. In contrast to those in previous searches with IceCube, the populations investigated contain up to hundreds of sources, the largest one being the entire blazar sample in the 2LAC catalog. No significant excess is observed, and upper limits for the cumulative flux from these populations are obtained. These constrain the maximum contribution of 2LAC blazars to the observed astrophysical neutrino flux to 27% or less between around 10 TeV and 2 PeV, assuming the equipartition of flavors on Earth and a single power-law spectrum with a spectral index of −2.5. We can still exclude the fact that 2LAC blazars (and their subpopulations) emit more than 50% of the observed neutrinos up to a spectral index as hard as −2.2 in the same energy range. Our result takes into account the fact that the neutrino source count distribution is unknown, and it does not assume strict proportionality of the neutrino flux to the measured 2LAC γ-ray signal for each source. Additionally, we constrain recent models for neutrino emission by blazars.

The methoxy radical (CH₃O) has recently been detected in the interstellar medium and may be an important tracer of methanol-related chemistry in cold sources. Despite its importance, the spectral information needed to guide further astronomical searches is limited. We have therefore studied the low-temperature rotational spectrum in the laboratory within the spectral range of 246–303 GHz. We have combined these new measurements with results from a number of literature reports to refine the molecular parameters and provide an updated and improved spectral line catalog. We present here the results of the laboratory studies and the refined analysis for the millimeter and submillimeter spectrum of methoxy.

Macrospicules (MSs) are localized small-scale jet-like phenomena in the solar atmosphere, which have the potential to transport a considerable amount of momentum and energy from the lower solar atmospheric regions to the transition region and the low corona. A detailed statistical analysis of their temporal behavior and spatial properties is carried out in this work. Using state-of-the-art spatial and temporal resolution observations, yielded by the Atmospheric Imaging Assembly of Solar Dynamics Observatory, we constructed a database covering a 5.5 year long period, containing 301 macrospicules that occurred between 2010 June and 2015 December, detected at 30.4 nm wavelength. Here, we report the long-term variation of the height, length, average speed, and width of MS in coronal holes and Quiet Sun areas both in the northern and southern hemisphere of the Sun. This new database helps to refine our knowledge about the physical properties of MSs. Cross-correlation of these properties shows a relatively strong correlation, but not always a dominant one. However, a more detailed analysis indicates a wave-like signature in the behavior of MS properties in time. The periods of these long-term oscillatory behaviors are just under two years. Also, in terms of solar north/south hemispheres, a strong asymmetry was found in the spatial distribution of MS properties, which may be accounted for by the solar dynamo. This latter feature may then indicate a strong and rather intrinsic link between global internal and local atmospheric phenomena in the Sun.

Electron acceleration in solar flares is well known to be efficient at generating energetic particles that produce the observed bremsstrahlung X-ray spectra. One mechanism proposed to explain the observations is electron acceleration within contracting magnetic islands formed by magnetic reconnection in the flare current sheet. In a previous study, a numerical magnetohydrodynamic simulation of an eruptive solar flare was analyzed to estimate the associated electron acceleration due to island contraction. That analysis used a simple analytical model for the island structure and assumed conservation of the adiabatic invariants of particle motion. In this paper, we perform the first-ever rigorous integration of the guiding-center orbits of electrons in a modeled flare. An initially isotropic distribution of particles is seeded in a contracting island from the simulated eruption, and the subsequent evolution of these particles is followed using guiding-center theory. We find that the distribution function becomes increasingly anisotropic over time as the electrons' energy increases by up to a factor of five, in general agreement with the previous study. In addition, we show that the energized particles are concentrated on the Sunward side of the island, adjacent to the reconnection X-point in the flare current sheet. Furthermore, our analysis demonstrates that the electron energy gain is dominated by betatron acceleration in the compressed, strengthened magnetic field of the contracting island. Fermi acceleration by the shortened field lines of the island also contributes to the energy gain, but it is less effective than the betatron process.

The EDGES High-Band experiment aims to detect the sky-average brightness temperature of the 21 cm signal from the epoch of reionization in the redshift range $14.8\gtrsim z\gtrsim 6.5$. To probe this redshifted signal, EDGES High-Band conducts single-antenna measurements in the frequency range 90–190 MHz from the Murchison Radio-astronomy Observatory in Western Australia. In this paper, we describe the current strategy for calibration of the EDGES High-Band receiver and report calibration results for the instrument used in the 2015–2016 observational campaign. We propagate uncertainties in the receiver calibration measurements to the antenna temperature using a Monte Carlo approach. We define a performance objective of 1 mK residual rms after modeling foreground subtraction from a fiducial temperature spectrum using a five-term polynomial. Most of the calibration uncertainties yield residuals of 1 mK or less at $95 \%$ confidence. However, current uncertainties in the antenna and receiver reflection coefficients can lead to residuals of up to 20 mK even in low-foreground sky regions. These dominant residuals could be reduced by (1) improving the accuracy in reflection measurements, especially their phase, (2) improving the impedance match at the antenna-receiver interface, and (3) decreasing the changes with frequency of the antenna reflection phase.

Asymptotic giant branch (AGB) stars are known to produce "cosmic" fluorine, but it is uncertain whether these stars are the main producers of fluorine in the solar neighborhood or if any of the other proposed formation sites, Type II supernovae (SNe II) and/or Wolf-Rayet (W-R) stars, are more important. Recent articles have proposed both AGB stars and SNe II as the dominant sources of fluorine in the solar neighborhood. In this paper we set out to determine the fluorine abundance in a sample of 49 nearby, bright K giants for which we previously have determined the stellar parameters, as well as alpha abundances homogeneously from optical high-resolution spectra. The fluorine abundance is determined from a 2.3 μm HF molecular line observed with the spectrometer Phoenix. We compare the fluorine abundances with those of alpha-elements mainly produced in SNe II and find that fluorine and the alpha-elements do not evolve in lockstep, ruling out SNe II as the dominating producers of fluorine in the solar neighborhood. Furthermore, we find a secondary behavior of fluorine with respect to oxygen, which is another evidence against the SNe II playing a large role in the production of fluorine in the solar neighborhood. This secondary behavior of fluorine will put new constraints on stellar models of the other two suggested production sites: AGB stars and W-R stars.

We investigate the influence of random variations of the Galactic gravitational field on the apparent celestial positions of extragalactic sources. The basic statistical characteristics of a stochastic process (first-order moments, an autocorrelation function and a power spectral density) are used to describe a light ray deflection in a gravitational field of randomly moving point masses as a function of the source coordinates. We map a 2D distribution of the standard deviation of the angular shifts in positions of distant sources (including reference sources of the International Celestial Reference Frame) with respect to their true positions. For different Galactic matter distributions the standard deviation of the offset angle can reach several tens of μas (microarcsecond) toward the Galactic center, decreasing down to 4–6 μas at high galactic latitudes. The conditional standard deviation ("jitter") of 2.5 μas is reached within 10 years at high galactic latitudes and within a few months toward the inner part of the Galaxy. The photometric microlensing events are not expected to be disturbed by astrometric random variations anywhere except the inner part of the Galaxy as the Einstein–Chvolson times are typically much shorter than the jittering timescale. While a jitter of a single reference source can be up to dozens of μas over some reasonable observational time, using a sample of reference sources would reduce the error in relative astrometry. The obtained results can be used for estimating the physical upper limits on the time-dependent accuracy of astrometric measurements.

We construct an analytic phenomenological model for extended warm/hot gaseous coronae of L_* galaxies. We consider UV O vi Cosmic Origins Spectrograph (COS)-Halos absorption line data in combination with Milky Way (MW) X-ray O vii and O viii absorption and emission. We fit these data with a single model representing the COS-Halos galaxies and a Galactic corona. Our model is multi-phased, with hot and warm gas components, each with a (turbulent) log-normal distribution of temperatures and densities. The hot gas, traced by the X-ray absorption and emission, is in hydrostatic equilibrium in an MW gravitational potential. The median temperature of the hot gas is $1.5\times {10}^{6}$ K and the mean hydrogen density is $\sim 5\times {10}^{-5}\,{\mathrm{cm}}^{-3}$. The warm component as traced by the O vi, is gas that has cooled out of the high density tail of the hot component. The total warm/hot gas mass is high and is $1.2\times {10}^{11}\,{M}_{\odot }$. The gas metallicity we require to reproduce the oxygen ion column densities is 0.5 solar. The warm O vi component has a short cooling time ($\sim 2\times {10}^{8}$ years), as hinted by observations. The hot component, however, is $\sim 80 \%$ of the total gas mass and is relatively long-lived, with ${t}_{\mathrm{cool}}\sim 7\times {10}^{9}$ years. Our model supports suggestions that hot galactic coronae can contain significant amounts of gas. These reservoirs may enable galaxies to continue forming stars steadily for long periods of time and account for "missing baryons" in galaxies in the local universe.

We report the results of high-resolution (R ∼ 80,000) spectroscopic observations of the emission-line object HD 85567, which has been classified as an FS CMa type object or a pre-main-sequence star. The main goal is to put more constraints on the object's fundamental parameters, as well as on its nature and evolutionary state. Absorption lines in the spectrum of HD 85567 were found to be similar to those of mid-B-type dwarfs and correspond to the following fundamental parameters: T_eff = 15,000 ± 500 K, $v\sin i=31\pm 3$ km s⁻¹, and $\mathrm{log}\,g\sim 4.0$. The interstellar extinction, A_V = 0.50 ± 0.02 mag, was measured using the strengths of some diffuse interstellar bands. We also obtained UBV(RI)_c images of a 10' × 10' region around the object. Photometry of projectionally close stars was used to derive an interstellar extinction law in this direction and resulted in a distance of 1300 ± 100 pc to the object and a luminosity of log L/L_⊙ = 3.3 ± 0.2. We found no significant radial velocity variations of the absorption lines in the spectra of HD 85567 obtained during two-month-long periods of time in 2012 and 2015. Our analysis of the spectroscopic and photometric data available for the star led us to a conclusion that it cannot be a pre-main-sequence Herbig Ae/Be star. We argue that the circumstellar gas and dust were produced during the object's evolution as most likely a binary system, which contains an undetected secondary component and is unlikely to be a merger product.

