adsabs/SciX_UAT_keywords huggingface dataset:
Extracting the Cold Neutral Medium from H I Emission with Deep Learning: Implications for Galactic Foregrounds at High Latitude

Resolving the phase structure of neutral hydrogen (H I) is crucial for understanding the life cycle of the interstellar medium (ISM). However, accurate measurements of H I temperature and density are limited by the availability of background continuum sources for measuring H I absorption. Here we test the use of deep learning for extracting H I properties over large areas without optical depth information. We train a 1D convolutional neural network using synthetic observations of 3D numerical simulations of the ISM to predict the fraction ( ${f}_{\mathrm{CNM}}$ ) of cold neutral medium (CNM) and the correction to the optically thin H I column density for optical depth ( ${{ \mathcal R }}_{{\rm{H}}{\rm\small{I}}}$ ) from 21 cm emission alone. We restrict our analysis to high Galactic latitudes ( $| b| \gt 30^\circ $ ), where the complexity of spectral line profiles is minimized. We verify that the network accurately predicts ${f}_{\mathrm{CNM}}$ and ${{ \mathcal R }}_{{\rm{H}}{\rm\small{I}}}$ by comparing the results with direct constraints from 21 cm absorption. By applying the network to the GALFA-H I survey, we generate large-area maps of ${f}_{\mathrm{CNM}}$ and ${{ \mathcal R }}_{{\rm{H}}{\rm\small{I}}}$ . Although the overall contribution to the total H I column of CNM-rich structures is small (∼5%), we find that these structures are ubiquitous. Our results are consistent with the picture that small-scale structures observed in 21 cm emission aligned with the magnetic field are dominated by CNM. Finally, we demonstrate that the observed correlation between H I column density and dust reddening ( $E(B-V)$ ) declines with increasing ${{ \mathcal R }}_{{\rm{H}}{\rm\small{I}}}$ , indicating that future efforts to quantify foreground Galactic $E(B-V)$ using H I, even at high latitudes, should increase fidelity by accounting for H I phase structure.

Keywords: interstellar medium; interstellar atomic gas; interstellar absorption; cold neutral medium; milky way galaxy; convolutional neural networks; radio astronomy
FIR-luminous [C II] Emitters in the ALMA-SCUBA-2 COSMOS Survey (AS2COSMOS): The Nature of Submillimeter Galaxies in a 10 Comoving Megaparsec-scale Structure at z ∼ 4.6

We report the discovery of a 10 comoving megaparsec (cMpc)-scale structure traced by massive submillimeter galaxies (SMGs) at z ∼ 4.6. These galaxies are selected from an emission line search of ALMA Band 7 observations targeting 184 luminous submillimeter sources (S850μm ≥ 6.2 mJy) across 1.6 degrees2 in the COSMOS field. We identify four [C II] emitting SMGs and two probable [C II] emitting SMG candidates at z = 4.60-4.64 with velocity-integrated signal-to-noise ratio of S/N > 8. Four of the six emitters are near-infrared blank SMGs. After excluding one SMG whose emission line is falling at the edge of the spectral window, all galaxies show clear velocity gradients along the major axes that are consistent with rotating gas disks. The estimated rotation velocities of the disks are 330-550 km s-1 and the inferred host dark-matter halo masses are ∼2-8 × 1012 M⊙. From their estimated halo masses and [C II] luminosity function, we suggest that these galaxies have a high (50%-100%) duty cycle and high (∼0.1) baryon conversion efficiency (SFR relative to baryon accretion rate), and that they contribute ≃2% to the total star formation rate density at z = 4.6. These SMGs are concentrated within just 0.3% of the full survey volume, suggesting they are strongly clustered. The extent of this structure and the individual halo masses suggest that these SMGs will likely evolve into members of a ∼1015 M⊙ cluster at z = 0. This survey reveals a synchronized dusty starburst in massive halos at z > 4, which could be driven by mergers or fed by smooth gas accretion.

