Sazuna/UAT_keywords huggingface dataset:
Constraints on Coasting Cosmological Models from Gravitational-wave Standard Sirens. We present the first test of coasting cosmological models with gravitational-wave (GW) standard sirens observed in the first three observing runs of the LIGO-Virgo-KAGRA detector network. We apply the statistical galaxy catalog method adapted to coasting cosmologies and infer constraints on the H 0 Hubble constant for the three fixed values of the curvature parameter $k=\left\{-1,0,+1\right\}$ in ${H}_{0}^{2}{c}^{-2}$ units. The maximum posteriors and 68.3% highest density intervals we obtained from a combined analysis of 46 dark siren detections and a single bright siren detection are ${H}_{0}=\left\{{68.1}_{-5.6}^{+8.5},{67.5}_{-5.2}^{+8.3},{67.1}_{-5.8}^{+6.6}\right\}\,\mathrm{km}\ {{\rm{s}}}^{-1}\ {\mathrm{Mpc}}^{-1}$ , respectively. All our constraints on H 0 are consistent within 1σ with the H 0 measured with the differential age method, which provides a constraint on H 0 in coasting cosmologies independently from k. Our results constrain all cosmological models with a(t) ∝ t linear expansion in the luminosity distance and redshift range of the 47 LIGO-Virgo detections, i.e., d L ≲ 5Gpc and z ≲ 0.8, which practically include all (both strictly linear and quasi-linear) models in the coasting model family. As we have found, the coasting models and the Lambda cold dark matter (or ΛCDM) model fit equally well to the applied set of GW detections.

Keywords: Gravitational wave astronomy, Observational cosmology, Cosmology, Hubble constant
Volume Density Structure of the Central Molecular Zone NGC 253 through ALCHEMI Excitation Analysis. We present a spatially resolved excitation analysis for the central molecular zone (CMZ) of the starburst galaxy NGC 253 using the data from the Atacama Large Millimeter/submillimeter Array Comprehensive High-resolution Extragalactic Molecular Inventory, whereby we explore parameters distinguishing NGC 253 from the quiescent Milky Way's Galactic center (GC). Non-LTE analyses employing a hierarchical Bayesian framework are applied to Band 3-7 transitions from nine molecular species to delineate the position-position-velocity distributions of column density ( ${N}_{{{\rm{H}}}_{2}}$ ), volume density ( ${n}_{{{\rm{H}}}_{2}}$ ), and temperature (T kin) at 27 pc resolution. Two distinct components are detected: a low-density component with $({n}_{{{\rm{H}}}_{2}},{T}_{\mathrm{kin}})\sim ({10}^{3.3}\ {\mathrm{cm}}^{-3},85\ {\rm{K}})$ and a high-density component with $({n}_{{{\rm{H}}}_{2}},{T}_{\mathrm{kin}})\,\sim ({10}^{4.4}\ {\mathrm{cm}}^{-3},110\ {\rm{K}})$ , separated at ${n}_{{{\rm{H}}}_{2}}\sim {10}^{3.8}\ {\mathrm{cm}}^{-3}$ . NGC 253 has ~10 times the high-density gas mass and ~3 times the dense-gas mass fraction of the GC. These properties are consistent with their HCN/CO ratio but cannot alone explain the factor of ~30 difference in their star formation efficiencies (SFEs), contradicting the dense-gas mass to star formation rate scaling law. The ${n}_{{{\rm{H}}}_{2}}$ histogram toward NGC 253 exhibits a shallow declining slope up to ${n}_{{{\rm{H}}}_{2}}\sim {10}^{6}\ {\mathrm{cm}}^{-3}$ , while that of the GC steeply drops in ${n}_{{{\rm{H}}}_{2}}\gtrsim {10}^{4.5}\ {\mathrm{cm}}^{-3}$ and vanishes at 105 cm-3. Their dense-gas mass fraction ratio becomes consistent with their SFEs when the threshold ${n}_{{{\rm{H}}}_{2}}$ for the dense gas is taken at ~104.2-4.6 cm-3. The rich abundance of gas above this density range in the NGC 253 CMZ, or its scarcity in the GC, is likely to be the critical difference characterizing the contrasting star formation in the centers of the two galaxies.

