adsabs/SciX_UAT_keywords huggingface dataset:
The Final Months of Massive Star Evolution from the Circumstellar Environment around SN Ic 2020oi

We present the results of Atacama Large Millimeter/submillimeter Array (ALMA) band 3 observations of the nearby type Ic supernova (SN) 2020oi. Under the standard assumptions on the SN-circumstellar medium (CSM) interaction and the synchrotron emission, the data indicate that the CSM structure deviates from a smooth distribution expected from the steady-state mass loss in the very vicinity of the SN (≲1015 cm), which is then connected to the outer smooth distribution (≳1016 cm). This structure is further confirmed through the light-curve modeling of the whole radio data set as combined with the previously reported data at lower frequency. Because this is an explosion of a bare carbon-oxygen (C+O) star with a fast wind, we can trace the mass-loss history of the progenitor of SN 2020oi in the final year. The inferred nonsmooth CSM distribution corresponds to fluctuations on the subyear timescale in the mass-loss history toward the SN explosion. Our finding suggests that the pre-SN activity is likely driven by the accelerated change in the nuclear burning stage in the last moments just before the massive star's demise. The structure of the CSM derived in this study is beyond the applicability of the other methods at optical wavelengths, highlighting the importance and uniqueness of quick follow-up observations of SNe by ALMA and other radio facilities.

Keywords: supernovae; circumstellar matter; radio sources; millimeter astronomy; stellar evolution
Deuterated Polycyclic Aromatic Hydrocarbons in the Interstellar Medium: The C-D Band Strengths of Monodeuterated Species

Deuterium (D) is one of the light elements created in the Big Bang. As the Galaxy evolves, the D/H abundance in the interstellar medium (ISM) decreases from its primordial value due to astration. However, the observed gas-phase D/H abundances of some sightlines in the local Galactic ISM are substantially lower than the expected reduction by astration. The missing D could have been depleted onto polycyclic aromatic hydrocarbon (PAH) molecules which are ubiquitous and abundant in interstellar regions. To quantitatively explore the hypothesis of PAHs as a possible reservoir of interstellar D, we quantum-chemically compute the infrared vibrational spectra of monodeuterated PAHs and their cations. We find that, as expected, when H in PAHs is replaced by D, the C-H stretching and bending modes at 3.3, 8.6, and 11.3 μm shift to longer wavelengths at ∼4.4, 11.4, and 15.4 μm, respectively, by a factor of ∼ $\sqrt{13/7}$ , the difference in reduced mass between the C-H and C-D oscillators. From the computed spectra we derive the mean intrinsic band strengths of the 3.3 μm C-H stretch and 4.4 μm C-D stretch to be $\langle {A}_{3.3}\rangle \approx 13.2\,\mathrm{km}\,{\mathrm{mol}}^{-1}$ and $\langle {A}_{4.4}\rangle \approx 7.3\,\mathrm{km}\,{\mathrm{mol}}^{-1}$ for neutral deuterated PAHs which would dominate the interstellar emission at 3.3 and 4.4 μm. By comparing the computationally derived mean band-strength ratio of $\langle {A}_{4.4}/{A}_{3.3}\rangle \approx 0.56$ for neutral PAHs with the mean ratio of the observed intensities of $\langle {I}_{4.4}/{I}_{3.3}\rangle \approx 0.019$ , we find that the degree of deuteration (i.e., the fraction of peripheral atoms attached to C atoms in the form of D) is ∼2.4%, corresponding to a D enrichment of a factor of ∼1200 with respect to the interstellar D/H abundance.

Keywords: polycyclic aromatic hydrocarbons; interstellar line emission; line intensities; astrochemistry; interstellar molecules
SAGAbg. I. A Near-unity Mass-loading Factor in Low-mass Galaxies via Their Low-redshift Evolution in Stellar Mass, Oxygen Abundance, and Star Formation Rate