Keywords: galaxy formation; galaxy evolution; galaxy environments; high-redshift galaxy clusters; submillimeter astronomy
Microscale Processes Determining Macroscale Evolution of Magnetic Flux Tubes along Earth's Magnetopause

An important process affecting solar wind-Earth's magnetosphere coupling is nonsteady dayside magnetic reconnection, observationally evidenced by a flux transfer event (FTE) that shows a bipolar variation of the magnetic field component normal to the magnetopause. FTEs often consist of two interlinked flux tubes, but, local kinetic processes between the flux tubes are not understood in the context of the FTE structuring, evolution, and impact. An FTE observed by the Magnetospheric Multiscale mission on 2017 December 18 consisted of two flux tubes of different topology. One includes field lines with ends connected to the northern and southern hemispheres while the other includes field lines with both ends connected to the magnetosheath. Reconnection occurring at the flux-tube interface indicates how interacting flux tubes evolve into a flux rope with helical magnetic topology that is either closed or open. This study demonstrates a new aspect of how micro- to meso-scale dynamics occurring within FTEs determines their macroscale characteristics and evolution.

Keywords: solar-terrestrial interactions; solar-planetary interactions; solar system terrestrial planets; planetary magnetospheres; solar system
A New Method for Direct Measurement of Isotopologue Ratios in Protoplanetary Disks: A Case Study of the 12CO/13CO Ratio in the TW Hya Disk

Planetary systems are thought to be born in protoplanetary disks. Isotope ratios are a powerful tool for investigating the material origin and evolution from molecular clouds to planetary systems via protoplanetary disks. However, it is challenging to measure the isotope (isotopologue) ratios, especially in protoplanetary disks, because the emission lines of major species are saturated. We developed a new method to overcome these challenges by using optically thin line wings induced by thermal broadening. As a first application of the method, we analyzed two carbon monoxide isotopologue lines, 12CO 3-2 and 13CO 3-2, from archival observations of a protoplanetary disk around TW Hya with the Atacama Large Millimeter/submillimeter Array. The 12CO/13CO ratio was estimated to be 21 ± 5 at disk radii of 70-110 au, which is significantly smaller than the value observed in the local interstellar medium, ~69. It implies that an isotope exchange reaction occurs in a low-temperature environment with C/O > 1. In contrast, it is suggested that 12CO/13CO is higher than ~84 in the outer disk (r > 130 au), which can be explained by the difference in the binding energy of the isotopologues on dust grains and the CO gas depletion processes. Our results imply that the gas-phase 12CO/13CO can vary by a factor of >4 even inside a protoplanetary disk and therefore can be used to trace material evolution in disks.

Keywords: protoplanetary disks; planet formation; astrochemistry; isotopic abundances
The Pulsating White Dwarf G117-B15A: Still the Most Stable Optical Clock Known

The pulsating hydrogen atmosphere white dwarf star G 117-B15A has been observed since 1974. Its main pulsation period at 215.19738823(63) s, observed in optical light curves, varies by only (5.12 ± 0.82) × 10-15 s s-1 and shows no glitches, as pulsars do. The observed rate of period change corresponds to a change of the pulsation period by 1 s in 6.2 million yr. We demonstrate that this exceptional optical clock can continue to put stringent limits on fundamental physics, such as constraints on interaction from hypothetical dark matter particles, as well as to search for the presence of external substellar companions.

Keywords: white dwarf stars; late stellar evolution
The Competing Effect of Gas and Stars in the Evolution of Massive Black Hole Binaries

Massive black hole binaries are predicted to form during the hierarchical assembly of cosmic structures and will represent the loudest sources of low-frequency gravitational waves (GWs) detectable by present and forthcoming GW experiments. Before entering the GW-driven regime, their evolution is driven by the interaction with the surrounding stars and gas. While stellar interactions are found to always shrink the binary, recent studies predict the possibility of binary outspiral mediated by the presence of a gaseous disk, which could endlessly delay the coalescence and impact the merger rates of massive binaries. Here we implement a semianalytical treatment that follows the binary evolution under the combined effect of stars and gas. We find that binaries may outspiral only if they accrete near or above their Eddington limit and only until their separation reaches the gaseous disk self-gravitating radius. Even in case of an outspiral, the binary eventually reaches a large enough mass for GW to take over and drive it to coalescence. The combined action of stellar hardening, mass growth, and GW-driven inspiral brings binaries to coalescence in a few hundreds of megayears at most, implying that gas-driven expansion will not severely affect the detection prospects of upcoming GW facilities.

