Sazuna/UAT_keywords huggingface dataset:
Takeout and Delivery: Erasing the Dusty Signature of Late-stage Terrestrial Planet Formation. The formation of planets like Earth is expected to conclude with a series of late-stage giant impacts that generate warm dusty debris, the most anticipated visible signpost of terrestrial planet formation in progress. While there is now evidence that Earth-sized terrestrial planets orbit a significant fraction of solar-type stars, the anticipated dusty debris signature of their formation is rarely detected. Here we discuss several ways in which our current ideas about terrestrial planet formation imply transport mechanisms capable of erasing the anticipated debris signature. A tenuous gas disk may be regenerated via takeout (i.e., the liberation of planetary atmospheres in giant impacts) or delivery (i.e., by asteroids and comets flung into the terrestrial planet region) at a level sufficient to remove the warm debris. The powerful stellar wind from a young star can also act, its delivered wind momentum producing a drag that removes warm debris. If such processes are efficient, terrestrial planets may assemble inconspicuously, with little publicity and hoopla accompanying their birth. Alternatively, the rarity of warm excesses may imply that terrestrial planets typically form very early, emerging fully formed from the nebular phase without undergoing late-stage giant impacts. In either case, the observable signposts of terrestrial planet formation appear more challenging to detect than previously assumed. We discuss observational tests of these ideas.

Keywords: Circumstellar matter, Debris disks, Planet formation, Circumstellar gas
Prospects of Gravitational-wave Follow-up through a Wide-field Ultraviolet Satellite: A Dorado Case Study. The detection of gravitational waves from the binary neuron star merger GW170817 and electromagnetic counterparts GRB170817A and AT2017gfo kick-started the field of gravitational-wave multimessenger astronomy. The optically red to near-infrared emission ("red" component) of AT2017gfo was readily explained as produced by the decay of newly created nuclei produced by rapid neutron capture (a kilonova). However, the ultraviolet to optically blue emission ("blue" component) that was dominant at early times (up to 1.5 days) received no consensus regarding its driving physics. Among many explanations, two leading contenders are kilonova radiation from a lanthanide-poor ejecta component and shock interaction (cocoon emission). In this work, we simulate AT2017gfo-like light curves and perform a Bayesian analysis to study whether an ultraviolet satellite capable of rapid gravitational-wave follow-up, could distinguish between physical processes driving the early "blue" component. We find that ultraviolet data starting at 1.2 hr distinguishes the two early radiation models up to 160 Mpc, implying that an ultraviolet mission like Dorado would significantly contribute to insights into the driving emission physics of the postmerger system. While the same ultraviolet data and optical data starting at 12 hr have limited ability to constrain model parameters separately, the combination of the two unlocks tight constraints for all but one parameter of the kilonova model up to 160 Mpc. We further find that a Dorado-like ultraviolet satellite can distinguish the early radiation models up to at least 130 (60) Mpc if data collection starts within 3.2 (5.2) hr for AT2017gfo-like light curves.

Keywords: Neutron stars, Bayesian statistics, Nucleosynthesis, Model selection, Ultraviolet astronomy, Gravitational waves
Making the Solar System. We model the early stages of planet formation in the solar system, including continual planetesimal formation, and planetesimal and pebble accretion onto planetary embryos in an evolving disk driven by a disk wind. The aim is to constrain aspects of planet formation that have large uncertainties by matching key characteristics of the solar system. The model produces a good fit to these characteristics for a narrow range of parameter space. Planetary growth beyond the ice line is dominated by pebble accretion. Planetesimal accretion is more important inside the ice line. Pebble accretion inside the ice line is slowed by higher temperatures, partial removal of inflowing pebbles by planetesimal formation and pebble accretion further out in the disk, and increased radial velocities due to gas advection. The terrestrial planets are prevented from accreting much water ice because embryos beyond the ice line reach the pebble-isolation mass before the ice line enters the terrestrial-planet region. When only pebble accretion is considered, embryos typically remain near their initial mass or grow to the pebble-isolation mass. Adding planetesimal accretion allows Mars-sized objects to form inside the ice line, and allows giant-planet cores to form over a wider region beyond the ice line. In the region occupied by Mercury, pebble Stokes numbers are small. This delays the formation of embryos and stunts their growth, so that only low-mass planets can form here.

