adsabs/SciX_UAT_keywords huggingface dataset:
CEERS: Diversity of Lyα Emitters during the Epoch of Reionization

We analyze rest-frame ultraviolet to optical spectra of three z ≃ 7.47–7.75 galaxies whose Lyα emission lines were previously detected with Keck/MOSFIRE observations, using the JWST/NIRSpec observations from the Cosmic Evolution Early Release Science survey. From NIRSpec data, we confirm the systemic redshifts of these Lyα emitters, and emission-line ratio diagnostics indicate these galaxies were highly ionized and metal-poor. We investigate Lyα line properties, including the line flux, velocity offset, and spatial extent. For the one galaxy where we have both NIRSpec and MOSFIRE measurements, we find a significant offset in their flux measurements (∼1.3–5× greater in MOSFIRE) and a marginal difference in the velocity shifts. The simplest interpretation is that the Lyα emission is extended and not entirely encompassed by the NIRSpec slit. The cross-dispersion profiles in NIRSpec reveal that Lyα in one galaxy is significantly more extended than the nonresonant emission lines. We also compute the expected sizes of ionized bubbles that can be generated by the Lyα sources and discuss viable scenarios for the creation of sizable ionized bubbles (>1 physical Mpc). The source with the highest-ionization condition is possibly capable of ionizing its own bubble, while the other two do not appear to be capable of ionizing such a large region, but require additional sources of ionizing photons. Therefore, the fact that we detect Lyα from these galaxies suggests diverse scenarios for the escape of Lyα during the epoch of reionization. High-spectral-resolution spectra with JWST/NIRSpec will be extremely useful for constraining the physics of patchy reionization.

Keywords: reionization; early universe; intergalactic medium; high-redshift galaxies; lyman-alpha galaxies; extragalactic astronomy
A Blueprint for the Milky Way's Stellar Populations: The Power of Large Photometric and Astrometric Surveys

Recent advances from astronomical surveys have revealed spatial, chemical, and kinematical inhomogeneities in the inner region of the stellar halo of the Milky Way. In particular, large spectroscopic surveys, combined with Gaia astrometric data, have provided powerful tools for analyzing the detailed abundances and accurate kinematics for individual stars. Despite these noteworthy efforts, however, spectroscopic samples are typically limited by the numbers of stars considered; their analysis and interpretation are also hampered by the complex selection functions that are often employed. Here we present a powerful alternative approach—a synoptic view of the spatial, chemical, and kinematical distributions of stars in the Milky Way based on large photometric survey databases, enabled by a well-calibrated technique for obtaining individual stellar metal abundances from broadband photometry. We combine metallicities with accurate proper motions from the Gaia mission along the prime meridian of the Galaxy, and find that various stellar components are clearly separated from each other in the metallicity versus rotation-velocity space. The observed metallicity distribution of the inner-halo stars deviates from the traditional single-peaked distribution, and exhibits complex substructures comprising varying contributions from individual stellar populations, sometimes with striking double peaks at low metallicities. The substructures revealed from our less-biased, comprehensive maps demonstrate the clear advantages of this approach, which can be built upon by future multiband photometric surveys, and used as a blueprint for identifying the stars of greatest interest for upcoming spectroscopic studies.

Keywords: milky way stellar halo; milky way dynamics; surveys; milky way formation; stellar abundances; milky way disk; galactic abundances; stellar populations; galaxy stellar content; milky way galaxy; galaxy structure
Outside the Wall: Hydrodynamics of Type I Supernovae Interacting with a Partially Swept-up Circumstellar Medium

