Sazuna/UAT_keywords huggingface dataset:
SQuIGG<inline-formula> </inline-formula>E: Observational Evidence of Low Ongoing Star Formation Rates in Gas-rich Post-starburst Galaxies. Atacama Large Millimeter/submillimeter Array observations have shown that candidate "post-starburst" galaxies (PSBs) at z ∼ 0.6 can retain significant molecular gas reservoirs. These results would imply that—unlike many model predictions—galaxies can shut down their star formation before their cold gas reservoirs are depleted. However, these studies inferred star formation rates (SFRs) either from [O II] line fluxes or from spectral energy distribution (SED) modeling and could have missed large dust-obscured contributions to the SFRs. In this study, we present Keck/NIRES observations of 13 massive (M* ≳ 1011 M⊙) PSBs, which allow us to estimate Hα SFRs in these gas-rich PSBs. We confirm the previously inferred low SFRs for the majority of the sample: 11/13 targets show clear Hα absorption, with minimal infilling indicating dust-corrected SFRs of &lt;4.1 M⊙ yr‑1. These SFRs are notably low given the large H2 reservoirs (∼(1–5) × 1010 M⊙) present in 5/13 of these galaxies, placing them significantly offset from star-forming galaxies on the Kennicutt–Schmidt relation for star-forming galaxies. The [N II]/Hα ratios of all 13 PSBs imply contributions from non-star-forming ionization mechanisms (e.g., active galactic nuclei, shocks, or hot evolved stars) to their Hα emission, suggesting that even these low ongoing SFRs may be overestimated. These low Hα SFRs, dust corrected using Av estimates from SED fitting, confirm that these galaxies are very likely quiescent and, thus, that galaxies can quench before their cold gas reservoirs are fully depleted.

Keywords: Quenched galaxies, Post-starburst galaxies, Galaxy evolution, Galaxy quenching, Galaxies
Predicting High-magnification Events in Microlensed Quasars in the Era of LSST Using Recurrent Neural Networks. Upcoming wide-field surveys, such as the Rubin Observatory's Legacy Survey of Space and Time (LSST), will monitor thousands of strongly lensed quasars over a 10 yr period. Many of these monitored quasars will undergo high-magnification events (HMEs) through microlensing, as the accretion disk crosses a caustic—places of infinite magnification. Microlensing allows us to map the inner regions of the accretion disk as it crosses a caustic, even at large cosmological distances. The observational cadences of LSST are not ideal for probing the inner regions of the accretion disk, so there is a need to predict HMEs as early as possible, to trigger high-cadence multiband or spectroscopic follow-up observations. Here, we simulate a diverse and realistic sample of 10 yr quasar microlensing light curves to train a recurrent neural network to predict HMEs before they occur, by classifying the locations of the peaks at each time step. This is the first deep-learning approach for predicting HMEs. We give estimates of how well we expect to predict HME peaks during LSST and benchmark how our metrics change with different cadence strategies. With LSST-like observations, we can predict approximately 55% of HME peaks, corresponding to tens to hundreds per year and a false-positive rate of around 20% compared to the total number of HMEs. Our network can be continuously applied throughout the LSST survey, providing crucial alerts for optimizing follow-up resources.

Keywords: Neural networks, Quasars, Gravitational lensing, Active galactic nuclei, Quasar microlensing, Time series analysis
Primordial Black Hole Mergers as Probes of Dark Matter in the Galactic Center. Primordial black holes (PBHs) from the early Universe that can contribute to dark matter (DM) abundance have been linked to gravitational-wave observations. Supermassive black holes at the centers of galaxies are expected to modify the distribution of DM in their vicinity and can result in highly concentrated DM spikes. We revisit PBH merger rates in the presence of DM spikes, tracking their history. We find novel peaked structure in the redshift evolution of PBH merger rates at low redshifts around z ∼ 5. These effects are generic and are present for distinct PBH mass functions and spike profiles, and also can be linked to peaked structure in the redshift evolution of the star formation rate. Redshift evolution characteristics of PBH merger rates can be distinguished from astrophysical black hole contributions and observable with gravitational waves, enabling them to serve as probes of DM in galactic centers.

