adsabs/SciX_UAT_keywords huggingface dataset:
Characterizing the 3D Structure of Molecular Cloud Envelopes in the Cloud Factory Simulations

We leverage recent numerical simulations of highly resolved star-forming regions in a Milky Way–like galaxy to explore the nature of extended gaseous envelopes around molecular clouds. We extract a sample of two dozen star-forming clouds from the feedback-dominated suite of Cloud Factory simulations. With the goal of exploring the 3D thermal and chemical structure of the gas, we measure and fit the clouds' radial profiles with multiple tracers, including ${n}_{{{\rm{H}}}_{I}}$ , ${n}_{{{\rm{H}}}_{2}}$ , ${n}_{{{\rm{H}}}_{\mathrm{tot}}}$ , n CO, and gas temperature. We find that while solar neighborhood clouds recently detected via 3D dust mapping have radially symmetric, low-density envelopes that extend ∼10–15 pc, the simulated cloud envelopes are primarily radially asymmetric with low-density envelopes that extend only ∼2–3 pc. One potential explanation for the absence of extended envelopes in the simulated clouds may be the lack of magnetic fields, while a stronger local feedback prescription compared to solar neighborhood conditions may drive the radially asymmetric cloud morphologies. We make the pipeline used to extract and characterize the radial profiles of the clouds publicly available, which can be used in complementary and future simulations to shed additional light on the key physics shaping the formation and evolution of star-forming structures in the Milky Way.

Keywords: diffuse molecular clouds; molecular clouds; interstellar clouds; hydrodynamical simulations
Understanding the Early Stages of Galaxy Formation Using Very Metal-poor Stars from the Hamburg/ESO Survey

We explore the chemodynamical properties of a sample of very metal-poor (VMP) stars selected from the Hamburg/ESO survey, matched with Gaia EDR3, in the phase space identified by the three integrals of motion (L z , E, I 3). Disk and halo orbits are separated by using the criteria defined in Carollo & Chiba. We found 26 stars with [Fe/H] ≤ -2.5 possessing disk kinematics, of which 13 are extremely metal-poor. At these metallicities, the number of stars with disk kinematics is three times its retrograde counterpart. In the same range of metallicity we also identified 37 halo stars most tightly bound to the gravitational potential of the progenitor halo. The origins of these stars are investigated by comparing the observational results with simulated galaxies from the Aquarius Project and the IllustrisTNG simulations. We found two mechanisms of formation of VMP stars with disk kinematics: accretion from early satellites (which is dominant), and in situ formation. These stars are very old, with ages >12.5 Gyr (z > 5), and they are α-enriched. Accretion and in situ formation are also found for the retrograde counterparts, with accretion also being the dominant mode. Contributing accreted satellites have stellar masses in the range 106-109 M ☉ and are very gas-rich. The most bound halo stars are the oldest detected, with a median age of ~13.3 Gyr (z ~ 11), and are α-enriched. Our finding clearly shows that very old, VMP stars store important information on the first stages of assembly of our Galaxy and its halo.

Keywords: galaxy formation; galaxy dynamics; population iii stars
Time-series and Phase-curve Photometry of the Episodically Active Asteroid (6478) Gault in a Quiescent State Using APO, GROWTH, P200, and ZTF

We observed the episodically active asteroid (6478) Gault in 2020 with multiple telescopes in Asia and North America and found that it is no longer active after its recent outbursts at the end of 2018 and the start of 2019. The inactivity during this apparition allowed us to measure the absolute magnitude of Gault of Hr = 14.63 ± 0.02, Gr = 0.21 ± 0.02 from our secular phase-curve observations. In addition, we were able to constrain Gault's rotation period using time-series photometric lightcurves taken over 17 hr on multiple days in 2020 August, September, and October. The photometric lightcurves have a repeating ≲0.05 mag feature suggesting that (6478) Gault has a rotation period of ∼2.5 hr and may have a semispherical or top-like shape, much like the near-Earth asteroids Ryugu and Bennu. The rotation period of ∼2.5 hr is near the expected critical rotation period for an asteroid with the physical properties of (6478) Gault, suggesting that its activity observed over multiple epochs is due to surface mass shedding from its fast rotation spin-up by the Yarkovsky-O'Keefe-Radzievskii-Paddack effect.