Keywords: Starburst galaxies, Galactic center, Giant molecular clouds, Star formation, Interstellar medium
JWST Confirms the Nature of CID-42. The galaxy CID-42 (CXOC J100043.1+020637.2) at z = 0.359 has been proposed to contain a promising candidate for a gravitational-wave recoiling supermassive black hole (SMBH), a slingshot SMBH from a triple-SMBH interaction, or a kiloparsec-scale dual active galactic nucleus (AGN). These claims were primarily based on a pair of bright cores separated by ~0.″5 resolved in optical Hubble Space Telescope (HST) imaging. Existing HST, Chandra, and ground-based imaging and spectroscopy are unable to confirm either scenario. With improved spatial resolution, depth, and IR wavelength coverage, NIRCam multiband imaging from the COSMOS-Web JWST treasury program well resolved the two cores in CID-42, revealing a significant stellar bulge for both cores (with stellar masses of ~1010 M ⊙ for both). JWST imaging further revealed that only the SE core contains an unobscured AGN point source, based on both image decomposition and spectral energy distribution fitting. There is no evidence for AGN activity in the NW core based on the current data. These new observations unambiguously rule out the gravitational-wave-recoiling and slingshot-SMBH scenarios and establish CID-42 as a low-redshift merging pair of galaxies, with likely only one active AGN in the system. These results demonstrate the unparalleled capabilities of JWST (even with imaging alone) in studying the galactic-scale environment of merging galaxies and SMBHs.

Keywords: Double quasars, Galaxy interactions, Active galactic nuclei
How Many Supermassive Black Hole Binaries Are Detectable through Tracking Relative Motions by (Sub)millimeter Very Long Baseline Interferometry?. The (sub)millimeter wavelengths (86-690 GHz) very long baseline interferometry will provide ~5-40 μas angular resolution, ~10 mJy baseline sensitivity, and ~1 μas yr-1 proper-motion precision, which can directly detect supermassive black hole binary (SMBHB) systems by imaging the two visible sources and tracking their relative motions. Such a way exhibits an advantage compared to indirect detect methods of observing periodic signals in motion and light curves, which are difficult to confirm from competing models. Moreover, tracking relative motion at (sub)millimeter wavelengths is more reliable, as there is a negligible offset between the emission region and the black hole center. In this way, it is unnecessary to correct the black hole location by a prior of jet morphology as it would be required at longer wavelengths. We extend the formalism developed in D'Orazio &amp; Loeb (2018) to link the observations with the orbital evolution of SMBHBs from the ≲10 kpc dynamical friction stages to the ≲0.01 pc gravitational radiation stages, and estimate the detectable numbers of SMBHBs. By assuming 5% of active galactic nuclei holding SMBHBs, we find that the number of detectable SMBHBs with redshift z ≤ 0.5 and mass M ≤ 1011 M ⊙ is about 20. Such a detection relies heavily on proper-motion precision and sensitivity. Furthermore, we propose that the simultaneous multifrequency technique plays a key role in meeting the observational requirements.

Keywords: Supermassive black holes, Very long baseline interferometry, Active galactic nuclei, Proper motions, Submillimeter astronomy
A Numerical Study of the Effects of a Corotating Interaction Region on Cosmic-Ray Transport. II. Features of Cosmic-Ray Composition and Rigidity. We continue the numerical modeling of a corotating interaction region (CIR) and the effects it has on solar-rotational recurrent variations of galactic cosmic rays (GCRs). A magnetohydrodynamic model is adapted to simulate the background solar wind plasma with a CIR structure in the inner heliosphere, which is incorporated into a comprehensive Parker-type transport model. The focus is on the simulation of the effects of a CIR on GCR protons and the two helium isotopes as a function of heliolongitude. This is to establish whether the difference in composition affects how they are modulated by the CIR in terms of their distribution in longitude. It is demonstrated that particle diffusion and drift influence the effects of the CIR with increasing rigidity from 100 MV up to 15 GV. It is found that protons and helium isotopes are modulated differently with longitude by the CIR and that particle drift influences the modulation effects in longitude. These differences dissipate with increasing rigidity. The final results are focused on the simulated amplitude of these GCR flux variations as a function of rigidity. The amplitude displays a power-law behavior above ~1 GV with an index similar to the power index of the rigidity dependence of the assumed diffusion coefficients. The simulations further show that below this rigidity, the amplitude at first flattens off, displaying a plateau-like profile, but it then increases systematically with decreasing rigidity below ~0.3 GV. Again, a power-law behavior is displayed, but it is completely different from that above 1 GV.

