adsabs/SciX_UAT_keywords huggingface dataset:
Reconstructing the Universe: Testing the Mutual Consistency of the Pantheon and SDSS/eBOSS BAO Data Sets with Gaussian Processes

We test the mutual consistency between the baryon acoustic oscillation measurements from the eBOSS SDSS final release and the Pantheon supernova compilation in a model-independent fashion using Gaussian process regression. We also test their joint consistency with the ΛCDM model in a model-independent fashion. We also use Gaussian process regression to reconstruct the expansion history that is preferred by these two data sets. While this methodology finds no significant preference for model flexibility beyond ΛCDM, we are able to generate a number of reconstructed expansion histories that fit the data better than the best-fit ΛCDM model. These example expansion histories may point the way toward modifications to ΛCDM. We also constrain the parameters Ωk and H0rd both with ΛCDM and with Gaussian process regression. We find that H0rd = 10,030 ± 130 km s-1 and Ωk = 0.05 ± 0.10 for ΛCDM and that H0rd = 10,040 ± 140 km s-1 and Ωk = 0.02 ± 0.20 for the Gaussian process case.

Keywords: cosmology; baryon acoustic oscillations; redshift surveys; dark energy; type ia supernovae; astrostatistics techniques
X-Ray Quasi-periodic Eruptions and Tidal Disruption Events Prefer Similar Host Galaxies

In the past 5 yr, six X-ray quasi-periodic eruption (QPE) sources have been discovered in the nuclei of nearby galaxies. Their origin remains an open question. We present Multi Unit Spectroscopic Explorer integral field spectroscopy of five QPE host galaxies to characterize their properties. We find that 3/5 galaxies host extended emission-line regions (EELRs) up to 10 kpc in size. The EELRs are photoionized by a nonstellar continuum, but the current nuclear luminosity is insufficient to power the observed emission lines. The EELRs are decoupled from the stars both kinematically and in projected sky position, and the low velocities and velocity dispersions (<100 km s‑1 and ≲75 km s‑1, respectively) are inconsistent with being driven by active galactic nuclei (AGNs) or shocks. The origin of the EELRs is likely a previous phase of nuclear activity. QPE host galaxies share several similarities with tidal disruption event (TDE) hosts, including an overrepresentation of galaxies with strong Balmer absorption and little ongoing star formation, as well as a preference for a short-lived (the typical EELR lifetime is ∼15,000 yr), gas-rich phase where the nucleus has recently faded significantly. This suggests that QPEs and TDEs may share a common formation channel, disfavoring AGN accretion disk instabilities as the origin of QPEs. If QPEs are related to extreme mass ratio inspiral systems (EMRIs), e.g., stellar-mass objects on bound orbits about massive black holes, the high incidence of EELRs and recently faded nuclei could be used to localize the hosts of EMRIs discovered by low-frequency gravitational-wave observatories.

Keywords: accretion; galaxy mergers; active galactic nuclei; high energy astrophysics
Estimated Orbital Parameters of Planetary Disk Particles as a Function of the Mass of Passing Stars

In this work, I present the effects of single passing stars on planetary disks and explore the orbital modification of their components. I analyze the effects of passing stars and look for differences between flyby masses of 0.25 M⊙, 0.5 M⊙, 0.75 M⊙, and 1 M⊙. Resultant eccentricities and inclinations of disk particles are fit to mathematical equations to estimate values for them as a function of their semimajor axes and the flyby mass.

Keywords: orbits; debris disks; exoplanet dynamics; stellar dynamics; protoplanetary disks
TOI 122b and TOI 237b: Two Small Warm Planets Orbiting Inactive M Dwarfs Found by TESS

We report the discovery and validation of TOI 122b and TOI 237b, two warm planets transiting inactive M dwarfs observed by the Transiting Exoplanet Survey Satellite (TESS). Our analysis shows that TOI 122b has a radius of 2.72 ± 0.18 R⊕ and receives 8.8 ± 1.0 times Earth's bolometric insolation, and TOI 237b has a radius of 1.44±0.12 R⊕ and receives 3.7 ± 0.5 times Earth's insolation, straddling the 6.7 × Earth insolation that Mercury receives from the Sun. This makes these two of the cooler planets yet discovered by TESS, even on their 5.08 and 5.43 day orbits. Together, they span the small-planet radius valley, providing useful laboratories for exploring volatile evolution around M dwarfs. Their relatively nearby distances (62.23 ± 0.21 pc and 38.11 ± 0.23 pc, respectively) make them potentially feasible targets for future radial velocity follow-up and atmospheric characterization, although such observations may require substantial investments of time on large telescopes.