Measuring the relation between star formation and galactic winds is observationally difficult. In this work we make an indirect measurement of the mass-loading factor (the ratio between the mass outflow rate and star formation rate) in low-mass galaxies using a differential approach to modeling the low-redshift evolution of the star-forming main sequence and mass–metallicity relation. We use Satellites Around Galactic Analogs (SAGA) background galaxies, i.e., spectra observed by the SAGA Survey that are not associated with the main SAGA host galaxies, to construct a sample of 11,925 spectroscopically confirmed low-mass galaxies from 0.01 ≲ z ≤ 0.21 and measure auroral line metallicities for 120 galaxies. The crux of the method is to use the lowest-redshift galaxies as the boundary condition of our model, and to infer a mass-loading factor for the sample by comparing the expected evolution of the low-redshift reference sample in stellar mass, gas-phase metallicity, and star formation rate against the observed properties of the sample at higher redshift. We infer a mass-loading factor of ${\eta }_{{\rm{m}}}={0.92}_{-0.74}^{+1.76}$ , which is in line with direct measurements of the mass-loading factor from the literature despite the drastically different sets of assumptions needed for each approach. While our estimate of the mass-loading factor is in good agreement with recent galaxy simulations that focus on resolving the dynamics of the interstellar medium, it is smaller by over an order of magnitude than the mass-loading factor produced by many contemporary cosmological simulations.

Keywords: amorphous irregular galaxies; dwarf irregular galaxies; galaxy winds; galaxy chemical evolution
A Featureless Infrared Transmission Spectrum for the Super-puff Planet Kepler-79d

Extremely low-density planets ("super-puffs") are a small but intriguing subset of the transiting planet population. With masses in the super-Earth range (1 - 10 ${M}_{\oplus }$ ) and radii akin to those of giant planets (> 4 ${R}_{\oplus }$ ), their large envelopes may have been accreted beyond the water snow line and many appear to be susceptible to catastrophic mass loss. Both the presence of water and the importance of mass loss can be explored using transmission spectroscopy. Here, we present new Hubble space telescope WFC3 spectroscopy and updated Kepler transit depth measurements for the super-puff Kepler-79d. We do not detect any molecular absorption features in the 1.1 - 1.7 μm WFC3 bandpass, and the combined Kepler and WFC3 data are consistent with a flat-line model, indicating the presence of aerosols in the atmosphere. We compare the shape of Kepler-79d's transmission spectrum to predictions from a microphysical haze model that incorporates an outward particle flux due to ongoing mass loss. We find that photochemical hazes offer an attractive explanation for the observed properties of super-puffs like Kepler-79d, as they simultaneously render the near-infrared spectrum featureless and reduce the inferred envelope mass-loss rate by moving the measured radius (optical depth unity surface during transit) to lower pressures. We revisit the broader question of mass-loss rates for super-puffs and find that the age estimates and mass-loss rates for the majority of super-puffs can be reconciled if hazes move the photosphere from the typically assumed pressure of ∼10 mbar to $\sim 10\ \mu $ bar.

Keywords: exoplanet atmospheres; exoplanet evolution; exoplanets
AT 2023clx: The Faintest and Closest Optical Tidal Disruption Event Discovered in Nearby Star-forming Galaxy NGC 3799

We report the discovery of a faint optical tidal disruption event (TDE) in the nearby star-forming galaxy NGC 3799. Identification of the TDE is based on its position at the galaxy nucleus, a light curve declining as t ‑5/3, a blue continuum with an almost constant blackbody temperature of ∼12,000 K, broad (≈15,000 km s‑1) Balmer lines, and characteristic He II 4686 Å emission. The light curve of AT 2023clx peaked at an absolute magnitude of ‑17.16 mag in the g band and a maximum blackbody bolometric luminosity of 4.56 × 1042 erg s‑1, making it the faintest TDE discovered to date. With a redshift of 0.01107 and a corresponding luminosity distance of 47.8 Mpc, it is also the closest optical TDE ever discovered to the best of our knowledge. Furthermore, our analysis of Swift/XRT observations of AT 2023clx yields a very tight 3σ upper limit of 9.53 × 1039 erg s‑1 in the range 0.3–10 keV. AT 2023clx, together with very few other faint TDEs such as AT 2020wey, prove that there are probably a large number of faint TDEs yet to be discovered at higher redshifts, which is consistent with the prediction of luminosity functions (LFs). The upcoming deeper optical time-domain surveys, such as the Legacy Survey of Space and Time and the Wide Field Survey Telescope, will discover more TDEs at even lower luminosities, allowing for a more precise constraint of the low end of the LF.