Keywords: Galaxy dark matter halos, Gravitational waves, Primordial black holes
Quantifying Advantages of a Moving Mesh in Nuclear Hydrodynamics. Many astrophysical explosions, such as type Ia supernovae, classical novae, and X-ray bursts, are dominated by thermonuclear runaway. To model these processes accurately, one must evolve nuclear reactions concurrently with hydrodynamics. We present an application of the moving mesh technique to this field of computation with the aim of explicitly testing the advantages of the method against the fixed mesh case. By way of traditional Strang splitting, our work couples a 13 isotope nuclear reaction network to a 1D moving mesh, Cartesian geometry hydrodynamics code. We explore three reacting problems: an acoustic pulse, a burning shock, and an advecting deflagration. Additionally, using the shock jump conditions, we semianalytically solve the burning shock problem under the assumption of quick, complete burning with the hope of establishing a useful and easy-to-set-up test problem. Strong moving mesh advantages are found in advecting, deflagrating flame fronts, where the technique dramatically reduces numerical diffusion that would otherwise lead to very fast artificial deflagration.

Keywords: Computational astronomy, Nuclear astrophysics, Hydrodynamics
Rotational Spectrum and Search for Lactonitrile toward Sgr B2(N). Laboratory experiments on interstellar ice analogs have demonstrated that ice mixtures containing acetaldehyde (CH3CHO) and hydrogen cyanide (HCN) in the presence of ammonia (NH3), water (H2O), or an NH3/H2O mixture allow the formation of the chiral molecule lactonitrile (2-hydroxypropionitrile; CH3CH(OH)CN). These findings place lactonitrile among possible interstellar molecules, especially when its methyl-shortened derivative glycolonitrile and the precursors are known interstellar species. To support the search for lactonitrile in interstellar space, we present measurements under supersonic expansion conditions in the 6─16 GHz frequency range, along with a detailed analysis of its room-temperature rotational spectrum from 75 to 325 GHz. Improved and extended sets of molecular parameters, determined from the newly measured data and selected literature measurements, are obtained for two conformers of lactonitrile, with accuracies conducive to reliable interstellar searches. We report the nondetection of lactonitrile toward the main hot core Sgr B2(N1S), with a column density upper limit 1 order of magnitude higher than the upper limit derived for the related molecule glycolonitrile.

Keywords: Millimeter-wave spectroscopy, Laboratory astrophysics, Microwave spectroscopy, Rotational spectroscopy
Sporadic E-like Topside Layer Driven by Wind Shear in the Martian Ionosphere. Ionospheric plasma density disturbances significantly affect radio wave propagation, impacting communication and planetary exploration. At Earth, sporadic E layers (Es) are commonly observed. They are characterized by thin, high-density plasma structures in the E-region ionosphere, primarily formed by electromagnetic forces induced by horizontal wind shears. Similar sharp vertical electron density changes have also been observed in the topside of the Martian ionosphere by missions like Mars Global Surveyor, Mars Express, and Mars Atmosphere and Volatile EvolutioN. Recent studies suggest that such structures observed on Mars can be attributed to a sporadic E-like mechanism induced by magnetic shear, which can be referred to as Es-like structures. While wind shear theoretically contributes to such events, no observational evidence currently reports wind shear as an explanation for these density gradients on Mars. In this study, we report a novel observation of an Es-like topside layer in the Martian ionosphere, characterized by both density layer and rift (an abrupt depletion in density), where wind and magnetic shear are simultaneously observed. Statistical analysis of 305 orbits with wind speed observations revealed wind shear is observed in nine Es-like events, primarily occurring in strong crustal magnetic field regions. Simulations suggest that the observed rift and layer can be explained either by "wind shear" or by "wind and magnetic shear" under strong crustal magnetic field. This study provides new observations of Es-like events on Mars and serves as a credible candidate for the contribution of wind shear to the formation of an Es-like topside layer.

Keywords: Space plasmas, Planetary ionospheres
Recovering Injected Astrophysics from the LISA Double White Dwarf Binaries. We present the successful recovery of common-envelope ejection efficiency assumed in a simulated population of double white dwarf (DWD) binaries like those which may be observed by the future Laser Interferometer Space Antenna (LISA) mission. We simulate the formation of DWD binaries by using the COSMIC population synthesis code to sample binary formation conditions such as initial mass function, metallicity of star formation, initial orbital period, and initial eccentricity. These binaries are placed in the m12i synthetic Milky Way–like galaxy, and their signal-to-noise ratio (SNR) for the LISA instrument is estimated, considering a Galactic gravitational-wave foreground informed by the population. Through the use of Fisher estimates, we construct a likelihood function for the measurement error of the LISA-bright DWD binaries (≥20 SNR, fGW ≥ 5 mHz), in their gravitational-wave frequency (fGW) and chirp mass. By repeating this process for different assumptions of the common-envelope ejection efficiency, we apply Bayesian hierarchical inference to find the best match to an injected astrophysical assumption for a fiducial population model. We conclude that the impact of common-envelope ejection efficiency on the mass-transfer processes involved in DWD formation may be statistically relevant in the future observed LISA population, and that constraints on binary formation may be found by comparing simulated populations to a future observed population.