Keywords: supermassive black holes; stellar dynamics; gravitational wave sources; galaxy accretion disks; computational astronomy
ASTERIA-Asteroid Thermal Inertia Analyzer

Thermal inertia estimates are available for a limited number of a few hundred objects, and the results are practically solely based on thermophysical modeling (TPM). We present a novel thermal inertia estimation method, the Asteroid Thermal Inertia Analyzer (ASTERIA). The core of the ASTERIA model is the Monte Carlo approach, based on the Yarkovsky drift detection. We validate our model on asteroid Bennu plus 10 well-characterized near-Earth asteroids (NEAs) for which a good estimation of the thermal inertia from TPM exists. The tests show that ASTERIA provides reliable results consistent with the literature values. The new method is independent of TPM, allowing an independent verification of the results. As the Yarkovsky effect is more pronounced in small asteroids, the noteworthy advantage of ASTERIA compared to TPM is the ability to work with smaller asteroids, for which TPM typically lacks input data. We used ASTERIA to estimate the thermal inertia of 38 NEAs, with 31 of them being sub-kilometer-sized asteroids. Twenty-nine objects in our sample are characterized as potentially hazardous asteroids. On the limitation side, ASTERIA is somewhat less accurate than TPM. The applicability of our model is limited to NEAs, as the Yarkovsky effect is yet to be detected in main-belt asteroids. However, we can expect a significant increase in high-quality measurements of the input parameters relevant to ASTERIA with upcoming surveys. This will surely increase the reliability of the results generated by ASTERIA and widen the model's applicability.

Keywords: asteroids
A Multiwavelength Study of ELAN Environments (AMUSE2). Mass Budget, Satellites Spin Alignment, and Gas Infall in a Massive z 3 Quasar Host Halo

The systematic targeting of extended Lyα emission around high-redshift quasars resulted in the discovery of rare and bright Enormous Lyα Nebulae (ELANe) associated with multiple active galactic nuclei (AGNs). We initiate here "a multiwavelength study of ELAN environments" (AMUSE2) focusing on the ELAN around the z ~ 3 quasar SDSS J1040+1020, aka the Fabulous ELAN. We report on VLT/HAWK-I, APEX/LABOCA, JCMT/SCUBA-2, SMA/850μm, and ALMA CO(5-4), and 2 mm observations and compare them to previously published VLT/MUSE data. The continuum and line detections enable a first estimate of the star formation rates, dust, stellar, and molecular gas masses in four objects associated with the ELAN (three AGNs and one Lyα emitter), confirming that the quasar host is the most star-forming (star formation rate of ~500 M ⊙ yr-1) and massive galaxy (M star ~ 1011 M ⊙) in the system, and thus can be assumed as central. All four embedded objects have similar molecular gas reservoirs ( ${M}_{{{\rm{H}}}_{2}}\sim {10}^{10}$ M ⊙), resulting in short depletion timescales. This fact together with the estimated total dark matter halo mass, M DM = (0.8-2) × 1013 M ⊙, imply that this ELAN will evolve into a giant elliptical galaxy. Consistently, the constraint on the baryonic mass budget for the whole system indicates that the majority of baryons should reside in a massive warm/hot reservoir (up to 1012 M ⊙), needed to complete the baryons count. Additionally, we discuss signatures of gas infall on the compact objects as traced by Lyα radiative transfer effects and the evidence for the alignment between the satellites' spins and their directions to the central.

Keywords: quasars; active galactic nuclei; circumgalactic medium; high-redshift galaxies
The Fleming Survey: High-cadence Survey for Variable Stars in the Northern Galactic Plane

We present first results from the Fleming Survey, a high-cadence search for variable stars in the northern Galactic Plane, conducted with the James Gregory Telescope in St Andrews (UK). After observing twelve fields, each over a timespan of 3-5 hr and with a cadence of 1 min, we identify 8 variable stars with clear periodic flux modulation in our lightcurves. Two of these are deemed to be δ Scuti pulsators, five are most likely eclipsing binaries. For most of our discoveries, the variability is known in the literature, but the exact period and shape of the lightcurve is not. This mini-survey demonstrates that high-cadence observations with small telescopes are a useful complement to ongoing and planned massive variability surveys.