Keywords: asteroids; asteroid dynamics; main belt asteroids
Resonant Mode Coupling in δ Scuti Stars

Delta Scuti (δ Sct) variables are intermediate-mass stars that lie at the intersection of the main sequence and the instability strip on the Hertzsprung-Russell diagram. Various lines of evidence indicate that nonlinear mode interactions shape their oscillation spectra, including the particularly compelling detection of resonantly interacting mode triplets in the δ Sct star KIC 8054146. Motivated by these observations, we use the theory of three-mode coupling to study the strength and prevalence of nonlinear mode interactions in 14 δ Sct models that span the instability strip. For each model, we calculate the frequency detunings and nonlinear coupling strengths of ~104 unique combinations of mode triplets. We find that all the models contain at least ~100 well-coupled triplets whose detunings and coupling strengths are consistent with the triplets identified in KIC 8054146. Our results suggest that resonant mode interactions can be significant in δ Sct stars and may explain why many exhibit rapid changes in amplitude and oscillation period.

Keywords: asteroseismology; delta scuti variable stars; stellar oscillations; internal waves; astrophysical fluid dynamics
Model Light Curves for Type Ib and Ic Supernovae

Using the Monte Carlo code SEDONA, multiband photometry and spectra are calculated for supernovae derived from stripped helium stars with presupernova masses of 2.2 to 10.0 M⊙. The models are representative of evolution in close binaries and have previously been exploded using a parameterized one-dimensional model for neutrino transport. A subset, those with presupernova masses in the range of 2.2-5.6 M⊙, have many properties in common with observed Type Ib and Ic supernovae, including a median ejected mass near 2 M⊙, explosion energies near 1 × 1051 erg, typical 56Ni masses of 0.07-0.09 M⊙, peak times of about 20 days, and a narrow range for the V - R color index 10 days post-V-maximum near 0.3 mag. The median peak bolometric luminosity, near 1042.3 erg s-1, is fainter, however, than several observational tabulations, and the brightest explosion has a bolometric luminosity of only 1042.50 erg s-1. The brightest absolute B, V, and R magnitudes at peak are -17.2, -17.8, and -18.0. These limits are fainter than some allegedly typical Type Ib and Ic supernovae and could reflect problems in our models or in the observational analysis. Helium stars with lower and higher masses also produce interesting transients that may have been observed, including fast, faint, blue transients and long, red, faint Type Ic supernovae. New models are specifically presented for SN 2007Y, SN 2007gr, SN 2009jf, LSQ 13abf, SN 2008D, and SN 2010X.

Keywords: type ib supernovae; type ic supernovae; core-collapse supernovae; close binary stars; light curves; spectroscopy
Revisiting Orbital Evolution in HAT-P-2 b and Confirmation of HAT-P-2 c

One possible formation mechanism for Hot Jupiters is that high-eccentricity gas giants experience tidal interactions with their host star that cause them to lose orbital energy and migrate inwards. We study these types of tidal interactions in an eccentric Hot Jupiter called HAT-P-2 b, which is a system where a long-period companion has been suggested and hints of orbital evolution were detected. Using 5 additional years of radial velocity (RV) measurements, we further investigate these phenomena. We investigated the long-period companion by jointly fitting RVs and Hipparcos-Gaia astrometry and confirmed this long-period companion, significantly narrowed down the range of possible periods ( ${P}_{2}={8500}_{-1500}^{+2600}$ days), and determined that it must be a substellar object ( ${10.7}_{-2.2}^{+5.2}$ M j). We also developed a modular pipeline to simultaneously model rapid orbital evolution and the long-period companion. We find that the rate and significance of evolution are highly dependent on the long-period companion modeling choices. In some cases the orbital rates of change reached ${de}/{dt}\,=\,{3.28}_{-1.72}^{+1.75}\times {10}^{-3}$ yr-1, d ω/dt = 1.12° ± 0.22° yr-1, which corresponds to a ~321 yr apsidal precession period. In other cases, the data is consistent with de/dt = 7.67 ± 18.6 × 10-4 yr-1, d ω/dt = 0.76° ± 0.24° yr-1. The most rapid changes found are significantly larger than the expected relativistic precession rate and could be caused by transient tidal planet-star interactions. To definitively determine the magnitude and significance of potential orbital evolution in HAT-P-2 b, we recommend further monitoring with RVs and precise transit and eclipse timings.