Keywords: White dwarf stars, Gravitational wave sources
TelescopeML. II. Convolutional Neural Networks for Predicting Brown Dwarf Atmospheric Parameters. Accurately and swiftly predicting the parameters of brown dwarf atmospheres from observational spectra is crucial for understanding their atmospheric composition and guiding future follow-up observations. Here, we utilized convolutional neural networks (CNNs) as a high-performance deep learning algorithm, training them with synthetic spectra generated from Sonora–Bobcat cloudless and equilibrium model grids to infer effective temperatures (Teff), surface gravities ( ), carbon-to-oxygen ratios (C/O), and metallicities ([M/H]). The performance metric, or R2 value (the coefficient of determination), of the trained CNNs in predicting Teff,  , C/O, and [M/H] is 1.0, 1.0, 0.99, and 0.93 on both the training and test sets, respectively. We apply our trained CNN model on the three well-known T dwarf benchmarks, HD 3651B, GJ 570D, and Ross 458C. For HD 3651B and GJ 570D, we find that our predicted Teff and   are in good agreement with some of the previous modeling studies from forward and retrieval approaches, but the [M/H] is underestimated up to ≈0.3 dex. For Ross 458C, our CNN model predicts the   accurately but tends to overestimate Teff by ≈150 K and [M/H] by ≈1.0 dex compared to the previous modelings, which likely happens because our model grids lack disequilibrium chemistry and clouds. We also find that the C/O ratio tends to be higher than solar if not kept fixed. Concurrently, all modules and functions used to train, develop, and deploy the CNNs and process the spectra are consolidated into a Python PyPI package named TelescopeML, which is publicly available along with a thoroughly documented tutorial covering installation, deployment, and core concepts.

Keywords: Atmospheric composition, Convolutional neural networks, Brown dwarfs, T dwarfs
The Radiowave Hunt for Young Stellar Object Emission and Demographics (RADIOHEAD): A Radio Luminosity–Spectral Type Dependence in Taurus–Auriga YSOs. We measure the radio continuum fluxes at the locations of all Gaia-confirmed members of Taurus–Auriga using Karl G. Jansky Very Large Array Sky Survey data (VLASS; 2–4 GHz, σVLASS ~ 110–140 μJy, 2 5 resolution) spanning three VLASS epochs (2019, 2021, and 2023). We present 35 detections coincident with young Taurus–Auriga stars (29 in individual VLASS images, 6 via stacking). We find a strong dependence on spectral type, wherein the fractional detection rate of radio emission coincident with early-type young stellar objects (YSOs) is systematically higher than late-type YSOs, ranging from 25% ± 13% for B–F YSOs, 21% ± 11% for G YSOs, 18.4% ± 6.3% for K0–K4 YSOs, 15.5% ± 5.4% for K5–K9 YSOs, 7.0% ± 2.7% for M0–M2 YSOs, 2.3% ± 0.9% for M3–M6 YSOs, and 1.9% ± 1.9% for YSOs with SpTs later than M7. We present cumulative density distributions of radio luminosity densities that demonstrate a significant luminosity enhancement for early- versus late-type YSOs. We find 25% of the detected sources to be significantly variable. We discuss possible interpretations of this dependence, which may reflect stellar magnetic activity, binary interactions, or stellar flaring. We find that the mid-infrared YSO class is a strong indicator of radio detectability consistent with higher frequency Taurus–Auriga VLA surveys, with class III stars detected at a rate of 8.8% ± 1.6%, class IIs at 2.0% ± 1.2%, and combined class 0s, Is and Fs at 8.0% ± 5.4%.

