Table of contents

The photon-scattering winds of M giants absorb parts of the chromospheric emission lines and produce self-reversed spectral features in high-resolution Hubble Space Telescope (HST)/GHRS spectra. These spectra provide an opportunity to assess fundamental parameters of the wind, including flow and turbulent velocities, the optical depth of the wind above the region of photon creation, and the star's mass-loss rate. This paper is the last paper in the series "GHRS Observations of Cool, Low-Gravity Stars"; the last several have compared empirical measurements of spectral emission lines with models of the winds and mass loss of K giants and supergiants. We have used the Sobolev with Exact Integration radiative transfer code, along with simple models of the outer atmosphere and wind, to determine and compare the wind characteristics of the two M-giant stars, γ Cru (M3.5III) and μ Gem (M3IIIab), with previously derived values for low-gravity K-stars. The analysis specifies the wind parameters and calculates line profiles for the Mg ii resonance lines, in addition to a range of unblended Fe ii lines. Our line sample covers a large range of wind opacities and, therefore, probes a range of heights in the atmosphere. Our results show that μ Gem has a slower and more turbulent wind than γ Cru. Also, μ Gem has a weaker chromosphere, in terms of surface flux, with respect to γ Cru. This suggests that μ Gem is more evolved than γ Cru. Comparing the two M giants in this work with previously studied K-giant and supergiant stars (α Tau, γ Dra, and λ Vel) reveals that the M giants have slower winds than the earlier giants, but exhibit higher mass-loss rates. Our results are interpreted in the context of the winds being driven by Alfvén waves.

Solar and stellar dynamos shed small-scale and large-scale magnetic helicity of opposite signs. However, solar wind observations and simulations have shown that some distance above the dynamo both the small-scale and large-scale magnetic helicities have reversed signs. With realistic simulations of the solar corona above an active region now being available, we have access to the magnetic field and current density along coronal loops. We show that a sign reversal in the horizontal averages of the magnetic helicity occurs when the local maximum of the plasma beta drops below unity and the field becomes nearly fully force free. Hence, this reversal is expected to occur well within the solar corona and would not directly be accessible to in situ measurements with the Parker Solar Probe or SolarOrbiter. We also show that the reversal is associated with subtle changes in the relative dominance of structures with positive and negative magnetic helicity.

The emergence of dipolar magnetic features on the solar surface is an idealization. Most of the magnetic flux emergence occurs in complex multipolar regions. Here, we show that the surface pattern of magnetic structures alone can reveal the sign of the underlying magnetic helicity in the nearly force-free coronal regions above. The sign of the magnetic helicity can be predicted to good accuracy by considering the three-dimensional position vectors of three spots on the sphere ordered by their relative strengths at the surface and compute from them the skew product. This product, which is a pseudoscalar, is shown to be a good proxy for the sign of the coronal magnetic helicity.

Massive Population II galaxies undergoing the first phase of vigorous star formation after the initial Population III stage should have high energy densities and silicate-rich interstellar dust. We have modeled the resulting far-infrared spectral energy distributions (SEDs), demonstrating that they are shifted substantially to bluer ("warmer") wavelengths relative to the best fitting ones at z ≈ 3, and with strong outputs in the 10–40 μm range. When combined with a low level of emission by carbon dust, their SEDs match that of Haro 11, a local moderately low-metallicity galaxy undergoing a very young and vigorous starburst that is likely to approximate the relevant conditions in young Population II galaxies. We expect to see similar SEDs at high redshifts (z ≳ 5) given the youth of galaxies at this epoch. In fact, we find a progression with redshift in observed galaxy SEDs, from those resembling local ones at 2 ≲ z < 4 to a closer resemblance with Haro 11 at 5 ≲ z < 7. In addition to the insight on conditions in high-redshift galaxies, this result implies that estimates of the total infrared luminosities at z ∼ 6 based on measurements near λ ∼ 1 mm can vary by factors of 2–4, depending on the SED template used. Currently popular modified blackbodies or local templates can result in significant underestimates compared with the preferred template based on the SED of Haro 11.

A fundamental endeavor in exoplanetary research is to characterize the bulk compositions of planets via measurements of their masses and radii. With future sample sizes of hundreds of planets to come from TESS and PLATO, we develop a statistical method that can flexibly yet robustly characterize these compositions empirically, via the exoplanet M–R relation. Although the M–R relation has been explored in many prior works, they mostly use a power-law model, with assumptions that are not flexible enough to capture important features in current and future M–R diagrams. To address these shortcomings, a nonparametric approach is developed using a sequence of Bernstein polynomials. We demonstrate the benefit of taking the nonparametric approach by benchmarking our findings with previous work and showing that a power law can only reasonably describe the M–R relation of the smallest planets and that the intrinsic scatter can change non-monotonically with different values of a radius. We then apply this method to a larger data set, consisting of all the Kepler observations in the NASA Exoplanet Archive. Our nonparametric approach provides a tool to estimate the M–R relation by incorporating heteroskedastic measurement errors into the model. As more observations will be obtained in the near future, this approach can be used with the provided R code to analyze a larger data set for a better understanding of the M–R relation.

We study the fraction of tidal interactions and mergers (TIMs) with well-identified observability timescales (f_TIM) in group, cluster, and accompanying field galaxies and its dependence on redshift (z), cluster velocity dispersion (σ), and environment analyzing Hubble Space Telescope/ACS images and catalogs from the ESO Distant Cluster Survey. Our sample consists of 11 clusters, seven groups, and accompanying field galaxies at 0.4 ≤ z ≤ 0.8. We derive f_TIM using both a visual classification of galaxy morphologies and an automated method, the G − M₂₀ method. We calibrate this method using the visual classifications that were performed on a subset of our sample. We find marginal evidence for a trend between f_TIM and z, in that higher z values correspond to higher f_TIM. However, we also cannot rule out the null hypothesis of no correlation at higher than 68% confidence. No trend is present between f_TIM and σ. We find that f_TIM shows suggestive peaks in groups, and tentatively in clusters at R > 0.5 × R₂₀₀, implying that f_TIM gets boosted in these intermediate-density environments. However, our analysis of the local densities of our cluster sample does not reveal a trend between f_TIM and density, except for a potential enhancement at the very highest densities. We also perform an analysis of projected radius–velocity phase space for our cluster members. Our results reveal that TIM and undisturbed galaxies only have a 6% probability of having been drawn from the same parent population in their velocity distribution and 37% in radii, in agreement with the modest differences obtained in f_TIM at the clusters.

We present high-speed optical observations of the nova ASASSN-17hx, taken both immediately after its discovery and close to its first peak in brightness, to search for second–minute pulsations associated with the convective eddy turnover timescale within the nova envelope. We do not detect any periodic signal with greater than 3σ significance. Through injection and recovery, we rule out periodic signals of fractional amplitude >7.08 × 10⁻⁴ on timescales of 2 s and fractional amplitude >1.06 × 10⁻³ on timescales of 10 minutes. Additional observations of novae are planned to further constrain ongoing simulations of the launch and propagation of nova winds.

Oscillation frequencies of even the best stellar models differ from those of the stars they represent, and the difference is predominantly a function of frequency. This difference is caused by limitations of modeling the near-surface layers of a star. This frequency-dependent frequency error, usually referred to as the "surface term" can result in erroneous interpretation of the oscillation frequencies unless treated properly. Several techniques have been developed to minimize the effect of the surface term; it is either subtracted out, or frequency combinations insensitive to the surface terms are used, or the asteroseismic phase  is used to determine a match between models and stars. In this paper we show that no matter what technique is used to account for the surface term, as long as the physics of the models is the same, the global parameters of a star—mass, radius, and age—obtained from frequency analyses are robust. This implies that even though we cannot model the internal structure of stars perfectly, we can have confidence in all results that use stellar global properties obtained through the analysis of stellar oscillation frequencies.

In this paper, we use a machine-learning method, random forest (RF), to identify reliable members of the old (4 Gyr) open cluster M67 based on the high-precision astrometry and photometry taken from the second Gaia data release (Gaia-DR2). The RF method is used to calculate membership probabilities of 71,117 stars within 25 of the cluster center in an 11-dimensional parameter space, the photometric data are also taken into account. Based on the RF membership probabilities, we obtain 1502 likely cluster members (≥0.6), 1361 of which are high-probability cluster members (≥0.8). Based on high-probability memberships with high-precision astrometric data, the mean parallax (distance) and proper-motion of the cluster are determined to be 1.1327 ± 0.0018 mas (883 ± 1 pc) and ($\langle {\mu }_{\alpha }\cos \delta \rangle$, $\langle {\mu }_{\delta }\rangle$) = (−10.9378 ±0.0078, −2.9465 ± 0.0074) mas yr⁻¹, respectively. We find the cluster to have a mean radial velocity of +34.06 ±0.09 km s⁻¹, using 74 high-probability cluster members with precise radial-velocity measures. We investigate the spatial structure of the cluster, the core and limiting radius are determined to be 480 ± 011 (∼1.23 ± 0.03 pc) and 6198 ± 150 (∼15.92 ± 0.39 pc), respectively. Our results reveal that an escaped member with high membership probability (∼0.91) is located at a distance of 77' (∼20 pc) from the cluster center. Furthermore, our results reveal that at least 26.4% of the main-sequence stars in M67 are binary stars. We confirm that significant mass segregation has taken place within M67.

HD 105 is a nearby, pre-main-sequence G0 star hosting a moderately bright debris disk (L_dust/L_⋆ ∼ 2.6 × 10⁻⁴). The star and its surroundings might therefore be considered an analog of the young solar system. We refine the stellar parameters based on an improved Gaia parallax distance and identify it as a pre-main-sequence star with an age of 50 ± 16 Myr. The circumstellar disk was marginally resolved by Herschel/PACS imaging at far-infrared wavelengths. Here, we present an archival ALMA observation at 1.3 mm, revealing the extent and orientation of the disk. We also present Hubble Space Telescope (HST)/NICMOS and VLT/SPHERE near-infrared images, where we recover the disk in scattered light at the ≥5σ level. This was achieved by employing a novel annular averaging technique and is the first time this has been achieved for a disk in scattered light. Simultaneous modeling of the available photometry, disk architecture, and detection in scattered light allow better determination of the disk's architecture, and dust grain minimum size, composition, and albedo. We measure the dust albedo to lie between 0.19 and 0.06, the lower value being consistent with Edgeworth–Kuiper Belt objects.

We investigate star-forming scaling relations using Bayesian inference on a comprehensive data sample of low- (z < 0.1) and high-redshift (1 < z < 5) star-forming regions. This full data set spans a wide range of host galaxy stellar mass (M_* ∼ 10⁶–10¹¹${M}_{\odot }$) and clump star formation rates (SFR ∼ 10⁻⁵ −10²${M}_{\odot }$ yr⁻¹). We fit the power-law relationship between the size (${r}_{{\rm{H}}\alpha }$) and luminosity (${L}_{{\rm{H}}\alpha }$) of the star-forming clumps using the Bayesian statistical modeling tool Stan, which makes use of Markov Chain Monte Carlo (MCMC) sampling techniques. Trends in the scaling relationship are explored for the full sample and subsets based on redshift and selection effects between samples. In our investigation, we find neither evidence of redshift evolution of the size–luminosity scaling relationship nor a difference in slope between lensed and unlensed data. There is evidence of a break in the scaling relationship between high and low SFR surface density (${{\rm{\Sigma }}}_{\mathrm{SFR}}$) clumps. The size–luminosity power-law fit results are ${L}_{{\rm{H}}\alpha }$ ∼ ${r}_{{\rm{H}}\alpha }$^2.8 and ${L}_{{\rm{H}}\alpha }$ ∼ ${r}_{{\rm{H}}\alpha }$^1.7 for low and high ${{\rm{\Sigma }}}_{\mathrm{SFR}}$ clumps, respectively. We present a model where star-forming clumps form at locations of gravitational instability and produce an ionized region represented by the Strömgren radius. A radius smaller than the scale height of the disk results in a scaling relationship of L ∝ r³ (high ${{\rm{\Sigma }}}_{\mathrm{SFR}}$ clumps), and a scaling of L ∝ r² (low ${{\rm{\Sigma }}}_{\mathrm{SFR}}$ clumps) if the radius is larger than the disk scale height.