A wind nebula generating extended X-ray emission was recently detected surrounding Swift J1834.9–0846. This is the first magnetar for which such a wind nebula was found. Here, we investigate whether there is a plausible scenario where the pulsar wind nebula (PWN) can be sustained without the need of advocating for additional sources of energy other than rotational. We do this by using a detailed radiative and dynamical code that studies the evolution of the nebula and its particle population in time. We find that such a scenario indeed exists: Swift J1834.9–0846's nebula can be explained as being rotationally powered, as all other known PWNe are, if it is currently being compressed by the environment. The latter introduces several effects, the most important of which is the appearance of adiabatic heating, being increasingly dominant over the escape of particles as reverberation goes by. The need of reverberation naturally explains why this is the only magnetar nebula detected and provides estimates for Swift 1834.9–0846's age.

The first 1.1 mm continuum survey toward the Small Magellanic Cloud (SMC) was performed using the AzTEC instrument installed on the ASTE 10 m telescope. This survey covered 4.5 deg² of the SMC with 1σ noise levels of 5–12 mJy beam⁻¹, and 44 extended objects were identified. The 1.1 mm extended emission has good spatial correlation with Herschel 160 μm, indicating that the origin of the 1.1 mm extended emission is thermal emission from a cold dust component. We estimated physical properties using the 1.1 mm and filtered Herschel data (100, 160, 250, 350, and 500 μm). The 1.1 mm objects show dust temperatures of 17–45 K and gas masses of 4 × 10³–3 × 10⁵ M_⊙, assuming single-temperature thermal emission from the cold dust with an emissivity index, β, of 1.2 and a gas-to-dust ratio of 1000. These physical properties are very similar to those of giant molecular clouds (GMCs) in our galaxy and the Large Magellanic Cloud. The 1.1 mm objects also displayed good spatial correlation with the Spitzer 24 μm and CO emission, suggesting that the 1.1 mm objects trace the dense gas regions as sites of massive star formation. The dust temperature of the 1.1 mm objects also demonstrated good correlation with the 24 μm flux connected to massive star formation. This supports the hypothesis that the heating source of the cold dust is mainly local star-formation activity in the 1.1 mm objects. The classification of the 1.1 mm objects based on the existence of star-formation activity reveals the differences in the dust temperature, gas mass, and radius, which reflects the evolution sequence of GMCs.

We analyze the relationship between star formation (SF), substructure, and supercluster environment in a sample of 107 nearby galaxy clusters using data from the Sloan Digital Sky Survey. Previous works have investigated the relationships between SF and cluster substructure, and cluster substructure and supercluster environment, but definitive conclusions relating all three of these variables has remained elusive. We find an inverse relationship between cluster SF fraction (f_SF) and supercluster environment density, calculated using the Galaxy luminosity density field at a smoothing length of 8 h⁻¹ Mpc (D8). The slope of f_SF versus D8 is −0.008 ± 0.002. The f_SF of clusters located in low-density large-scale environments, 0.244 ± 0.011, is higher than for clusters located in high-density supercluster cores, 0.202 ± 0.014. We also divide superclusters, according to their morphology, into filament- and spider-type systems. The inverse relationship between cluster f_SF and large-scale density is dominated by filament- rather than spider-type superclusters. In high-density cores of superclusters, we find a higher f_SF in spider-type superclusters, 0.229 ± 0.016, than in filament-type superclusters, 0.166 ± 0.019. Using principal component analysis, we confirm these results and the direct correlation between cluster substructure and SF. These results indicate that cluster SF is affected by both the dynamical age of the cluster (younger systems exhibit higher amounts of SF); the large-scale density of the supercluster environment (high-density core regions exhibit lower amounts of SF); and supercluster morphology (spider-type superclusters exhibit higher amounts of SF at high densities).

Radio observations suggest that 3C 75, located in the dumbbell shaped galaxy NGC 1128 at the center of Abell 400, hosts two colliding jets. Motivated by this source, we perform three-dimensional hydrodynamical simulations using a modified version of the GPU-accelerated Adaptive-MEsh-Refinement hydrodynamical parallel code (GAMER) to study colliding extragalactic jets. We find that colliding jets can be cast into two categories: (1) bouncing jets, in which case the jets bounce off each other keeping their identities, and (2) merging jets, when only one jet emerges from the collision. Under some conditions the interaction causes the jets to break up into oscillating filaments of opposite helicity, with consequences for their downstream stability. When one jet is significantly faster than the other and the impact parameter is small, the jets merge; the faster jet takes over the slower one. In the case of merging jets, the oscillations of the filaments, in projection, may show a feature that resembles a double helix, similar to the radio image of 3C 75. Thus we interpret the morphology of 3C 75 as a consequence of the collision of two jets with distinctly different speeds at a small impact parameter, with the faster jet breaking up into two oscillating filaments.

We present the light curves of the hydrogen-poor superluminous supernovae (SLSNe I) PTF 12dam and iPTF 13dcc, discovered by the (intermediate) Palomar Transient Factory. Both show excess emission at early times and a slowly declining light curve at late times. The early bump in PTF 12dam is very similar in duration (∼10 days) and brightness relative to the main peak (2–3 mag fainter) compared to that observed in other SLSNe I. In contrast, the long-duration (>30 days) early excess emission in iPTF 13dcc, whose brightness competes with that of the main peak, appears to be of a different nature. We construct bolometric light curves for both targets, and fit a variety of light-curve models to both the early bump and main peak in an attempt to understand the nature of these explosions. Even though the slope of the late-time decline in the light curves of both SLSNe is suggestively close to that expected from the radioactive decay of ⁵⁶Ni and ⁵⁶Co, the amount of nickel required to power the full light curves is too large considering the estimated ejecta mass. The magnetar model including an increasing escape fraction provides a reasonable description of the PTF 12dam observations. However, neither the basic nor the double-peaked magnetar model is capable of reproducing the light curve of iPTF 13dcc. A model combining a shock breakout in an extended envelope with late-time magnetar energy injection provides a reasonable fit to the iPTF 13dcc observations. Finally, we find that the light curves of both PTF 12dam and iPTF 13dcc can be adequately fit with the model involving interaction with the circumstellar medium.

Transitional protostellar disks have inner cavities that are heavily depleted in dust and gas, yet most of them show signs of ongoing accretion, often at rates comparable to full disks. We show that recent constraints on the gas surface density in a few well-studied disk cavities suggest that the accretion speed is at least transsonic. We propose that this is the natural result of accretion driven by magnetized winds. Typical physical conditions of the gas inside these cavities are estimated for plausible X-ray and FUV radiation fields. The gas near the midplane is molecular and predominantly neutral, with a dimensionless ambipolar parameter in the right general range for wind solutions of the type developed by Königl, Wardle, and others. That is to say, the density of ions and electrons is sufficient for moderately good coupling to the magnetic field, but it is not so good that the magnetic flux needs to be dragged inward by the accreting neutrals.

We study a model of rapidly cooling shocked stellar winds in young massive clusters and estimate the circumstances under which secondary star formation, out of the reinserted winds from a first stellar generation (1G), is possible. We have used two implementations of the model: a highly idealized, computationally inexpensive, spherically symmetric semi-analytic model, and a complex, three-dimensional radiation-hydrodynamic, simulation; they are in a good mutual agreement. The results confirm our previous findings that, in a cluster with 1G mass 10⁷M_⊙ and half-mass–radius 2.38 pc, the shocked stellar winds become thermally unstable, collapse into dense gaseous structures that partially accumulate inside the cluster, self-shield against ionizing stellar radiation, and form the second generation (2G) of stars. We have used the semi-analytic model to explore a subset of the parameter space covering a wide range of the observationally poorly constrained parameters: the heating efficiency, η_he, and the mass loading, η_ml. The results show that the fraction of the 1G stellar winds accumulating inside the cluster can be larger than 50% if η_he ≲ 10%, which is suggested by the observations. Furthermore, for low η_he, the model provides a self-consistent mechanism predicting 2G stars forming only in the central zones of the cluster. Finally, we have calculated the accumulated warm gas emission in the H30α recombination line, analyzed its velocity profile, and estimated its intensity for super star clusters in interacting galaxies NGC4038/9 (Antennae) showing that the warm gas should be detectable with ALMA.

A large sample of over 38,000 chromospherically active candidate solar-like stars and cooler dwarfs from the RAVE survey is addressed in this paper. An improved activity identification with respect to the previous study was introduced to build a catalog of field stars in the solar neighborhood with an excess emission flux in the calcium infrared triplet wavelength region. The central result of this work is the calibration of the age–activity relation for main-sequence dwarfs in a range from a few $10\ \mathrm{Myr}$ up to a few Gyr. It enabled an order of magnitude age estimation of the entire active sample. Almost 15,000 stars are shown to be younger than $1\ \mathrm{Gyr}$ and ∼2000 younger than $100\ \mathrm{Myr}$. The young age of the most active stars is confirmed by their position off the main sequence in the J − K versus ${N}_{{UV}}-V$ diagram showing strong ultraviolet excess, mid-infrared excess in the J − K versus ${W}_{1}-{W}_{2}$ diagram, and very cool temperatures ($J-K\gt 0.7$). They overlap with the reference pre-main-sequence RAVE stars often displaying X-ray emission. The activity level increasing with the color reveals their different nature from the solar-like stars and probably represents an underlying dynamo-generating magnetic fields in cool stars. Of the RAVE objects from DR5, 50% are found in the TGAS catalog and supplemented with accurate parallaxes and proper motions by Gaia. This makes the database of a large number of young stars in a combination with RAVE's radial velocities directly useful as a tracer of the very recent large-scale star formation history in the solar neighborhood. The data are available online in the Vizier database.

The study of solar active longitudes has generated great interest in recent years. In this work we have used a unique, continuous sunspot data series obtained from the Kodaikanal observatory and revisited the problem. An analysis of the data shows a persistent presence of active longitudes during the whole 90 years of data. We compared two well-studied analysis methods and presented their results. The separation between the two most active longitudes is found be roughly 180° for the majority of time. Additionally, we also find a comparatively weaker presence of separations at 90° and 270°. The migration pattern of these active longitudes as revealed by our data is found to be consistent with the solar differential rotation curve. We also study the periodicities in the active longitudes and found two dominant periods of ≈1.3 and ≈2.2 years. These periods, also found in other solar proxies, indicate their relation with the global solar dynamo mechanism.