Keywords: Galactic cosmic rays, Solar wind, Solar activity, Heliosphere
Potential Melting of Extrasolar Planets by Tidal Dissipation. Tidal heating on Io due to its finite eccentricity was predicted to drive surface volcanic activity, which was subsequently confirmed by the Voyager spacecraft. Although the volcanic activity in Io is more complex, in theory volcanism can be driven by runaway melting in which the tidal heating increases as the mantle thickness decreases. We show that this runaway melting mechanism is generic for a composite planetary body with liquid core and solid mantle, provided that (i) the mantle rigidity, μ, is comparable to the central pressure, i.e., μ/(ρ gR P) ≳ 0.1 for a body with density ρ, surface gravitational acceleration g, and radius R P; (ii) the surface is not molten; (iii) tides deposit sufficient energy; and (iv) the planet has nonzero eccentricity. We calculate the approximate liquid core radius as a function of μ/(ρ gR P), and find that more than 90% of the core will melt due to this runaway for μ/(ρ gR P) ≳ 1. From all currently confirmed exoplanets, we find that the terrestrial planets in the L 98-59 system are the most promising candidates for sustaining active volcanism. However, uncertainties regarding the quality factors and the details of tidal heating and cooling mechanisms prohibit definitive claims of volcanism on any of these planets. We generate synthetic transmission spectra of these planets assuming Venus-like atmospheric compositions with an additional 5%, 50%, and 98% SO2 component, which is a tracer of volcanic activity. We find a ≳3σ preference for a model with SO2 with 5-10 transits with JWST for L 98-59bcd.

Keywords: Tides, Exoplanet tides, Volcanism
Multiwavelength Campaign Observations of a Young Solar-type Star, EK Draconis. I. Discovery of Prominence Eruptions Associated with Superflares. Young solar-type stars frequently produce superflares, serving as a unique window into the young Sun-Earth environments. Large solar flares are closely linked to coronal mass ejections (CMEs) associated with filament/prominence eruptions, but observational evidence for stellar superflares remains scarce. Here, we present a 12-day, multiwavelength campaign observation of young solar-type star EK Draconis (G1.5V, 50-120 Myr age) utilizing the Transiting Exoplanet Survey Satellite, the Neutron star Interior Composition ExploreR, and the Seimei telescope. The star has previously exhibited blueshifted Hα absorptions as evidence for a filament eruption associated with a superflare. Our simultaneous optical and X-ray observations identified three superflares of 1.5 × 1033-1.2 × 1034 erg. We report the first discovery of two prominence eruptions on a solar-type star, observed as blueshifted Hα emissions at speeds of 690 and 430 km s-1 and masses of 1.1 × 1019 and 3.2 × 1017 g, respectively. The faster, massive event shows a candidate of post-flare X-ray dimming with the amplitude of up to ~10%. Several observational aspects consistently point to the occurrence of a fast CME associated with this event. The comparative analysis of the estimated length scales of flare loops, prominences, possible dimming region, and starspots provides the overall picture of the eruptive phenomena. Furthermore, the energy partition of the observed superflares in the optical and X-ray bands is consistent with flares from the Sun, M-dwarfs, and close binaries, yielding the unified empirical relations. These discoveries provide profound implications of the impact of these eruptive events on early Venus, Earth, and Mars and young exoplanets.