Keywords: Very Large Array, Galactic radio sources, Young stellar objects, Variable stars, Radio continuum emission, Stellar evolution
Pseudo-Newtonian Simulation of a Thin Accretion Disk Around a Reissner–Nordström Naked Singularity. We present the first numerical simulations of a thin accretion disk around a Reissner–Nordström (RN) naked singularity (NkS; a charged point mass). The gravity of the RN NkS is modeled with a pseudo-Newtonian potential that reproduces exactly the radial dependence of the RN Keplerian orbital frequency; in particular, orbital angular velocity vanishes at the zero gravity radius and has a maximum at 4/3 of that radius. Angular momentum is transported outward by viscous stresses only outside the location of this maximum. Nonetheless, even at that radius, accretion proceeds at higher latitudes, the disk having thickened there owing to excess pressure. The accretion stops at a certain distance away from the singularity, with the material accumulating in a toroidal structure close to the zero-gravity sphere. The shape of the structure obtained in our simulations is reminiscent of fluid figures of equilibrium analytically derived in full general relativity for the RN singularity. The presence of a rotating ring, such as the one found in our simulations, could be an observational signature of an NkS. For charge-to-mass ratios close to but larger than unity, the inner edge of the quasi-toroidal inner accretion structure would be located well within the Schwarzschild marginally stable orbit (ISCO), and the maximum orbital frequency in thin accretion disks would be much higher than the Schwarzschild ISCO frequency.

Keywords: Gravitational singularities
MAMMOTH-Subaru. IV. Large Scale Structure and Clustering Analysis of Lyα Emitters and Lyα Blobs at z = 2.2–2.3. We report the large scale structure and clustering analysis of Lyα emitters (LAEs) and Lyα blobs (LABs) at z = 2.2–2.3. Using 3341 LAEs, 117 LABs, and 58 bright (Lyα luminosity LLyα &gt; 1043.4 erg s‑1) LABs at z = 2.2–2.3 selected with Subaru/Hyper Suprime-Cam, we calculate the LAE overdensity to investigate the large scale structure at z = 2. We show that 79% of LABs and 83% of bright LABs are located in overdense regions, which is consistent with the trend found by previous studies that LABs are generally located in overdense regions. We find that one of our eight fields, dubbed J1349, contains 39/117 ≈ 33% of our LABs and 22/58 ≈ 38% of our bright LABs. A unique and overdense  (40 × 20 comoving Mpc2) region (J1347 protocluster) has 12 LABs (eight bright LABs). By comparing to SSA22, which is one of the most overdense LAB regions found by previous studies, we show that the J1347 protocluster region has a higher bright LAB density than the SSA22 protocluster region with a 1σ significance. We calculate the angular correlation functions (ACFs) of LAEs and LABs in the unique J1349 field and fit the ACFs with a power-law function to measure the slopes. The bright LABs show a 5σ larger slope, suggesting that bright LABs are more clustered than faint LAEs. Our LABs have a large galaxy bias of ∼5–7, which suggests that LABs generally reside in more massive dark matter halos (halo masses M ≳ 1013 M⊙) than faint LAEs.

Keywords: Lyman-alpha galaxies, High-redshift galaxies, Galaxies
The Assembly of Supermassive Black Holes at z &lt; 1 in Early-type Galaxies from Scaling Relations. The assembly of supermassive black hole (SMBH) mass (M•) and stellar mass (M*) in galaxies can be studied via the redshift evolution of the M•–M* relation, but the ways in which selection bias and physical assembly channels affect this evolution are uncertain. To address this, we compare the M•–M* relation for local massive (M* &gt; 1010.5 M⊙) quiescent early-type galaxies (ETGs) to that for massive ETGs hosting active galactic nuclei (AGN) at z ∼ 0.8. The restrictions on stellar mass and galaxy type limit the assembly channels that may connect the two relations. For the local sample we find  , in line with prior work. For the z ∼ 0.8 sample we find a bias-corrected relation:  . We show, however, that this relation depends on the stellar and SMBH mass functions used to compute the selection bias, the virial relation, the virial factor, and the active fraction, which together introduce uncertainty of up to ∼0.6 dex in the z ∼ 0.8 relation. Adopting reasonable choices of these parameters then our z ∼ 0.8 relation lies above that for z ∼ 0 AGN by ∼0.5 dex, but below our z ∼ 0 ETG relation by 0.4–1 dex in SMBH mass. We discuss possible sources of this offset, including further bias corrections, "downsizing" in SMBH mass assembly, and preferential SMBH growth. Our results highlight the need to reduce uncertainties from selection and measurement bias in SMBH and stellar masses at all redshifts.