Keywords: tidal disruption; time domain astronomy
Constraints on the Velocity Dispersion of Dark Matter from Cosmology and New Bounds on Scattering from the Cosmic Dawn

The observational value of the velocity dispersion, ${\rm{\Delta }}\upsilon $ , is missing in the dark matter (DM) puzzle. Nonzero or nonthermal DM velocities can drastically influence large-scale structure and the 21 cm temperature at the epoch of the cosmic dawn, as well as the estimation of DM physical parameters, such as mass and interaction couplings. To study the phenomenology of ${\rm{\Delta }}\upsilon $ , we model the evolution of DM in terms of a simplistic and generic Boltzmann-like momentum distribution. Using cosmological data from the cosmic microwave background, baryonic acoustic oscillations, and red luminous galaxies, we constrain the DM velocity dispersion for a broad range of masses, ${10}^{-3}\,\mathrm{eV}\lt {{\rm{m}}}_{\chi }\lt {10}^{9}\,\mathrm{eV}$ , finding ${\rm{\Delta }}{\upsilon }_{0}\lesssim 0.33\mathrm{km}\ {{\rm{s}}}^{-1}$ (99% CL). Including the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) T21 measurements, we extend our study to constrain the baryon-DM interaction in the range of DM velocities allowed by our analysis. As a consequence, we present new bounds on two electromagnetic models of DM, namely minicharged particles (MCPs) and the electric dipole moment (EDM). For MCPs, the parameter region that is consistent with EDGES and independent bounds on cosmological and stellar physics is very small, pointing to the subelectronvolt mass regime of DM. A window in the MeV-GeV may still be compatible with these bounds for MCP models without a hidden photon. But the EDM parameter region consistent with EDGES is excluded by Big Bang nucleosynthesis and collider physics.

Keywords: dark matter; cosmology; large-scale structure of the universe; reionization; cosmological neutrinos; particle astrophysics; warm dark matter; cold dark matter; hot dark matter; solar particle emission; dark matter detectors
Excess C/H in Protoplanetary Disk Gas from Icy Pebble Drift Across the CO Snowline

The atmospheric composition of giant planets carries the information of their formation history. Superstellar C/H ratios are seen in atmospheres of Jupiter, Saturn, and various giant exoplanets. Also, giant exoplanets show a wide range of C/O ratio. To explain these ratios, one hypothesis is that protoplanets accrete carbon-enriched gas when a large number of icy pebbles drift across the CO snowline. Here we report the first direct evidence of an elevated C/H ratio in disk gas. We use two thermo-chemical codes to model the 13C18O, C17O, and C18O (2-1) line spectra of the HD 163296 disk. We show that the gas inside the CO snowline (∼70 au) has a C/H ratio that is 1-2 times higher than the stellar value. This ratio exceeds the expected value substantially, as only 25%-60% of the carbon should be in gas at these radii. Although we cannot rule out the case of a normal C/H ratio inside 70 au, the most probable solution is an elevated C/H ratio that is 2-8 times higher than the expectation. Our model also shows that the gas outside 70 au has a C/H ratio that is 0.1× the stellar value. This picture of enriched C/H gas at the inner region and depleted gas at the outer region is consistent with numerical simulations of icy pebble growth and drift in protoplanetary disks. Our results demonstrate that the large-scale drift of icy pebble can occur in disks and may significantly change the disk gas composition for planet formation.

Keywords: planet formation; exoplanet atmospheres; astrochemistry; protoplanetary disks
Lyα Emission at z = 7–13: Clear Evolution of Lyα Equivalent Width Indicating a Late Cosmic Reionization History