Explaining the observed diversity of supernovae (SNe) and the physics of explosion requires knowledge of their progenitor stars, which can be obtained by constraining the circumstellar medium (CSM). Models of the SN ejecta colliding with the CSM are necessary to infer the structure of the CSM and tie it back to a progenitor model. Recent SNe I revealed CSM concentrated at a distance r ∼ 1016 cm, for which models of SN interaction are extremely limited. In this paper, we assume the concentrated region is a "wall" representing swept-up material, and unswept material lies outside the wall. We simulate one-dimensional hydrodynamics of SNe Ia and Ib impacting 300 unique CSM configurations using RT1D, which captures the Rayleigh-Taylor instability. We find that the density ratio between the wall and ejecta—denoted A0 or "wall height"—is key, and higher walls deviate more from self-similar evolution. Functional fits accounting for A0 are presented for the forward-shock radius evolution. We show that higher walls have more degeneracy between CSM properties in the deceleration parameter, slower shocks, deeper-probing reverse shocks, slower shocked ejecta, less ejecta mass than CSM in the shock, and more mixing of ejecta into the CSM at early times. We analyze observations of SN 2014C (Type Ib) and suggest that it had a moderately high wall (10 ≲ A0 ≲ 200) and wind-like outer CSM. We also postulate an alternate interpretation for the radio data of SN 2014C, that the radio rise occurs in the wind rather than the wall. Finally, we find that hydrodynamic measurements at very late times cannot distinguish the presence of a wall, except perhaps as an anomalously wide shock region.

Keywords: circumstellar gas; type ia supernovae; type ib supernovae; stellar mass loss; shocks
Type IIP Supernova IV. Shock Breakout from Progenitor Stars Modeled with Convective Overshoot and Mass Loss

Red supergiant stars lose a lot of mass in slow winds that forms a circumstellar medium (CSM) around the star. When the star retains a substantial hydrogen envelope at the time of explosion, it displays characteristic light curves and spectra of a Type II plateau supernova (SN), e.g., the nearby SN 2013ej. When the shock wave launched deep inside the star exits the surface, it probes the CSM and scripts the history of mass loss from the star. We simulate with the STELLA code the SN radiative display resulting from shock breakout (SBO) for a set of progenitor stars. We evolved these stars with the MESA code from their main-sequence to core-collapse phase using diverse evolutionary inputs. We explore the SN display for different internal convective overshoot and compositional mixing inside the progenitor stars and two sets of mass-loss schemes, one the standard "Dutch" scheme and the other an enhanced, episodic and late mass loss. The SBO from the star shows closely time-separated double-peaked bolometric light curves for the Dutch case, as well as high-velocity ejecta with minuscule mass accelerated during SBO. The earlier of the peaks, which we call the precursor peaks, are compared with analytical expressions for SBO of stars. We also contrast the breakout flash from an optically thick CSM with that of the rarefied medium established by Dutch wind. We describe how the multigroup photon spectra of the breakout flashes differ between these cases.

Keywords: core-collapse supernovae; stellar mass loss; shocks; stellar convective zones
Star Formation Activity beyond the Outer Arm. II. Distribution and Properties of Star Formation

The outer Galaxy beyond the Outer Arm represents a promising opportunity to study star formation in an environment vastly different from the solar neighborhood. In our previous study, we identified 788 candidate star-forming regions in the outer Galaxy (at galactocentric radii R G ≥ 13.5 kpc) based on the Wide-field Infrared Survey Explorer (WISE) mid-infrared (MIR) all-sky survey. In this paper, we investigate the statistical properties of the candidates and their parental molecular clouds derived from the Five College Radio Astronomy Observatory (FCRAO) CO survey. We show that the molecular clouds with candidates have cloud mass functions with shallower slopes, larger fractions of clouds bound by self-gravity, and a greater density than the molecular clouds without candidates. To investigate the star formation efficiency (SFE) at different R G, we used two parameters: (1) the fraction of molecular clouds with candidates and (2) the monochromatic MIR luminosities of candidates per parental molecular cloud mass. We did not find any clear correlation between SFE parameters and R G at R G of 13.5-20.0 kpc, suggesting that the SFE is independent of environmental parameters such as metallicity and gas surface density, which vary considerably with R G. Previous studies reported that the SFE per year (SFE/yr) derived from the star formation rate surface density per total gas surface density, H I plus H2, decreases with increased R G. Our results might suggest that the decreasing trend is due to a decrease in the conversion of H I gas to H2 gas.