We use cosmological hydrodynamical simulations of Milky Way–mass galaxies from the FIRE project to evaluate various strategies for estimating the mass of a galaxy's stellar halo from deep, integrated-light images. We find good agreement with integrated-light observations if we mimic observational methods to measure the mass of the stellar halo by selecting regions of an image via projected radius relative to the disk scale length or by their surface density in stellar mass. However, these observational methods systematically underestimate the accreted stellar component, defined in our (and most) simulations as the mass of stars formed outside of the host galaxy, by up to a factor of 10, since the accreted component is centrally concentrated and therefore substantially obscured by the galactic disk. Furthermore, these observational methods introduce spurious dependencies of the estimated accreted stellar component on the stellar mass and size of galaxies that can obscure the trends in accreted stellar mass predicted by cosmological simulations, since we find that in our simulations, the size and shape of the central galaxy are not strongly correlated with the assembly history of the accreted stellar halo. This effect persists whether galaxies are viewed edge-on or face-on. We show that metallicity or color information may provide a way to more cleanly delineate in observations the regions dominated by accreted stars. Absent additional data, we caution that estimates of the mass of the accreted stellar component from single-band images alone should be taken as lower limits.

Three-dimensional magnetic topology is crucial to understanding the explosive release of magnetic energy in the corona during solar flares. Much attention has been given to the pre-flare magnetic topology to identify candidate sites of magnetic reconnection, yet it is unclear how the magnetic reconnection and its attendant topological changes shape the eruptive structure and how the topology evolves during the eruption. Here we employed a realistic, data-constrained magnetohydrodynamic simulation to study the evolving magnetic topology for an X9.3 eruptive flare that occurred on 2017 September 6. The simulation successfully reproduces the eruptive features and processes in unprecedented detail. The numerical results reveal that the pre-flare corona contains multiple twisted flux systems with different connections, and during the eruption these twisted fluxes form a coherent flux rope through tether-cutting-like magnetic reconnection below the rope. Topological analysis shows that the rising flux rope is wrapped by a quasi-separatrix layer, which intersects itself below the rope, forming a topological structure known as a hyperbolic flux tube, where a current sheet develops, triggering the reconnection. By mapping footpoints of the newly reconnected field lines, we are able to reproduce both the spatial location and, for the first time, the temporal separation of the observed flare ribbons, as well as the dynamic boundary of the flux rope's feet. Furthermore, the temporal profile of the total reconnection flux is comparable to the soft X-ray light curve. Such a sophisticated characterization of the evolving magnetic topology provides important insight into the eventual understanding and forecasting of solar eruptions.

We present β-delayed neutron emission and β-delayed fission (βdf) calculations for heavy, neutron-rich nuclei using the coupled Quasi-Particle Random Phase Approximation plus Hauser-Feshbach (QRPA+HF) approach. From the initial population of a compound nucleus after β-decay, we follow the statistical decay, taking into account competition between neutrons, γ-rays, and fission. We find a region of the chart of nuclides where the probability of βdf is ∼100%, which likely prevents the production of superheavy elements in nature. For a subset of nuclei near the neutron dripline, neutron multiplicity and the probability of fission are both large, leading to the intriguing possibility of multi-chance βdf, a decay mode for extremely neutron-rich heavy nuclei. In this decay mode, β-decay can be followed by multiple neutron emission, leading to subsequent daughter generations that each have a probability to fission. We explore the impact of βdf in rapid neutron-capture process (r-process) nucleosynthesis in the tidal ejecta of a neutron star–neutron star merger and show that it is a key fission channel that shapes the final abundances near the second r-process peak.

The stellar mass–metallicity relation (M_⋆–Z; MZR) indicates that the metallicities of galaxies increase with increasing stellar masses. The fundamental metallicity relation (FMR) suggests that galaxies with higher star formation rates (SFRs) tend to have lower metallicities for a given stellar mass. To examine whether the MZR and FMR still hold at poorer metallicities and higher redshifts, we compile a sample of 35 star-forming galaxies (SFGs) at 0.6 < z < 0.9 using the public spectral database (v5_10_0) of emission-line galaxies from the extended Baryon Oscillation Spectroscopic Survey. These galaxies are identified for their significant auroral [O iii]λ4363 emission line (S/N ≥ 3). With the electronic temperature metallicity calibration, we find nine SFGs that are extremely metal-poor galaxies with 12 + log(O/H) ≤ 7.69 (1/10 Z_⊙). The metallicity of the most metal-deficient galaxy is 7.35 ± 0.09 (about 1/20 Z_⊙). Compared to the SFGs with normal metallicities in the local and high-redshift universe, our metal-poor SFGs have more than 10 times higher SFRs at a fixed stellar mass. We create a new mass–SFR relation for these metal-poor galaxies at 0.6 < z < 0.9. Due to the higher SFRs and younger stellar ages, our metal-poor SFGs deviate from the MZR and FMR in the local universe toward lower metallicities, confirming the existence of FMR, as well as the cosmic evolution of MZR and FMR with redshift.

It has been well established that particular centrophilic orbital families in non-spherical galaxies can, in principle, drive a black hole binary to shrink its orbit through three-body scattering until the black holes are close enough to strongly emit gravitational waves. Most of these studies rely on the orbital analysis of a static supermassive black hole (SMBH)-embedded galaxy potential to support this view; it is not clear, however, how these orbits transform as the second SMBH enters the center. So our understanding of which orbits actually interact with an SMBH binary is not ironclad. Here, we analyze two flattened galaxy models, one with a single SMBH and one with a binary, to determine which orbits actually do interact with the SMBH binary and how they compare with the set predicted in single SMBH-embedded models. We find close correspondence between the centrophilic orbits predicted to interact with the binary and those that are actually scattered by the binary, in terms of energy and L_z distribution, where L_z is the z component of a stellar particle's angular momentum. Of minor note: because of the larger mass, the binary SMBH has a larger radius of influence than in the single SMBH model, which allows the binary to draw from a larger reservoir of orbits to scatter. Of the prediction particles and scattered particles, nearly half have chaotic orbits, 40% have f_x:f_y = 1:1 orbits and 10% have other resonant orbits.

Rings are the most frequently revealed substructure in Atacama Large Millimeter/submillimeter Array (ALMA) dust observations of protoplanetary disks, but their origin is still hotly debated. In this paper, we identify dust substructures in 12 disks and measure their properties to investigate how they form. This subsample of disks is selected from a high-resolution (∼012) ALMA 1.33 mm survey of 32 disks in the Taurus star-forming region, which was designed to cover a wide range of brightness and to be unbiased to previously known substructures. While axisymmetric rings and gaps are common within our sample, spiral patterns and high-contrast azimuthal asymmetries are not detected. Fits of disk models to the visibilities lead to estimates of the location and shape of gaps and rings, the flux in each disk component, and the size of the disk. The dust substructures occur across a wide range of stellar mass and disk brightness. Disks with multiple rings tend to be more massive and more extended. The correlation between gap locations and widths, the intensity contrast between rings and gaps, and the separations of rings and gaps could all be explained if most gaps are opened by low-mass planets (super-Earths and Neptunes) in the condition of low disk turbulence (α = 10⁻⁴). The gap locations are not well correlated with the expected locations of CO and N₂ ice lines, so condensation fronts are unlikely to be a universal mechanism to create gaps and rings, though they may play a role in some cases.

We present detections of methane in R ∼ 1300, L-band spectra of VHS 1256 b and PSO 318.5, two low-gravity, red, late L dwarfs that share the same colors as the HR 8799 planets. These spectra reveal shallow methane features, which indicate VHS 1256 b and PSO 318.5 have photospheres that are out of chemical equilibrium. Directly imaged exoplanets usually have redder near-infrared colors than the field-age population of brown dwarfs on a color–magnitude diagram. These objects along the L-to-T transition show reduced methane absorption and evidence of photospheric clouds. Compared to the H- and K-bands, L-band (3 μm–4 μm) spectroscopy provides stronger constraints on the methane abundances of brown dwarfs and directly imaged exoplanets that have similar effective temperatures to L-to-T transition objects. When combined with near-infrared spectra, the L-band extends our conventional wavelength coverage, increasing our understanding of atmospheric cloud structure. Our model comparisons show that relatively strong vertical mixing and photospheric clouds can explain the molecular absorption features and continua of VHS 1256 b and PSO 318.5. We also discuss the implications of this work for future exoplanet-focused instruments and observations with the James Webb Space Telescope.

An accretion–decretion (A–D) circumstellar disk model, suitable for analysis of light and radial velocity (RV) curves, is developed for application to double contact binaries. A foundational hypothesis is that systems as different as cataclysmic variables and W Serpentis binaries—types that appear to have next to nothing in common other than being highly evolved, share the morphological trait of double contact and the related evolutionary trait of having A–D disks. The development is built upon a globally self-gravitating equipotential disk model and allows disk semi-transparency by attenuation of internal disk light and the light of both binary components. Tidal stretching of the disk with consequent brightness variation, as in the "ellipticity" effect for ordinary binaries, is a natural consequence of the disk's tidally distended structure. Light/velocity curve fitting for β Lyrae and CI Aquilae explores the idea that accretion and decretion can co-exist in statistical equilibrium. The basic similarity between CI Aql's pre- and post-eruption light curves—in both form and overall brightness, establishes that its disk was not seriously affected by the outburst of early 2000. Model computations show that in principle the Rossiter–McLaughlin RV disturbance should be very large for disks and a good diagnostic of orbital inclination, although absorption line disk velocities have not yet been measured for β Lyr or CI Aql.

Identifying the source population of ionizing radiation, responsible for the reionization of the universe, is currently a hotly debated subject with conflicting results. Studies of faint, high-redshift star-forming galaxies, in most cases, fail to detect enough escaping ionizing radiation to sustain the process. Recently, the capacity of bright quasi-stellar objects to ionize their surrounding medium has been confirmed also for faint active galactic nuclei (AGNs), which were found to display an escaping fraction of ∼74% at z ∼ 4. Such levels of escaping radiation could sustain the required UV background, given the number density of faint AGNs is adequate. Thus, it is mandatory to accurately measure the luminosity function of faint AGNs (L ∼ L*) in the same redshift range. For this reason we have conducted a spectroscopic survey, using the wide field spectrograph IMACS at the 6.5 m Baade Telescope, to determine the nature of our sample of faint AGN candidates in the COSMOS field. This sample was assembled using photometric redshifts, color, and X-ray information. We ended up with 16 spectroscopically confirmed AGNs at $3.6\lt z\lt 4.2$ down to a magnitude of i_AB = 23.0 for an area of 1.73 deg². This leads to an AGN space density of $\sim 1.6\times {10}^{-6}{\mathrm{Mpc}}^{-3}$ (corrected) at z ∼ 4 for an absolute magnitude of M₁₄₅₀ = −23.5. This is higher than previous measurements and seems to indicate that AGNs could make a substantial contribution to the ionizing background at z ∼ 4. Assuming that AGN physical parameters remain unchanged at higher redshifts and fainter luminosities, these sources could be regarded as the main drivers of cosmic reionization.

The photospheric response to solar flares, also known as coronal back reaction, is often observed as sudden flare-induced changes in the vector magnetic field and sunspot motions. However, it remains obscure whether evolving flare ribbons, the flare signature closest to the photosphere, are accompanied by changes in vector magnetic field therein. Here we explore the relationship between the dynamics of flare ribbons in the chromosphere and variations of magnetic fields in the underlying photosphere, using high-resolution off-band Hα images and near-infrared vector magnetograms of the M6.5 flare on 2015 June 22 observed with the 1.6 m Goode Solar Telescope. We find that changes of photospheric fields occur at the arrival of the flare ribbon front, thus propagating analogously to flare ribbons. In general, the horizontal field increases and the field lines become more inclined to the surface. When ribbons sweep through regions that undergo a rotational motion, the fields transiently become more vertical with decreased horizontal field and inclination angle, and then restore and/or become more horizontal than before the ribbon arrival. The ribbon propagation decelerates near the sunspot rotation center, where the vertical field becomes permanently enhanced. Similar magnetic field changes are discernible in magnetograms from the Helioseismic and Magnetic Imager (HMI), and an inward collapse of coronal magnetic fields is inferred from the time sequence of nonlinear force-free field models extrapolated from HMI magnetograms. We conclude that photospheric fields respond nearly instantaneously to magnetic reconnection in the corona.

We obtained high-resolution spectra and multicolor photometry of V1082 Sgr to study the donor star in this 20.8 hr orbital period binary, which is assumed to be a detached system. We measured the rotational velocity ($v\sin i=26.5\pm 2.0$ km s⁻¹), which, coupled with the constraints on the white dwarf mass from the X-ray spectroscopy, leads to the conclusion that the donor star barely fills 70% of its corresponding Roche lobe radius. It appears to be a slightly evolved K2-type star. This conclusion was further supported by a recently published distance to the binary system measured by the Gaia mission. At the same time, it becomes difficult to explain a very high (>10⁻⁹${M}_{\odot }\,{\mathrm{yr}}^{-1}$) mass transfer and mass accretion rate in a detached binary via stellar wind and magnetic coupling.