We present the evolution of Lyα emission derived from 53 galaxies at z = 6.6–13.2, which have been identified by multiple JWST/NIRSpec spectroscopy programs of Early Release Science, General Observer, Director's Discretionary Time, and Guaranteed Time Observations. These galaxies fall on the star formation main sequence and are typical star-forming galaxies with UV magnitudes of ‑22.5 ≤ M UV ≤ ‑17.0. We find that 15 out of 53 galaxies show Lyα emission at the >3σ level, and we obtain Lyα equivalent width (EW) measurements and stringent 3σ upper limits for the 15 and 38 galaxies, respectively. Confirming that Lyα velocity offsets and line widths of our galaxies are comparable to those of low-redshift Lyα emitters, we investigate the redshift evolution of the Lyα EW. We find that Lyα EWs statistically decrease toward high redshifts on the Lyα EW versus the M UV plane for various probability distributions of the uncertainties. We then evaluate neutral hydrogen fractions x H I with the redshift evolution of the Lyα EW and the cosmic reionization simulation results on the basis of a Bayesian inference framework, and obtain x H I < 0.79, $={0.62}_{-0.36}^{+0.15}$ <?MML = 0.62 ‑ 0.36 + 0.15 ?> , and ${0.93}_{-0.07}^{+0.04}$ <?MML 0.93 ‑ 0.07 + 0.04 ?> at z ∼ 7, 8, and 9–13, respectively. These moderately large x H I values are consistent with the Planck cosmic microwave background optical depth measurement and previous x H I constraints from galaxy and QSO Lyα damping wing absorption and strongly indicate a late reionization history. Such a late reionization history suggests that major sources of reionization would emerge late and be hosted by moderately massive halos compared with the widely accepted picture of abundant low-mass objects for the sources of reionization.

Keywords: galaxy evolution; high-redshift galaxies; reionization
Multiepoch Optical Spectroscopy of the Post-AGB Star HD 161796

The evolutionary rate of the pulsating post-asymptotic giant branch (post-AGB) star HD 161796 was suspected to be high. Spectra of HD 161796 acquired during a time span of 18 yr are analyzed with the main goal of determining the evolutionary increase in temperature and comparing it with the latest post-AGB star evolutionary models. Inspection of the spectra reveals splitting and significant temporal variation in strong absorption lines, suggesting the presence of shock waves in the atmosphere of the pulsating star. The Hα profiles point to variable incipient mass loss. Most medium-strength lines have variable blue wings, while the red wings remain stationary, presumably due to variations in the warm outflow from the stellar surface. The modeling of the spectra suggests the average value for the effective temperature to be 7275 K, and for surface gravity, a value of log g = 0.7. Different iron abundances are found for different spectra, probably due to the inability to model the pulsating photosphere with stationary atmospheric models. On average, we arrive at [Fe/H] = -0.06. The observed underabundance in neutron capture and some other elements is inferred to be a consequence of dust-gas separation. It is confirmed that, during pulsation, the stellar surface is hotter when the star is smaller in size. The spectra show a 420 K range in effective temperature-a smaller variation than can be found from pulsation-related changes in color. No significant rate of evolution is seen, contrary to earlier suggestions. The initial mass of the star is evaluated to be ⪅2 M ⊙.

Keywords: post-asymptotic giant branch stars; uu herculis stars; stellar atmospheres; late stellar evolution; stellar pulsations; interstellar abundances
Lower Bounds on the Thickness and Dust Content of Layers within the North Polar Layered Deposits of Mars from Radar Forward Modeling

The Mars Reconnaissance Orbiter's Shallow Radar (SHARAD) emits radar signals and records their reflections from layer boundaries within the Martian north polar ice cap. Previous studies have suggested that the ice cap is composed of thin dust-rich layers between thicker layers of nearly pure water ice. The prevailing hypotheses suggest that each dust-rich layer represents either a period of ice sublimation at the poles or a period of reduced ice deposition relative to dust deposition. To test whether thin dust beds are a plausible hypothesis for the observed SHARAD reflectors, we use RadSPy (radar sounding simulator in Python, https://github.com/scourvil/RadSPy.git), an open-source N-layer radar sounder forward-modeling software that we have developed and describe herein. We forward model radar data from thin dust-rich beds interspersing pure ice, and compare them to observed radar reflection data over Gemina Lingula in the north polar layered deposits (NPLD). We consider two end-member cases: (1) thin beds composed entirely of dust, but with thickness varying from 0.05 m to 0.4 m; and (2) dust beds all with the same thickness, but with varying dust content. We find that the observed reflections can be explained by either scenario, i.e., varying thickness or varying dust content, and we conclude that a combination of both is likely. More importantly, our results provide lower bounds on the layer thickness and dust fraction for the flat-lying reflectors of Gemina Lingula in the NPLD. Our findings support the thin dust layer hypothesis, providing new constraints on layer composition and geometry for Mars climate researchers.