Here we use the PFSS model and photospheric data from Wilcox Solar Observatory, SOHO/MDI, SDO/HMI, and SOLIS to compare the coronal field with heliospheric magnetic field measured at 1 au, compiled in the NASA/NSSDC OMNI 2 data set. We calculate their mutual polarity match and the power of the radial decay, p, of the radial field using different source surface distances and different number of harmonic multipoles. We find the average polarity match of 82% for the declining phase, 78%–79% for maxima, 76%–78% for the ascending phase, and 74%–76% for minima. On an average, the source surface of 3.25 R_S gives the best polarity match. We also find strong evidence for solar cycle variation of the optimal source surface distance, with highest values (3.3 R_S) during solar minima and lowest values (2.6 R_S–2.7 R_S) during the other three solar cycle phases. Raising the number of harmonic terms beyond 2 rarely improves the polarity match, showing that the structure of the HMF at 1 au is most of the time rather simple. All four data sets yield fairly similar polarity matches. Thus, polarity comparison is not affected by photospheric field scaling, unlike comparisons of the field intensity.

We present the Open Supernova Catalog, an online collection of observations and metadata for presently 36,000+ supernovae and related candidates. The catalog is freely available on the web (https://sne.space), with its main interface having been designed to be a user-friendly, rapidly searchable table accessible on desktop and mobile devices. In addition to the primary catalog table containing supernova metadata, an individual page is generated for each supernova, which displays its available metadata, light curves, and spectra spanning X-ray to radio frequencies. The data presented in the catalog is automatically rebuilt on a daily basis and is constructed by parsing several dozen sources, including the data presented in the supernova literature and from secondary sources such as other web-based catalogs. Individual supernova data is stored in the hierarchical, human- and machine-readable JSON format, with the entirety of each supernova's data being contained within a single JSON file bearing its name. The setup we present here, which is based on open-source software maintained via git repositories hosted on github, enables anyone to download the entirety of the supernova data set to their home computer in minutes, and to make contributions of their own data back to the catalog via git. As the supernova data set continues to grow, especially in the upcoming era of all-sky synoptic telescopes, which will increase the total number of events by orders of magnitude, we hope that the catalog we have designed will be a valuable tool for the community to analyze both historical and contemporary supernovae.

We conduct a multiwavelength continuum variability study of the Seyfert 1 galaxy NGC 5548 to investigate the temperature structure of its accretion disk. The 19 overlapping continuum light curves ($1158\,\mathring{\rm A}$ to $9157\,\mathring{\rm A}$) combine simultaneous Hubble Space Telescope, Swift, and ground-based observations over a 180 day period from 2014 January to July. Light-curve variability is interpreted as the reverberation response of the accretion disk to irradiation by a central time-varying point source. Our model yields the disk inclination $i=36^\circ \pm 10^\circ$, temperature ${T}_{1}=(44\pm 6)\times {10}^{3}$ K at 1 light day from the black hole, and a temperature–radius slope ($T\propto {r}^{-\alpha }$) of $\alpha =0.99\pm 0.03$. We also infer the driving light curve and find that it correlates poorly with both the hard and soft X-ray light curves, suggesting that the X-rays alone may not drive the ultraviolet and optical variability over the observing period. We also decompose the light curves into bright, faint, and mean accretion-disk spectra. These spectra lie below that expected for a standard blackbody accretion disk accreting at $L/{L}_{\mathrm{Edd}}=0.1$.

We report on six new Chandra observations of the Geminga pulsar wind nebula (PWN). The PWN consists of three distinct elongated structures—two $\approx 0.2{d}_{250}$ pc long lateral tails and a segmented axial tail of $\approx 0.05{d}_{250}$ pc length, where ${d}_{250}=d/(250\,\mathrm{pc})$. The photon indices of the power-law spectra of the lateral tails, ${\rm{\Gamma }}\approx 1$, are significantly harder than those of the pulsar (${\rm{\Gamma }}\approx 1.5$) and the axial tail (${\rm{\Gamma }}\approx 1.6$). There is no significant diffuse X-ray emission between the lateral tails—the ratio of the X-ray surface brightness between the south tail and this sky area is at least 12. The lateral tails apparently connect directly to the pulsar and show indications of moving footpoints. The axial tail comprises time-variable emission blobs. However, there is no evidence for constant or decelerated outward motion of these blobs. Different physical models are consistent with the observed morphology and spectra of the Geminga PWN. In one scenario, the lateral tails could represent an azimuthally asymmetric shell whose hard emission is caused by the Fermi acceleration mechanism of colliding winds. In another scenario, the lateral tails could be luminous, bent polar outflows, while the blobs in the axial tail could represent a crushed torus. In a resemblance to planetary magnetotails, the blobs of the axial tail might also represent short-lived plasmoids, which are formed by magnetic field reconnection in the relativistic plasma of the pulsar wind tail.

The deuterium-to-hydrogen ratio (D/H) in water found in the coma of Jupiter family comet (JFC) 67P/Churyumov–Gerasimenko was reported to be (5.3 ± 0.7) × 10⁻⁴, the highest among comets and three times the value for other JFCs with an ocean-like ratio. This discrepancy suggests the diverse origins of JFCs and clouds the issue of the origin of Earth's oceanic water. Here we demonstrate that Eley–Rideal reactions between accelerated water ions and deuterated cometary surface analogs can lead to instantaneous deuterium enrichment in water scattered from the surface. The reaction proceeds with H₂O⁺ abstracting adsorbed D atoms, forming an excited H₂DO* state, which dissociates subsequently to produce energetic HDO. Hydronium ions are also produced readily by the abstraction of H atoms, consistent with H₃O⁺ detection and abundance in various comets. Experiments with water isotopologs and kinematic analysis on deuterated platinum surfaces confirmed the dynamic abstraction mechanism. The instantaneous fractionation process is independent of the surface temperature and may operate on the surface of cometary nuclei or dust grains, composed of deuterium-rich silicates and carbonaceous chondrites. The requisite energetic water ions have been detected in the coma of 67P in two populations. This dynamic fractionation process may temporarily increase the water D/H ratio, especially as the comet gets closer to the Sun. The magnitude of the effect depends on the water ion energy-flux and the deuterium content of the exposed cometary surfaces.

We have compiled the most comprehensive burst sample from magnetar 4U 0142+61, comprising 27 bursts from its three burst-active episodes in 2011, 2012 and the latest one in 2015 observed with Swift/Burst Alert Telescope and Fermi/Gamma-ray Burst Monitor. Bursts from 4U 0142+61 morphologically resemble typical short bursts from other magnetars. However, 4U 0142+61 bursts are less energetic compared to the bulk of magnetar bursts. We uncovered an extended tail emission following a burst on 2015 February 28, with a thermal nature, cooling over a timescale of several minutes. During this tail emission, we also uncovered pulse peak phase aligned X-ray bursts, which could originate from the same underlying mechanism as that of the extended burst tail, or an associated and spatially coincident but different mechanism.

Following up on previous studies, we complete here a full analysis of the void size distributions of the Cosmic Void Catalog based on three different simulation and mock catalogs: dark matter (DM), haloes, and galaxies. Based on this analysis, we attempt to answer two questions: Is a three-parameter log-normal distribution a good candidate to satisfy the void size distributions obtained from different types of environments? Is there a direct relation between the shape parameters of the void size distribution and the environmental effects? In an attempt to answer these questions, we find here that all void size distributions of these data samples satisfy the three-parameter log-normal distribution whether the environment is dominated by DM, haloes, or galaxies. In addition, the shape parameters of the three-parameter log-normal void size distribution seem highly affected by environment, particularly existing substructures. Therefore, we show two quantitative relations given by linear equations between the skewness and the maximum tree depth, and between the variance of the void size distribution and the maximum tree depth, directly from the simulated data. In addition to this, we find that the percentage of voids with nonzero central density in the data sets has a critical importance. If the number of voids with nonzero central density reaches ≥3.84% in a simulation/mock sample, then a second population is observed in the void size distributions. This second population emerges as a second peak in the log-normal void size distribution at larger radius.

We present and analyze the possibility of using optical u-band luminosities to estimate star-formation rates (SFRs) of galaxies based on the data from the South Galactic Cap u band Sky Survey (SCUSS), which provides a deep u-band photometric survey covering about 5000 deg² of the South Galactic Cap. Based on two samples of normal star-forming galaxies selected by the BPT diagram, we explore the correlations between u-band, Hα, and IR luminosities by combing SCUSS data with the Sloan Digital Sky Survey and Wide-field Infrared Survey Explorer (WISE). The attenuation-corrected u-band luminosities are tightly correlated with the Balmer decrement-corrected Hα luminosities with an rms scatter of ∼0.17 dex. The IR-corrected u luminosities are derived based on the correlations between the attenuation of u-band luminosities and WISE 12 (or 22) μm luminosities, and then calibrated with the Balmer-corrected Hα luminosities. The systematic residuals of these calibrations are tested against the physical properties over the ranges covered by our sample objects. We find that the best-fitting nonlinear relations are better than the linear ones and recommended to be applied in the measurement of SFRs. The systematic deviations mainly come from the pollution of old stellar population and the effect of dust extinction; therefore, a more detailed analysis is needed in future work.

Heavy ion ratio abundances in solar energetic particle (SEP) events, e.g., Fe/O, often exhibit decreases over time. Using particle instruments on the Advanced Composition Explorer, Solar and Heliospheric Observatory and Solar Terrestrial Relations Observatory spacecraft, we analyzed heavy ion data from 4 SEP events taking place between 2006 December and 2014 December. We constructed 36 different ionic pairs and studied their time evolution in each event. We quantified the temporal behavior of abundant SEP ratios by fitting the data to derive a decay time constant B. We also considered the ratio of ionic mass-to-charge for each pair, the S value given, e.g., for Fe/O by ${S}_{\mathrm{Fe}/{\rm{O}}}={(M/Q)}_{\mathrm{Fe}}/{(M/Q)}_{{\rm{O}}}$. We found that the temporal behavior of SEP ratios is ordered by the value of S: ratios with $S\gt 1$ showed decreases over time (i.e., $B\lt 0$) and those with $S\lt 1$ showed increases ($B\gt 0$). We plotted B as a function of S and observed a clear monotonic dependence: ratios with a large S decayed at a higher rate. A prominent discontinuity at S = 2.0 (corresponding to He/H) was found in three of the four events, suggesting anomalous behavior of protons. The X/H ratios often show an initial increase followed by a decrease, and decay at a slower rate. We discuss possible causes of the observed B versus S trends within current understanding of SEP propagation.