Keywords: Black holes
Supersensitive Seismic Magnetometry of White Dwarfs. The origin of the magnetic fields in white dwarfs (WDs) remains mysterious. Magnetic WDs are traditionally associated with field strengths ≳1 MG, set by the sensitivity of typical spectroscopic magnetic field measurements. Informed by recent developments in red giant magnetoasteroseismology, we revisit the use of WD pulsations as a seismic magnetometer. WD pulsations primarily probe near-surface magnetic fields, whose effect on oscillation mode frequencies is to asymmetrize rotational multiplets and, if strong enough, suppress gravity-mode propagation altogether. The sensitivity of seismology to magnetic fields increases strongly with mode period and decreases quickly with the depth of the partial ionization-driven surface convective zone. We place upper limits for the magnetic fields in 24 pulsating WDs: 20 hydrogen-atmosphere (DAV) and three helium-atmosphere (DBV) carbon–oxygen WDs, and one extremely low-mass (helium-core) pulsator. These bounds are typically ∼1–10 kG, although they can reach down to ∼10–100 G for DAVs and helium-core WDs in which lower-frequency modes are excited. Seismic magnetometry may enable new insights into the formation and evolution of WD magnetism.

Keywords: White dwarf stars, Asteroseismology, Magnetic fields
Theoretical Calculations on the Effect of Adsorbed Atom Coverage on the Sodium Exospheres of Airless Bodies. Our ability to understand the formation of the exospheres of airless bodies such as the Moon and Mercury has been hindered by uncertainties in how surface processes influence exospheric sources. Ejection processes important for exosphere formation rely on the notion that an emitted atom must first overcome an attractive energy with the surface to be ejected into the exosphere (the surface binding energy, SBE). Recent studies have shown that atoms from minerals are more tightly bound than commonly assumed, making it difficult to reconcile how such high volatile concentrations are being observed in the exospheres of airless bodies. Here, we used molecular dynamics modeling to explain the physics underlying the interaction of low-energy returning atoms, initially ejected below the escape energy of the body, with mineral surfaces. Global exosphere models make ill-informed assumptions for these interactions due to a lack of SBEs for adsorbed atoms. Results provide first-of-their-kind SBE distributions for adsorbed atoms and can be used by global models to better understand exosphere formation on airless bodies. We highlight the importance of adsorbate coverage and the atomic arrangement of a surface on the SBE. At low absorbate coverage sodium forms ionic bonds with oxygen, leading to tightly bound adsorbates (SBE ∼6 eV). At 1 ML of coverage the free O is terminated and Na is unable to form strong ionic bonds, leading to loosely bound adsorbates (SBE 1–3 eV). Emission processes from covered surfaces will be far more efficient than those without adsorbates. These improvements will allow for better interpretation of mission data such as from MESSENGER, BepiColombo, LADEE, Europa Clipper, and Artemis.

Keywords: Planetary surfaces, Theoretical models, Exosphere, Surface processes, The Moon, Solar wind, Lunar surface, Lunar mineralogy, Mercury (planet), Comet volatiles
A Long-term Study of Mrk 50: Appearance and Disappearance of Soft Excess. We present an extensive temporal and spectral study of the Seyfert 1 AGN Mrk 50 using 15 yr (2007–2022) of multiwavelength observations from XMM-Newton, Swift, and NuSTAR for the first time. From the timing analysis, we found that the source exhibited variability of ∼20% during the 2007 observation, which reduced to below 10% in the subsequent observations and became nonvariable in the observations from 2010 onward. From the spectral study, we found that the spectra are nearly featureless. Nondetection of absorption in the low-energy domain during the 15 yr of observation infers the absence of obscuration around the central engine, rendering the nucleus a "bare" type. A prominent soft X-ray excess below 2 keV was detected in the source spectrum during the observations between 2007 and 2010, which vanished during the later observations. To describe the nature of the soft excess, we use two physical models, such as warm Comptonization and blurred reflection from the ionized accretion disk. Both of the physical models explain the nature and origin of the soft excess in this source. Our analysis found that Mrk 50 accretes at a sub-Eddington accretion rate (λEdd = 0.13–0.02) during all of the observations used in this work.

Keywords: Seyfert galaxies, X-ray active galactic nuclei, Active galactic nuclei