Keywords: Solar nebulae, Solar system, Solar system terrestrial planets, Solar system gas giant planets, Mercury (planet), Planet formation, Planetesimals
Wide-band Timing of the Parkes Pulsar Timing Array UWL Data. In 2018 an ultra-wide-bandwidth low-frequency (UWL) receiver was installed on the 64 m Parkes Radio Telescope, enabling observations with an instantaneous frequency coverage from 704 to 4032 MHz. Here we present the analysis of a 3 yr data set of 35 ms pulsars observed with the UWL by the Parkes Pulsar Timing Array, using wide-band timing methods. The two key differences compared to typical narrowband methods are (1) generation of two-dimensional templates accounting for pulse shape evolution with frequency and (2) simultaneous measurements of the pulse time of arrival (TOA) and dispersion measure (DM). This is the first time that wide-band timing has been applied to a uniform data set collected with a single large fractional bandwidth receiver, for which such techniques were originally developed. As a result of our study, we present a set of profile evolution models and new timing solutions, including initial noise analysis. Precision of our TOA and DM measurements is in the range of 0.005-2.08 μs and (0.043-14.24) × 10-4 cm-3 pc, respectively, with 94% of the pulsars achieving a median TOA uncertainty of less than 1 μs.

Keywords: Pulsar timing method, Millisecond pulsars
Updated High-temperature Opacities for the Dartmouth Stellar Evolution Program and Their Effect on the Jao Gap Location. The Jao Gap, a 17% decrease in stellar density at M  G  ~ 10 identified in both Gaia Data Release 2 and Early Data Release 3, presents a new method to probe the interior structure of stars near the fully convective transition mass. The Gap is believed to originate from convective-kissing instability wherein asymmetric production of 3He causes the core convective zone of a star to periodically expand and contract and consequently causes the star luminosities to vary. Modeling of the Gap has revealed a sensitivity in its magnitude to a population metallicity primarily through opacity. Thus far, models of the Jao Gap have relied on OPAL high-temperature radiative opacities. Here we present updated synthetic population models tracing the Gap location modeled with the Dartmouth stellar evolution code using the OPLIB high-temperature radiative opacities. Use of these updated opacities changes the predicted location of the Jao Gap by ~0.05 mag as compared to models that use the OPAL opacities. This difference is likely too small to be detectable in empirical data.

Keywords: Stellar evolutionary models, Stellar evolution
Exotic Compact Objects with Two Dark Matter Fluids. The generic properties of compact objects made of two different fluids of dark matter are studied in a scale-invariant approach. We investigate compact objects with a core-shell structure, where the two fluids are separated, and with mixed dark matter components, where both dark matter fluids are immersed within each other. The constellations considered are combinations of incompressible fluids, free and interacting Fermi gases, and equations of state with a vacuum term, i.e., self-bound dark matter. We find novel features in the mass-radius relations for combined dark matter compact objects, which distinguishes them from compact objects with a single dark matter fluid and compact stars made of ordinary baryonic matter, such as white dwarfs, neutron stars, and quark stars. The maximum compactness of certain combined dark matter stars can reach values up to the causality limit for compact stars but not beyond that limit if causality of the dark matter fluids is ensured.