Keywords: mini neptunes; exoplanets; transits; m stars; super earths
A Sharp Rise in the Detection Rate of Broad Absorption Line Variations in a Quasar SDSS J141955.26+522741.1

We present an analysis of the variability of broad absorption lines (BALs) in a quasar SDSS J141955.26+522741.1 at z = 2.145 with 72 observations from the Sloan Digital Sky Survey Data Release 16 (SDSS DR16). The strong correlation between the equivalent widths of BALs and the continuum luminosity, reveals that the variation of BAL troughs is dominated by the photoionization. The photoionization model predicts that when the time interval ΔT between two observations is longer than the recombination timescale trec, the BAL variations can be detected. This can be characterized as a "sharp rise" in the detection rate of BAL variation at ΔT = trec. For the first time, we detect such a "sharp rise" signature in the detection rate of BAL variations. As a result, we propose that the trec can be obtained from the "sharp rise" of the detection rate of BAL variation. It is worth mentioning that the BAL variations are detected at the time intervals less than the trec for half an order of magnitude in two individual troughs. This result indicates that there may be multiple components with different trec but the same velocity in an individual trough.

Keywords: broad-absorption line quasar; quasar absorption line spectroscopy; galaxy winds
Characterizing the Manx Candidate A/2018 V3

Manx objects approach the inner solar system on long-period comet (LPC) orbits with the consequent high inbound velocities, but unlike comets, Manxes display very little to no activity even near perihelion. This suggests that they may have formed in circumstances different from typical LPCs; moreover, this lack of significant activity also renders them difficult to detect at large distances. Thus, analyzing their physical properties can help constrain models of solar system formation as well as sharpen detection methods for those classified as NEOs. Here, we focus on the Manx candidate A/2018 V3 as part of a larger effort to characterize Manxes as a whole. This particular object was observed to be inactive even at its perihelion at q = 1.34 au in 2019 September. Its spectral reflectivity is consistent with typical organic-rich comet surfaces with colors of $g^{\prime} -r^{\prime} =0.67\pm 0.02$ , $r^{\prime} -i^{\prime} =0.26\pm 0.02$ , and $r^{\prime} -z^{\prime} =0.45\pm 0.02$ , corresponding to a spectral reflectivity slope of 10.6 ± 0.9%/100 nm. A least-squares fit of our constructed light curve to the observational data yields an average nucleus radius of ≈2 km assuming an albedo of 0.04. This is consistent with the value measured from NEOWISE. A surface brightness analysis for data taken 2020 July 13 indicated possible low activity (≲0.68 g s-1), but not enough to lift optically significant amounts of dust. Finally, we discuss Manxes as a constraint on solar system dynamical models as well as their implications for planetary defense.

Keywords: comets; long period comets; oort cloud objects
Carbon-chain Chemistry versus Complex-organic-molecule Chemistry in Envelopes around Three Low-mass Young Stellar Objects in the Perseus Region

We have analyzed ALMA Cycle 5 data in Band 4 toward three low-mass young stellar objects, IRAS 03235+3004 (hereafter IRAS 03235), IRAS 03245+3002 (IRAS 03245), and IRAS 03271+3013 (IRAS 03271), in the Perseus region. The HC3N (J = 16-15; Eup/k = 59.4 K) line has been detected in all of the target sources, while four CH3OH lines (Eup/k = 15.4-36.3 K) have been detected only in IRAS 03245. Sizes of the HC3N distributions (∼2930-3230 au) in IRAS 03235 and IRAS 03245 are similar to those of the carbon-chain species in the warm carbon-chain chemistry (WCCC) source L1527. The size of the CH3OH emission in IRAS 03245 is ∼1760 au, which is slightly smaller than that of HC3N in this source. We compare the CH3OH/HC3N abundance ratios observed in these sources with predictions of chemical models. We confirm that the observed ratio in IRAS 03245 agrees with the modeled values at temperatures around 30-35 K, which supports the HC3N formation by the WCCC mechanism. In this temperature range, CH3OH does not thermally desorb from dust grains. Nonthermal desorption mechanisms or gas-phase formation of CH3OH seem to work efficiently around IRAS 03245. The fact that IRAS 03245 has the highest bolometric luminosity among the target sources seems to support these mechanisms, in particular the nonthermal desorption mechanisms.