Keywords: planetary science
The Atacama Cosmology Telescope: Millimeter Observations of a Population of Asteroids or: ACTeroids

We present fluxes and light curves for a population of asteroids at millimeter wavelengths, detected by the Atacama Cosmology Telescope (ACT) over 18,000 deg2 of the sky using data from 2017 to 2021. We utilize high cadence maps, which can be used in searching for moving objects such as asteroids and trans-Neptunian Objects, as well as for studying transients. We detect 170 asteroids with a signal-to-noise of at least 5 in at least one of the ACT observing bands, which are centered near 90, 150, and 220 GHz. For each asteroid, we compare the ACT measured flux to predicted fluxes from the near-Earth asteroid thermal model fit to WISE data. We confirm previous results that detected a deficit of flux at millimeter wavelengths. Moreover, we report a spectral characteristic to this deficit, such that the flux is relatively lower at 150 and 220 GHz than at 90 GHz. Additionally, we find that the deficit in flux is greater for S-type asteroids than for C-type.

Keywords: asteroids; cosmic microwave background radiation; millimeter astronomy
Testing the Galaxy-collision-induced Formation Scenario for the Trail of Dark-matter-deficient Galaxies with the Susceptibility of Globular Clusters to the Tidal Force

It has been suggested that a trail of diffuse galaxies, including two dark-matter-deficient galaxies (DMDGs), in the vicinity of NGC 1052 formed because of a high-speed collision between two gas-rich dwarf galaxies, one bound to NGC 1052 and the other one on an unbound orbit. The collision compresses the gas reservoirs of the colliding galaxies, which in turn triggers a burst of star formation. In contrast, the dark matter and preexisting stars in the progenitor galaxies pass through it. Since the high pressures in the compressed gas are conducive to the formation of massive globular clusters (GCs), this scenario can explain the formation of DMDGs with large populations of massive GCs, consistent with the observations of NGC 1052-DF2 (DF2) and NGC 1052-DF4. A potential difficulty with this "mini bullet cluster" scenario is that the observed spatial distributions of GCs in DMDGs are extended. GCs experience dynamical friction causing their orbits to decay with time. Consequently, their distribution at formation should have been even more extended than that observed at present. Using a semianalytic model, we show that the observed positions and velocities of the GCs in DF2 imply that they must have formed at a radial distance of 5-10 kpc from the center of DF2. However, as we demonstrate, the scenario is difficult to reconcile with the fact that the strong tidal forces from NGC 1052 strip the extendedly distributed GCs from DF2, requiring 33-59 massive GCs to form at the collision to explain observations.

Keywords: dark matter; galaxy formation; galaxy evolution; galaxy interactions; low surface brightness galaxies
The Automatic Learning for the Rapid Classification of Events (ALeRCE) Alert Broker

We introduce the Automatic Learning for the Rapid Classification of Events (ALeRCE) broker, an astronomical alert broker designed to provide a rapid and self-consistent classification of large etendue telescope alert streams, such as that provided by the Zwicky Transient Facility (ZTF) and, in the future, the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). ALeRCE is a Chilean-led broker run by an interdisciplinary team of astronomers and engineers working to become intermediaries between survey and follow-up facilities. ALeRCE uses a pipeline that includes the real-time ingestion, aggregation, cross-matching, machine-learning (ML) classification, and visualization of the ZTF alert stream. We use two classifiers: a stamp-based classifier, designed for rapid classification, and a light curve-based classifier, which uses the multiband flux evolution to achieve a more refined classification. We describe in detail our pipeline, data products, tools, and services, which are made public for the community (see https://alerce.science). Since we began operating our real-time ML classification of the ZTF alert stream in early 2019, we have grown a large community of active users around the globe. We describe our results to date, including the real-time processing of 1.5 × 108 alerts, the stamp classification of 3.4 × 107 objects, the light-curve classification of 1.1 × 106 objects, the report of 6162 supernova candidates, and different experiments using LSST-like alert streams. Finally, we discuss the challenges ahead in going from a single stream of alerts such as ZTF to a multistream ecosystem dominated by LSST.

Keywords: supernovae; variable stars; active galactic nuclei; astroinformatics; surveys; classification; astrostatistics; convolutional neural networks; random forests; cloud computing; distributed computing; small solar system bodies