The New Horizons Solar Wind Around Pluto (NH SWAP) instrument has provided the first direct observations of interstellar ${\rm{H}}{}^{+}$ and He${}^{+}$ pickup ions (PUIs) at distances between ∼11.26 and 38 au in the solar wind. The observations demonstrate that the distant solar wind beyond the hydrogen ionization cavity is indeed mediated by PUIs. The creation of PUIs modifies the underlying low-frequency turbulence field responsible for their own scattering. The dissipation of these low-frequency fluctuations serves to heat the solar wind plasma, and accounts for the observed non-adiabatic solar wind temperature profile and a possible slow temperature increase beyond ∼30 au. We develop a very general theoretical model that incorporates PUIs, solar wind thermal plasma, the interplanetary magnetic field, and low-frequency turbulence to describe the evolution of the large-scale solar wind, PUIs, and turbulence from 1–84 au, the structure of the perpendicular heliospheric termination shock, and the transmission of turbulence into the inner heliosheath, extending the classical models of Holzer and Isenberg. A detailed comparison of the theoretical model solutions and observations derived from the Voyager 2 and NH SWAP data sets shows excellent agreement between the two for reasonable physical parameters.

The Dark Energy Spectroscopic Instrument (DESI) is a Stage IV ground-based dark energy experiment that will be employed on the Mayall 4 m Telescope to study the expansion history of the universe. In the era of massively multiplexed fiber-fed spectrographs, DESI will push the boundaries of fiber spectroscopy with a design capable of taking 5000 simultaneous spectra over 360 to 980 nm. The instrument utilizes a suite of three-channel spectrographs, where volume-phase holographic (VPH) gratings provide dispersions. Thirty-six VPH gratings were produced and their performances were evaluated at the Lawrence Berkeley National Laboratory. We present the design and the evaluation tests for the production run of the VPH gratings, verifying the incidence angle, area-weighted efficiency, and wavefront errors (WFEs). We also present the specialized test set-up developed on-site to assess the grating performances. Measurements of the VPH gratings show high consistency in area-weighted efficiency to within an rms of 2% for the red and near-infrared and 6.2% for the blue gratings. Measured WFEs also showed high consistency per bandpass. Comprehensive evaluations show that the VPH gratings meet DESI performance requirements and have been approved for integration.

The 2D power spectrum is a cornerstone of the modern toolkit for analysis of the low-frequency radio interferometric observations of the 21 cm signal arising from the early universe. Its familiar form disentangles a great deal of systematic information concerning both the sky and telescope and is displayed as a foreground-dominated "brick" and "wedge" on large line-of-sight scales and a complementary "window" on smaller scales. This paper builds on many previous works in the literature that seek to elucidate the varied instrumental and foreground factors that contribute to these familiar structures in the 2D power spectrum. In particular, we consider the effects of uv sampling on the emergence of the wedge. Our results verify the expectation that arbitrarily dense instrument layouts in principle restore the missing information that leads to mode mixing and can therefore mitigate the wedge feature. We derive rule-of-thumb estimates for the required baseline density for complete wedge mitigation, showing that these will be unachievable in practice. We also discuss the optimal shape of the layout, showing that logarithmic regularity in the radial separation of baselines is favorable. While complete suppression of foreground leakage into the wedge is practically unachievable, we find that designing layouts that promote radial density and regularity is able to reduce the amplitude of foreground power by one to three orders of magnitude.

The recent measurement of the global 21 cm absorption signal reported by the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) Collaboration is in tension with the prediction of the ΛCDM model at a 3.8σ significance level. In this work, we report that this tension can be released by introducing an interaction between dark matter and vacuum energy. We perform a model parameter estimation using a combined data set including EDGES and other recent cosmological observations, and find that the EDGES measurement can marginally improve the constraint on parameters that quantify the interacting vacuum, and that the combined data set favors the ΛCDM at a 68% confidence level. This proof-of-concept study demonstrates the potential power of future 21 cm experiments to constrain the interacting dark energy models.

We present the first results of an Atacama Large Millimeter Array survey of the lower fine-structure line of atomic carbon [C i] ${(}^{3}{P}_{1}\,\mbox{--}{}^{3}{P}_{0})$ in far-infrared-selected galaxies on the main sequence at z ∼ 1.2 in the COSMOS field. We compare our sample with a comprehensive compilation of data available in the literature for local and high-redshift starbursting systems and quasars. We show that the [C i] (³P₁ → ³P₀) luminosity correlates on global scales with the infrared luminosity ${L}_{\mathrm{IR}}$, similar to low-J CO transitions. We report a systematic variation of ${L}_{{[{\rm{C}}{\rm{I}}]}^{3}{P}_{1}\,\mbox{--}{}^{3}{P}_{0}}^{{\prime} }$/${L}_{\mathrm{IR}}$ as a function of the galaxy type, with the ratio being larger for main-sequence galaxies than for starbursts and submillimeter galaxies at fixed ${L}_{\mathrm{IR}}$. The ${L}_{{[{\rm{C}}{\rm{I}}]}^{3}{P}_{1}\,\mbox{--}{}^{3}{P}_{0}}^{{\prime} }$/${L}_{\mathrm{CO}(2-1)}^{{\prime} }$ and ${M}_{[{\rm{C}}{\rm{I}}]}$/${M}_{\mathrm{dust}}$ mass ratios are similar for main-sequence galaxies and for local and high-redshift starbursts within a 0.2 dex intrinsic scatter, suggesting that [C i] is a good tracer of molecular gas mass as CO and dust. We derive a fraction of ${f}_{[{\rm{C}}{\rm{I}}]}={M}_{[{\rm{C}}{\rm{I}}]}/{M}_{{\rm{C}}}\sim 3 \% \mbox{--}13 \%$ of the total carbon mass in the atomic neutral phase. Moreover, we estimate the neutral atomic carbon abundance, the fundamental ingredient to calibrate [C i] as a gas tracer, by comparing ${L}_{{[{\rm{C}}{\rm{I}}]}^{3}{P}_{1}\,\mbox{--}{}^{3}{P}_{0}}^{{\prime} }$ and available gas masses from CO lines and dust emission. We find lower [C i] abundances in main-sequence galaxies than in starbursting systems and submillimeter galaxies as a consequence of the canonical α_CO and gas-to-dust conversion factors. This argues against the application to different galaxy populations of a universal standard [C i] abundance derived from highly biased samples.

In this paper we present 3D atmospheric simulations of the hot Jupiter HD 189733b under two different scenarios: local chemical equilibrium and including advection of the chemistry by the resolved wind. Our model consistently couples the treatment of dynamics, radiative transfer, and chemistry, completing the feedback cycle between these three important processes. The effect of wind-driven advection on the chemical composition is qualitatively similar to our previous results for the warmer atmosphere of HD 209458b, found using the same model. However, we find more significant alterations to both the thermal and dynamical structure for the cooler atmosphere of HD 189733b, with changes in both the temperature and wind velocities reaching ∼10%. We also present the contribution function, diagnosed from our simulations, and show that wind-driven chemistry has a significant impact on its 3D structure, particularly for regions where methane is an important absorber. Finally, we present emission phase curves from our simulations and show the significant effect of wind-driven chemistry on the thermal emission, particularly within the 3.6 μm Spitzer/IRAC channel.

Large-scale galactic shocks, predicted by density wave theory, trigger star formation (SF-arms) downstream from the potential of the oldest stars (P-arms), resulting in a color jump from red to blue across spiral arms in the direction of rotation, while aging of these newly formed young stars induces the opposite but coexisting classic age gradient further downstream from the SF-arms. As the techniques for measuring pitch angle are intensity-weighted, they trace both the SF-arms and P-arms and are not sensitive to the classic age gradient. Consequently, the measured pitch angle of spiral arms should be systematically smaller in bluer bandpasses compared to redder bandpasses. We test these predictions using a comprehensive sample of high-quality optical (BVRI) images of bright, nearby spiral galaxies acquired as part of the Carnegie-Irvine Galaxy Survey, supplemented by Spitzer 3.6 μm data to probe evolved stars and Galaxy Evolution Explorer ultraviolet images to trace recent star formation. We apply one-dimensional and two-dimensional techniques to measure the pitch angle of spiral arms, paying close attention to adopt consistent procedures across the different bandpasses to minimize error and systematic bias. We find that the pitch angle of spiral arms decreases mildly but statistically significantly from the reddest to the bluest bandpass, demonstrating conclusively that young stars trace tighter spiral arms than old stars. Furthermore, the correlation between the pitch angle of blue and red bandpasses is nonlinear, such that the absolute value of pitch angle offset increases with increasing pitch angle. Both effects can be naturally explained in the context of the density wave theory for spiral structure.

We present a multiwavelength observational study of IRAS 17008-4040 and IRAS 17009-4042 to probe the star formation (SF) mechanisms operational in both the sites. Each IRAS site is embedded within a massive ATLASGAL 870 μm clump (∼2430–2900 M_⊙), and several parsec-scale filaments at 160 μm are radially directed toward these clumps (at T_d ∼ 25–32 K). The analysis of the Spitzer and VVV photometric data depicts a group of infrared-excess sources toward both the clumps, suggesting the ongoing SF activities. In each IRAS site, high-resolution GMRT radio maps at 0.61 and 1.28 GHz confirm the presence of H ii regions, which are powered by B-type stars. In the site IRAS 17008-4040, a previously known O-star candidate without an H ii region is identified as an infrared counterpart of the 6.7 GHz methanol maser emission (i.e., IRcmme). Based on the Very Large Telescope/NAOS-CONICA adaptive-optics L' image (resolution ∼01), the source IRcmme is resolved into two objects (i.e., IRcmme1 and IRcmme2) within a scale of 900 au that are found to be associated with the Atacama Large Millimeter/submillimeter Array core G345.50M. IRcmme1 is characterized as the main accreting high mass protostellar object candidate before the onset of an ultracompact H ii region. In the site IRAS 17009-4042, the 1.28 GHz map has resolved two radio sources that were previously reported as a single radio peak. Altogether, in each IRAS site, the junction of the filaments (i.e., massive clump) is investigated with the cluster of infrared-excess sources and the ongoing massive SF. This evidence is consistent with the "hub-filament" systems as proposed by Myers.

Understanding the mechanism of core-collapse supernova explosions requires knowledge of the nuclear equation of state (EoS). Recent multi-dimensional numerical simulations indicate that explosions are possible. Nevertheless, it is not yet fully understood which equation of state is realized in the proto-neutron star formed during SN explosions. We examine the EoS sensitivity of the relic supernova neutrino spectrum as a probe of the nuclear EoS. This sensitivity arises largely from the contribution to neutrino emission from failed supernovae. We consider a variety of astrophysical scenarios, which include different progenitor masses for a successful explosion, the cosmological star formation rate, starbursts, quiescent star formation, and the metallicity dependence of the initial mass function. We find that the EoS signature remains robust under a variety of conditions. We demonstrate the viability of future neutrino detectors to distinguish the nuclear EoS via the relic supernova neutrino spectrum.

The enormous sizes and variability of emission of radio-loud active galactic nuclei arise from the relativistic flows of plasma along two oppositely directed jets. We use the Athena hydrodynamics code to simulate an extensive suite of 54 propagating three-dimensional relativistic jets with wide ranges of input jet velocities and jet-to-ambient matter density ratios. We determine which parameter sets yield unstable jets that produce jet-dominated Fanaroff–Riley I (FR I) radio galaxy morphologies and which tend to produce stable jets with hot spots and FR II morphologies. Nearly all our simulations involve jets with internal pressures matched to those of the ambient medium but we also consider over-pressured jets and discuss differences from the standard ones. We also show that the results are not strongly dependent on the adiabatic index of the fluid. We focus on simulations that remain stable for extended distances (60–240 times the initial jet radius). Scaled to the much smaller sizes probed by very long baseline interferometry observations, the fluctuations in such simulated flows yield variability in the observed emissivity on timescales from months. Adopting results for the densities, pressures, and velocities from these simulations, we estimate normalized rest frame synchrotron emissivities from individual cells in the jets. The observed emission from each cell is strongly dependent upon its variable Doppler boosting factor. We sum the fluxes from thousands of zones around the primary reconfinement shock. The light curves and power spectra, with red-noise slopes between −2.1 and −2.5, so produced are similar to those observed from blazars.