Keywords: star-planet interactions; orbital evolution; astrometry; radial velocity; exoplanets; hot jupiters
Three-dimensional Shape Explains Star Formation Mystery of California and Orion A

The new Gaia data release (EDR3) with improved astrometry has opened a new era in studying our Milky Way in fine detail. We use Gaia EDR3 astrometry together with 2MASS and WISE photometry to study two of the most massive molecular clouds in the solar vicinity: Orion A and California. Despite having remarkable similarities in the plane of the sky in terms of shape, size, and extinction, California has an order of magnitude lower star formation efficiency. We use our state-of-the-art dust mapping technique to derive the detailed three-dimensional (3D) structure of the two clouds, taking into account both distance and extinction uncertainties, and a full 3D spatial correlation between neighboring points. We discover that, despite the apparent filamentary structure in the plane of the sky, California is a flat 120 pc-long sheet extending from 410 to 530 pc. We show that not only Orion A and California differ substantially in their 3D shapes, but also Orion A has considerably higher density substructures in 3D than California. This result presents a compelling reason why the two clouds have different star formation activities. We also demonstrate how the viewing angle of California can substantially change the cloud's position in the Kennicutt-Schmidt relation. This underlines the importance of 3D information in interpreting star formation relations and challenges studies that rely solely on the column density thresholds to determine star formation activities in molecular clouds. Finally, we provide accurate distance estimates to multiple lines of sight toward various parts of the two clouds.

Keywords: interstellar medium; interstellar dust; molecular clouds; star forming regions; star formation
The Variability of Lunar Mare Basalt Properties from Surface Rock Abundance

We use the Lunar Reconnaissance Orbiter Diviner Lunar Radiometer Experiment surface rock abundance data set to investigate how rock content changes with surface age in the maria. We find that surface rock abundance decreases with unit age as expected for a thickening regolith, but age alone cannot explain most of the observed regional variability in rock abundance. We propose that this additional variability is primarily caused by differences in the initial mare basalt properties such that some flows break down more readily than others. We calculate the best-fit relationship between the surface rock abundance and unit age and investigate the regional variability in the residual errors of this fit. Relative to this best-fit relationship, we find that Mare Humorum and parts of Oceanus Procellarum are anomalously rocky, and Mare Australe is rock-poor for its age. These regional differences, which cannot be explained by unit age, are likely due to variability in the initial properties of mare basalts.

Keywords: lunar maria; lunar regolith; volcanism; surface processes; planetary surfaces; regolith
The Observed Cosmic Star Formation Rate Density Has an Evolution that Resembles a Γ(a, bt) Distribution and Can Be Described Successfully by Only Two Parameters

A debate is emerging regarding the recent inconsistent results of different studies for the cosmic star formation rate density (CSFRD) at high-z. We employ UV and IR data sets to investigate the SFR function (SFRF) at z ~ 0-9. We find that the SFRFs derived from the dust-corrected UV (UVcorr) data contradict those from IR on some key issues because they are described by different distributions (Schechter versus double power law), imply different physics for galaxy formation (UVcorr data suggest an SFR limit/strong mechanism that diminish the number density of highly star-forming systems with respect to IR) and compare differently with the stellar mass density evolution obtained from spectral energy distribution fitting (UVcorr is in agreement, while IR differs up to 0.5 dex). However, both tracers agree on a constant CSFRD evolution at z ~ 1-4 and point to a plateau instead of a peak. In addition, using both indicators, we demonstrate that the evolution of the observed CSFRD can be described by only two parameters and a function that has the form of a Gamma distribution (Γ(a, bt)). In contrast to previous parameterizations used in the literature, our framework connects the parameters to physical properties such as the SFR depletion time and cosmic baryonic gas density. The build-up of stellar mass occurs in Γ(a, bt) distributed steps and is the result of gas consumption up to the limit at which no eligible gas for SF at t = ∞ remains, resulting in a final cosmic stellar mass density of ~ $0.5\times {10}^{9}\,\tfrac{{M}_{\odot }}{{\mathrm{Mpc}}^{3}}$ .