There are two distinct breaks in the cosmic ray (CR) spectrum: the so-called "knee" around 3 × 10¹⁵ eV and the so-called "ankle" around 10¹⁸ eV. Diffusive shock acceleration (DSA) at supernova remnant (SNR) shock fronts is thought to accelerate galactic CRs to energies below the knee, while an extragalactic origin is presumed for CRs with energies beyond the ankle. CRs with energies between 3 × 10¹⁵ and 10¹⁸ eV, which we dub the "shin," have an unknown origin. It has been proposed that DSA at galactic wind termination shocks, rather than at SNR shocks, may accelerate CRs to these energies. This paper uses the galactic wind model of Bustard et al. to analyze whether galactic wind termination shocks may accelerate CRs to shin energies within a reasonable acceleration time and whether such CRs can subsequently diffuse back to the Galaxy. We argue for acceleration times on the order of 100 Myr rather than a few billion years, as assumed in some previous works, and we discuss prospects for magnetic field amplification at the shock front. Ultimately, we generously assume that the magnetic field is amplified to equipartition. This formalism allows us to obtain analytic formulae, applicable to any wind model, for CR acceleration. Even with generous assumptions, we find that very high wind velocities are required to set up the necessary conditions for acceleration beyond 10¹⁷ eV. We also estimate the luminosities of CRs accelerated by outflow termination shocks, including estimates for the Milky Way wind.

GRB 140903A, a short duration γ-ray burst (SGRB) detected by Swift, is characterized by its long-lasting radio emission among SGRBs. In addition to the $\sim {10}^{6}$ s radio afterglow emission, the afterglow of GRB 140903A displays a plateau from 10³ s to $7\times {10}^{3}\,{\rm{s}}$ in the X-rays. In this work, we attribute the X-ray plateau to the energy injection into the decelerating blast wave and then model the later radio/optical/X-ray afterglow emission within the standard fireball afterglow model. The afterglow emission has been well reproduced with reasonable physical parameters, including a jet half-opening angle of ∼0.05.

We systematically investigate the near- to far-infrared (FIR) photometric properties of a nearly complete sample of local active galactic nuclei (AGNs) detected in the Swift/Burst Alert Telescope (BAT) all-sky ultra-hard X-ray (14–195 keV) survey. Out of 606 non-blazar AGNs in the Swift/BAT 70 month catalog at high galactic latitudes of $| b| \gt 10^\circ$, we obtain IR photometric data of 604 objects by cross-matching the AGN positions with catalogs from the WISE, AKARI, IRAS, and Herschel infrared observatories. We find a good correlation between the ultra-hard X-ray and mid-IR luminosities over five orders of magnitude ($41\lt \mathrm{log}{L}_{14\mbox{--}195}\lt 46$). Informed by previous measurements of the intrinsic spectral energy distribution of AGNs, we find FIR pure-AGN candidates whose FIR emission is thought to be AGN-dominated with low star-formation activity. We demonstrate that the dust covering factor decreases with the bolometric AGN luminosity, confirming the luminosity-dependent unified scheme. We also show that the completeness of the WISE color–color cut in selecting Swift/BAT AGNs increases strongly with 14–195 keV luminosity.

In a search of proper motion catalogs for common proper motion stars in the field of the Kepler spacecraft I identified 93 likely binary systems. A comparison of their rotation periods is a test of the gyrochronology concept. To find their periods I calculated the autocorrelation function (ACF) of the Kepler mission photometry for each star. In most systems for which good periods can be found, the cooler star has a longer period than the hotter component, in general agreement with models. However, there is a wide range in the gradients of lines connecting binary pairs in a period–color diagram. Furthermore, near the solar color, only a few stars have longer periods than the Sun, suggesting that they, and their cooler companions, are not much older than the Sun. In addition, there is an apparent gap at intermediate periods in the period distribution of the late K and early M stars. Either star formation in this direction has been variable, or stars evolve in period at a non-uniform rate, or some stars evolve more rapidly than others at the same mass. Finally, using the ACF as a measure of the activity level, I found that while the F, G, and early K stars become less active as their periods increase, there is no correlation between period and activity for the mid K to early M stars.

We investigate the correlation of HCN 1-0 with gas mass in the central 300 pc of the Galaxy. We find that on the ∼10 pc size scale of individual cloud cores, HCN 1-0 is well correlated with dense gas mass when plotted as a log–log relationship. There is ∼0.75 dex of scatter in this relationship from clouds like Sgr B2, which has an integrated HCN 1-0 intensity of a cloud less than half its mass, and others that have HCN 1-0 enhanced by a factor of 2–3 relative to clouds of comparable mass. We identify the two primary sources of scatter to be self-absorption and variations in HCN abundance. We also find that the extended HCN 1-0 emission is more intense per unit mass than in individual cloud cores. In fact the majority (80%) of HCN 1-0 emission comes from extended gas with column densities below 7 × 10²² cm⁻², accounting for 68% of the total mass. We find variations in the brightness of HCN 1-0 would only yield a ∼10% error in the dense gas mass inferred from this line in the Galactic center. However, the observed order of magnitude HCN abundance variations, and the systematic nature of these variations, warn of potential biases in the use of HCN as dense gas mass tracer in more extreme environments such as an active galactic nucleus and shock-dominated regions. We also investigate other 3 mm tracers, finding that HNCO is better correlated with mass than HCN, and might be a better tracer of cloud mass in this environment.

We introduce a new generation of PARSEC–COLIBRI stellar isochrones that includes a detailed treatment of the thermally pulsing asymptotic giant branch (TP-AGB) phase, covering a wide range of initial metallicities (0.0001 < Z_i < 0.06). Compared to previous releases, the main novelties and improvements are use of new TP-AGB tracks and related atmosphere models and spectra for M and C-type stars; inclusion of the surface H+He+CNO abundances in the isochrone tables, accounting for the effects of diffusion, dredge-up episodes and hot-bottom burning; inclusion of complete thermal pulse cycles, with a complete description of the in-cycle changes in the stellar parameters; new pulsation models to describe the long-period variability in the fundamental and first-overtone modes; and new dust models that follow the growth of the grains during the AGB evolution, in combination with radiative transfer calculations for the reprocessing of the photospheric emission. Overall, these improvements are expected to lead to a more consistent and detailed description of properties of TP-AGB stars expected in resolved stellar populations, especially in regard to their mean photometric properties from optical to mid-infrared wavelengths. We illustrate the expected numbers of TP-AGB stars of different types in stellar populations covering a wide range of ages and initial metallicities, providing further details on the "C-star island" that appears at intermediate values of age and metallicity, and about the AGB-boosting effect that occurs at ages close to 1.6-Gyr for populations of all metallicities. The isochrones are available through a new dedicated web server.

Two galaxies that lie deep within the Local Void provide a test of the expectation that voids expand. The modest (${M}_{B}\sim -14$) HI bearing dwarf galaxies ALFAZOAJ1952+1428 and KK246 have been imaged with Hubble Space Telescope in order to study the stellar populations and determine distances from the luminosities of stars at the tip of the red giant branch. The mixed age systems have respective distances of 8.39 Mpc and 6.95 Mpc and inferred line-of-sight peculiar velocities of −114 km s⁻¹ and −66 km s⁻¹ toward us and away from the void center. These motions compound on the Milky Way motion of ∼230 km s⁻¹ away from the void. The orbits of the two galaxies are reasonably constrained by a numerical action model encompassing an extensive region that embraces the Local Void. It is unambiguously confirmed that these two void galaxies are moving away from the void center at several hundred km s⁻¹.

New detections of HNC have been made toward 11 planetary nebulae (PNe), including K4-47, K3-58, K3-17, M3-28, and M4-14. These sources, which represent a wide range of ages and morphologies, had previously been observed in HCN by Schmidt & Ziurys. Measurements of the $J=1\to 0$ and $J=3\to 2$ transitions of HNC near 90 and 271 GHz were conducted using the new 12 m and the Sub-Millimeter Telescope of the Arizona Radio Observatory. HCN and HNC were also identified via their $J=1\to 0$ lines toward eight positions across the Helix Nebula (NGC 7293). Column densities for HNC, determined from radiative transfer modeling, were N_tot(HNC) ∼ (0.06–4.0) × 10¹³ cm⁻², corresponding to fractional abundances with respect to H₂ of f  ∼ (0.02–1.4) × 10⁻⁷. The HCN and HNC column densities across the Helix were found to be ${N}_{\mathrm{tot}}(\mathrm{HCN})$ ∼ (0.2–2.4) × 10¹² cm⁻² and ${N}_{\mathrm{tot}}(\mathrm{HNC})$ ∼ (0.07–1.6) × 10¹² cm⁻², with fractional abundances of (0.2–3.2) × 10⁻⁷ and (0.09–2.2) × 10⁻⁷. The [HCN]/[HNC] ratio varied between ∼1–8 for all PNe, with [HCN]/[HNC] ∼1–4 across the Helix. These values are greatly reduced from what has been found in asymptotic giant branch stars, where the ratio is typically >100. Both the abundance of HNC and the [HCN]/[HNC] ratio do not appear to vary significantly with nebular age across a time span of ∼10,000 years, in contrast to predictions of chemical models. The increase in HNC appears to arise in the proto-planetary stage, but becomes "frozen" once the PN phase is reached.

We select a sample of galaxies from the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7) where galaxies are classified, through visual inspection, as hosting strong bars, weak bars, or as unbarred galaxies, and make use of H i mass and kinematic information from the Arecibo Legacy Fast ALFA survey catalog, to study the stellar, atomic gas, and dark matter content of barred disk galaxies. We find, in agreement with previous studies, that the bar fraction increases with increasing stellar mass. A similar trend is found with total baryonic mass, although the dependence is not as strong as with stellar mass, due to the contribution of gas. The bar fraction shows a decrease with increasing gas mass fraction. This anticorrelation between the likelihood of a galaxy hosting a bar with the gas richness of the galaxy results from the inhibiting effect the gas has in the formation of bars. We also find that for massive galaxies with stellar masses larger than 10¹⁰M_⊙, at fixed stellar mass, the bar fraction decreases with increasing global halo mass (i.e., halo mass measured up to a radius of the order of the H i disk extent).