Gravitational three-body interaction among binary stars and the supermassive black hole at the center of the Milky Way occasionally ejects a hypervelocity star (HVS) with a velocity of $\sim 1000\,\mathrm{km}\,{{\rm{s}}}^{-1}$. Due to the ejection location, such an HVS initially has negligible azimuthal angular momentum ${L}_{z}\simeq 0\,\mathrm{kpc}\,\mathrm{km}\,{{\rm{s}}}^{-1}$. Even if the halo is mildly triaxial, L_z of a recently ejected nearby HVS remains negligible, since its flight time from the Galactic center is too short to accumulate noticeable torque. However, if we make a wrong assumption about the solar position and velocity, such an HVS would apparently have noticeable nonzero azimuthal angular momentum, due to the wrong reflex motion of the Sun. Conversely, with precise astrometric data for a nearby HVS, we can measure the solar position and velocity by assuming that the HVS has zero azimuthal angular momentum. Based on this idea, here we propose a method to estimate the Galactocentric distance of the Sun R₀ and the Galactocentric solar azimuthal velocity V_⊙ by using an HVS. We demonstrate with mock data for a nearby HVS candidate that the Gaia astrometric data, along with the currently available constraint on V_⊙/R₀ from the proper motion measurement of Sgr A*, can constrain R₀ and V_⊙ with uncertainties of ∼0.27 kpc and ∼7.8 km s⁻¹ (or fractional uncertainties of 3%), respectively. Our method will be a promising tool to constrain (R₀, V_⊙), given that Gaia is expected to discover many nearby HVSs in the near future.

We examine the Planck 2015 cosmic microwave background (CMB) anisotropy data by using a physically consistent energy density inhomogeneity power spectrum generated by quantum-mechanical fluctuations during an early epoch of inflation in the non-flat XCDM model. Here dark energy is parameterized using a fluid with a negative equation of state parameter but with the speed of fluid acoustic inhomogeneities set to the speed of light. We find that the Planck 2015 data in conjunction with baryon acoustic oscillation distance measurements are reasonably well fit by a closed-XCDM model in which spatial curvature contributes a percent of the current cosmological energy density budget. In this model, the measured non-relativistic matter density parameter and Hubble constant are in good agreement with values determined using most other data. Depending on cosmological parameter values, the closed-XCDM model has reduced power, relative to the tilted, spatially flat ΛCDM case, and can partially alleviate the low multipole CMB temperature anisotropy deficit and can help partially reconcile the CMB anisotropy and weak lensing σ₈ constraints, at the expense of somewhat worsening the fit to higher multipole CMB temperature anisotropy data. However, the closed-XCDM inflation model does not seem to improve the agreement much, if at all, compared to the closed ΛCDM inflation case, even though it has one additional free parameter.

In order to investigate the origin of multiple stellar populations found in globular clusters (GCs) in the halo and bulge of the Milky Way, we have constructed chemical evolution models for their putative low-mass progenitors. In light of recent theoretical developments, we assume that supernova blast waves undergo blowout without expelling the pre-enriched ambient gas, while relatively slow winds of massive stars (WMSs), together with the winds and ejecta from low- to high-mass asymptotic giant branch stars, are all locally retained in these less massive systems. Interestingly, we find that the observed Na–O anti-correlations in metal-poor GCs can be reproduced when multiple episodes of starburst and enrichment are allowed to continue in these subsystems. A specific form of star formation history with decreasing time intervals between the successive stellar generations, however, is required to obtain this result, which is in good agreement with the parameters obtained from synthetic horizontal branch models. The "mass budget problem" is also much alleviated by our models without ad hoc assumptions on star formation efficiency, initial mass function, and the preferential loss of first-generation stars. We also apply these models to investigate the origin of super-He-rich red clump stars in the metal-rich bulge suggested by Lee et al. We find that chemical enrichment by the WMSs can naturally reproduce the required strong He enhancement in metal-rich subsystems. Our results further underscore that gas expulsion or retention is a key factor in understanding the multiple populations in GCs.

We investigate the behavior of acoustic waves in a nonisothermal atmosphere based on the analytical solution of the wave equation. Specifically, we consider acoustic waves propagating upwardly in a simple nonisothermal layer where temperature either increases or decreases monotonically with height. We present the solutions for both velocity fluctuation and pressure fluctuation. In these solutions, either velocity or pressure is spatially oscillatory in one part of the layer and nonoscillatory in the other part, with the two parts being smoothly connected to one another. Since the two parts transmit the same amount of wave energy in each frequency, it is unreasonable to identify the oscillating solution with the propagating solution and the nonoscillating solution with the nonpropagating solution. The acoustic cutoff frequency is defined as the frequency that separates the solution that is spatially oscillatory for both velocity and pressure and the solution that is not oscillatory for either velocity or pressure. The cutoff frequency is found to be the same as the Lamb frequency at the bottom in the temperature-decreasing layer but higher than this in the temperature-increasing layer. Based on the transmission efficiency introduced to quantify the wave propagation, we suggest that the acoustic cutoff frequency should be understood as the center of the frequency band where the transition from low acoustic transmission to high transmission takes place, rather than as the frequency sharply separating the propagating solution and the nonpropagating solution.

We present interferometric observations of six O-type stars that were made with the Precision Astronomical Visible Observations beam combiner at the Center for High Angular Resolution Astronomy (CHARA) Array. The observations include multiple brackets for three targets, λ Ori A, ζ Oph, and 10 Lac, but there are only preliminary, single observations of the other three stars, ξ Per, α Cam, and ζ Ori A. The stellar angular diameters range from 0.55 mas for ζ Ori A down to 0.11 mas for 10 Lac, the smallest star yet resolved with the CHARA Array. The rotational oblateness of the rapidly rotating star ζ Oph is directly measured for the first time. We assembled ultraviolet to infrared flux measurements for these stars, and then derived angular diameters and reddening estimates using model atmospheres and an effective temperature set by published results from analysis of the line spectrum. The model-based angular diameters are in good agreement with those observed. We also present estimates for the effective temperatures of these stars, derived by setting the interferometric angular size and fitting the spectrophotometry.

We perform a comparison of ${\text{}}{WMAP}$ 9 year (${\text{}}{WMAP}$ 9) and ${\text{}}{Planck}$ 2015 cosmic microwave background temperature power spectra across multipoles 30 ≤ ℓ ≤ 1200. We generate simulations to estimate the correlation between the two data sets due to cosmic variance from observing the same sky. We find that their spectra are consistent within 1σ. While we do not implement the optimal "C⁻¹" estimator on ${\text{}}{WMAP}$ maps as in the ${\text{}}{WMAP}$ 9 analysis, we demonstrate that the change of pixel weighting only shifts our results at most at the 0.66σ level. We also show that changing the fiducial power spectrum for simulations only impacts the comparison at around 0.1σ level. We exclude ℓ < 30 both because ${\text{}}{WMAP}$ 9 data were included in the ${\text{}}{Planck}$ 2015 ℓ < 30 analysis and because the cosmic variance uncertainty on these scales is large enough that any remaining systematic difference between the experiments is extremely unlikely to affect cosmological constraints. The consistency shown in our analysis provides high confidence in both the ${\text{}}{WMAP}$ 9 temperature power spectrum and the overlapping multipole region of ${\text{}}{Planck}$ 2015's, virtually independent of any assumed cosmological model. Our results indicate that cosmological model differences between ${\text{}}{Planck}$ and ${\text{}}{WMAP}$ do not arise from measurement differences, but from the high multipoles not measured by ${\text{}}{WMAP}$.

In this paper, we present a detailed analysis of a coronal blowout jet eruption that was associated with an obvious extreme-ultraviolet (EUV) wave and one complicated coronal mass ejection (CME) event based on the multiwavelength and multi-view-angle observations from the Solar Dynamics Observatory and the Solar Terrestrial Relations Observatory. It is found that the triggering of the blowout jet was due to the emergence and cancellation of magnetic fluxes on the photosphere. During the rising stage of the jet, the EUV wave appeared just ahead of the jet top, lasting about 4 minutes and at a speed of 458–762 km s⁻¹. In addition, obvious dark material is observed along the EUV jet body, which confirms the observation of a mini-filament eruption at the jet base in the chromosphere. Interestingly, two distinct but overlapped CME structures can be observed in corona together with the eruption of the blowout jet. One is a narrow jet shape, while the other one is a bubble shape. The jet-shaped component was unambiguously related to the outwardly running jet itself, while the bubble-like one might either be produced due to the reconstruction of the high coronal fields or by the internal reconnection during the mini-filament ejection according to the double-CME blowout jet model first proposed by Shen et al., suggesting more observational evidence should be supplied to clear the current ambiguity based on large samples of blowout jets in future studies.

The cosmological numerical simulations tell us that accretion of external metal-poor gas drives star formation (SF) in galaxy disks. One the best pieces of observational evidence supporting this prediction is the existence of low-metallicity star-forming regions in relatively high-metallicity host galaxies. The SF is thought to be fed by metal-poor gas recently accreted. Since the gas accretion is stochastic, there should be galaxies with all the properties of a host but without the low-metallicity starburst. These galaxies have not been identified yet. The exception may be UGC 2162, a nearby ultra-diffuse galaxy (UDG) that combines low surface brightness and relatively high metallicity. We confirm the high metallicity of UGC 2162 ($12+\mathrm{log}({\rm{O}}/{\rm{H}})={8.52}_{-0.24}^{+0.27}$) using spectra taken with the 10 m GTC telescope. UGC 2162 has the stellar mass, metallicity, and star formation rate surface density expected for a host galaxy in between outbursts. This fact suggests a physical connection between some UDGs and metal-poor galaxies, which may be the same type of object in a different phase of the SF cycle. UGC 2162 is a high-metallicity outlier of the mass–metallicity relation, a property shared by the few UDGs with known gas-phase metallicity.

Analyses of infrared signatures of CO₂ in water-dominated ices in the ISM can give information on the physical state of CO₂ in icy grains and on the thermal history of the ices themselves. In many sources, CO₂ was found in the "pure" crystalline form, as signatured by the splitting in the bending mode absorption profile. To a large extent, pure CO₂ is likely to have formed from segregation of CO₂ from a CO₂:H₂O mixture during thermal processing. Previous laboratory studies quantified the temperature dependence of segregation, but no systematic measurement of the concentration dependence of segregation is available. In this study, we measured both the temperature dependence and concentration dependence of CO₂ segregation in CO₂:H₂O mixtures, and found that no pure crystalline CO₂ forms if the CO₂:H₂O ratio is less than 23%. Therefore, the segregation of CO₂ is not always a good thermal tracer of the ice mantle. We found that the position and width of the broad component of the asymmetric stretching vibrational mode of ¹³CO₂ change linearly with the temperature of CO₂:H₂O mixtures, but are insensitive to the concentration of CO₂. We recommend using this mode, which will be observable toward low-mass protostellar envelopes and dense clouds with the James Webb Space Telescope, to trace the thermal history of the ice mantle, especially when segregated CO₂ is unavailable. We used the laboratory measured ¹³CO₂ profile to analyze the ISO-SWS observations of ice mantles toward Young Stellar Objects, and the astrophysical implications are discussed.

We make an analytical estimate of the maximum 21 cm absorption signal from the cosmic dawn, taking into account the inhomogeneity of gas distribution in the intergalactic medium (IGM) due to nonlinear structure formation. The gas located near halos is overdense but adiabatically heated, while the gas far from halos is underdense and hence cooler. The cumulative effect of adiabatic heating and cooling from this gas inhomogeneity results in a reduction in the maximum global 21 cm absorption depth by about 40% as compared with the homogeneous IGM model, assuming saturated coupling between the spin temperature of neutral hydrogen (H i) and the adiabatic gas kinetic temperature.

Intergalactic space is believed to contain nonzero magnetic fields (the Intergalactic Magnetic Field: IGMF), which at scales of megaparsecs would have intensities below 10⁻⁹ G. Very high energy (VHE > 100 GeV) gamma-rays coming from blazars can produce e⁺e⁻ pairs when interacting with the extragalactic background light (EBL) and the cosmic microwave background, generating an electromagnetic cascade of megaparsec scale. The IGMF may produce a detectable broadening of the emission beam that could lead to important constrains both on the IGMF intensity and its coherence length. Using the Monte Carlo–based Elmag code, we simulate the electromagnetic cascade corresponding to two detected TeV sources: PKS 2155-304 visible from the south and H1426+428 visible from the north. Assuming an EBL model and intrinsic spectral properties of the sources, we obtain the spectral and angular distribution of photons when they arrive at Earth. We include the response of the next generation Cherenkov telescopes by using simplified models for Cherenkov Telescope Array (CTA)-south and CTA-north based on a full simulation of each array performance. Combining the instrument properties with the simulated source fluxes, we calculate the telescope point-spread function for null and non-null IGMF intensities and develop a method to test the statistical feasibility of detecting IGMF imprints by comparing the resulting angular distributions. Our results show that for the analyzed source PKS 2155-304 corresponding to the southern site, CTA should be able to detect IGMF with intensities stronger than 10^−14.5 G within an observation time of ∼100 hr.