Keywords: galaxy evolution
Detection of a Water Tracer in Interstellar Comet 2I/Borisov

We present high spectral resolution optical spectra obtained with the ARCES instrument at Apache Point Observatory showing detection of the [O I] 6300 Å line in interstellar comet 2I/Borisov. We employ the observed flux in this line to derive an H2O production rate of (6.3 ± 1.5) × 1026 mol s-1. Comparing to previously reported observations of CN, this implies a CN/H2O ratio of ∼0.3%-0.6%. The lower end of this range is consistent with the average value in comets, while the upper end is higher than the average value for solar system comets, but still within the range of observed values. C2/H2O is depleted, with a value likely less than 0.1%. The dust-to-gas ratio is consistent with the normal value for solar system comets. Using a simple sublimation model we estimate an H2O active area of 1.7 km2, which for current estimates for the size of Borisov suggests active fractions between 1% and 150%, consistent with values measured in solar system comets. More detailed characterization of 2I/Borisov, including compositional information and properties of the nucleus, is needed to fully interpret the observed H2O production rate.

Keywords: comets; astrochemistry; planet formation
Meteoritic Molybdenum and Ruthenium Isotopic Abundances Document Nucleosynthetic p-process Components

Anomalies in isotopic abundances of Mo and Ru in solar system matter were found to document variable contributions of the nucleosynthetic s-process component. We report isotopic relations of ϵ 92Mo versus ϵ 100Ru in meteorites from chondritic parent bodies, iron meteorites, and achondrites that reveal deviations from expected s-process abundance variations. We show that two p-process isotopes 92Mo and 94Mo require the presence of distinct p-process components in meteoritic materials. The nucleosynthetic origin of abundant magic (N = 50) p-process nuclides, covering the mass range of Zr, Mo, and Ru, has long been an enigma, but contributions by several recognized pathways, including alpha and νp-antineutrino reactions on protons, may account for the observed relatively large solar system abundances. Specific core-collapse supernovae explosive regions may carry proton-rich matter. Since Mo and Ru isotopic records in solar system matter reveal the presence of more than one nucleosynthetic p-process component, these records are expected to be helpful in documenting different explosive synthesis pathways and the implied galactic evolution of p-nuclides.

Keywords: nucleosynthesis; isotopic abundances; meteorites
A Study of Preflare Solar Coronal Magnetic Fields: Magnetic Energy and Helicity

Solar flares fall into two types, with eruptive ones associated with coronal mass ejection (CME) and confined ones without CME. To explore whether there are preflare conditions in terms of magnetic energy and helicity that can effectively determine the types of flares, here we analyzed a suite of related parameters of the reconstructed preflare coronal magnetic field of major solar flares, either eruptive or confined, from 2011 to 2017 near the solar disk center. The investigated parameters include extensive-type quantities such as the total magnetic energy E T , the potential energy E P , the free energy E F , the relative helicity H R , and the nonpotential helicity H J , as well as the intensive-type indices E F /E P , ∣H J /H R ∣, $| {H}_{R}/{\phi }^{{\prime} 2}| $ , and $| {H}_{J}/{\phi }^{{\prime} 2}| $ , where ${\phi }^{{\prime} }$ is half of the total unsigned magnetic flux. We have the following key findings: (1) None of the extensive parameters can effectively distinguish the eruptive and confined potential of the preflare coronal fields, though the confined events have averagely larger values. (2) All the intensive parameters have significantly larger average and median values for eruptive flares than the confined events, which indicates that the field for eruptive flares has overall higher degree of nonpotentiality and complexity than that of the confined flares. (3) The energy ratio E F /E P and the normalized nonpotential helicity $| {H}_{J}/{\phi }^{{\prime} 2}| $ , which are strongly correlated with each other, have among the highest capability of distinguishing the fields that possibly produce a major eruptive or confined flare, as over 75% of all the events are successfully discriminated between eruptive and confined flares by using critical values of E F /E P ≥ 0.27 and $| {H}_{J}/{\phi }^{{\prime} 2}| \geqslant 0.009$ .

Keywords: solar flares; solar coronal mass ejections; magnetic fields; solar corona
LATIS: Constraints on the Galaxy-Halo Connection at z 2.5 from Galaxy-Galaxy and Galaxy-Lyα Clustering