Keywords: delta cepheid variable stars; algol variable stars; eclipsing binary stars; w ursae majoris variable stars; surveys
GenetIC—A New Initial Conditions Generator to Support Genetically Modified Zoom Simulations

We present genetIC, a new code for generating initial conditions for cosmological N-body simulations. The code allows precise, user-specified alterations to be made to arbitrary regions of the simulation (while maintaining consistency with the statistical ensemble). These "genetic modifications" allow, for example, the history, mass, or environment of a target halo to be altered in order to study the effect on their evolution. The code natively supports initial conditions with nested zoom regions at progressively increasing resolution. Modifications in the high-resolution region must propagate self-consistently onto the lower-resolution grids; to enable this while maintaining a small memory footprint, we introduce a Fourier-space filtering approach to generating fields at variable resolution. Due to a close correspondence with modifications, constrained initial conditions can also be produced by genetIC (for example, with the aim of matching structures in the local universe). We test the accuracy of modifications performed within zoom initial conditions. The code achieves subpercent precision, which is easily sufficient for current applications in galaxy formation.

Keywords: n-body simulations
X-Raying the Birth of Binary Neutron Stars and Neutron Star-Black Hole Binaries

We consider fallback accretion after an ultrastripped supernova (USSN) that accompanies formation of a binary neutron star (BNS) or a neutron star-black hole binary (NS-BH). The fallback matter initially accretes directly to the nascent NS, while it starts to accrete to the circumbinary disk, typically 0.1-1 day after the onset of the USSN explosion. The circumbinary disk mass further accretes, forming mini disks around each compact object, with a super-Eddington rate up to a few years. We show that such a system constitutes a binary ultraluminous X-ray source, and a fraction of the X-rays can emerge through the USSN ejecta. We encourage follow-up observations of USSNe within ≲100 Mpc and ~100-1000 days after the explosion using Chandra, XMM Newton, and NuSTAR, which could detect the X-ray counterpart with time variations representing the properties of the nascent compact binary, e.g., the orbital motion of the binary, the spin of the NS, and/or the quasiperiodic oscillation of the mini disks.

Keywords: neutron stars; black holes; compact binary stars; supernovae; x-ray binary stars
PLATON II: New Capabilities and a Comprehensive Retrieval on HD 189733b Transit and Eclipse Data

Recently, we introduced PLanetary Atmospheric Tool for Observer Noobs (PLATON), a Python package that calculates model transmission spectra for exoplanets and retrieves atmospheric characteristics based on observed spectra. We now expand its capabilities to include the ability to compute secondary eclipse depths. We have also added the option to calculate models using the correlated-k method for radiative transfer, which improves accuracy without sacrificing speed. Additionally, we update the opacities in PLATON—many of which were generated using old or proprietary line lists—using the most recent and complete public line lists. These opacities are made available at R = 1000 and R = 10,000 over the 0.3-30 μm range, and at R = 375,000 in select near-IR bands, making it possible to utilize PLATON for ground-based high-resolution cross-correlation studies. To demonstrate PLATON's new capabilities, we perform a retrieval on published Hubble Space Telescope (HST) and Spitzer transmission and emission spectra of the archetypal hot Jupiter HD 189733b. This is the first joint transit and secondary eclipse retrieval for this planet in the literature, as well as the most comprehensive set of both transit and eclipse data assembled for a retrieval to date. We find that these high signal-to-noise data are well matched by atmosphere models with a C/O ratio of ${0.66}_{-0.09}^{+0.05}$ and a metallicity of ${12}_{-5}^{+8}$ times solar where the terminator is dominated by extended nanometer-sized haze particles at optical wavelengths. These are among the smallest uncertainties reported to date for an exoplanet, demonstrating both the power and the limitations of HST and Spitzer exoplanet observations.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; astronomical models; transmission spectroscopy
Flux Tubes Forming Instability Near the Base of the Rotating Convection Zone: A Possible Explanation for the Low Latitudes of Sunspots

The rise of flux tubes with intense magnetic fields from the base of the convection zone to the solar surface has been substantiated as a probable mechanism for sunspot formation. The origin of flux tubes of a sufficient strength (∼105 G) is, however, uncertain. This paper considers the instability of a large-scale toroidal magnetic field caused by the magnetic suppression of convective heat transport as a candidate for the flux-tube formation mechanism. The consideration employs the analytical dependence of eddy diffusion on the magnetic field supplied by mean-field magnetohydrodynamics. The instability tends to produce regions of increased field strength with spatial scales of the order of 100 Mm at the base of the convection zone. Characteristic growth times of the instability are short compared to the 11 yr cycle. The threshold field strength for the onset of the instability increases from several hundred Gauss in the vicinity of the equator to some kilo-Gauss at middle latitudes. Growth rates of unstable disturbances decrease with latitude. These latitudinal trends can be the reason for the observed confinement of sunspot activity to a near-equatorial belt.