We obtain estimates of stellar atmospheric parameters for a previously published sample of 1777 relatively bright ($9\lt B\lt 14$) metal-poor candidates from the Hamburg/ESO Survey. The original Frebel et al. analysis of these stars was able to derive estimates of [Fe/H] and [C/Fe] only for a subset of the sample, due to limitations in the methodology then available. A new spectroscopic analysis pipeline has been used to obtain estimates of ${T}_{\mathrm{eff}}$, $\mathrm{log}\,g$, [Fe/H], and [C/Fe] for almost the entire data set. This sample is very local—about 90% of the stars are located within 0.5 kpc of the Sun. We consider the chemodynamical properties of these stars in concert with a similarly local sample of stars from a recent analysis of the Bidelman and MacConnell "weak metal" candidates by Beers et al. We use this combined sample to identify possible members of the halo stream of stars suggested by Helmi et al. and Chiba & Beers, as well as stars that may be associated with stripped debris from the putative parent dwarf of the globular cluster Omega Centauri, suggested to exist by previous authors. We identify a clear increase in the cumulative frequency of carbon-enhanced metal-poor (CEMP) stars with declining metallicity, as well as an increase in the fraction of CEMP stars with distance from the Galactic plane, consistent with previous results. We also identify a relatively large number of CEMP stars with kinematics consistent with the metal-weak thick-disk population, with possible implications for its origin.

We present the Fermi Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) observations of the LIGO binary black hole merger event GW151226 and candidate LVT151012. At the time of the LIGO triggers on LVT151012 and GW151226, GBM was observing 68% and 83% of the localization regions, and LAT was observing 47% and 32%, respectively. No candidate electromagnetic counterparts were detected by either the GBM or LAT. We present a detailed analysis of the GBM and LAT data over a range of timescales from seconds to years, using automated pipelines and new techniques for characterizing the flux upper bounds across large areas of the sky. Due to the partial GBM and LAT coverage of the large LIGO localization regions at the trigger times for both events, differences in source distances and masses, as well as the uncertain degree to which emission from these sources could be beamed, these non-detections cannot be used to constrain the variety of theoretical models recently applied to explain the candidate GBM counterpart to GW150914.

NASA's K2 mission is observing tens of thousands of stars along the ecliptic, providing data suitable for large-scale asteroseismic analyses to inform galactic archaeology studies. Its first campaign covered a field near the north Galactic cap, a region never covered before by large asteroseismic-ensemble investigations, and was therefore of particular interest for exploring this part of our Galaxy. Here we report the asteroseismic analysis of all stars selected by the K2 Galactic Archaeology Program during the mission's "north Galactic cap" campaign 1. Our consolidated analysis uses six independent methods to measure the global seismic properties, in particular the large frequency separation and the frequency of maximum power. From the full target sample of 8630 stars we find about 1200 oscillating red giants, a number comparable with estimates from galactic synthesis modeling. Thus, as a valuable by-product we find roughly 7500 stars to be dwarfs, which provide a sample well suited for galactic exoplanet occurrence studies because they originate from our simple and easily reproducible selection function. In addition, to facilitate the full potential of the data set for galactic archaeology, we assess the detection completeness of our sample of oscillating red giants. We find that the sample is at least nearly complete for stars with $40\,\lesssim$${\nu }_{\max }$/μHz $\lesssim \,270$ and ${\nu }_{\max ,\mathrm{detect}}\lt 2.6\times {10}^{6}\cdot {2}^{-{\text{Kp}}}\,$μHz. There is a detection bias against helium core burning stars with ${\nu }_{\max }$$\sim \,30\,$μHz, affecting the number of measurements of ${\rm{\Delta }}\nu$ and possibly also ${\nu }_{\max }$. Although we can detect oscillations down to ${\text{Kp}}\,=\,15$, our campaign 1 sample lacks enough faint giants to assess the detection completeness for stars fainter than ${\text{Kp}}\,\sim \,14.5$.

Observations of the Sun suggest that solar activities systematically create north–south hemispheric asymmetries. For instance, the hemisphere in which sunspot activity is more active tends to switch after the early half of each solar cycle. Svalgaard & Kamide recently pointed out that the time gaps of polar field reversal between the northern and southern hemispheres are simply consequences of the asymmetry of sunspot activity. However, the mechanism underlying the asymmetric feature in solar cycle activity is not yet well understood. In this paper, in order to explain the cause of the asymmetry from the theoretical point of view, we investigate the relationship between the dipole- and quadrupole-type components of the magnetic field in the solar cycle using the mean-field theory based on the flux transport dynamo model. As a result, we found that there are two different attractors of the solar cycle, in which either the north or the south polar field is first reversed, and that the flux transport dynamo model explains well the phase-asymmetry of sunspot activity and the polar field reversal without any ad hoc source of asymmetry.

Two of the most widely observed and striking features of the Sun's magnetic field are coronal loops, which are smooth and laminar, and prominences or filaments, which are strongly sheared. Loops are puzzling because they show little evidence of tangling or braiding, at least on the quiet Sun, despite the chaotic nature of the solar surface convection. Prominences are mysterious because the origin of their underlying magnetic structure—filament channels—is poorly understood at best. These two types of features would seem to be quite unrelated and wholly distinct. We argue that, on the contrary, they are inextricably linked and result from a single process: the injection of magnetic helicity into the corona by photospheric motions and the subsequent evolution of this helicity by coronal reconnection. In this paper, we present numerical simulations of the response of a Parker (1972) corona to photospheric driving motions that have varying degrees of helicity preference. We obtain four main conclusions: (1) in agreement with the helicity condensation model of Antiochos (2013), the inverse cascade of helicity by magnetic reconnection in the corona results in the formation of filament channels localized about polarity inversion lines; (2) this same process removes most complex fine structure from the rest of the corona, resulting in smooth and laminar coronal loops; (3) the amount of remnant tangling in coronal loops is inversely dependent on the net helicity injected by the driving motions; and (4) the structure of the solar corona depends only on the helicity preference of the driving motions and not on their detailed time dependence. We discuss the implications of our results for high-resolution observations of the corona.

We use 28 measurements of the Hubble parameter, H(z), at intermediate redshifts $0.07\leqslant z\leqslant 2.3$ to determine the present-day Hubble constant H₀ in four cosmological models. We measure ${H}_{0}={68.3}_{-2.6}^{+2.7},{68.4}_{-3.3}^{+2.9},{65.0}_{-6.6}^{+6.5}$, and ${67.9}_{-2.4}^{+2.4}\,\mathrm{km}\ {{\rm{s}}}^{-1}$ Mpc⁻¹ (1σ errors) in the ΛCDM (spatially flat and non-flat), ωCDM, and ϕCDM models, respectively. These measured H₀ values are more consistent with the lower values determined from recent data on the cosmic microwave background and baryon acoustic oscillations, as well as with the value found from a median statistical analysis of Huchra's compilation of H₀ measurements, but include the higher local measurements of H₀ within the 2σ confidence limits.

Building on previous work, we have expanded our catalog of evolutionary models for stars with variable composition; here we present models for stars of mass 0.5–1.2 M_⊙, at scaled metallicities of 0.1–1.5 Z_⊙, and specific C/Fe, Mg/Fe, and Ne/Fe values of 0.58–1.72 C/Fe_⊙, 0.54–1.84 Mg/Fe_⊙, and 0.5–2.0 Ne/Fe_⊙, respectively. We include a spread in abundance values for carbon and magnesium based on observations of their variability in nearby stars; we choose an arbitrary spread in neon abundance values commensurate with the range seen in other low Z elements due to the difficult nature of obtaining precise measurements of neon abundances in stars. As indicated by the results of Truitt et al., it is essential that we understand how differences in individual elemental abundances, and not just the total scaled metallicity, can measurably impact a star's evolutionary lifetime and other physical characteristics. In that work, we found that oxygen abundances significantly impacted the stellar evolution; carbon, magnesium, and neon are potentially important elements to individually consider due to their relatively high (but also variable) abundances in stars. We present 528 new stellar main-sequence models, and we calculate the time-dependent evolution of the associated habitable zone boundaries for each based on mass, temperature, and luminosity. We also reintroduce the 2 Gyr "Continuously Habitable Zone" (CHZ₂) as a useful tool to help gauge the habitability potential for a given planetary system.

We investigate the physical conditions of ionized gas in high-z star-forming galaxies using diagnostic diagrams based on the rest-frame optical emission lines. The sample consists of 701 galaxies with an Hα detection at $1.4\lesssim z\lesssim 1.7$, from the Fiber Multi-Object Spectrograph (FMOS)-COSMOS survey, that represent the normal star-forming population over the stellar mass range ${10}^{9.6}\lesssim {M}_{* }/{M}_{\odot }\lesssim {10}^{11.6}$, with those at ${M}_{* }\gt {10}^{11}\,{M}_{\odot }$ being well sampled. We confirm an offset of the average location of star-forming galaxies in the Baldwin–Phillips–Terlevich (BPT) diagram (${\rm{[O}}\,{\rm{III}}]/{\rm{H}}\beta$ versus ${\rm{[N}}\,{\rm{II}}]/{\rm{H}}\alpha$), primarily toward higher ${\rm{[O}}\,{\rm{III}}]/{\rm{H}}\beta$, compared with local galaxies. Based on the [S ii] ratio, we measure an electron density (${n}_{{\rm{e}}}={220}_{-130}^{+170}\,{\mathrm{cm}}^{-3}$), which is higher than that of local galaxies. Based on comparisons to theoretical models, we argue that changes in emission-line ratios, including the offset in the BPT diagram, are caused by a higher ionization parameter both at fixed stellar mass and at fixed metallicity, with additional contributions from a higher gas density and possibly a hardening of the ionizing radiation field. Ionization due to active galactic nuclei is ruled out as assessed with Chandra. As a consequence, we revisit the mass–metallicity relation using ${\rm{[N}}{\rm{II}}]/{\rm{H}}\alpha$ and a new calibration including ${\rm{[N}}\,{\rm{II}}]/{\rm{[S}}\,{\rm{II}}]$ as recently introduced by Dopita et al. Consistent with our previous results, the most massive galaxies (${M}_{* }\gtrsim {10}^{11}\,{M}_{\odot }$) are fully enriched, while those at lower masses have metallicities lower than local galaxies. Finally, we demonstrate that the stellar masses, metallicities, and star formation rates of the FMOS sample are well fit with a physically motivated model for the chemical evolution of star-forming galaxies.