The connection between galaxies and dark matter halos is often quantified using the stellar mass-halo mass (SMHM) relation. Optical and near-infrared imaging surveys have led to a broadly consistent picture of the evolving SMHM relation based on measurements of galaxy abundances and angular correlation functions. Spectroscopic surveys at z ≳ 2 can also constrain the SMHM relation via the galaxy autocorrelation function and through the cross-correlation between galaxies and Lyα absorption measured in transverse sight lines; however, such studies are very few and have produced some unexpected or inconclusive results. We use ~3000 spectra of z ~ 2.5 galaxies from the Lyα Tomography IMACS Survey (LATIS) to measure the galaxy-galaxy and galaxy-Lyα correlation functions in four bins of stellar mass spanning 109.2 ≲ M */M ⊙ ≲ 1010.5. Parallel analyses of the MultiDark N-body and ASTRID hydrodynamic cosmological simulations allow us to model the correlation functions, estimate covariance matrices, and infer halo masses. We find that results of the two methods are mutually consistent and broadly accord with standard SMHM relations. This consistency demonstrates that we are able to measure and model Lyα transmission fluctuations δ F in LATIS accurately. We also show that the galaxy-Lyα cross-correlation, a free by-product of optical spectroscopic galaxy surveys at these redshifts, can constrain halo masses with similar precision to galaxy-galaxy clustering.

Keywords: galaxy dark matter halos; lyman alpha forest; lyman-break galaxies
Absorption Line Search through Three Local Group Dwarf Galaxy Halos

Dwarf galaxies are missing nearly all of their baryons and metals from the stellar disk, which are presumed to be in a bound halo or expelled beyond the virial radius. The virial temperature for galaxies with M h ~ 109-1010 M ⊙ is similar to the collisional ionization equilibrium temperature for the C IV ion. We search for UV absorption from C IV in six sightlines toward three dwarf galaxies in the anti-M31 direction and at the periphery of the Local Group (D ≈ 1.3 Mpc; Sextans A, Sextans B, and NGC 3109). The C IV doublet is detected in only one of six sightlines, toward Sextans A, with $\mathrm{log}N({\rm{C}}\,{\rm\small{IV}})=13.06\pm 0.08$ . This is consistent with our gaseous halo models, where the halo gas mass is determined by the cooling rate, feedback, and the star formation rate; the inclusion of photoionization is an essential ingredient. This model can also reproduce the higher detection rate of O VI absorption in other dwarf samples (beyond the Local Group), with C IV only detectable within ~0.5R vir.

Keywords: dwarf galaxies; circumgalactic medium; local group
Transient Formation of Loops in the Core of an Active Region

We study the formation of transient loops in the core of the AR 11890. For this purpose, we have used the observations recorded by the Atmospheric Imaging Assembly (AIA) and the Interface Region Imaging Spectrograph (IRIS). For photospheric field configuration, we have used the line-of-sight (LOS) magnetograms obtained from the Helioseismic and Magnetic Imager. The transient is simultaneously observed in all the UV and EUV channels of AIA and the three slit-jaw images from IRIS. The coexistence of the transient in all AIA and IRIS SJI channels suggests the transient's multithermal nature. The transient consists of short loops located at the base of the transient, as well as long loops. A differential emission measure analysis shows that the transient has a clumpy structure. The highest emission observed at the base is within the temperature bin of $\mathrm{log}T=6.65\mbox{--}6.95$ . We observe the longer loops at a similar temperature, albeit very feeble. Using LOS magnetograms, we conclude that the magnetic reconnection may have caused the transient. Our observations further suggest that the physics of the formation of such transients may be similar to those of typical coronal jets, albeit in different topological configurations. Such multiwavelength observations shed light on the formation of hot plasma in the solar corona and provide further essential constraints on modeling the thermodynamics of such transients.

Keywords: active sun; solar active regions; solar coronal heating; solar flares; solar active region filaments
M31N 2017-01e: Discovery of a Previous Eruption in this Enigmatic Recurrent Nova

We report the discovery of a previously unknown eruption of the recurrent nova M31N 2017-01e that took place on 2012 January 11. The earlier eruption was detected by Pan-STARRS and occurred 1847 days (5.06 yr) prior to the eruption on 2017 January 31 (M31N 2017-01e). The nova has now been seen to have had a total of four recorded eruptions (M31N 2012-01c, 2017-01e, 2019-09d, and 2022-03d) with a mean time between outbursts of just 929.5 ± 6.8 days (2.545 ± 0.019 yr), the second shortest recurrence time known for any nova. We also show that there is a blue variable source (<V> = 20.56 ± 0.17, B - V ≃ 0.045), apparently coincident with the position of the nova, that exhibits a 14.3 days periodicity. Possible models of the system are proposed, but none are entirely satisfactory.

Keywords: cataclysmic variable stars; novae; recurrent novae; andromeda galaxy; time domain astronomy