Keywords: Dark matter, Compact objects
Numerical Simulations and Observations of Mg II in the Solar Chromosphere. The Mg II h and k lines are among the best diagnostic tools of the upper solar chromosphere. This region of the atmosphere is of particular interest, as it is the lowest region of the Sun's atmosphere where the magnetic field is dominant in the energetics and dynamics, defining its structure. While highly successful in the photosphere and lower to mid-chromosphere, numerical models have produced synthetic Mg II lines that do not match the observations well. We present a number of large-scale models with magnetic field topologies representative of the quiet Sun, ephemeral flux regions and plage, and also models where the numerical resolution is high and where we go beyond the MHD paradigm. The results of this study show models with a much improved correspondence with IRIS observations in terms of both intensities and widths, especially underscoring the importance of chromospheric mass loading and of capturing the magnetic field topology and evolution in simulations. This comes in addition to the importance of capturing the generation of small-scale velocity fields and including nonequilibrium ionization and ion-neutral interaction effects. However, it should be noted that difficulties in achieving a good correspondence remain, especially when considering the width of Mg II h and k lines in plage. Understanding and modeling all these effects and their relative importance is necessary in order to reproduce observed spectral features and in isolating the missing pieces necessary to fully comprehend Mg II formation.

Keywords: Solar chromospheric heating, Radiative magnetohydrodynamics, Solar chromosphere, Solar magnetic flux emergence
Gas Sloshing and Cold Fronts in Pre-merging Galaxy Cluster A98. We present deep Chandra observations of the pre-merger galaxy cluster Abell 98 (A98). A98 is a complex merging system. While the northern (A98N) and central subclusters (A98S) are merging along the north-south direction, A98S is undergoing a separate late-stage merger, with two distinct X-ray cores. We report the detection of a gas sloshing spiral and two cold front edges in A98N. We find two more surface brightness edges along the east direction of the eastern core and west direction of the western core of A98S. By measuring the gas temperatures and densities across those edges, we confirm that the eastern edge appears to be a cold front while the western edge is a shock front with a Mach number ${ \mathcal M }$ ≈ 1.5. We detect a spiral structure and a "tail" of X-ray emission associated with the eastern core of A98S. Our measurement indicates that the tail is cooler than the surrounding gas at a 4.2σ level. This may suggest that the tail and the spiral structures are the results of ram-pressure stripping, as the eastern core orbits in the main cluster's gravitational potential.

Keywords: X-ray astronomy
The Origin of Persistently Nonthermal Solar Wind Electrons: the Steady Electron Runaway Model's Demonstration of Dreicer Bifurcation using Measured {{E}}_{allel } and Ion-Electron Coulomb Drag. The Steady Electron Runaway Model (SERM) develops the hypothesis that the solar wind's observed ubiquitous nonthermal electron velocity distribution functions (eVDFs) are caused by Dreicer's velocity space bifurcation in the strong dimensionless ${{\mathbb{E}}}_{\parallel }$ required by quasi-neutrality. SERM's predicted partitions for the pressure and density are contrasted with appropriately adapted eVDF properties from the Wind 3DP experiment (1995-1998), based on in situ observations of ${{\mathbb{E}}}_{\parallel }$ . The observed number fraction of electrons in runaway, δ 3DP, follows a thousandfold decline of Dreicer's predicted fraction, δ, across the observed tenfold reduction of ${{\mathbb{E}}}_{\parallel }$ , satisfying δ 3DP ≃ δ 0.89. SERM's predictions are shown to reproduce the observed variations with ${{\mathbb{E}}}_{\parallel }$ of the electron partial pressure and excess kurtosis, ${{ \mathcal K }}_{e}$ . ${{ \mathcal K }}_{e}$ and ${{\mathbb{E}}}_{\parallel }$ are positively correlated across 4 yr, as expected by the SERM-Dreicer origin of the suprathermals. SERM quantitatively explains the observed 50 yr anticorrelation between δ 3DP and the partition slope temperature ratios. This documentation quantitatively establishes Coulomb runaway physics as the missing determinant of the ubiquitous nonthermal solar wind eVDF. Astrophysical plasmas, like stellar winds, are unavoidably inhomogeneous, requiring ${{\mathbb{E}}}_{\parallel }$ to enforce quasi-neutrality. Between the stars ${{\mathbb{E}}}_{\parallel }$ is expected to be sufficiently large that measurable runaway density fractions (0.1%-30%) will occur, producing widespread leptokurtic eVDFs. Using inhomogeneous two-fluid information, SERM predicts spatially dependent leptokurtic eVDF profiles consonant with Coulomb collisions and the fluid's E ∥(r). SERM can also comment on its eVDFs' consistency with Maxwellians presumed in the Spitzer-Härm closure. The solar wind profile shows the implied strong radial gradient of the plasma eVDF's transformation from near thermal to strongly leptokurtic across 1.5-6 R ⊙.

