Sazuna/UAT_keywords huggingface dataset:
Information-theoretical Limits of Recursive Estimation and Closed-loop Control in High-contrast Imaging. A lower bound on unbiased estimates of wave front errors (WFEs) is presented for the linear regime of small perturbation and active control of a high-contrast region (dark hole). Analytical approximations and algorithms for computing the closed-loop covariance of the WFE modes are provided for discrete- and continuous-time linear WFE dynamics. Our analysis applies to both image-plane and non-common-path wave front sensing (WFS) with Poisson-distributed measurements and noise sources (i.e., photon-counting mode). Under this assumption, we show that recursive estimation benefits from infinitesimally short exposure times, is more accurate than batch estimation and, for high-order WFE drift dynamical processes, scales better than batch estimation with amplitude and star brightness. These newly derived contrast scaling laws are a generalization of previously known theoretical and numerical results for turbulence-driven adaptive optics. For space-based coronagraphs, we propose a scheme for combining models of WFE drift, low-order non-common-path WFS (LOWFS) and high-order image-plane WFS (HOWFS) into closed-loop contrast estimates. We also analyze the impact of residual low-order WFE, sensor noise, and other sources incoherent with the star, on closed-loop dark hole maintenance and the resulting contrast. As an application example, our model suggests that the Roman Space Telescope might operate in a regime that is dominated by incoherent sources rather than WFE drift, where the WFE drift can be actively rejected throughout the observations with residuals significantly dimmer than the incoherent sources. The models proposed in this paper make possible the assessment of the closed-loop contrast of coronagraphs with combined LOWFS and HOWFS capabilities, and thus help estimate WFE stability requirements of future instruments.

Keywords: Space telescopes, Coronagraphic imaging, Ground telescopes
A Hubble Space Telescope Imaging Survey of Low-redshift Swift-BAT Active Galaxies. We present initial results from a Hubble Space Telescope snapshot imaging survey of the host galaxies of Swift-BAT active galactic nuclei (AGN) at z &lt; 0.1. The hard X-ray selection makes this sample relatively unbiased in terms of obscuration, compared to optical AGN selection methods. The high-resolution images of 154 target AGN enable us to investigate the detailed photometric structure of the host galaxies, such as the Hubble type and merging features. We find 48% and 44% of the sample to be hosted by early-type and late-type galaxies, respectively. The host galaxies of the remaining 8% of the sample are classified as peculiar galaxies because they are heavily disturbed. Only a minor fraction of host galaxies (18%-25%) exhibit merging features (e.g., tidal tails, shells, or major disturbance). The merging fraction increases strongly as a function of bolometric AGN luminosity, revealing that merging plays an important role in triggering luminous AGN in this sample. However, the merging fraction is weakly correlated with the Eddington ratio, suggesting that merging does not necessarily lead to an enhanced Eddington ratio. Type 1 and Type 2 AGN are almost indistinguishable in terms of their Hubble type distribution and merging fraction. However, the merging fraction of Type 2 AGN peaks at a lower bolometric luminosity compared with those of Type 1 AGN. This result may imply that the triggering mechanism and evolutionary stages of Type 1 and Type 2 AGN are not identical. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with program #15444.

Keywords: Active galaxies
A Grid of Synthetic Spectra for Subdwarfs: Non-LTE Line-blanketed Atmosphere Models. A new grid of detailed atmosphere model spectra for hot and moderately cool subdwarf stars is presented. High-resolution spectra and synthetic photometry are calculated in the range from 1000-10,000 Å using non-LTE fully line-blanketed atmosphere structures. Our grid covers eight temperatures within 10,000 ≤ Teff [K] ≤ 65,000, three surface gravities in the range 4.5 ≤ log g [cgs] ≤ 6.5, two helium abundances matching two extreme helium-rich and helium-poor scenarios, and two limiting metallicity boundaries regarding both solar ([Fe/H] = 0) and Galactic halos ([Fe/H] = -1.5 and [α/Fe] = +0.4). Besides its application in the determination of fundamental parameters of subdwarfs in isolation and in binaries, the resulting database is also of interest for population synthesis procedures in a wide variety of stellar systems.