We evaluate several basic electrodynamic processes as modified by the presence of a very strong magnetic field, exceeding ${B}_{{\rm{Q}}}\equiv {m}^{2}/e=4.4\times {10}^{13}$ G. These results are needed to build models of dissipative phenomena outside magnetars and some other neutron stars. Differential and total cross sections and rates are presented for electron–photon scattering, the annihilation of an electron–positron pair into two photons, the inverse process of two-photon pair creation, and single-photon pair creation into the lowest Landau state. The relative importance of these interactions changes as the background magnetic field grows in strength. The particle phase space relevant for a given process may be restricted by single-photon pair creation, which also opens up efficient channels for pair multiplication, e.g., in combination with scattering. Our results are presented in the form of compact formulae that allow for relativistic electron (positron) motion, in the regime where Landau excitations can be neglected (corresponding to 10³B_Q ≫ B ≫ B_Q for moderately relativistic motion along the magnetic field). Where a direct comparison is possible, our results are tested against earlier calculations, and a brief astrophysical context is provided. A companion paper considers electron–positron scattering, scattering of electrons and positrons by ions, and relativistic electron–ion bremsstrahlung.

The inner part of protoplanetary disks can be threaded by strong magnetic fields. In laboratory levitation experiments, we study how magnetic fields up to 7 mT influence the aggregation of dust by observing the self-consistent collisional evolution of particle ensembles. As dust samples we use mixtures of iron and quartz in different ratios. Without magnetic fields, particles in all samples grow into a bouncing barrier. These aggregates reversibly form larger clusters in the presence of magnetic fields. The size of these clusters depends on the strength of the magnetic field and the ratio between iron and quartz. The clustering increases the size of the largest entities by a factor of a few. If planetesimal formation is sensitive to the size of the largest aggregates, e.g., relying on streaming instabilities, then planetesimals will preferentially grow iron-rich in the inner region of protoplanetary disks. This might explain the iron gradient in the solar system and the formation of dense Mercury-like planets.

The planetary mass and radius sensitivity of exoplanet discovery capabilities has reached into the terrestrial regime. The focus of such investigations is to search within the Habitable Zone where a modern Earth-like atmosphere may be a viable comparison. However, the detection bias of the transit and radial velocity methods lies close to the host star where the received flux at the planet may push the atmosphere into a runaway greenhouse state. One such exoplanet discovery, Kepler-1649b, receives a similar flux from its star as modern Venus does from the Sun, and so was categorized as a possible exoVenus. Here we discuss the planetary parameters of Kepler-1649b in relation to Venus to establish its potential as a Venus analog. We utilize the general circulation model ROCKE-3D to simulate the evolution of the surface temperature of Kepler-1649b under various assumptions, including relative atmospheric abundances. We show that in all our simulations the atmospheric model rapidly diverges from temperate surface conditions toward a runaway greenhouse with rapidly escalating surface temperatures. We calculate transmission spectra for the evolved atmosphere and discuss these spectra within the context of the James Webb Space Telescope Near-Infrared Spectrograph capabilities. We thus demonstrate the detectability of the key atmospheric signatures of possible runaway greenhouse transition states and outline the future prospects of characterizing potential Venus analogs.

We report high-resolution (<100 nm) Mg and Si isotope data of 12 presolar silicate grains (230–440 nm) from red giant and/or asymptotic giant branch stars that were previously identified based on their anomalous O-isotopic compositions (11 Group 1 grains and one Group 2 grain) in five primitive meteorites. The data were acquired by NanoSIMS ion imaging with the new Hyperion ion source that permits Mg and Si isotope measurements of presolar silicates with higher precision than was possible before. For a subset of five Group 1 ("category A") grains, ²⁵Mg/²⁴Mg and ²⁹Si/²⁸Si ratios correlate with the inferred initial ¹⁸O/¹⁶O ratios of their parent stars, a measure of stellar metallicity. The Mg and Si isotope data of category A grains show positive correlations in the δ²⁵Mg–δ²⁶Mg, δ²⁹Si–δ³⁰Si, and δ²⁵Mg–δ²⁹Si spaces. The correlations between O-, Mg, and Si-isotopic compositions are best explained by Galactic chemical evolution (GCE), with only minor imprints of nucleosynthetic and mixing processes in the grains' parent stars. Six Group 1 silicate ("category B") grains have close-to-normal Mg and Si isotopic compositions, possibly the result of isotope exchange in interstellar space or the meteorite parent bodies. For Si in category A grains, we find, with ∼2σ significance, a slightly shallower slope in the δ²⁹Si–δ³⁰Si space for the GCE than inferred from presolar SiC mainstream grains. The 2σ upper limit on the slope for the linear trend in the δ²⁵Mg–δ²⁶Mg space of category A grains is slightly lower than the slope-1 predicted by GCE models around solar metallicity.

Solar cycles are studied with the Version 2 monthly smoothed international sunspot number, the variations of which are found to be well represented by a modified logistic differential equation with four parameters: maximum cumulative sunspot number or total sunspot number x_m, initial cumulative sunspot number x₀, maximum emergence rate r₀, and asymmetry α. A two-parameter function is obtained by taking α and r₀ as fixed values. In addition, it is found that x_m and x₀ can be well determined at the start of a cycle. Therefore, a predictive model of sunspot number is established based on the two-parameter function. The prediction for cycles 4–23 shows that the solar maximum can be predicted with an average relative error of 8.8% and maximum relative error of 22% in cycle 15 at the start of solar cycles if solar minima are already known. The quasi-online method for determining the moment of solar minimum shows that we can obtain the solar minimum 14 months after the start of a cycle. Besides, our model can predict the cycle length with an average relative error of 9.5% and maximum relative error of 22% in cycle 4. Furthermore, we predict the variations in sunspot number of cycle 24 with the relative errors of the solar maximum and ascent time being 1.4% and 12%, respectively, and the predicted cycle length is 11.0 yr (95% confidence interval is 8.3–12.9 yr). A comparison to the observations of cycle 24 shows that our predictive model has good effectiveness.

We report the discovery of an active intermediate-mass black hole (IMBH) candidate in the center of nearby barred bulgeless galaxy NGC 3319. The point X-ray source revealed by archival Chandra and XMM-Newton observations is spatially coincident with the optical and UV galactic nuclei from Hubble Space Telescope observations. The spectral energy distribution derived from the unresolved X-ray and UV-optical flux is comparable with active galactic nuclei rather than ultraluminous X-ray sources, although its bolometric luminosity is only $3.6\times {10}^{40}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$. Assuming an Eddington ratio range between 0.001 and 1, the black hole mass (${M}_{\mathrm{BH}}$) will be in the range 3 × 10² −3 × 10⁵${M}_{\odot }$, placing it in the so-called IMBH regime and making it possibly one of the lowest reported so far. Estimates from other approaches (e.g., fundamental plane, X-ray variability) also suggest ${M}_{\mathrm{BH}}$ ≲ 10⁵${M}_{\odot }$. Similar to other BHs in bulgeless galaxies, the discovered IMBH resides in a nuclear star cluster with mass of ∼6 × 10⁶${M}_{\odot }$. The detection of such a low-mass BH offers us an ideal chance to study the formation and early growth of SMBH seeds, which may result from the bar-driven inflow in late-type galaxies with a prominent bar such as NGC 3319.

There are many candidate sites of the r-process: core-collapse supernovae (CCSNe; including rare magnetorotational core-collapse supernovae), neutron star mergers (NSMs), and neutron star/black hole mergers. The chemical enrichment of galaxies—specifically dwarf galaxies—helps distinguish between these sources based on the continual build-up of r-process elements. This technique can distinguish between the r-process candidate sites by the clearest observational difference—how quickly these events occur after the stars are created. The existence of several nearby dwarf galaxies allows us to measure robust chemical abundances for galaxies with different star formation histories. Dwarf galaxies are especially useful because simple chemical evolution models can be used to determine the sources of r-process material. We have measured the r-process element barium with Keck/DEIMOS medium-resolution spectroscopy. We present the largest sample of barium abundances (almost 250 stars) in dwarf galaxies ever assembled. We measure [Ba/Fe] as a function of [Fe/H] in this sample and compare with existing [α/Fe] measurements. We have found that a large contribution of barium needs to occur at more delayed timescales than CCSNe in order to explain our observed abundances, namely the significantly more positive trend of the r-process component of [Ba/Fe] versus [Fe/H] seen for $[\mathrm{Fe}/{\rm{H}}]\lesssim -1.6$ when compared to the [Mg/Fe] versus [Fe/H] trend. We conclude that NSMs are the most likely source of r-process enrichment in dwarf galaxies at early times.

A survey observation of the DNC (J = 1−0 and J = 3−2) and HN¹³C (J = 1−0 and J = 3−2) emission toward 34 Class 0 and I protostellar sources in the Perseus molecular cloud has been conducted with the NRO 45 m and IRAM 30 m telescopes to explore how the deuterium ratio of the neutral species changes after the birth of a protostar. We have detected the J = 1−0 and J = 3−2 lines of DNC toward 32 sources and the J = 1−0 and J = 3−2 lines of HN¹³C toward 31 and 26 sources, respectively. A mean deuterium ratio of HNC, which is defined as R_D(HNC) = N(DNC)/N(HNC), is found to be 0.049–0.056. We compare R_D(HNC) with physical parameters of the sources, and find a negative correlation between R_D(HNC) and the bolometric temperature. This result suggests that R_D(HNC) decreases as a protostar evolves. Compared with the deuterium ratio of the molecular ion ${{\rm{N}}}_{2}{{\rm{H}}}^{+}$, R_D(HNC) seems to decrease slowly with the protostellar evolution.

Binary–single and binary–binary encounters play a pivotal role in the evolution of star clusters, as they may lead to the disruption or hardening of binaries, a novel prediction of the Hills–Heggie law. Based on our recent Chandra survey of Galactic globular clusters (GCs), we revisit the role of stellar dynamical interactions in GCs, focusing on main-sequence (MS) binary encounters as a potential formation channel of the observed X-ray sources in GCs. We show that the cumulative X-ray luminosity (L_X), a proxy of the total number of X-ray-emitting binaries (primarily cataclysmic variables and coronally active binaries) in a given GC, is highly correlated with the MS binary encounter rate (Γ_b), as ${L}_{{\rm{X}}}\propto {{\rm{\Gamma }}}_{b}^{0.77\pm 0.11}$. We further test the Hills–Heggie law against the binary hardness ratio, defined as the relative number of X-ray-emitting hard binaries to MS binaries and approximated by ${L}_{{\rm{X}}}/({L}_{K}{f}_{b})$, with L_K being the GC K-band luminosity and f_b the MS binary fraction. We demonstrate that the binary hardness ratio of most GCs is larger than that of the solar neighborbood stars, and exhibits a positive correlation with the cluster specific encounter rate (γ), as ${L}_{{\rm{X}}}/({L}_{K}{f}_{b})\propto {\gamma }^{0.65\pm 0.12}$. We also find a strong correlation between the binary hardness ratio and cluster velocity dispersion (σ), with ${L}_{{\rm{X}}}/({L}_{K}{f}_{b})\propto {\sigma }^{1.71\pm 0.48}$, which is consistent with the Hills–Heggie law. We discuss the role of binary encounters in the context of the Nuclear Star Cluster, arguing that the X-ray-emitting, close binaries detected therein could have been predominantly formed in GCs that later inspiralled to the Galactic center.

Following evidence for an east–west elongated virial ring around the Coma galaxy cluster in a ∼220 GeV VERITAS mosaic, we search for corresponding signatures in >GeV γ-rays from Fermi-Large Area Telescope (LAT), and in soft, ∼0.1 keV X-rays from ROSAT. For the ring elongation and orientation inferred from VERITAS, we find a nominal $3.4\sigma$ LAT excess, and the expected signature ($\gt 5\sigma$) in ROSAT bands R1 and R1+R2. The significances of both LAT and ROSAT signals are maximal near the VERITAS ring parameters. The intensities of the ROSAT, Fermi, and VERITAS signals are consistent with the virial shock depositing $\sim 0.3 \%$ (with an uncertainty factor of ∼3) of its energy over a Hubble time in a nearly flat, $p\equiv -d\mathrm{ln}{N}_{e}/d\mathrm{ln}E\simeq 2.0\mbox{--}2.2$ spectrum of cosmic-ray electrons. The sharp radial profiles of the LAT and ROSAT signals suggest preferential accretion in the plane of the sky, as indicated by the distribution of neighboring large-scale structures. The X-ray signal gauges the compression of cosmic-rays as they are advected deeper into the cluster.