Magnetized plasma jets are generally modeled as magnetic flux tubes filled with flowing plasma governed by magnetohydrodynamics (MHD). We outline here a more fundamental approach based on flux tubes of canonical vorticity, where canonical vorticity is defined as the circulation of the species' canonical momentum. This approach extends the concept of magnetic flux tube evolution to include the effects of finite particle momentum and enables visualization of the topology of plasma jets in regimes beyond MHD. A flared, current-carrying magnetic flux tube in an ion-electron plasma with finite ion momentum is thus equivalent to either a pair of electron and ion flow flux tubes, a pair of electron and ion canonical momentum flux tubes, or a pair of electron and ion canonical vorticity flux tubes. We examine the morphology of all these flux tubes for increasing electrical currents, different radial current profiles, different electron Mach numbers, and a fixed, flared, axisymmetric magnetic geometry. Calculations of gauge-invariant relative canonical helicities track the evolution of magnetic, cross, and kinetic helicities in the system, and show that ion flow fields can unwind to compensate for an increasing magnetic twist. The results demonstrate that including a species' finite momentum can result in a very long collimated canonical vorticity flux tube even if the magnetic flux tube is flared. With finite momentum, particle density gradients must be normal to canonical vorticities, not to magnetic fields, so observations of collimated astrophysical jets could be images of canonical vorticity flux tubes instead of magnetic flux tubes.

Aiming at testing the validity of our magnesium atomic model and investigating the effects of non-local thermodynamical equilibrium (NLTE) on the formation of the H-band neutral magnesium lines, we derive the differential Mg abundances from selected transitions for 13 stars either adopting or relaxing the assumption of local thermodynamical equilibrium (LTE). Our analysis is based on high-resolution and high signal-to-noise ratio H-band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and optical spectra from several instruments. The absolute differences between the Mg abundances derived from the two wavelength bands are always less than 0.1 dex in the NLTE analysis, while they are slightly larger for the LTE case. This suggests that our Mg atomic model is appropriate for investigating the NLTE formation of the H-band Mg lines. The NLTE corrections for the Mg iH-band lines are sensitive to the surface gravity, becoming larger for smaller log g values, and strong lines are more susceptible to departures from LTE. For cool giants, NLTE corrections tend to be negative, and for the strong line at 15765 Å they reach −0.14 dex in our sample, and up to −0.22 dex for other APOGEE stars. Our results suggest that it is important to include NLTE corrections in determining Mg abundances from the H-band Mg i transitions, especially when strong lines are used.

We present the Chandra imaging and spectral analysis of NGC 4968, a nearby (z = 0.00986) Seyfert 2 galaxy. We discover extended (∼1 kpc) X-ray emission in the soft band (0.5–2 keV) that is neither coincident with the narrow line region nor the extended radio emission. Based on spectral modeling, it is linked to on-going star formation (∼2.6–4 M_⊙ yr⁻¹). The soft emission at circumnuclear scales (inner ∼400 pc) originates from hot gas, with kT ∼ 0.7 keV, while the most extended thermal emission is cooler (kT ∼ 0.3 keV). We refine previous measurements of the extreme Fe Kα equivalent width in this source ($\mathrm{EW}={2.5}_{-1.0}^{+2.6}\,\mathrm{keV}$), which suggests the central engine is completely embedded within Compton-thick levels of obscuration. Using physically motivated models fit to the Chandra spectrum, we derive a Compton-thick column density (N_H > 1.25 × 10²⁴ cm⁻²) and an intrinsic hard (2–10 keV) X-ray luminosity of ∼3–8 × 10⁴² erg s⁻¹ (depending on the presumed geometry of the obscurer), which is over two orders of magnitude larger than that observed. The large Fe Kα EW suggests a spherical covering geometry, which could be confirmed with X-ray measurements above 10 keV. NGC 4968 is similar to other active galaxies that exhibit extreme Fe Kα EWs (i.e., >2 keV) in that they also contain on-going star formation. This work supports the idea that gas associated with nuclear star formation may increase the covering factor of the enshrouding gas and play a role in obscuring active galactic nuclei.

Based on a mass-selected sample of galaxy-scale strong gravitational lenses from the SLACS, BELLS, LSD, and SL2S surveys and using a well-motivated fiducial set of lens-galaxy parameters, we tested the weak-field metric on kiloparsec scales and found a constraint on the post-Newtonian parameter $\gamma ={0.995}_{-0.047}^{+0.037}$ under the assumption of a flat ΛCDM universe with parameters taken from Planck observations. General relativity (GR) predicts exactly γ = 1. Uncertainties concerning the total mass density profile, anisotropy of the velocity dispersion, and the shape of the light profile combine to systematic uncertainties of ∼25%. By applying a cosmological model-independent method to the simulated future LSST data, we found a significant degeneracy between the PPN γ parameter and the spatial curvature of the universe. Setting a prior on the cosmic curvature parameter −0.007 < Ω_k < 0.006, we obtained the constraint on the PPN parameter that $\gamma ={1.000}_{-0.0025}^{+0.0023}$. We conclude that strong lensing systems with measured stellar velocity dispersions may serve as another important probe to investigate validity of the GR, if the mass-dynamical structure of the lensing galaxies is accurately constrained in future lens surveys.

Stellar masses of galaxies are frequently obtained by fitting stellar population synthesis models to galaxy photometry or spectra. The state of the art method resolves spatial structures within a galaxy to assess the total stellar mass content. In comparison to unresolved studies, resolved methods yield, on average, higher fractions of stellar mass for galaxies. In this work we improve the current method in order to mitigate a bias related to the resolved spatial distribution derived for the mass. The bias consists in an apparent filamentary mass distribution and a spatial coincidence between mass structures and dust lanes near spiral arms. The improved method is based on iterative Bayesian marginalization, through a new algorithm we have named Bayesian Successive Priors (BSP). We have applied BSP to M51 and to a pilot sample of 90 spiral galaxies from the Ohio State University Bright Spiral Galaxy Survey. By quantitatively comparing both methods, we find that the average fraction of stellar mass missed by unresolved studies is only half what previously thought. In contrast with the previous method, the output BSP mass maps bear a better resemblance to near-infrared images.

It has been revealed that the magnetic topology in the solar atmosphere displays hemispheric preference, i.e., helicity is mainly negative/positive in the northern/southern hemispheres, respectively. However, the strength of the hemispheric rule and its cyclic variation are controversial. In this paper, we apply a new method based on the filament drainage to 571 erupting filaments from 2010 May to 2015 December in order to determine the filament chirality and its hemispheric preference. It is found that 91.6% of our sample of erupting filaments follows the hemispheric rule of helicity sign. It is also found that the strength of the hemispheric preference of the quiescent filaments decreases slightly from ∼97% in the rising phase to ∼85% in the declining phase of solar cycle 24, whereas the strength of the intermediate filaments keeps a high value around 96 ± 4% at all times. Only the active-region filaments show significant variations. Their strength of the hemispheric rule rises from ∼63% to ∼95% in the rising phase, and keeps a high value of 82% ± 5% during the declining phase. Furthermore, during a half-year period around the solar maximum, their hemispheric preference totally vanishes. Additionally, we also diagnose the magnetic configurations of the filaments based on our indirect method and find that in our sample of erupting events, 89% are inverse-polarity filaments with a flux rope magnetic configuration, whereas 11% are normal-polarity filaments with a sheared arcade configuration.

We use ultradeep 20 cm data from the Karl G. Jansky Very Large Array and 850 μm data from SCUBA-2 and the Submillimeter Array of an 124 arcmin² region of the Chandra Deep Field-north to analyze the high radio power (${P}_{20\mathrm{cm}}\gt {10}^{31}$ erg s⁻¹ Hz⁻¹) population. We find that 20 (42 ± 9%) of the spectroscopically identified $z\gt 0.8$ sources have consistent star formation rates (SFRs) inferred from both submillimeter and radio observations, while the remaining sources have lower (mostly undetected) submillimeter fluxes, suggesting that active galactic nucleus (AGN) activity dominates the radio power in these sources. We develop a classification scheme based on the ratio of submillimeter flux to radio power versus radio power and find that it agrees with AGN and star-forming galaxy classifications from Very Long Baseline Interferometry. Our results provide support for an extremely rapid drop in the number of high SFR galaxies above about a thousand solar masses per year (Kroupa initial mass function) and for the locally determined relation between X-ray luminosity and radio power for star-forming galaxies applying at high redshifts and high radio powers. We measure far-infrared (FIR) luminosities and find that some AGNs lie on the FIR-radio correlation, while others scatter below. The AGNs that lie on the correlation appear to do so based on their emission from the AGN torus. We measure a median radio size of 10 ± 0.3 for the star-forming galaxies. The radio sizes of the star-forming galaxies are generally larger than those of the AGNs.

We provide an example of an analysis to explore the optimization of observations of transiting hot Jupiters with the James Webb Space Telescope (JWST) to characterize their atmospheres based on a simple three-parameter forward model. We construct expansive forward model sets for 11 hot Jupiters, 10 of which are relatively well characterized, exploring a range of parameters such as equilibrium temperature and metallicity, as well as considering host stars over a wide range in brightness. We compute posterior distributions of our model parameters for each planet with all of the available JWST spectroscopic modes and several programs of combined observations and compute their effectiveness using the metric of estimated mutual information per degree of freedom. From these simulations, clear trends emerge that provide guidelines for designing a JWST observing program. We demonstrate that these guidelines apply over a wide range of planet parameters and target brightnesses for our simple forward model.

The solar s-process abundances have been analyzed in the framework of a Galactic Chemical Evolution (GCE) model. The aim of this work is to implement the study by Bisterzo et al., who investigated the effect of one of the major uncertainties of asymptotic giant branch (AGB) yields, the internal structure of the ¹³C pocket. We present GCE predictions of s-process elements computed with additional tests in the light of suggestions provided in recent publications. The analysis is extended to different metallicities, by comparing GCE results and updated spectroscopic observations of unevolved field stars. We verify that the GCE predictions obtained with different tests may represent, on average, the evolution of selected neutron-capture elements in the Galaxy. The impact of an additional weak s-process contribution from fast-rotating massive stars is also explored.