Keywords: Subdwarf stars, Stellar spectral lines, Spectral energy distribution, Stellar atmospheres
A Coscaling Grid for Athena++. We present a coscaling-grid formalism and its implementation in the magnetohydrodynamics code Athena++. The formalism relies on flow symmetries in astrophysical problems involving expansion, contraction, and center-of-mass motion. The grid is evolved at the same time order as the fluid variables. The user specifies grid evolution laws, which can be independent of the fluid motion. Applying our implementation to standard hydrodynamic test cases leads to improved results and higher efficiency, compared to the fixed-grid solutions.

Keywords: Hydrodynamical simulations, Computational methods, Astronomical simulations
A New Catalog of Asymptotic Giant Branch Stars in Our Galaxy. We present a new catalog of 11,209 O-rich asymptotic giant branch (AGB) stars and 7172 C-rich AGB stars in our Galaxy, identifying more AGB stars in the bulge component and considering more visual carbon stars. For each object, we cross-identify the Infrared Astronomical Satellite (IRAS), AKARI, Midcourse Space Experiment, Wide-field Infrared Survey Explorer (WISE), Two-Micron All-Sky Survey, and American Association of Variable Star Observers counterparts. We present the new catalog in two parts: one is based on the IRAS PSC for brighter or more isolated objects; the other one is based on the ALLWISE source catalog for less bright objects or objects in crowded regions. We present various infrared two-color diagrams (2CDs) for the sample stars. We find that the theoretical dust shell models can roughly explain the observations of AGB stars on the various IR 2CDs. We investigate IR properties of SiO and OH maser emission sources in the catalog. For Mira variables in the sample stars, we find that the IR colors get redder for longer pulsation periods. We also study infrared variability of the sample stars using the WISE photometric data in the last 12 yr: the ALLWISE multiepoch data and the Near-Earth Object WISE Reactivation 2021 data release. We generate light curves using the WISE data at W1 and W2 bands and compute the Lomb-Scargle periodograms for all of the sample stars. From the WISE light curves, we have found useful variation parameters for 3710 objects in the catalog, for which periods were either known or unknown in previous works.

Keywords: Infrared astronomy, Asymptotic giant branch stars, Long period variable stars, Radiative transfer, Circumstellar dust, Milky Way Galaxy
The Large Early Galaxy Astrophysics Census (LEGA-C) Data Release 3: 3000 High-quality Spectra of K<SUB>s</SUB>-selected Galaxies at z &gt; 0.6. We present the third and final data release of the Large Early Galaxy Astrophysics Census (LEGA-C), an ESO/Very Large Telescope public spectroscopic survey targeting 0.6 &lt; z &lt; 1.0, Ks-selected galaxies. The data release contains 3528 spectra with measured stellar velocity dispersions and stellar population properties, a 25-fold increase in sample size compared to previous work. This Ks-selected sample probes the galaxy population down to ~0.3L*, for all colors and morphological types. Along with the spectra, we publish a value-added catalog with stellar and ionized gas velocity dispersions, stellar absorption line indices, emission-line fluxes, and equivalent widths, complemented with structural parameters measured from Hubble Space Telescope Advanced Camera for Surveys imaging. With its combination of high precision and large sample size, LEGA-C provides a new benchmark for galaxy evolution studies.

Keywords: Galaxies, Late-type galaxies, Surveys, Stellar populations, Galaxy kinematics, Spectroscopy, Galaxy spectroscopy, Early-type galaxies
Breaking the Degeneracy in Magnetic Cataclysmic Variable X-Ray Spectral Modeling Using X-Ray Light Curves. We present an analysis of mock X-ray spectra and light curves of magnetic cataclysmic variables using an upgraded version of the 3D CYCLOPS code. This 3D representation of the accretion flow allows us to properly model total and partial occultation of the postshock region by the white dwarf as well as the modulation of the X-ray light curves due to the phase-dependent extinction of the preshock region. We carried out detailed postshock region modeling in a four-dimensional parameter space by varying the white dwarf mass and magnetic field strength as well as the magnetosphere radius and the specific accretion rate. To calculate the postshock region temperature and density profiles, we assumed equipartition between ions and electrons; took into account the white dwarf gravitational potential, the finite size of the magnetosphere, and a dipole-like magnetic field geometry; and considered cooling by both bremsstrahlung and cyclotron radiative processes. By investigating the impact of the parameters on the resulting X-ray continuum spectra, we show that there is an inevitable degeneracy in the four-dimensional parameter space investigated here, which compromises X-ray continuum spectral fitting strategies and can lead to incorrect parameter estimates. However, the inclusion of X-ray light curves in different energy ranges can break this degeneracy, and it therefore remains, in principle, possible to use X-ray data to derive fundamental parameters of magnetic cataclysmic variables, which represents an essential step toward understanding their formation and evolution.