This paper focuses on the problem of tracking solar phenomena by creating spatiotemporal trajectories from solar event detection reports. Though tracking of multiple objects in video sequences has seen much research and improvement in recent years, there has been relatively little focus on the domain of tracking solar phenomena (events). In this work, we improve on our previous endeavors by eliminating offline model training requirements and utilizing crowd-sourced human labels to evaluate our performance. We apply our method to the metadata of two solar event types spanning 4 yr of detection reports from the automated detection modules for the Solar Dynamics Observatory mission. We compare our results with those produced by the detection module for active regions and coronal holes by using a crowd-sourced trajectory database as the ground truth. We show that our results are as good as or better than the event-specific detection module for these two event types. This is especially promising because our tracking algorithm is a generalized module for all solar events, and not specific to a single event type, allowing it to be applied to other solar event types reported to the Heliophysics Event Knowledgebase that do not contain tracking information.

The multiwavelength nonthermal emission from the binary neutron star merger event GW170817/GRB170817A has raised a heated debate concerning the post-merger outflow structure. Both a relativistic structured jet viewed off-axis and a mildly relativistic quasi-spherical outflow can explain the observational data up to ∼260 days. We utilize a physically motivated analytic two-parameter model called the "boosted fireball," for the outflow structure after it has expanded far from the merger site. This model consists of a family of outflows with structures varying smoothly between a highly collimated ultra-relativistic jet and an isotropic outflow. We simulate the dynamical evolution of 240 "boosted fireball" outflows using the moving-mesh relativistic hydrodynamics code JET following their evolution through the full afterglow phase. We compute ∼2,000,000 synchrotron spectra from the hydrodynamic simulations. Using scaling relations for the hydrodynamic and radiation equations, we develop a synthetic light-curve generator with efficient sampling speed. This allows the observational data to be fit using Markov Chain Monte Carlo analysis in an eight-dimensional parameter space of hydrodynamic, radiation, and observational parameters. Our results favor the relativistic structured jet, with an opening angle θ₀ ≈ 5° and Lorentz factor Γ ≈ 175, viewed from off-axis angle ${\theta }_{\mathrm{obs}}={27}_{-3}^{+9}$ degrees. Due to parameter degeneracies, we find broad distributions for the explosion energy E₀, the circumburst density n₀, and the electron and magnetic energy fractions _e and _B. High n₀ and low _B can also produce a good fit, indicating that very low n₀ may not be required for GW170817/GRB170817A.

We present an analysis of the final data release of the Carnegie Supernova Project I, focusing on the absolute calibration of the luminosity–decline rate relation for Type Ia supernovae (SNe Ia) using new intrinsic color relations with respect to the color-stretch parameter, s_BV, enabling improved dust extinction corrections. We investigate to what degree the so-called fast-declining SNe Ia can be used to determine accurate extragalactic distances. We estimate the intrinsic scatter in the luminosity–decline rate relation and find it ranges from ±0.13 mag to ±0.18 mag with no obvious dependence on wavelength. Using the Cepheid variable star data from the SH0ES project, the SN Ia distance scale is calibrated and the Hubble constant is estimated using our optical and near-infrared sample, and these results are compared to those determined exclusively from a near-infrared subsample. The systematic effect of the supernova's host galaxy mass is investigated as a function of wavelength and is found to decrease toward redder wavelengths, suggesting this effect may be due to dust properties of the host. Using estimates of the dust extinction derived from optical and near-infrared wavelengths and applying these to the H band, we derive a Hubble constant ${H}_{0}=73.2+/-2.3\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$, whereas using a simple B − V color correction applied to the B band yields ${H}_{0}=72.7+/-2.1\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$. Photometry of two calibrating SNe Ia from the CSP-II sample, SN 2012ht and SN 2015F, is presented and used to improve the calibration of the SN Ia distance ladder.

The Carrington storm (1859 September 1/2) is one of the largest magnetic storms ever observed, and it caused global auroral displays in low-latitude areas, together with a series of multiple magnetic storms from 1859 August 28 to September 4. In this study, we revisit contemporary auroral observation records to extract information on their elevation angle, color, and direction to investigate this stormy interval in detail. We first examine the equatorward boundary of the "auroral emission with multiple colors" based on descriptions of elevation angle and color. We find that their locations were 365 ILAT on August 28/29 and 327 ILAT on September 1/2, suggesting that trapped electrons moved to, at least, L ∼ 1.55 and L ∼ 1.41, respectively. The equatorward boundary of "purely red emission" was likely located at 308 ILAT on September 1/2. If the "purely red emission" was a stable auroral red arc, it would suggest that trapped protons moved to, at least, L ∼ 1.36. This reconstruction with observed auroral emission regions provides conservative estimations of magnetic storm intensities. We compare the auroral records with magnetic observations. We confirm that multiple magnetic storms occurred during this stormy interval, and that the equatorward expansion of the auroral oval is consistent with the timing of magnetic disturbances. It is possible that the August 28/29 interplanetary coronal mass ejections (ICMEs) cleared out the interplanetary medium, making the ICME for the Carrington storm on September 1/2 more geoeffective.

Observations of the baryon to dark matter fraction in galaxies through cosmic time are a fundamental test for galaxy formation models. Recent observational studies have suggested that some disk galaxies at z > 1 host declining rotation curves, in contrast with observations of low redshift disk galaxies where stellar or H i rotation curves flatten at large radii. We present an observational counterexample, a galaxy named DSFG850.95 at z = 1.555 (4.1 Gyr after the big bang) that hosts a flat rotation curve between radii of ∼6–14 kpc (1.2–2.8 disk scale lengths) and has a dark matter fraction of 0.44 ± 0.08 at the H-band half light radius, similar to the Milky Way. We create position–velocity and position–dispersion diagrams using Keck/MOSFIRE spectroscopic observations of Hα and [N ii] emission features, which reveal a flat rotation velocity of V_flat = 285 ± 12 km s⁻¹ and an ionized gas velocity dispersion of σ₀ = 48 ± 4 km s⁻¹. This galaxy has a rotation-dominated velocity field with V_flat/σ₀ ∼ 6. Ground-based H-band imaging reveals a disk with Sérsic index of 1.29 ± 0.03, an edge-on inclination angle of 87° ± 2°, and an H-band half light radius of 8.4 ± 0.1 kpc. Our results point to DSFG850.95 being a massive, rotationally supported disk galaxy with a high dark-matter-to-baryon fraction in the outer galaxy, similar to disk galaxies at low redshift.

We report our Submillimeter Array (SMA) observations of the Class I–II protostar HL Tau in ¹³CO (2–1), C¹⁸O (2–1), SO(5₆–4₅), and 1.3 mm dust-continuum emission and our analyses of the ALMA long baseline data of HCO⁺ (1–0) emission. The 1.3 mm continuum emission observed with the SMA shows compact (∼08 × 05) and extended (∼65 × 43) components, tracing the protoplanetary disk and the protostellar envelope, respectively. The ¹³CO, C¹⁸O, and HCO⁺ show a compact (∼200 au) component at velocities higher than 3 km s⁻¹ from the systemic velocity and an extended (∼1000 au) component at lower velocities. The high-velocity component traces the Keplerian rotating disk, and the low-velocity component traces the infalling envelope. The HCO⁺ high-velocity component is fitted with a Keplerian disk model with a central stellar mass of 1.4 M_⊙. The radial intensity profiles of ¹³CO and C¹⁸O along the disk major axis are fitted with a disk+envelope model, and the gas masses of the disk and envelope are estimated to be (2–40) × 10^–4M_⊙ and $2.9\times {10}^{-3}$M_⊙, respectively. The disk dust mass has been estimated to be (1–3) × 10⁻³M_⊙ in the literature. Thus, our estimated disk gas mass suggests that the gas-to-dust mass ratio in the disk is <10, a factor of 10 lower than the estimated ratio in the envelope. We discuss possible gas depletion or CO depletion in the planet-forming candidate HL Tau in the context of disk and envelope evolution.

The topology of coronal magnetic fields near the open-closed magnetic flux boundary is important to the the process of interchange reconnection, whereby plasma is exchanged between open and closed flux domains. Maps of the magnetic squashing factor in coronal field models reveal the presence of the Separatrix-Web (S-Web), a network of separatrix surfaces and quasi-separatrix layers, along which interchange reconnection is highly likely. Under certain configurations, interchange reconnection within the S-Web could potentially release coronal material from the closed magnetic field regions to high-latitude regions far from the heliospheric current sheet, where it is observed as slow solar wind. It has also been suggested that transport along the S-Web may be a possible cause for the observed large longitudinal spreads of some impulsive, ³He-rich solar energetic particle events. Here, we demonstrate that certain features of the S-Web reveal structural aspects of the underlying magnetic field, specifically regarding the arcing bands of highly squashed magnetic flux observed at the outer boundary of global magnetic field models. In order for these S-Web arcs to terminate or intersect away from the helmet streamer apex, there must be a null spine line that maps a finite segment of the photospheric open-closed boundary up to a singular point in the open flux domain. We propose that this association between null spine lines and arc termination points may be used to identify locations in the heliosphere that are preferential for the appearance of solar energetic particles and plasma from the closed corona, with characteristics that may inform our understanding of interchange reconnection and the acceleration of the slow solar wind.

We detect widespread [C ii] 157.7 μm emission from the inner 5 kpc of the active galaxy NGC 4258 with the SOFIA integral field spectrometer FIFI-LS. The emission is found to be associated with warm H₂, distributed along and beyond the end of the southern jet, in a zone known to contain shock-excited optical filaments. It is also associated with soft X-ray hotspots, which are the counterparts of the "anomalous radio arms" of NGC 4258, and a 1 kpc long filament on the minor axis of the galaxy that contains young star clusters. Palomar CWI Hα integral field spectroscopy shows that the filament exhibits non-circular motions within NGC 4258. Many of the [C ii] profiles are very broad, with the greatest line width, 455 km s⁻¹, observed at the position of the southern jet bow-shock. Abnormally high ratios of L([C ii])/L(FIR) and L([C ii])/L(PAH 7.7 μm) are found along and beyond the southern jet and in the X-ray hotspots. These are the same regions that exhibit unusually large intrinsic [C ii] line widths. This suggests that the [C ii] traces warm molecular gas in shocks and turbulence associated with the jet. We estimate that as much as 40% (3.8 × 10³⁹ erg s⁻¹) of the total [C ii] luminosity from the inner 5 kpc of NGC 4258 arises in shocks and turbulence (<1% bolometric luminosity from the active nucleus), the rest being consistent with [C ii] excitation associated with star formation. We propose that the highly inclined jet is colliding with, and being deflected around, dense irregularities in a thick disk, leading to significant energy dissipation over a wide area of the galaxy.

Solar filaments exhibit a global chirality pattern where dextral/sinistral filaments, corresponding to negative/positive magnetic helicity, are dominant in the northern/southern hemisphere. This pattern is opposite to the sign of magnetic helicity injected by differential rotation along east–west oriented polarity inversion lines, posing a major conundrum for solar physics. A resolution of this problem is offered by the magnetic helicity-condensation model of Antiochos. To investigate the global consequences of helicity condensation for the hemispheric chirality pattern, we apply a temporally and spatially averaged statistical approximation of helicity condensation. Realistic magnetic field configurations in both the rising and declining phases of the solar cycle are simulated. For the helicity-condensation process, we assume convective cells consisting of positive/negative vorticities in the northern/southern hemisphere that inject negative/positive helicity. The magnitude of the vorticity is varied as a free parameter, corresponding to different rates of helicity injection. To reproduce the observed percentages of dominant and minority filament chiralities, we find that a vorticity of magnitude 2.5 × 10⁻⁶ s⁻¹ is required. This rate, however, is insufficient to produce the observed unimodal profile of chirality with latitude. To achieve this, a vorticity of at least 5 × 10⁻⁶ s⁻¹ is needed. Our results place a lower limit on the small-scale helicity injection required to dominate differential rotation and reproduce the observed hemispheric pattern. Future studies should aim to establish whether the helicity injection rate due to convective flows and/or flux emergence across all latitudes of the Sun is consistent with our results.

The Extreme ultraviolet Variability Experiment (EVE) was designed to observe the Sun-as-a-star in the extreme ultraviolet—a wavelength range that has remained spectrally unresolved for many years. It has provided a wealth of data on solar flares, perhaps most uniquely, on the Lyman spectrum of hydrogen at high cadence and moderate spectral resolution. In this paper, we concentrate on the analysis of Lyman continuum (LyC) observations and their temporal evolution in a sample of six major solar flares. By fitting both the pre-flare and flare excess spectra with a blackbody function, we show that the color temperature derived from the slope of LyC reveals temperatures in excess of 10⁴ K in the six events studied—an increase of a few thousand Kelvin above quiet-Sun values (typically ∼8000–9500 K). This was found to be as high as 17000 K for the 2017 September 6 X9.3 flare. Using these temperature values, and assuming a flaring area of 10¹⁸ cm², estimates of the departure coefficient of hydrogen, b₁, were calculated. It was found that b₁ decreased from 10²–10³ in the quiet-Sun, to around unity during the flares. This implies that LyC is optically thick and formed in local thermodynamic equilibrium during flares. It also emanates from a relatively thin (≲100 km) shell formed at deeper, denser layers than in the quiescent solar atmosphere. We show that in terms of temporal coverage and resolution, EVE provides a more comprehensive picture of the response of the chromosphere to the flare energy input with respect to those of the Skylab/Harvard College Observatory spatially resolved observations of the 1970s.