Keywords: solar magnetic fields
Synthetic Gaia Surveys from the FIRE Cosmological Simulations of Milky Way-mass Galaxies

With Gaia Data Release 2, the astronomical community is entering a new era of multidimensional surveys of the Milky Way. This new phase-space view of our Galaxy demands new tools for comparing observations to simulations of Milky Way-mass galaxies in a cosmological context, to test the physics of both dark matter and galaxy formation. We present ananke, a framework for generating synthetic phase-space surveys from high-resolution baryonic simulations, and use it to generate a suite of synthetic surveys resembling Gaia DR2 in data structure, magnitude limits, and observational errors. We use three cosmological simulations of Milky Way-mass galaxies from the Latte suite of the Feedback In Realistic Environments project, which feature self-consistent clustering of star formation in dense molecular clouds and thin stellar/gaseous disks in live cosmological halos with satellite dwarf galaxies and stellar halos. We select three solar viewpoints from each simulation to generate nine synthetic Gaia-like surveys. We sample synthetic stars by assuming each star particle (of mass 7070 M ⊙) represents a single stellar population. At each viewpoint, we compute dust extinction from the simulated gas metallicity distribution and apply a simple error model to produce a synthetic Gaia-like survey that includes both observational properties and a pointer to the generating star particle. We provide the complete simulation snapshot at z = 0 for each simulated galaxy. We describe data access points, the data model, and plans for future upgrades. These synthetic surveys provide a tool for the scientific community to test analysis methods and interpret Gaia data.

Keywords: astrometry; astronomical simulations
Exploring Climate with Obliquity in a Variable-eccentricity Earth-like World

Exploring planetary systems similar to our solar system can provide a means to explore a large range of possibly temperate climates on Earth-like worlds. Rather than run hundreds of simulations with different eccentricities at fixed obliquities, our variable-eccentricity approach provides a means to cover an incredibly large parameter space. Herein Jupiter's orbital radius is moved substantially inward in two different scenarios, causing a forcing on Earth's eccentricity. In one case, the eccentricity of Earth varies from 0 to 0.27 over ~7000 yr for three different fixed obliquities (0°, 23°, and 45°). In another case, the eccentricity varies from 0 to 0.53 over ~9400 yr in a single case with zero obliquity. In all cases, we find that the climate remains stable, but regional habitability changes through time in unique ways. At the same time, the moist greenhouse state is approached but only when at the highest eccentricities.

Keywords: exoplanet astronomy; exoplanet atmospheres; exoplanet dynamics
The NuSTAR View of Perseus: The Intracluster Medium and a Peculiar Hard Excess

As the brightest galaxy cluster in the X-ray sky, Perseus is an excellent target for studying the intracluster medium (ICM), but until recently, its active galactic nucleus (AGN) made studies of the diffuse emission near its center nearly impossible to accomplish with NuSTAR, due to the extended wings of NuSTAR's point-spread function. The development of a new open-source software package—nucrossarf—now allows the contribution from point and diffuse sources to be modeled so that scattered light from the AGN can be accounted for. Using this technique, we present an analysis of diffuse hard X-ray (3–25 keV) emission from the ICM using three archival NuSTAR observations of the Perseus cluster. We find a ∼10% excess of emission beyond 20 keV not describable by purely thermal models. By performing similar analyses of AGNs in archival observations, we have characterized the systematic uncertainty of the modeled AGN contribution to be 3.4%. However, in order to explain the excess, the total scattered AGN emission would have to be 39% stronger than we have measured. We test physical explanations for the excess, such as diffuse inverse-Compton emission potentially originating from the radio mini-halo, but we determine that none of the models are compelling. An upper limit on the inverse-Compton flux (≤1.5 × 10‑11 erg s‑1 cm‑2) and a corresponding lower limit on the global magnetic field strength (≥0.35 μG) are derived. We discuss the potential origin and implications of the excess and present our characterization of the nucrossarf systematic uncertainty, which should be useful for future work.

Keywords: galaxy clusters; intracluster medium; x-ray astronomy; perseus cluster