Keywords: Cataclysmic variable stars, Magnetic variable stars
The Extinction and Distance of the MBM Molecular Clouds at High Galactic Latitude. Based on the accurate color excess {E}_{{{\rm{G}}}_{\mathrm{BP}},{{\rm{G}}}_{\mathrm{RP}}}$ of more than 4 million stars and the {E}_{\mathrm{NUV},{{\rm{G}}}_{\mathrm{BP}}}$ of more than 1 million stars from Sun et al., the distance and extinction of the molecular clouds (MCs) in the Magnani-Blitz-Mundy catalog at ∣b∣ &gt; 20° are studied in combination with the distance measurement of Gaia/EDR3. The distance, as well as the color excess, is determined for 66 MCs. The color excess ratio {E}_{{\rm{N}}{\rm{U}}{\rm{V}},{{\rm{G}}}_{{\rm{B}}{\rm{P}}}}/{E}_{{{\rm{G}}}_{{\rm{B}}{\rm{P}}},{{\rm{G}}}_{{\rm{R}}{\rm{P}}}}$ is derived for 39 of them, which is obviously larger and implies more small particles at smaller extinction. In addition, the scale height of the dust disk is found to be about 100 pc and becomes large at the anticenter direction due to the disk flaring.

Keywords: Interstellar dust, High latitude field, Ultraviolet extinction, Molecular clouds
A Parametric Model to Reproduce the Background of the Insight-HXMT/HE Blind Detector. The estimation of instrumental background is the basis of essentially all data analysis on observations with Insight-HXMT. The current Insight-HXMT/HE background model made by Liao et al. depends on the data from the HE blind detector, i.e., using historical data to make a preliminary estimation of the background spectra and using the real-time data from the blind detector to make a further modification. In order to decouple the dependence of background method on the blind detector, a parametric physical model has been developed to rebuild the light curve and spectrum of the HE blind detector. In this parametric model, several physical processes between the space environment and the satellite are considered to rebuild the prompt and delayed background signals of the HE blind detector. With the genetic algorithm and Markov Chain Monte Carlo procedure, the model parameters are determined by fitting the data from the HE blind detector. For all 62 energy bands in the range 28-334 keV for an exposure of 10 ks, the average systematic error of the background energy spectrum is ~2.2% and the average total error of spectrum estimation ~3.4%. It is found that more accurate background can be attained using this model than using the data from the Insight-HXMT/HE blind detector for exposures of less than 2 ks. These results show that the background of the Insight-HXMT/HE blind detector can be reproduced reliably with this parametric model and this method can also be applied to the background estimation of other detectors in principle.

Keywords: Space vehicle instruments, X-ray detectors, Astronomy data modeling, X-ray telescopes
Molecules with ALMA at Planet-forming Scales (MAPS). I. Program Overview and Highlights. Planets form and obtain their compositions in dust- and gas-rich disks around young stars, and the outcome of this process is intimately linked to the disk chemical properties. The distributions of molecules across disks regulate the elemental compositions of planets, including C/N/O/S ratios and metallicity (O/H and C/H), as well as access to water and prebiotically relevant organics. Emission from molecules also encodes information on disk ionization levels, temperature structures, kinematics, and gas surface densities, which are all key ingredients of disk evolution and planet formation models. The Molecules with ALMA at Planet-forming Scales (MAPS) ALMA Large Program was designed to expand our understanding of the chemistry of planet formation by exploring disk chemical structures down to 10 au scales. The MAPS program focuses on five disks-around IM Lup, GM Aur, AS 209, HD 163296, and MWC 480-in which dust substructures are detected and planet formation appears to be ongoing. We observed these disks in four spectral setups, which together cover ~50 lines from over 20 different species. This paper introduces the Astrophysical Journal Supplement's MAPS Special Issue by presenting an overview of the program motivation, disk sample, observational details, and calibration strategy. We also highlight key results, including discoveries of links between dust, gas, and chemical substructures, large reservoirs of nitriles and other organics in the inner disk regions, and elevated C/O ratios across most disks. We discuss how this collection of results is reshaping our view of the chemistry of planet formation.