Keywords: astrochemistry; interstellar molecules; low mass stars
Historical Perspectives on the Concept of Galaxy Size

A brief narrative on how the effective radius and isophotal diameters were accepted as galaxy size measures is presented. Evidence suggests that these parameters were defined only based on observational premises, independent of any astrophysical theories. An alternative, new physically motivated size definition based on the expected gas density threshold required for star formation in galaxies is proposed. The intrinsic scatter of the size-stellar mass relation using the new size measure is 0.06 dex, three times smaller than that of the relation with the effective radius as size. The new physically motivated size measure can be adopted in upcoming deep, wide imaging surveys.

Keywords: galaxy formation; galaxy evolution; galaxy properties; history of astronomy
First Resolved Dust Continuum Measurements of Individual Giant Molecular Clouds in the Andromeda Galaxy

In our local Galactic neighborhood, molecular clouds are best studied using a combination of dust measurements, to determine robust masses, sizes, and internal structures of the clouds, and molecular-line observations to determine cloud kinematics and chemistry. We present here the first results of a program designed to extend such studies to nearby galaxies beyond the Magellanic Clouds. Utilizing the wideband upgrade of the Submillimeter Array (SMA) at 230 GHz, we have obtained the first continuum detections of the thermal dust emission on sub-GMC scales (∼15 pc) within the Andromeda galaxy (M31). These include the first resolved continuum detections of dust emission from individual giant molecular clouds (GMCs) beyond the Magellanic Clouds. Utilizing a powerful capability of the SMA, we simultaneously recorded CO(2-1) emission with identical (u, V) coverage, astrometry, and calibration, enabling the first measurements of the CO conversion factor, αCO(2-1), toward individual GMCs across an external galaxy. Our direct measurement yields an average CO-to-dust mass conversion factor of ${\alpha }_{\mathrm{CO}-\mathrm{dust}}^{{\prime} }=0.042\pm 0.018$ M⊙ (K km s-1 pc2)-1 for the J = 2-1 transition. This value does not appear to vary with galactocentric radius. Assuming a constant gas-to-dust ratio of 136, the resulting αCO = 5.7 ± 2.4 M⊙ (K km s-1 pc2)-1 for the 2-1 transition is in excellent agreement with that of GMCs in the Milky Way, given the uncertainties. Finally, using the same analysis techniques, we compare our results with observations of the local Orion molecular clouds, placed at the distance of M31 and simulated to appear as they would if observed by the SMA.

Keywords: andromeda galaxy; giant molecular clouds; dust continuum emission; co line emission
Updated BaSTI Stellar Evolution Models and Isochrones. II. α-enhanced Calculations

This is the second paper of a series devoted to presenting an updated release of the BaSTI (a Bag of Stellar Tracks and Isochrones) stellar model and isochrone library. Following the publication of the updated solar-scaled library, here we present the library for an α-enhanced heavy element distribution. These new α-enhanced models account for all improvements and updates in the reference solar metal distribution and physics inputs, as in the new solar-scaled library. The models cover a mass range between 0.1 and 15 M⊙, 18 metallicities between [Fe/H] = -3.20 and +0.06 with [α/Fe] = +0.4, and a He-to-metal enrichment ratio ΔY/ΔZ = 1.31. For each metallicity, He-enhanced stellar models are also provided. The isochrones cover (typically) an age range between 20 Myr and 14.5 Gyr, including consistently the pre-main-sequence phase. The asteroseismic properties of the theoretical models have also been calculated. Models and isochrones have been compared with results from independent calculations, with the previous BaSTI release, and also with selected observations, to test the accuracy/reliability of these new calculations. All stellar evolution tracks, asteroseismic properties, and isochrones are publicly available at http://basti-iac.oa-teramo.inaf.it.