Electromagnetic waves (EMWs) below or near the proton gyrofrequency can be left-hand (LH) or right-hand (RH) polarized waves, which are believed to be fundamentally important in the energization of plasma particles. Proton and alpha beams that are associated with EMW activities are ubiquitous in space and astrophysical plasmas. Based upon linear Vlasov theory, we study the effect of alpha beams on the LH and RH instabilities driven by both the presence of proton and alpha beam populations in a compensated-current system. The results show that the thresholds, real frequencies, and growth rates of both instabilities are highly sensitive to the density and drift velocity of alpha beams. In particular, alpha beams with ${v}_{\mathrm{He}}\lt {v}_{\mathrm{He}}^{L(R)\min }$ inhibit two kinds of instabilities; where ${v}_{\mathrm{He}}^{L(R)\min }$ is the drift velocity of alpha beams with minimum values of growth rates, while for ${v}_{\mathrm{He}}\gt {v}_{\mathrm{He}}^{L(R)\min }$ both the growth rates are enhanced with the density or drift velocity of alpha beams, especially for the LH waves. We also investigate the competition between the LH and RH instabilities. The RH waves have a lower threshold and higher growth rate than the LH waves. Additionally, a comparison of the approximate analytical solutions with the exact numerical calculations based on WHAMP indicates that the analytical results are in good agreement with the numerical calculations. A possible application to EMW activities with respect to the formation and evolution of ion beams in the solar wind is briefly discussed.

We use a linear shallow-water model to investigate the global circulation of the atmospheres of tidally locked planets. Simulations, observations, and simple models show that if these planets are sufficiently rapidly rotating, their atmospheres have an eastward equatorial jet and a hotspot east of the substellar point. We linearize the shallow-water model about this eastward flow and its associated height perturbation. The forced solutions of this system show that the shear flow explains the form of the global circulation, particularly the hotspot shift and the positions of the cold standing waves on the nightside. We suggest that the eastward hotspot shift seen in observations and 3D simulations of these atmospheres is caused by the zonal flow Doppler shifting the stationary wave response eastwards, summed with the height perturbation from the flow itself. This differs from other studies that explained the hotspot shift as pure advection of heat from air flowing eastwards from the substellar point, or as equatorial waves traveling eastwards. We compare our solutions to simulations in our climate model Exo-FMS, and show that the height fields and wind patterns match. We discuss how planetary properties affect the global circulation, and how they change observables such as the hotspot shift or day–night contrast. We conclude that the wave-mean flow interaction between the stationary planetary waves and the equatorial jet is a vital part of the equilibrium circulation on tidally locked planets.

We report a novel radio autocorrelation search for extraterrestrial intelligence. For selected frequencies across the terrestrial microwave window (1–10 GHz), observations were conducted at the Allen Telescope Array to identify artificial non-sinusoidal periodic signals with radio bandwidths greater than 4 Hz, which are capable of carrying substantial messages with symbol rates from 4 to 10⁶ Hz. Out of 243 observations, about half (101) were directed toward sources with known continuum flux >∼1 Jy over the sampled bandwidth (quasars, pulsars, supernova remnants, and masers), based on the hypothesis that they might harbor heretofore undiscovered natural or artificial repetitive, phase or frequency modulation. The rest of the observations were directed mostly toward exoplanet stars with no previously discovered continuum flux. No signals attributable to extraterrestrial technology were found in this study. We conclude that the maximum probability that future observations like the ones described here will reveal repetitively modulated emissions is less than 5% for continuum sources and exoplanets alike. The paper concludes by describing a new approach to expanding this survey to many more targets and much greater sensitivity using archived data from interferometers all over the world.

To understand grain size evolution on the lunar surface in detail, we analyze the distribution of the average grain size $\langle d\rangle$ for the lunar near side obtained by Jeong et al. Furthermore, we analyze the polarimetric properties of the regolith simulants SiC and JSC-1A in a laboratory. We find two characteristics of grain size evolution on the Moon. First, the lunar regolith has evolved on a specific evolutionary pathway in $\langle d\rangle \mbox{--}{\rm{\Phi }}$ space. Here, Φ is defined as the ratio of the perpendicular (${I}_{\perp }$) and parallel (${I}_{\parallel }$) components of the reflectance. Second, we also find that the evolutionary pathway depends on the FeO abundance and selenographic latitude of the surface. The dependence on the FeO content seems to result from the different resistance to comminution of regolith materials, and the dependence on the latitude seems to result from differences in the resurfacing environment. We present the probable causes of these characteristics of grain size evolution on the lunar surface.

With the ever-growing popularity of integral field unit (IFU) spectroscopy, countless observations are being performed over multiple object systems such as blank fields and galaxy clusters. With this, an increasing amount of time is being spent extracting one-dimensional object spectra from large three-dimensional data cubes. However, a great deal of information available within these data cubes is overlooked in favor of photometrically based spatial information. Here we present a novel yet simple approach of optimal source identification utilizing the wealth of information available within an IFU data cube, rather than relying on ancillary imaging. Through the application of these techniques, we show that we are able to obtain object spectra comparable to deep photometry-weighted extractions without the need for ancillary imaging. Further, implementing our custom-designed algorithms can improve the signal-to-noise ratio of extracted spectra and successfully deblend sources from nearby contaminants. This will be a critical tool for future IFU observations of blank and deep fields, especially over large areas where automation is necessary. We implement these techniques in the Python-based spectral extraction software, AutoSpec, which is available via GitHub at https://github.com/a-griffiths/AutoSpec and Zenodo at https://doi.org/10.5281/zenodo.1305848.

In this article, we present a multiwavelength analysis of two X-class solar eruptive flares of classes X2.2 and X9.3 that occurred in the sigmoidal active region NOAA 12673 on 2017 September 6, by combining observations of Atmospheric Imaging Assembly and Helioseismic Magnetic Imager instruments on board the Solar Dynamics Observatory. On the day of the reported activity, the photospheric structure of the active region displayed a very complex network of δ-sunspots that gave rise to the formation of a coronal sigmoid observed in the hot extreme-ultraviolet channels. Both X-class flares initiated from the core of the sigmoid sequentially within an interval of ∼3 hr and progressed as a single sigmoid-to-arcade event. Differential emission measure analysis reveals strong heating of plasma at the core of the active region right from the preflare phase, which further intensified and spatially expanded during each event. The identification of a preexisting magnetic null by non-force-free-field modeling of the coronal magnetic fields at the location of early flare brightenings and remote faint ribbon-like structures during the preflare phase, which were magnetically connected with the core region, provide support for the breakout model of solar eruption. The magnetic extrapolations also reveal flux rope structures before both flares, which are subsequently supported by the observations of the eruption of hot extreme-ultraviolet channels. The second X-class flare diverged from the standard flare scenario in the evolution of two sets of flare ribbons, which are spatially well separated, providing firm evidence of magnetic reconnections at two coronal heights.

In this paper, we provide a physical model for the origin of variations in the shapes and bump strengths of dust attenuation laws in galaxies by combining a large suite of cosmological "zoom-in" galaxy formation simulations with 3D Monte Carlo dust radiative transfer calculations. We model galaxies over three orders of magnitude in stellar mass, ranging from Milky Way–like systems to massive galaxies at high redshift. Critically, for these calculations, we employ a constant underlying dust extinction law in all cases and examine how the role of geometry and radiative transfer effects impacts the resultant attenuation curves. Our main results follow. Despite our usage of a constant dust extinction curve, we find dramatic variations in the derived attenuation laws. The slopes of normalized attenuation laws depend primarily on the complexities of star-to-dust geometry. Increasing fractions of unobscured young stars flatten normalized curves, while increasing fractions of unobscured old stars steepen curves. Similar to the slopes of our model attenuation laws, we find dramatic variation in the 2175 Å ultraviolet bump strength, including a subset of curves with little to no bump. These bump strengths are primarily influenced by the fraction of unobscured O and B stars in our model, with the impact of scattered light having only a secondary effect. Taken together, these results lead to a natural relationship between the attenuation curve slope and 2175 Å bump strength. Finally, we apply these results to a 25 Mpc h⁻¹ box cosmological hydrodynamic simulation in order to model the expected dispersion in attenuation laws at integer redshifts from z = 0 to 6. A significant dispersion is expected at low redshifts and decreases toward z = 6. We provide tabulated results for the best-fit median attenuation curve at all redshifts.

We carry out a blind search of 3 mm continuum sources using the ALMA Science Archive to derive the first galaxy number counts at this wavelength. The analyzed data are drawn from observations toward three extragalactic legacy fields: COSMOS, CDF-S, and the UDS comprising more than 130 individual ALMA Band 3 pointings and an effective survey area of ≈200 arcmin² with a continuum sensitivity that allows for the direct detection of unlensed Dusty Star-forming Galaxies (DSFGs) dust emission beyond the epoch of reionization. We present a catalog of 16 sources detected at >5σ with flux densities ${S}_{3\mathrm{mm}}\approx 60\mbox{--}600\,\mu \mathrm{Jy}$ from which number counts are derived. These number counts are then used to place constraints on the volume density of DSFGs with an empirical backward evolution model. Our measured 3 mm number counts indicate that the contribution of DSFGs to the cosmic star formation rate density at z ≳ 4 is non-negligible. This is contrary to the generally adopted assumption of a sharply decreasing contribution of obscured galaxies at z > 4 as inferred by optical and near-infrared surveys. This work demonstrates the power of ALMA-3 mm observations, which can reach outstanding continuum sensitivities during typical spectral line science programs. Further constraints on 3 mm selected galaxies will be essential to refine models of galaxy formation and evolution as well as models of early universe dust production mechanisms.

In this paper, we address two issues related to primordial disk evolution in three clusters (NGC 1333, IC 348, and Orion A) observed by the INfrared Spectra of Young Nebulous Clusters (IN-SYNC) project. First, in each cluster, averaged over the spread of age, we investigate how disk lifetime is dependent on stellar mass. The general relation in IC 348 and Orion A is that primordial disks around intermediate-mass stars (2–5 M_⊙) evolve faster than those around loss-mass stars (0.1–1 M_⊙), which is consistent with previous results. However, considering only low-mass stars, we do not find a significant dependence of disk frequency on stellar mass. These results can help to better constrain theories on gas giant planet formation timescales. Second, in the Orion A molecular cloud, in the mass range of 0.35–0.7M_⊙, we provide the most robust evidence to date for disk evolution within a single cluster exhibiting modest age spread. By using surface gravity as an age indicator and employing 4.5 μm excess as a primordial disk diagnostic, we observe a trend of decreasing disk frequency for older stars. The detection of intra-cluster disk evolution in NGC 1333 and IC 348 is tentative, since the slight decrease of disk frequency for older stars is a less than 1σ effect.

The H₂ mass of molecular clouds has traditionally been traced by the CO(J = 1−0) rotational transition line. This said, CO is relatively easily photodissociated and can also be destroyed by cosmic rays, thus rendering some fraction of molecular gas to be "CO-dark." We investigate the amount and physical properties of CO-dark gas in two z ∼ 0 disk galaxies and develop predictions for the expected intensities of promising alternative tracers ([C i] 609 μm and [C ii] 158 μm emission). We do this by combining cosmological zoom simulations of disk galaxies with thermal-radiative-chemical equilibrium interstellar medium (ISM) calculations to model the predicted H i and H₂ abundances and CO (J = 1−0), [C i] 609 μm, and [C ii] 158 μm emission properties. Our model treats the ISM as a collection of radially stratified clouds whose properties are dictated by their volume and column densities, the gas-phase metallicity, and the interstellar radiation field (ISRF) and CR ionization rates. Our main results follow. Adopting an observationally motivated definition of CO-dark gas, i.e., H₂ gas with W_CO < 0.1 K km s⁻¹, we find that a significant amount (≳50%) of the total H₂ mass lies in CO-dark gas, most of which is diffuse gas, poorly shielded due to low dust column density. The CO-dark molecular gas tends to be dominated by [C ii], though [C i] also serves as a bright tracer of the dark gas in many instances. At the same time, [C ii] also tends to trace neutral atomic gas. As a result, when we quantify the conversion factors for the three carbon-based tracers of molecular gas, we find that [C i] suffers the least contamination from diffuse atomic gas and is relatively insensitive to secondary parameters.