Keywords: molecular clouds; star formation; interstellar medium; milky way galaxy
The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). XI. Statistical Study of Early Fragmentation

Fragmentation during the early stages of high-mass star formation is crucial for understanding the formation of high-mass clusters. We investigated fragmentation within 39 high-mass star-forming clumps as part of the Atacama Large Millimeter/submillimeter Array Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES) survey. Considering projection effects, we have estimated core separations for 839 cores identified from the continuum emission and found mean values between 0.08 and 0.32 pc within each clump. We find compatibility of the observed core separations and masses with the thermal Jeans length and mass, respectively. We also present subclump structures revealed by the 7 m array continuum emission. Comparison of the Jeans parameters using clump and subclump densities with the separation and masses of gravitationally bound cores suggests that they can be explained by clump fragmentation, implying the simultaneous formation of subclumps and cores within rather than a step-by-step hierarchical fragmentation. The number of cores in each clump positively correlates with the clump surface density and the number expected from the thermal Jeans fragmentation. We also find that the higher the fraction of protostellar cores, the larger the dynamic range of the core mass, implying that the cores are growing in mass as the clump evolves. The ASHES sample exhibits various fragmentation patterns: aligned, scattered, clustered, and subclustered. Using the ${ \mathcal Q }$ -parameter, which can help distinguish between centrally condensed and subclustered spatial core distributions, we finally find that in the early evolutionary stages of high-mass star formation, cores tend to follow a subclustered distribution.

Keywords: star formation; infrared dark clouds
Anharmonic Vibrational Spectrum and Experimental Matrix Isolation Study of Thioformic Acid Conformers-Potential Candidates for Molecular Cloud and Solar System Observations?

Thioformic acid (TFA) is the sulfur analog of formic acid, the simplest organic acid. It has three analogs, HCOSH, HCSOH, and HCSSH, each of them having two rotational isomeric (rotameric) forms: trans and cis where the trans form is energetically more stable. In this article, we study computational energetics and anharmonic vibrational spectrum of TFA, including overtone and combination vibrations. We also studied experimental photoisomerization and photodecomposition channels of HCOSH molecules with different wavelengths. We suggest that TFA is a potential sulfur-containing candidate molecule for interstellar and planetary observations and discuss these in light of different radiation environments in space. More generally, we discuss that infrared radiation-driven photoisomerization reactions may be a common phenomenon in such environments and can affect the chemical reaction pathways of organic and other interstellar molecules.

Keywords: molecular clouds; molecular spectroscopy; astrochemistry
Synthetic Detections of Interstellar Objects with the Rubin Observatory Legacy Survey of Space and Time

The discovery of two interstellar objects passing through the solar system, 1I/'Oumuamua and 2I/Borisov, implies that a galactic population exists with a spatial number density of order ~0.1 au-3. The forthcoming Rubin Observatory Legacy Survey of Space and Time (LSST) has been predicted to detect more asteroidal interstellar objects like 1I/'Oumuamua. We apply recently developed methods to simulate a suite of galactic populations of interstellar objects with a range of assumed kinematics, albedos, and size-frequency distributions (SFDs). We incorporate these populations into the objectsInField algorithm, which simulates detections of moving objects by an arbitrary survey. We find that the LSST should detect between ~0 and 70 asteroidal interstellar objects every year (assuming the implied number density), with sensitive dependence on the SFD slope and characteristic albedo of the host population. The apparent rate of motion on the sky-along with the associated trailing loss-appears to be the largest barrier to detecting interstellar objects. Specifically, a relatively large number of synthetic objects would be detectable by the LSST if not for their rapid sky motion (>0.°5 day-1). Therefore, algorithms that could successfully link and detect rapidly moving objects would significantly increase the number of interstellar object discoveries with the LSST (and in general). The mean diameter of detectable, inactive interstellar objects ranges from ~50 to 600 m and depends sensitively on the SFD slope and albedo.