Keywords: stellar evolution; stellar evolutionary models; stellar physics; stellar evolutionary tracks; population ii stars; stellar populations; halo stars; astronomy databases
Simulating Secondary Electron and Ion Emission from the Cassini Spacecraft in Saturn's Ionosphere

The Cassini spacecraft's Grand Finale flybys through Saturn's ionosphere provided unprecedented insight into the composition and dynamics of the gas giant's upper atmosphere and a novel and complex spacecraft-plasma interaction. In this article, we further study Cassini's interaction with Saturn's ionosphere using three-dimensional particle-in-cell simulations. We focus on how electrons and ions, emitted from spacecraft surfaces due to the high-velocity impact of atmospheric water molecules, could have affected the spacecraft potential and low-energy plasma measurements. The simulations show emitted electrons extend upstream along the magnetic field, and for sufficiently high emission rates, charge the spacecraft to positive potentials. The lack of accurate emission rates and characteristics, however, makes differentiation between the prominence of secondary electron emission and ionospheric charged dust populations, which induce similar charging effects, difficult for Cassini. These results provide further context for Cassini's final measurements and highlight the need for future laboratory studies to support high-velocity flyby missions through planetary and cometary ionospheres.

Keywords: planetary ionospheres; saturn; astrophysical dust processes; planetary atmospheres; planetary rings; space plasmas
A Link between Ram Pressure Stripping and Active Galactic Nuclei

The dense environment of a galaxy cluster can radically transform the content of in-falling galaxies. Recent observations have found a significant population of active galactic nuclei (AGN) within "jellyfish galaxies," galaxies with trailing tails of gas and stars that indicate significant ram pressure stripping. The relationship between AGN and ram pressure stripping is not well understood. In this Letter, we investigate the connection between AGN activity and ram pressure in a fully cosmological setting for the first time using the ROMULUS C simulation, one of the highest resolution simulations of a galaxy cluster to date. For lower mass galaxies (with stellar masses M* ≲ 109.5 M⊙) both star formation and black hole accretion are suppressed by ram pressure before they reach pericenter, whereas for more massive galaxies accretion onto the black hole is enhanced during pericentric passage. Our analysis also indicates that as long as the galaxy retains gas, AGN with higher Eddington ratios are more likely to be found in galaxies experiencing higher ram pressure. We conclude that prior to quenching star formation, ram pressure triggers enhanced accretion onto the black hole, which in our model then produces heating and outflows due to AGN feedback. These simulations suggest that AGN feedback may in turn serve to aid in the quenching of star formation in tandem with ram pressure.

Keywords: active galactic nuclei; agn host galaxies; supermassive black holes; galaxy clusters; galaxy quenching
The Atari Disk, a Metal-poor Stellar Population in the Disk System of the Milky Way

We have developed a chemodynamical approach to assign 36,010 metal-poor SkyMapper stars to various Galactic stellar populations. Using two independent techniques (velocity and action space behavior), Gaia EDR3 astrometry, and photometric metallicities, we selected stars with the characteristics of the "metal-weak" thick-disk population by minimizing contamination by the canonical thick disk or other Galactic structures. This sample comprises 7127 stars, spans a metallicity range of -3.50 < [Fe/H] < -0.8, and has a systematic rotational velocity of <V ϕ > = 154 km s-1 that lags that of the thick disk. Orbital eccentricities have intermediate values between typical thick-disk and halo values. The scale length is ${h}_{R}={2.48}_{-0.05}^{+0.05}$ kpc, and the scale height is ${h}_{Z}={1.68}_{-0.15}^{+0.19}$ kpc. The metallicity distribution function is well fit by an exponential with a slope of ${\rm{\Delta }}\mathrm{log}N/{\rm{\Delta }}[\mathrm{Fe}/{\rm{H}}]=1.13\,\pm \,0.06$ . Overall, we find a significant metal-poor component consisting of 261 SkyMapper stars with [Fe/H] < -2.0. While our sample contains only 11 stars with [Fe/H] ≲ -3.0, investigating the JINAbase compilation of metal-poor stars reveals another 18 such stars (five have [Fe/H] < -4.0) that kinematically belong to our sample. These distinct spatial, kinematic, and chemical characteristics strongly suggest that this metal-poor, phase-mixed kinematic sample represents an independent disk component with an accretion origin in which a massive dwarf galaxy radially plunged into the early Galactic disk. Going forward, we propose to call the metal-weak thick-disk population the Atari disk, given its likely accretion origin, and in reference to it sharing space with the Galactic thin and thick disks.