We present results from a deep 2' × 3' (comoving scale of 3.7 Mpc × 5.5 Mpc at z = 3) survey at 1.1 mm, taken with the Atacama Large Millimeter/submillimeter Array (ALMA) in the SSA22 field. We observe the core region of a z = 3.09 protocluster, achieving a typical rms sensitivity of 60 μJy beam⁻¹ at a spatial resolution of 07. We detect 18 robust ALMA sources at a signal-to-noise ratio (S/N) > 5. Comparison between the ALMA map and a 1.1 mm map, taken with the AzTEC camera on the Atacama Submillimeter Telescope Experiment (ASTE), indicates that three submillimeter sources discovered by the AzTEC/ASTE survey are resolved into eight individual submillimeter galaxies (SMGs) by ALMA. At least 10 of our 18 ALMA SMGs have spectroscopic redshifts of z ≃ 3.09, placing them in the protocluster. This shows that a number of dusty starburst galaxies are forming simultaneously in the core of the protocluster. The nine brightest ALMA SMGs with S/N > 10 have a median intrinsic angular size of $0\buildrel{\prime\prime}\over{.} {32}_{-0.06}^{+0.13}$ (${2.4}_{-0.4}^{+1.0}$ physical kpc at z = 3.09), which is consistent with previous size measurements of SMGs in other fields. As expected, the source counts show a possible excess compared to the counts in the general fields at S_1.1mm ≥ 1.0 mJy, due to the protocluster. Our contiguous mm mapping highlights the importance of large-scale structures on the formation of dusty starburst galaxies.

The variation in area of quiet magnetic network measured over the sunspot cycle should modulate the spatially averaged photospheric temperature gradient, since temperature declines with optical depth more gradually in magnetic flux tube atmospheres. Yet, limb darkening measurements show no dependence upon activity level, even at an rms precision of 0.04%. We study the sensitivity of limb darkening to changes in area filling factor using a 3D MHD model of the magnetized photosphere. The limb darkening change expected from the measured 11-year area variation lies below the level of measured limb darkening variations, for a reasonable range of magnetic flux in quiet network and internetwork regions. So the remarkably constant limb darkening observed over the solar activity cycle is not inconsistent with the measured 11-year change in area of quiet magnetic network. Our findings offer an independent constraint on photospheric temperature gradient changes reported from measurements of the solar spectral irradiance from the Spectral Irradiance Monitor, and recently, from wavelength-differential spectrophotometry using the Solar Optical Telescope aboard the HINODE spacecraft.

We present multiple spectropolarimetric observations of the nearby Type Ia supernova (SN) 2011fe in M101, obtained before, during, and after the time of maximum apparent visual brightness. The excellent time coverage of our spectropolarimetry has allowed better monitoring of the evolution of polarization features than is typical, which has allowed us new insight into the nature of normal SNe Ia. SN 2011fe exhibits time-dependent polarization in both the continuum and strong absorption lines. At early epochs, red wavelengths exhibit a degree of continuum polarization of up to 0.4%, likely indicative of a mild asymmetry in the electron-scattering photosphere. This behavior is more common in subluminous SNe Ia than in normal events, such as SN 2011fe. The degree of polarization across a collection of absorption lines varies dramatically from epoch to epoch. During the earliest epoch, a λ4600–5000 Å complex of absorption lines shows enhanced polarization at a different position angle than the continuum. We explore the origin of these features, presenting a few possible interpretations, without arriving at a single favored ion. During two epochs near maximum, the dominant polarization feature is associated with the Si iiλ6355 Å absorption line. This is common for SNe Ia, but for SN 2011fe the polarization of this feature increases after maximum light, whereas for other SNe Ia, that polarization feature was strongest before maximum light.

We present new deep photometry of the rich globular cluster (GC) systems around the Brightest Cluster Galaxies UGC 9799 (Abell 2052) and UGC 10143 (Abell 2147), obtained with the Hubble Space Telescope (HST) ACS and WFC3 cameras. For comparison, we also present new reductions of similar HST/ACS data for the Coma supergiants NGC 4874 and 4889. All four of these galaxies have huge cluster populations (to the radial limits of our data, comprising from 12,000 to 23,000 clusters per galaxy). The metallicity distribution functions (MDFs) of the GCs can still be matched by a bimodal-Gaussian form where the metal-rich and metal-poor modes are separated by $\simeq 0.8$ dex, but the internal dispersions of each mode are so large that the total MDF becomes very broad and nearly continuous from [Fe/H] ≃ −2.4 to solar. There are, however, significant differences between galaxies in the relative numbers of metal-rich clusters, suggesting that they underwent significantly different histories of mergers with massive gas-rich halos. Last, the proportion of metal-poor GCs rises especially rapidly outside projected radii $R\gtrsim 4\,{R}_{\mathrm{eff}}$, suggesting the importance of accreted dwarf satellites in the outer halo. Comprehensive models for the formation of GCs as part of the hierarchical formation of their parent galaxies will be needed to trace the systematic change in structure of the MDF with galaxy mass, from the distinctly bimodal form in smaller galaxies up to the broad continuum that we see in the very largest systems.

Assessing the interaction between solar acoustic waves and sunspots is a scattering problem. The scattering matrix elements are the most commonly used measured quantities to describe scattering problems. We use the wavefunctions of scattered waves of NOAAs 11084 and 11092 measured in the previous study to compute the scattering matrix elements, with plane waves as the basis. The measured scattered wavefunction is from the incident wave of radial order n to the wave of another radial order n', for $n=0\mbox{--}5$. For a time-independent sunspot, there is no mode mixing between different frequencies. An incident mode is scattered into various modes with different wavenumbers but the same frequency. Working in the frequency domain, we have the individual incident plane-wave mode, which is scattered into various plane-wave modes with the same frequency. This allows us to compute the scattering matrix element between two plane-wave modes for each frequency. Each scattering matrix element is a complex number, representing the transition from the incident mode to another mode. The amplitudes of diagonal elements are larger than those of the off-diagonal elements. The amplitude and phase of the off-diagonal elements are detectable only for $n-1\leqslant n^{\prime} \leqslant n+1$ and $-3{\rm{\Delta }}k\leqslant \delta {k}_{x}\leqslant 3{\rm{\Delta }}k$, where $\delta {k}_{x}$ is the change in the transverse component of the wavenumber and Δk = 0.035 rad Mm⁻¹.

In this study we demonstrate that general relativity predicts arrival time differences between gravitational wave (GW) and electromagnetic (EM) signals caused by the wave effects in gravitational lensing. The GW signals can arrive earlier than the EM signals in some cases if the GW/EM signals have passed through a lens, even if both signals were emitted simultaneously by a source. GW wavelengths are much larger than EM wavelengths; therefore, the propagation of the GWs does not follow the laws of geometrical optics, including the Shapiro time delay, if the lens mass is less than approximately 10⁵M_⊙(f/Hz)⁻¹, where f is the GW frequency. The arrival time difference can reach ∼0.1 s (f/Hz)⁻¹ if the signals have passed by a lens of mass ∼8000 M_⊙(f/Hz)⁻¹ with the impact parameter smaller than the Einstein radius; therefore, it is more prominent for lower GW frequencies. For example, when a distant supermassive black hole binary (SMBHB) in a galactic center is lensed by an intervening galaxy, the time lag becomes of the order of 10 days. Future pulsar timing arrays including the Square Kilometre Array and X-ray detectors may detect several time lags by measuring the orbital phase differences between the GW/EM signals in the SMBHBs. Gravitational lensing imprints a characteristic modulation on a chirp waveform; therefore, we can deduce whether a measured arrival time lag arises from intrinsic source properties or gravitational lensing. Determination of arrival time differences would be extremely useful in multimessenger observations and tests of general relativity.

Recent cosmological hydrodynamical simulations suggest that integral field spectroscopy can connect the high-order stellar kinematic moments h₃ (∼skewness) and h₄ (∼kurtosis) in galaxies to their cosmological assembly history. Here, we assess these results by measuring the stellar kinematics on a sample of 315 galaxies, without a morphological selection, using two-dimensional integral field data from the SAMI Galaxy Survey. Proxies for the spin parameter (${\lambda }_{{R}_{{\rm{e}}}}$) and ellipticity (${\epsilon }_{{\rm{e}}}$) are used to separate fast and slow rotators; there exists a good correspondence to regular and non-regular rotators, respectively, as also seen in earlier studies. We confirm that regular rotators show a strong h₃ versus $V/\sigma$ anti-correlation, whereas quasi-regular and non-regular rotators show a more vertical relation in h₃ and $V/\sigma$. Motivated by recent cosmological simulations, we develop an alternative approach to kinematically classify galaxies from their individual h₃ versus $V/\sigma$ signatures. Within the SAMI Galaxy Survey, we identify five classes of high-order stellar kinematic signatures using Gaussian mixture models. Class 1 corresponds to slow rotators, whereas Classes 2–5 correspond to fast rotators. We find that galaxies with similar ${\lambda }_{{R}_{{\rm{e}}}}\mbox{--}{\epsilon }_{{\rm{e}}}$ values can show distinctly different ${h}_{3}\mbox{--}V/\sigma$ signatures. Class 5 objects are previously unidentified fast rotators that show a weak h₃ versus $V/\sigma$ anti-correlation. From simulations, these objects are predicted to be disk-less galaxies formed by gas-poor mergers. From morphological examination, however, there is evidence for large stellar disks. Instead, Class 5 objects are more likely disturbed galaxies, have counter-rotating bulges, or bars in edge-on galaxies. Finally, we interpret the strong anti-correlation in h₃ versus $V/\sigma$ as evidence for disks in most fast rotators, suggesting a dearth of gas-poor mergers among fast rotators.