Keywords: Millimeter astronomy, Astrochemistry, Astrobiology, Protoplanetary disks, Submillimeter astronomy, Planet formation
Molecules with ALMA at Planet-forming Scales (MAPS). II. CLEAN Strategies for Synthesizing Images of Molecular Line Emission in Protoplanetary Disks. The Molecules with ALMA at Planet-forming Scales Large Program (MAPS LP) surveyed the chemical structures of five protoplanetary disks across more than 40 different spectral lines at high angular resolution (0"15 and 0"30 beams for Bands 6 and 3, respectively) and sensitivity (spanning 0.3-1.3 mJy beam-1 and 0.4-1.9 mJy beam-1 for Bands 6 and 3, respectively). In this article, we describe the multistage workflow-built around the CASA tclean image deconvolution procedure-that we used to generate the core data product of the MAPS LP: the position-position-velocity image cubes for each spectral line. Owing to the expansive nature of the survey, we encountered a range of imaging challenges: some are familiar to the submillimeter protoplanetary disk community, like the need to use an accurate CLEAN mask, and others are less well known, like the incorrect default flux scaling of the CLEAN residual map first described by Jorsater &amp; van Moorsel (the "JvM effect"). We distill lessons learned into recommended workflows for synthesizing image cubes of molecular emission. In particular, we describe how to produce image cubes with accurate fluxes via "JvM correction," a procedure that is generally applicable to any image synthesized via CLEAN deconvolution but is especially critical for low signal-to-noise ratio (S/N) emission. We further explain how we used visibility tapering to promote a common, fiducial beam size and contextualize the interpretation of S/N when detecting molecular emission from protoplanetary disks. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

Keywords: Submillimeter astronomy, Radio interferometry, Protoplanetary disks, Deconvolution
Molecules with ALMA at Planet-forming Scales (MAPS). III. Characteristics of Radial Chemical Substructures. The Molecules with ALMA at Planet-forming Scales (MAPS) Large Program provides a detailed, high-resolution (~10-20 au) view of molecular line emission in five protoplanetary disks at spatial scales relevant for planet formation. Here we present a systematic analysis of chemical substructures in 18 molecular lines toward the MAPS sources: IM Lup, GM Aur, AS 209, HD 163296, and MWC 480. We identify more than 200 chemical substructures, which are found at nearly all radii where line emission is detected. A wide diversity of radial morphologies-including rings, gaps, and plateaus-is observed both within each disk and across the MAPS sample. This diversity in line emission profiles is also present in the innermost 50 au. Overall, this suggests that planets form in varied chemical environments both across disks and at different radii within the same disk. Interior to 150 au, the majority of chemical substructures across the MAPS disks are spatially coincident with substructures in the millimeter continuum, indicative of physical and chemical links between the disk midplane and warm, elevated molecular emission layers. Some chemical substructures in the inner disk and most chemical substructures exterior to 150 au cannot be directly linked to dust substructure, however, which indicates that there are also other causes of chemical substructures, such as snowlines, gradients in UV photon fluxes, ionization, and radially varying elemental ratios. This implies that chemical substructures could be developed into powerful probes of different disk characteristics, in addition to influencing the environments within which planets assemble. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