Keywords: interstellar objects
Observations of Binary Stars with the Differential Speckle Survey Instrument. IX. Observations of Known and Suspected Binaries, and a Partial Survey of Be Stars

We report 370 measures of 170 components of binary and multiple-star systems, obtained from speckle imaging observations made with the Differential Speckle Survey Instrument at Lowell Observatory's Discovery Channel Telescope in 2015 through 2017. Of the systems studied, 147 are binary stars, 10 are seen as triple systems, and 1 quadruple system is measured. Seventy-six high-quality nondetections and 15 newly resolved components are presented in our observations. The uncertainty in relative astrometry appears to be similar to our previous work at Lowell, namely, linear measurement uncertainties of approximately 2 mas, and the relative photometry appears to be uncertain at the 0.1-0.15 mag level. Using these measures and those in the literature, we calculate six new visual orbits, including one for the Be star 66 Oph and two combined spectroscopic-visual orbits. The latter two orbits, which are for HD 22451 (YSC 127) and HD 185501 (YSC 135), yield individual masses of the components at the level of 2% or better, and independent distance measures that in one case agrees with the value found in the Gaia DR2 and in the other disagrees at the 2σ level. We find that HD 22451 consists of an F6V+F7V pair with orbital period of 2401.1 ± 3.2 days and masses of 1.342 ± 0.029 and $1.236\pm 0.026\,{M}_{\odot } . For HD 185501, both stars are G5 dwarfs that orbit one another with a period of 433.94 ± 0.15 days, and the masses are 0.898 ± 0.012 and $0.876\pm 0.012\,{M}_{\odot } . We discuss the details of both the new discoveries and the orbit objects.

Keywords: interferometric binary stars; spectroscopic binary stars; visual binary stars; astronomical techniques; be stars
The HOSTS Survey: Evidence for an Extended Dust Disk and Constraints on the Presence of Giant Planets in the Habitable Zone of β Leo

The young (50-400 Myr) A3V star β Leo is a primary target to study the formation history and evolution of extrasolar planetary systems as one of the few stars with known hot (∼1600 K), warm (∼600 K), and cold (∼120 K) dust belt components. In this paper, we present deep mid-infrared measurements of the warm dust brightness obtained with the Large Binocular Telescope Interferometer (LBTI) as part of its exozodiacal dust survey (HOSTS). The measured excess is 0.47% ± 0.050% within the central 1.5 au, rising to 0.81% ± 0.026% within 4.5 au, outside the habitable zone of β Leo. This dust level is 50 ± 10 times greater than in the solar system's zodiacal cloud. Poynting-Robertson drag on the cold dust detected by Spitzer, and Herschel underpredicts the dust present in the habitable zone of β Leo, suggesting an additional delivery mechanism (e.g., comets) or an additional belt at ∼5.5 au. A model of these dust components is provided that implies the absence of planets more than a few Saturn masses between ∼5 au and the outer belt at ∼40 au. We also observationally constrain giant planets with the LBTI imaging channel at 3.8 μm wavelength. Assuming an age of 50 Myr, any planet in the system between approximately 5-50 au must be less than a few Jupiter masses, consistent with our dust model. Taken together, these observations showcase the deep contrasts and detection capabilities attainable by the LBTI for both warm exozodiacal dust and giant exoplanets in or near the habitable zone of nearby stars.

Keywords: exozodiacal dust; exoplanets; direct imaging; long baseline interferometry
The Open Cataclysmic Variable Catalog

The Open Cataclysmic Variable Catalog is a publicly available live catalog through a University of Washington website that contains over 12,000 candidate and known cataclysmic variables compiled from major ongoing sky surveys. Using software based on AstroCats, a daily updated catalog of the names, R.A., decl. and discovery date and other available information is constructed. The magnitude and type of cataclysmic variable is listed only if the original source contained this information. Comments can be added on entries to include any follow-up data obtained. The number of entries will continue to grow as future sky surveys are added to the catalog.