Keywords: Stellar coronal dimming, Solar prominences, Stellar x-ray flares, G dwarf stars, Solar analogs, Flare stars, Solar filament eruptions, Stellar flares, Stellar coronal mass ejections, Optical flares
Evidence of Third Dredge-up in Post-AGB Stars in Galactic Globular Clusters. To better understand the mixing and mass loss experienced by low-mass stars as they ascend the asymptotic giant branch (AGB), I have gathered from the literature the abundances of CNO and s-process elements in post-AGB stars in Galactic globular clusters. These species are mixed to the surface during third dredge-up (3DU) events, so their abundance should increase as the star ascends the AGB. Of the 17 stars in this sample, CNO abundances are available for 11. Of these, four are enhanced in CNO relative to the red giant branch stars from which they descended, which I take as evidence of 3DU on the AGB. The enhancement is mainly in the form of carbon. Of the six stars for which only heavy-element abundances are available, one shows s-process enhancements that previous authors have interpreted as evidence of 3DU. Combining these 17 stars with other recent samples reveals that most globular-cluster post-AGB stars have luminosities $\mathrm{log}(L/{L}_{\odot })\sim 3.25$ . They are the progeny of blue horizontal-branch (HB) stars in clusters with intermediate metallicity ([Fe/H] ~ -1.5). A second group consists of sub-luminous stars associated with high-metallicity clusters ([Fe/H] ~ -1.0) with red HBs. They may be burning helium, rather than hydrogen. A third group of hot, super-luminous stars is evolving quickly across the Hertzsprung-Russell diagram. Some of them may be merger remnants.

Keywords: Stellar abundances, Asymptotic giant branch stars, Post-asymptotic giant branch stars, Stellar atmospheres
The Scaling of Vortical Electron Acceleration in Thin-current Magnetic Reconnection and Its Implications in Solar Flares. To investigate how magnetic reconnection (MR) accelerates electrons to a power-law energy spectrum in solar flares, we explore the scaling of a kinetic model proposed by Che &amp; Zank (CZ) and compare it to observations. Focusing on thin current sheet MR particle-in-cell (PIC) simulations, we analyze the impact of domain size on the evolution of the electron Kelvin-Helmholtz instability (EKHI). We find that the duration of the growth stage of the EKHI ( ${t}_{G}\sim {{\rm{\Omega }}}_{e}^{-1}$ ) is short and remains nearly unchanged because the electron gyrofrequency Ω e  is independent of domain size. The quasi-steady stage of the EKHI (t MR) dominates the electron acceleration process and scales linearly with the size of the simulations as L/v A0, where v A0 is the Alfvén speed. We use the analytical results obtained by CZ to calculate the continuous temporal evolution of the electron energy spectra from PIC simulations and linearly scale them to solar flare observational scales. For the first time, an electron acceleration model predicts the sharp two-stage transition observed in typical soft-hard-harder electron energy spectra, implying that the electron acceleration model must be efficient with an acceleration timescale that is a small fraction of the duration of solar flares. Our results suggest that we can use PIC MR simulations to investigate the observational electron energy spectral evolution of solar flares if the ratio t MR/t  G  is sufficiently small, i.e., ≲10%.

Keywords: Solar energetic particles, Solar flares, Solar magnetic reconnection
Chandra X-Ray Observatory Observations of 13 Fermi LAT Sources. In the latest data release from the Fermi Gamma-ray Space Telescope (the 4th Fermi LAT 14 yr Catalog, or 4FGL), more than 50% of the Galactic sources are yet to be identified. We observed 13 unidentified Fermi LAT sources with the Chandra X-Ray Observatory to explore their nature. We report the results of the classification of X-ray sources in the fields of these γ-ray sources and discuss the implications for their nature. We use multiwavelength (MW) data for a machine-learning classification, accompanied by a more detailed spectral/variability analysis for brighter sources. Eight 4FGL sources have γ-ray pulsars within their position error ellipses. We consider three of these pulsars (PSR J1906+0722, PSR J1105-6037, and PSR J1358-6025) to be detected in X-rays, while PSR J1203-6242 shows a hint of X-ray emission. Within the positional uncertainties of three of the 4FGL sources, we detect X-ray sources that may be yet unknown pulsars, depending on the MW association. In addition to point sources, we discovered two extended sources, one of which is likely to be a bow-shock pulsar-wind nebula associated with PSR J1358-6025. Finally, we classify other X-ray sources detected in these observations and report the most interesting classifications.