Recently, Chen et al. accurately determined the volume weighted halo velocity bias in simulations and found that the deviation of velocity bias from unity is much weaker than the peak model prediction. Here we present a possible explanation of this vanishing velocity bias. The starting point is that halos are peaks in the low redshift non-Gaussian density field with smoothing scale R_Δ (virial radius), instead of peaks in the high-redshift initial Gaussian density field with a factor of ${ \mathcal O }({{\rm{\Delta }}}^{1/3})$ larger smoothing scale. Based on the approximation that the density field can be Gaussianized by a local and monotonic transformation, we extend the peak model to the non-Gaussian density field and derive the analytical expression of velocity dispersion and velocity power spectrum of these halos. The predicted deviation of velocity bias from unity is indeed much weaker than the previous prediction, and the agreement with the simulation results is significantly improved.

We present Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm (230 GHz) observations of the HD 32297 and HD 61005 debris disks, two of the most iconic debris disks because of their dramatic swept-back wings seen in scattered light images. These observations achieve sensitivities of 14 and 13 μJy beam⁻¹ for HD 32297 and HD 61005, respectively, and provide the highest resolution images of these two systems at millimeter wavelengths to date. By adopting a Markov Chain Monte Carlo modeling approach, we determine that both disks are best described by a two-component model consisting of a broad (ΔR/R > 0.4) planetesimal belt with a rising surface density gradient and a steeply falling outer halo aligned with the scattered light disk. The inner and outer edges of the planetesimal belt are located at 78.5 ± 8.1 au and 122 ± 3 au for HD 32297, and 41.9 ± 0.9 au and 67.0 ± 0.5 au for HD 61005. The halos extend to 440 ± 32 au and 188 ± 8 au, respectively. We also detect ¹²CO J = 2–1 gas emission from HD 32297 co-located with the dust continuum. These new ALMA images provide observational evidence that larger, millimeter-sized grains may also populate the extended halos of these two disks previously thought to only be composed of small, micron-sized grains. We discuss the implications of these results for potential shaping and sculpting mechanisms of asymmetric debris disks.

We present a systematic study of the cosmic variance that existed in the formation of the first stars and galaxies. We focus on the cosmic variance induced by the large-scale density and velocity environment engraved at the epoch of recombination. The density environment is predominantly determined by the dark-matter overdensity, and the velocity environment by the dark matter–baryon streaming velocity. Toward this end, we introduce a new cosmological initial condition generator, BCCOMICS, which solves the quasi-linear evolution of small-scale perturbations in the large-scale density and streaming-velocity environment and generates the initial condition for dark matter and baryons, as either particles or grid data at a specific redshift. We also describe a scheme to simulate the formation of the first galaxies inside density peaks and voids, where a local environment is treated as a separate universe. The resulting cosmic variance in the number density of minihalos and the amount of cooling mass are presented as an application. Density peaks become a site for enhanced formation of the first galaxies, which compete with the negative effect from the dark matter–baryon streaming velocity on structure formation.

We examine new and pre-existing wide-field, continuum-corrected, narrowband images in H₂ 1-0 S(1) and Brγ of three regions of massive star formation: IC 1396, Cygnus OB2, and Carina. These regions contain a variety of globules, pillars, and sheets, so we can quantify how the spatial profiles of emission lines behave in photodissociation regions (PDRs) that differ in their radiation fields and geometries. We have measured 450 spatial profiles of H₂ and Brγ along interfaces between H ii regions and PDRs. Brγ traces photoevaporative flows from the PDRs, and this emission declines more rapidly with distance as the radius of curvature of the interface decreases, in agreement with models. As noted previously, H₂ emission peaks deeper into the cloud relative to Brγ, where the molecular gas absorbs far-UV radiation from nearby O stars. Although PDRs in IC 1396, Cygnus OB2, and Carina experience orders of magnitude different levels of ionizing flux and have markedly differing geometries, all of the PDRs have spatial offsets between Brγ and H₂ on the order of 10¹⁷cm. There is a weak negative correlation between the offset size and the intensity of ionizing radiation and a positive correlation with the radius of curvature of the cloud. We can reproduce both the size of the offsets and the dependencies of the offsets on these other variables with simple photoevaporative flow models. Both Brγ and H₂ 1-0 S(1) will undoubtedly be targeted in future James Webb Space Telescope observations of PDRs, so this work can serve as a guide to interpreting these images.

In this paper, we study the onset process of a solar eruption on 2015 February 21, focusing on its unambiguous precursor phase. With multiwavelength imaging observations from the Atmospheric Imaging Assembly (AIA), definitive tether-cutting (TC) reconnection signatures, i.e., flux convergence and cancellation, bidirectional jets, and topology change of hot loops, were clearly observed below the pre-eruption filament. As TC reconnection progressed between the sheared arcades that enveloped the filament, a channel-like magnetic flux rope (MFR) arose in multiwavelength AIA passbands wrapping around the main axis of the filament. With the subsequent ascent of the newborn MFR, the filament surprisingly split into three branches. After a 7 hr slow-rise phase, the high-lying branch containing the MFR abruptly accelerated causing a two-ribbon flare; while the two low-lying branches remained stable forming a partial eruption. Complemented by kinematic analysis and decay index calculation, we conclude that TC reconnection played a key role in building up the eruptive MFR and triggering its slow rise. The onset of the torus instability may have led the high-lying branch into the standard eruption scenario in the fashion of a catastrophe.

Foregrounds with polarization states that are not smooth functions of frequency present a challenge to H i Epoch of Reionization (EOR) power spectrum measurements if they are not cleanly separated from the desired Stokes I signal. The intrinsic polarization impurity of an antenna's electromagnetic response limits the degree to which components of the polarization state on the sky can be separated from one another, leading to the possibility that this frequency structure could be confused for H i emission. We investigate the potential of Faraday rotation by Earth's ionosphere to provide a mechanism for both mitigation of and systematic tests for this contamination. Specifically, we consider the delay power spectrum estimator, which relies on the expectation that foregrounds will be separated from the cosmological signal by a clearly demarcated boundary in Fourier space and is being used by the Hydrogen Epoch of Reionization Array (HERA) experiment. Through simulations of visibility measurements that include the ionospheric Faraday rotation calculated from real historical ionospheric plasma density data, we find that the incoherent averaging of the polarization state over repeated observations of the sky may attenuate polarization leakage in the power spectrum by a factor of 10 or more. Additionally, this effect provides a way to test for the presence of polarized foreground contamination in the EOR power spectrum estimate.

We imaged silicon monoxide masers toward the asymptotic giant branch star R Cas at 23 intervals covering almost 2 pulsation cycles. The masers are concentrated in a shell within 4 stellar radii. Between 19 and 62 features were identified per epoch and 184 of these were matched at 3 or more epochs, forming 38 series. The features probably survive more epochs than their detectable masers. We compared the proper motions and polarization of these clumps, providing the first complete assessment of the net expansion velocity over more than one cycle and the significance of the magnetic field. Proper motions are irregular, dominated by outflow (infall) in the first (second) cycles. Sixty-five matched pairs had maser polarization angles consistent within π/8. A small excess (22) of this subsample has proper motion vectors within ±225 of being parallel to the inferred magnetic field, 10 of which have approximately radial proper motions. The average field strength needed to provide a magnetic energy density equivalent to the bulk kinetic and thermal energy densities of a clump is ∼2 G, similar to direct magnetic field measurements. While some clumps possess a consistent magnetic field, capable of influencing the direction of motion, only a minority flow along magnetic field lines. The resultant SiO expansion proper motion over the entire periods is ∼0.4 km s⁻¹ (taking ∼67 yr to cross the shell), which, compared with the mass in the shell, implies a wind similar to mass-loss rates from the literature measured on larger scales.

High-resolution spectroscopic observations of the K0 II–III star α UMa were taken at the Elginfield Observatory over 11 years. Radial velocities were measured for nine of these years. They do not cover enough of the 44.5 year orbital period to give definitive elements on their own, but combined with published visual orbits, the spectroscopic-orbit parameters are well constrained. The spectra show no evidence of the secondary star, which remains an unsolved puzzle. Line-depth ratios show that α UMa has temperature variations ∼3 K, possibly periodic, over the 2001–2010 interval. Fourier analysis of the line broadening gives the projected rotation velocity of 2.66 ± 0.15 km s⁻¹ and a radial-tangential macroturbulence dispersion of 4.97 ± 0.08 km s⁻¹. The third-granulation signature shows the granulation velocities of α UMa to be essentially solar, with a scale factor of 0.98 ± 0.10. The absolute radial velocity of the star, with granulation blueshifts removed is −10,035 ± 100 m s⁻¹ at the mean time of the observations, 2005.2544. The line bisector of Fe iλ6253 is normal and shows the classic "C" shape with the blue-most point commensurate with its absolute magnitude. Mapping this bisector on to the third signature gives a flux deficit similar to those of other giants, with a fractional area of 0.131, suggesting a temperature difference between granules and lanes of 127 K. The velocity position of the deficit is slightly higher than that for previously analyzed giants, extending the correlation with absolute magnitude.

We present photometry of 30 Galactic RR Lyrae variables taken with HST WFC3/IR for the Carnegie-Chicago Hubble Program. These measurements form the base of the distance-ladder measurements that comprise a pure Population II base to a measurement of H_o at an accuracy of 3%. These data are taken with the same instrument and filter (F160W) as our observations of RR Lyrae stars in external galaxies so as to minimize sources of systematic error in our calibration of the extragalactic distance scale. We calculate mean magnitudes based on one to three measurements for each RR Lyrae star using star-by-star templates generated from densely time-sampled data at optical and midinfrared wavelengths. We use four RR Lyrae stars from our sample with well-measured HST parallaxes to determine a zero-point. This zero-point will soon be improved with the large number of precise parallaxes to be provided by Gaia. We also provide preliminary calibration with the TGAS and Gaia DR2 data, and all three zero points are in agreement, to within their uncertainties.

We present a new technique to determine distances to major star-forming regions across the Perseus Molecular Cloud, using a combination of stellar photometry, astrometric data, and ¹²CO spectral-line maps. Incorporating the Gaia DR2 parallax measurements when available, we start by inferring the distance and reddening to stars from their Pan-STARRS1 and Two Micron All Sky Survey photometry, based on a technique presented by Green et al. and implemented in their 3D "Bayestar" dust map of three-quarters of the sky. We then refine their technique by using the velocity slices of a CO spectral cube as dust templates and modeling the cumulative distribution of dust along the line of sight toward these stars as a linear combination of the emission in the slices. Using a nested sampling algorithm, we fit these per-star distance–reddening measurements to find the distances to the CO velocity slices toward each star-forming region. This results in distance estimates explicitly tied to the velocity structure of the molecular gas. We determine distances to the B5, IC 348, B1, NGC 1333, L1448, and L1451 star-forming regions and find that individual clouds are located between ≈275 and 300 pc, with typical combined uncertainties of ≈5%. We find that the velocity gradient across Perseus corresponds to a distance gradient of about 25 pc, with the eastern portion of the cloud farther away than the western portion. We determine an average distance to the complex of 294 ± 17 pc, about 60 pc further than the distance derived to the western portion of the cloud using parallax measurements of water masers associated with young stellar objects. The method we present is not limited to the Perseus Complex, but may be applied anywhere on the sky with adequate CO data in the pursuit of more accurate 3D maps of molecular clouds in the solar neighborhood and beyond.

We carry out a series of local, shearing-box simulations of the outer regions of protoplanetary disks, where ambipolar diffusion is important due to low ionization levels, to better characterize the nature of turbulence and angular momentum transport in these disks. These simulations are divided into two groups, one with far-ultraviolet (FUV) ionization included, and one without FUV. In both cases, we explore a large range in diffusivity values. We find that in the simulations without FUV, the properties of the turbulence are similar to the unstratified simulations of Bai & Stone; for a given diffusivity, the magnetorotational instability (MRI) can still be present so long as the magnetic field is sufficiently weak. Furthermore, the dynamics of the midplane in these simulations are primarily controlled by the MRI. In the FUV simulations on the other hand, the MRI-active FUV layers transport strong toroidal magnetic flux to the midplane, which shuts off the MRI. Instead, angular momentum transport at the midplane is dominated by laminar magnetic fields, resulting in lower levels of turbulent Maxwell stress compared to the no-FUV simulations. Finally, we perform a temporal correlation analysis on the FUV simulations, confirming our result that the dynamics in the midplane region is strongly controlled by the FUV-ionized layers.