Keywords: galaxy disks; galaxy structure; galaxy formation; galaxy kinematics; galaxy dynamics; galaxy abundances
Simulating Turbulence-aided Neutrino-driven Core-collapse Supernova Explosions in One Dimension

The core-collapse supernova (CCSN) mechanism is fundamentally 3D, with instabilities, convection, and turbulence playing crucial roles in aiding neutrino-driven explosions. Simulations of CCNSe including accurate treatments of neutrino transport and sufficient resolution to capture key instabilities remain among the most expensive numerical simulations in astrophysics, prohibiting large parameter studies in 2D and 3D. Studies spanning a large swath of the incredibly varied initial conditions of CCSNe are possible in 1D, though such simulations must be artificially driven to explode. We present a new method for including the most important effects of convection and turbulence in 1D simulations of neutrino-driven CCSNe, called Supernova Turbulence In Reduced-dimensionality, or STIR. Our new approach includes crucial terms resulting from the turbulent and convective motions of the flow. We estimate the strength of convection and turbulence using a modified mixing-length theory approach, introducing a few free parameters to the model that are fit to the results of 3D simulations. For sufficiently large values of the mixing-length parameter, turbulence-aided neutrino-driven explosions are obtained. We compare the results of STIR to high-fidelity 3D simulations and perform a parameter study of CCSN explosion using 200 solar-metallicity progenitor models from 9 to 120 ${M}_{\odot }$ . We find that STIR is a better predictor of which models will explode in multidimensional simulations than other methods of driving explosions in 1D. We also present a preliminary investigation of predicted observable characteristics of the CCSN population from STIR, such as the distributions of explosion energies and remnant masses.

Keywords: core-collapse supernovae; supernovae; hydrodynamical simulations; supernova neutrinos; massive stars; stellar convective zones
tdescore: An Accurate Photometric Classifier for Tidal Disruption Events

Optical surveys have become increasingly adept at identifying candidate tidal disruption events (TDEs) in large numbers, but classifying these generally requires extensive spectroscopic resources. Here we present tdescore, a simple binary photometric classifier that is trained using a systematic census of ∼3000 nuclear transients from the Zwicky Transient Facility (ZTF). The sample is highly imbalanced, with TDEs representing ∼2% of the total. tdescore is nonetheless able to reject non-TDEs with 99.6% accuracy, yielding a sample of probable TDEs with recall of 77.5% for a precision of 80.2%. tdescore is thus substantially better than any available TDE photometric classifier scheme in the literature, with performance not far from spectroscopy as a method for classifying ZTF nuclear transients, despite relying solely on ZTF data and multiwavelength catalog cross matching. In a novel extension, we use "Shapley additive explanations" to provide a human-readable justification for each individual tdescore classification, enabling users to understand and form opinions about the underlying classifier reasoning. tdescore can serve as a model for photometric identification of TDEs with time-domain surveys, such as the upcoming Rubin observatory.

Keywords: tidal disruption; time domain astronomy; black holes; galaxy nuclei; sky surveys
Unlocking Starlight Subtraction in Full-data-rate Exoplanet Imaging by Efficiently Updating Karhunen-Loève Eigenimages

Starlight subtraction algorithms based on the method of Karhunen-Loève eigenimages have proved invaluable to exoplanet direct imaging. However, they scale poorly in runtime when paired with differential imaging techniques. In such observations, reference frames and frames from which starlight is to be subtracted are drawn from the same set of data, requiring a new subset of references (and eigenimages) for each frame processed to avoid self-subtraction of the signal of interest. The data rates of extreme adaptive optics instruments are such that the only way to make this computationally feasible has been to downsample the data. We develop a technique that updates a precomputed singular value decomposition of the full data set to remove frames (i.e., a "downdate") without a full recomputation, yielding the modified eigenimages. This not only enables analysis of much larger data volumes in the same amount of time, but also exhibits near-linear scaling in runtime as the number of observations increases. We apply this technique to archival data and investigate its scaling behavior for very large numbers of frames N. The resulting algorithm provides speed improvements of 2.6× (for 200 eigenimages at N = 300) to 140× (at N = 104) with the advantage only increasing as N grows. This algorithm has allowed us to substantially accelerate Karhunen-Loève image projection (KLIP) even for modest N, and will let us quickly explore how KLIP parameters affect exoplanet characterization in large-N data sets.

Keywords: exoplanet detection methods; exoplanets; direct imaging; astronomy data reduction; astronomy data analysis