Keywords: Gamma-ray sources, X-ray surveys, Catalogs
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-break galaxies, Lyman alpha forest
Dual-band Observations of the Asymmetric Ring around CIDA 9A: Dead or Alive?. While the most exciting explanation of the observed dust asymmetries in protoplanetary disks is the presence of protoplanets, other mechanisms can also form the dust features. This paper presents dual-wavelength Atacama Large Millimeter/submillimeter Array observations of a large asymmetric dusty ring around the M-type star CIDA 9A. We detect a dust asymmetry in both 1.3 and 3.1 mm data. To characterize the asymmetric structure, a parametric model is used to fit the observed visibilities. We report a tentative azimuthal shift of the dust emission peaks between the observations at the two wavelengths. This shift is consistent with a dust trap caused by a vortex, which may be formed by an embedded protoplanet or other hydrodynamical instabilities, such as a dead zone. Deep high-spatial-resolution observations of dust and molecular gas are needed to constrain the mechanisms that formed the observed millimeter cavity and dust asymmetry in the protoplanetary disk around CIDA 9A.

Keywords: Protoplanetary disks, Planet formation, Circumstellar disks
Filamentary Dust Polarization and the Morphology of Neutral Hydrogen Structures. Filamentary structures in neutral hydrogen (H I) emission are well aligned with the interstellar magnetic field, so H I emission morphology can be used to construct templates that strongly correlate with measurements of polarized thermal dust emission. We explore how the quantification of filament morphology affects this correlation. We introduce a new implementation of the Rolling Hough Transform (RHT) using spherical harmonic convolutions, which enables efficient quantification of filamentary structure on the sphere. We use this Spherical RHT algorithm along with a Hessian-based method to construct H I-based polarization templates. We discuss improvements to each algorithm relative to similar implementations in the literature and compare their outputs. By exploring the parameter space of filament morphologies with the Spherical RHT, we find that the most informative H I structures for modeling the magnetic field structure are the thinnest resolved filaments. For this reason, we find a ~10% enhancement in the B-mode correlation with polarized dust emission with higher-resolution H I observations. We demonstrate that certain interstellar morphologies can produce parity-violating signatures, i.e., nonzero TB and EB, even under the assumption that filaments are locally aligned with the magnetic field. Finally, we demonstrate that B modes from interstellar dust filaments are mostly affected by the topology of the filaments with respect to one another and their relative polarized intensities, whereas E modes are mostly sensitive to the shapes of individual filaments.

Keywords: Interstellar dust, Galaxy magnetic fields, Interstellar phases, Interstellar filaments, Interstellar atomic gas, Milky Way magnetic fields, Cosmic microwave background radiation, Neutral hydrogen clouds, Interstellar magnetic fields, Interstellar medium, Magnetic fields, Algorithms
To Sample or Not to Sample: Retrieving Exoplanetary Spectra with Variational Inference and Normalizing Flows. Current endeavours in exoplanet characterization rely on atmospheric retrieval to quantify crucial physical properties of remote exoplanets from observations. However, the scalability and efficiency of said technique are under strain with increasing spectroscopic resolution and forward model complexity. The situation has become more acute with the recent launch of the James Webb Space Telescope and other upcoming missions. Recent advances in machine learning provide optimization-based variational inference as an alternative approach to perform approximate Bayesian posterior inference. In this investigation we developed a normalizing-flow-based neural network, combined with our newly developed differentiable forward model, Diff-τ, to perform Bayesian inference in the context of atmospheric retrievals. Using examples from real and simulated spectroscopic data, we demonstrate the advantages of our proposed framework: (1) training our neural network does not require a large precomputed training set and can be trained with only a single observation; (2) it produces high-fidelity posterior distributions in excellent agreement with sampling-based retrievals; (3) it requires up to 75% fewer forward model calls to converge to the same result; and (4) this approach allows formal Bayesian model selection. We discuss the computational efficiencies of Diff-τ in relation to TauREx3's nominal forward model and provide a "lessons learned" account of developing radiative transfer models in differentiable languages. Our proposed framework contributes toward the latest development of neural network-powered atmospheric retrieval. Its flexibility and significant reduction in forward model calls required for convergence holds the potential to be an important addition to the retrieval tool box for large and complex data sets along with sampling-based approaches.

Keywords: Observational astronomy, Bayesian statistics, Exoplanets, Neural networks, Posterior distribution, Transmission spectroscopy, Exoplanet atmospheres