Hot dust-obscured galaxies (hot DOGs), selected from Wide-Field Infrared Survey Explorer's all-sky infrared survey, host some of the most powerful active galactic nuclei known and may represent an important stage in the evolution of galaxies. Most known hot DOGs are located at $z\gt 1.5$, due in part to a strong bias against identifying them at lower redshift related to the selection criteria. We present a new selection method that identifies 153 hot DOG candidates at $z\sim 1$, where they are significantly brighter and easier to study. We validate this approach by measuring a redshift z = 1.009 and finding a spectral energy distribution similar to that of higher-redshift hot DOGs for one of these objects, WISE J1036+0449 (${L}_{\mathrm{Bol}}\simeq 8\times {10}^{46}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$). We find evidence of a broadened component in Mg ii, which would imply a black hole mass of ${M}_{\mathrm{BH}}\simeq 2\times {10}^{8}\,{M}_{\odot }$ and an Eddington ratio of ${\lambda }_{\mathrm{Edd}}\simeq 2.7$. WISE J1036+0449 is the first hot DOG detected by the Nuclear Spectroscopic Telescope Array, and observations show that the source is heavily obscured, with a column density of ${N}_{{\rm{H}}}\simeq (2\mbox{--}15)\times {10}^{23}\,{\mathrm{cm}}^{-2}$. The source has an intrinsic 2–10 keV luminosity of $\sim 6\times {10}^{44}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$, a value significantly lower than that expected from the mid-infrared/X-ray correlation. We also find that other hot DOGs observed by X-ray facilities show a similar deficiency of X-ray flux. We discuss the origin of the X-ray weakness and the absorption properties of hot DOGs. Hot DOGs at $z\lesssim 1$ could be excellent laboratories to probe the characteristics of the accretion flow and of the X-ray emitting plasma at extreme values of the Eddington ratio.

We present a new approach for quantifying the abundance of galaxy clusters and constraining cosmological parameters using dynamical measurements. In the standard method, galaxy line-of-sight velocities, v, or velocity dispersions are used to infer cluster masses, M, to quantify the halo mass function (HMF), ${dn}(M)/d\mathrm{log}(M)$, which is strongly affected by mass measurement errors. In our new method, the probability distributions of velocities for each cluster in the sample are summed to create a new statistic called the velocity distribution function (VDF), ${dn}(v)/{dv}$. The VDF can be measured more directly and precisely than the HMF and can be robustly predicted with cosmological simulations that capture the dynamics of subhalos or galaxies. We apply these two methods to realistic (ideal) mock cluster catalogs with (without) interlopers and forecast the bias and constraints on the matter density parameter Ω_m and the amplitude of matter fluctuations σ₈ in flat ΛCDM cosmologies. For an example observation of 200 massive clusters, the VDF with (without) interloping galaxies constrains the parameter combination ${\sigma }_{8}\,{{\rm{\Omega }}}_{m}^{0.29(0.29)}=0.589\pm 0.014\,(0.584\pm 0.011)$ and shows only minor bias. However, the HMF with interlopers is biased to low Ω_m and high σ₈ and the fiducial model lies well outside of the forecast constraints, prior to accounting for Eddington bias. When the VDF is combined with constraints from the cosmic microwave background, the degeneracy between cosmological parameters can be significantly reduced. Upcoming spectroscopic surveys that probe larger volumes and fainter magnitudes will provide clusters for applying the VDF as a cosmological probe.

A large number of interstellar absorption features at ∼4000 Å–1.8 μm, known as the "diffuse interstellar bands" (DIBs), remains unidentified. Most recent works relate them to large polycyclic aromatic hydrocarbon (PAH) molecules or ultrasmall carbonaceous grains which are also thought to be responsible for the $2175\,\mathring{\rm A}$ extinction bump and/or the far-ultraviolet (UV) extinction rise at ${\lambda }^{-1}\gt 5.9\,\mu {{\rm{m}}}^{-1}$. Therefore, one might expect some relation between UV extinction and DIBs. Such a relationship, if established, could put important constraints on the carrier of DIBs. Over the past four decades, whether DIBs are related to the shape of the UV extinction curves has been extensively investigated. However, the results are often inconsistent, partly due to the inconsistencies in characterizing UV extinction. Here we re-examine the connection between the UV extinction curve and DIBs. We compile the extinction curves and the equivalent widths of 40 DIBs along 97 sightlines. We decompose the extinction curve into three Drude-like functions composed of the visible/near-infrared component, the $2175\,\mathring{\rm A}$ bump, and the far-UV (FUV) extinction at ${\lambda }^{-1}\gt 5.9\,\mu {{\rm{m}}}^{-1}$. We argue that the wavelength-integrated FUV extinction derived from this decomposition technique best measures the strength of the FUV extinction. No correlation is found between the FUV extinction and most (∼90%) of the DIBs. We have also shown that the color excess $E(1300\mbox{--}1700)$, the extinction difference at 1300 and $1700\,\mathring{\rm A}$ often used to measure the strength of the FUV extinction, does not correlate with DIBs. Finally, we confirm the earlier findings of no correlation between the $2175\,\mathring{\rm A}$ bump and DIBs or between the $2175\,\mathring{\rm A}$ bump and the FUV extinction.

We present the ALMA Band 3 and Band 6 results of ¹²CO(2-1), ¹³CO(2-1), H30α recombination line, free–free emission around 98 GHz, and the dust thermal emission around 230 GHz toward the N159 East Giant Molecular Cloud (N159E) in the Large Magellanic Cloud (LMC). LMC is the nearest active high-mass star-forming face-on galaxy at a distance of 50 kpc and is the best target for studing high-mass star formation. ALMA observations show that N159E is the complex of filamentary clouds with the width and length of ∼1 pc and several parsecs. The total molecular mass is 0.92 × 10⁵M_⊙ from the ¹³CO(2-1) intensity. N159E harbors the well-known Papillon Nebula, a compact high-excitation H ii region. We found that a YSO associated with the Papillon Nebula has the mass of 35 M_⊙ and is located at the intersection of three filamentary clouds. It indicates that the formation of the high-mass YSO was induced by the collision of filamentary clouds. Fukui et al. reported a similar kinematic structure toward two YSOs in the N159 West region, which are the other YSOs that have the mass of ≳35 M_⊙. This suggests that the collision of filamentary clouds is a primary mechanism of high-mass star formation. We found a small molecular hole around the YSO in Papillon Nebula with a sub-parsec scale. It is filled by free–free and H30α emission. The temperature of the molecular gas around the hole reaches ∼80 K. It indicates that this YSO has just started the distruction of parental molecular cloud.

Some scenarios for planetesimal formation go through a phase of collapse of gravitationally bound clouds of millimeter- to centimeter-size pebbles. Such clouds can form, for example, through the streaming instability in protoplanetary disks. We model the collapse process with a statistical model to obtain the internal structure of planetesimals with solid radii between 10 and 1000 km. During the collapse, pebbles collide, and depending on their relative speeds, collisions have different outcomes. A mixture of particle sizes inside a planetesimal leads to better packing capabilities and higher densities. In this paper we apply results from new laboratory experiments of dust aggregate collisions (presented in a companion paper) to model collision outcomes. We find that the internal structure of a planetesimal is strongly dependent on both its mass and the applied fragmentation model. Low-mass planetesimals have no/few fragmenting pebble collisions in the collapse phase and end up as porous pebble piles. The number of fragmenting collisions increases with increasing cloud mass, resulting in wider particle size distributions and higher density. The collapse is nevertheless "cold" in the sense that collision speeds are damped by the high collision frequency. This ensures that a significant fraction of large pebbles survive the collapse in all but the most massive clouds. Our results are in broad agreement with the observed increase in density of Kuiper Belt objects with increasing size, as exemplified by the recent characterization of the highly porous comet 67P/Churyumov–Gerasimenko.

We observed the [C ii] line in 15 lensed galaxies at redshifts 1 < z < 3 using HIFI on the Herschel Space Observatory and detected 14/15 galaxies at 3σ or better. High magnifications enable even modestly luminous galaxies to be detected in [C ii] with Herschel. The [C ii] luminosity in this sample ranges from 8 × 10⁷L_⊙ to 3.7 × 10⁹L_⊙ (after correcting for magnification), confirming that [C ii] is a strong tracer of the ISM at high redshifts. The ratio of the [C ii] line to the total far-infrared (FIR) luminosity serves as a measure of the ratio of gas to dust cooling and thus the efficiency of the grain photoelectric heating process. It varies between 3.3% and 0.09%. We compare the [C ii]/FIR ratio to that of galaxies at z = 0 and at high redshifts and find that they follow similar trends. The [C ii]/FIR ratio is lower for galaxies with higher dust temperatures. This is best explained if increased UV intensity leads to higher FIR luminosity and dust temperatures, but gas heating does not rise due to lower photoelectric heating efficiency. The [C ii]/FIR ratio shows weaker correlation with FIR luminosity. At low redshifts highly luminous galaxies tend to have warm dust, so the effects of dust temperature and luminosity are degenerate. Luminous galaxies at high redshifts show a range of dust temperatures, showing that [C ii]/FIR correlates most strongly with dust temperature. The [C ii] to mid-IR ratio for the HELLO sample is similar to the values seen for low-redshift galaxies, indicating that small grains and PAHs dominate the heating in the neutral ISM, although some of the high [CII]/FIR ratios may be due to turbulent heating.

We have analyzed a sample of 327 clusters of galaxies, spanning the range of 0.06–0.70 in redshift. Strong constraints on their mean intracluster emission of dust have been obtained using maps and catalogs from the Herschel MerMES project; within a radius of 5 arcmin centered in each cluster, the 95% C.L. limits obtained are 86.6, 48.2, and 30.9 mJy at the observed frequencies of 250, 350, and 500 μm. From these restrictions, and assuming physical parameters typical of interstellar media in the Milky Way, we have obtained tight upper limits on the visual extinction of background galaxies due to the intracluster media (ICM): A_V(95% C.L.) ≲ 10⁻³ mag. Strong constraints are also obtained for the mass of such dust; for instance, using the data at 350 μm we establish a 95% upper limit of <10⁹M_⊙ within a circle with a radius of 5 arcmin centered in the clusters. This corresponds to a fraction of the total mass of the clusters of 9.5 × 10⁻⁶, and indicates a deficiency in the gas-to-dust ratio in the ICM by about three orders of magnitude in relation to the value found in the Milky Way. Computing the total infrared luminosity of the clusters in three ranges of redshift (0.05–0.24, 0.24–0.42, and 0.42–0.71) and two ranges of mass (<10¹⁴ and >10¹⁴M_⊙), respectively, a strong evolution of luminosity in redshift (L ∼ z^1.5) for both ranges of masses is found. The results indicate a strong declining in star formation rate with time in the last ∼6 Gyr.