Keywords: Interstellar molecules, Planet formation, Astrochemistry, Protoplanetary disks, High angular resolution
Molecules with ALMA at Planet-forming Scales (MAPS). IV. Emission Surfaces and Vertical Distribution of Molecules. The Molecules with ALMA at Planet-forming Scales (MAPS) Large Program provides a unique opportunity to study the vertical distribution of gas, chemistry, and temperature in the protoplanetary disks around IM Lup, GM Aur, AS 209, HD 163296, and MWC 480. By using the asymmetry of molecular line emission relative to the disk major axis, we infer the emission height (z) above the midplane as a function of radius (r). Using this method, we measure emitting surfaces for a suite of CO isotopologues, HCN, and C2H. We find that 12CO emission traces the most elevated regions with $z/r\gt 0.3$ , while emission from the less abundant 13CO and C18O probes deeper into the disk at altitudes of $z/r\,\lesssim \,0.2$ . C2H and HCN have lower opacities and signal-to-noise ratios, making surface fitting more difficult, and could only be reliably constrained in AS 209, HD 163296, and MWC 480, with $z/r\,\lesssim \,0.1$ , i.e., relatively close to the planet-forming midplanes. We determine peak brightness temperatures of the optically thick CO isotopologues and use these to trace 2D disk temperature structures. Several CO temperature profiles and emission surfaces show dips in temperature or vertical height, some of which are associated with gaps and rings in line and/or continuum emission. These substructures may be due to local changes in CO column density, gas surface density, or gas temperatures, and detailed thermochemical models are necessary to better constrain their origins and relate the chemical compositions of elevated disk layers with those of planet-forming material in disk midplanes. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

Keywords: Interstellar molecules, Planet formation, Astrochemistry, Protoplanetary disks, Circumstellar disks, High angular resolution
Molecules with ALMA at Planet-forming Scales (MAPS). V. CO Gas Distributions. Here we present high-resolution (15-24 au) observations of CO isotopologue lines from the Molecules with ALMA on Planet-forming Scales (MAPS) ALMA Large Program. Our analysis employs observations of the (J = 2-1) and (1-0) lines of 13CO and C18O and the (J = 1-0) line of C17O for five protoplanetary disks. We retrieve CO gas density distributions, using three independent methods: (1) a thermochemical modeling framework based on the CO data, the broadband spectral energy distribution, and the millimeter continuum emission; (2) an empirical temperature distribution based on optically thick CO lines; and (3) a direct fit to the C17O hyperfine lines. Results from these methods generally show excellent agreement. The CO gas column density profiles of the five disks show significant variations in the absolute value and the radial shape. Assuming a gas-to-dust mass ratio of 100, all five disks have a global CO-to-H2 abundance 10-100 times lower than the interstellar medium ratio. The CO gas distributions between 150 and 400 au match well with models of viscous disks, supporting the long-standing theory. CO gas gaps appear to be correlated with continuum gap locations, but some deep continuum gaps do not have corresponding CO gaps. The relative depths of CO and dust gaps are generally consistent with predictions of planet-disk interactions, but some CO gaps are 5-10 times shallower than predictions based on dust gaps. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

Keywords: Exoplanet formation, Protoplanetary disks, Astrochemistry
Molecules with ALMA at Planet-forming Scales (MAPS). VI. Distribution of the Small Organics HCN, C<SUB>2</SUB>H, and H<SUB>2</SUB>CO. Small organic molecules, such as C2H, HCN, and H2CO, are tracers of the C, N, and O budget in protoplanetary disks. We present high-angular-resolution (10-50 au) observations of C2H, HCN, and H2CO lines in five protoplanetary disks from the Molecules with ALMA at Planet-forming Scales (MAPS) ALMA Large Program. We derive column density and excitation temperature profiles for HCN and C2H, and find that the HCN emission arises in a temperate (20-30 K) layer in the disk, while C2H is present in relatively warmer (20-60 K) layers. In the case of HD 163296, we find a decrease in column density for HCN and C2H inside one of the dust gaps near ~83 au, where a planet has been proposed to be located. We derive H2CO column density profiles assuming temperatures between 20 and 50 K, and find slightly higher column densities in the colder disks around T Tauri stars than around Herbig Ae stars. The H2CO column densities rise near the location of the CO snowline and/or millimeter dust edge, suggesting an efficient release of H2CO ices in the outer disk. Finally, we find that the inner 50 au of these disks are rich in organic species, with abundances relative to water that are similar to cometary values. Comets could therefore deliver water and key organics to future planets in these disks, similar to what might have happened here on Earth. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

Keywords: Protoplanetary disks