Keywords: cataclysmic variable stars; catalogs
Gravitoviscous Protoplanetary Disks with a Dust Component. V. The Dynamic Model for Freeze-out and Sublimation of Volatiles

The snowlines of various volatile species in protoplanetary disks are associated with abrupt changes in gas composition and dust physical properties. Volatiles may affect dust growth, as they cover grains with icy mantles that can change the fragmentation velocity of the grains. In turn, dust coagulation, fragmentation, and drift through the gas disk can contribute to the redistribution of volatiles between the ice and gas phases. Here we present the hydrodynamic model FEOSAD for protoplanetary disks with two dust populations and volatile dynamics. We compute the spatial distributions of major volatile molecules (H2O, CO2, CH4, and CO) in the gas, on small and grown dust, and analyze the composition of icy mantles over the initial 0.5 Myr of disk evolution. We show that most of the ice arrives to the surface of the grown dust through coagulation with small grains. Spiral structures and dust rings forming in the disk, as well as photodissociation in the outer regions, lead to the formation of complex snowline shapes and multiple snowlines for each volatile species. During the considered disk evolution, the snowlines shift closer to the star, with their final position being a factor of 4-5 smaller than that at the disk formation epoch. We demonstrate that volatiles tend to collect in the vicinity of their snowlines, both in the ice and gas phases, leading to the formation of thick icy mantles potentially important for dust dynamics. The dust size is affected by a lower fragmentation velocity of bare grains in the model with a higher turbulent viscosity.

Keywords: protoplanetary disks; circumstellar dust; protostars
High-resolution Imaging of a TESS Control Sample: Verifying a Deficit of Close-in Stellar Companions to Exoplanet Host Stars

The large number of exoplanets discovered with the Transiting Exoplanet Survey Satellite (TESS) means that any observational biases from TESS could influence the derived stellar multiplicity statistics of exoplanet host stars. To investigate this problem, we obtained speckle interferometry of 207 control stars whose properties in the TESS Input Catalog (TIC) closely match those of an exoplanetary host star in the TESS Object of Interest (TOI) catalog, with the objective of measuring the fraction of these stars that have companions within ∼1.″2. Our main result is the identification of a bias in the creation of the control sample that prevents the selection of binaries with 0.″1 ≲ ρ ≲ 1.″2 and Δmag ≲3. This bias is the result of large astrometric residuals that cause binaries with these parameters to fail the quality checks used to create the TIC, which in turn causes them to have incomplete stellar parameters (and uncertainties) in the TIC. Any stellar multiplicity study that relies exclusively upon TIC stellar parameters to identify its targets will struggle to select unresolved binaries in this parameter space. Left uncorrected, this selection bias disproportionately excludes high-mass-ratio binaries, causing the mass-ratio distribution of the companions to deviate significantly from the uniform distribution expected of FGK-type field binaries. After accounting for this bias, the companion rate of the FGK control stars is consistent with the canonical 46% ± 2% rate from Raghavan et al., and the mass-ratio distribution agrees with that of binary TOI host stars. There is marginal evidence that the control-star companions have smaller projected orbital separations than TOI host stars from previous studies.

Keywords: speckle interferometry; exoplanet astronomy
High-mass Starless Clumps: Dynamical State and Correlation between Physical Parameters

In order to study the initial conditions of massive star formation, we have previously built a sample of 463 high-mass starless clumps (HMSCs) across the inner Galactic plane covered by multiple continuum surveys. Here, we use 13CO(2-1) line data from the SEDIGISM survey, which covers 78° in longitude (-60° < l < 18°, ∣b∣ < 0.°5) with 30″ resolution, to investigate the global dynamical state of these parsec-scale HMSCs (207 sources with good-quality data, mass 102-105 M ⊙, size 0.1-3.6 pc). We find that most HMSCs are highly turbulent with a median Mach number ${{ \mathcal M }}_{{ \mathcal S }}\sim 8.2$ , and 44%-55% of them are gravitationally bound (with virial parameter α vir ≲ 2) if no magnetic fields are present. A median magnetic field strength of 0.33-0.37 mG would be needed to support these bound clumps against collapse, in agreement with previous observations of magnetic fields in regions of massive star formation. Luminosity-to-mass ratio, an important tracer of evolutionary stage, is strongly correlated with dust temperature. Magnetic field strength is also correlated with density. The Larson line width-size scaling does not hold in HMSCs. This study advances our understanding of the global properties of HMSCs, and our high-resolution observations with the Atacama Large Millimeter/submillimeter Array are in progress to study the resolved properties.

Keywords: molecular clouds; interstellar medium; star formation; interstellar dynamics; interstellar magnetic fields