Keywords: Space plasmas, Solar wind, Collisional processes
Molecular Outflows in z &gt; 6 Unobscured QSO Hosts Driven by Star Formation. Feedback and outflows in galaxies that are associated with a quasar phase are expected to be pivotal in quenching the most massive galaxies. However, observations targeting the molecular outflow phase, which dominates both the mass and momentum and removes the immediate fuel for star formation, are limited in high-z QSO hosts. Massive quiescent galaxies found at z ~ 4 are predicted to have quenched star formation already by z ~ 5 and undergone their most intense growth at z &gt; 6. Here, we present two Atacama Large Millimeter/submillimeter Array (ALMA) detections of molecular outflows, traced by blueshifted absorption of the OH 119 μm doublet, from a sample of three z &gt; 6 infrared luminous QSO hosts: J2310+1855 and P183+05. OH 119 μm is also detected in emission from P183+05, and tentatively in the third source: P036+03. Using similar assumptions as for high-z dusty star-forming galaxy outflows, we find that our QSOs drive molecular outflows with comparable mass outflow rates, which are comparably energetic except for J2310+1855's significantly lower outflow energy flux. We do not find evidence, nor require additional input from the central active galactic nucleus (AGN) to drive the molecular outflow in J2310+1855, but we cannot rule out an AGN contribution in P183+05 if a significant AGN contribution to L FIR is assumed and/or if the outflow covering fraction is high (≥53%), which evidence from the literature suggests is unlikely in these sources. Differences observed in the blueshifted absorption spectral properties may instead be caused by the QSO hosts' more compact dust continuums, limiting observations to lower altitude and more central regions of the outflow.

Keywords: AGN host galaxies, Galactic winds, Stellar feedback, Quasars, High-redshift galaxies
The Mass Accretion Rate and Stellar Properties in Class I Protostars. Stars collect most of their mass during the protostellar stage, yet the accretion luminosity and stellar parameters, which are needed to compute the mass accretion rate, are poorly constrained for the youngest sources. The aim of this work is to fill this gap, computing the stellar properties and the accretion rates for a large sample of Class I protostars located in nearby (&lt;500 pc) star-forming regions and analyzing their interplay. We used a self-consistent method to provide accretion and stellar parameters by modeling the spectral energy distribution and using veiling information from near-IR observations when possible. We calculated accretion and stellar properties for the first time for 50 young stars. We focused our analysis on the 39 confirmed protostars, finding that their mass accretion rate varies between ~10-8 and ~10-4 M ☉ yr-1 in a stellar mass range between ~0.1 and 3 M ☉. We find systematically larger mass accretion rates for our Class I sample than for Class II objects. Although the mass accretion rate we found is high, it still suggests that either stars collect most of their mass before the Class I stage, or eruptive accretion is needed during the overall protostellar phase. Indeed, our results suggest that for a large number of protostars the disk can be unstable, which can result in accretion bursts and disk fragmentation in the past or in the future.

Keywords: Stellar properties, Star formation, Low mass stars, Circumstellar disks, Stellar accretion disks, Protostars, Circumstellar dust
The Swansong of the Galactic Center Source X7: An Extreme Example of Tidal Evolution near the Supermassive Black Hole. We present two decades of new high-angular-resolution near-infrared data from the W. M. Keck Observatory that reveal extreme evolution in X7, an elongated dust and gas feature, presently located half an arcsecond from the Galactic Center supermassive black hole. With both spectro-imaging observations of Br-γ line emission and Lp (3.8 μm) imaging data, we provide the first estimate of its orbital parameters and quantitative characterization of the evolution of its morphology and mass. We find that the leading edge of X7 appears to be on a mildly eccentric (e ~ 0.3), relatively short-period (170 yr) orbit and is headed toward periapse passage, estimated to occur in ~2036. Furthermore, our kinematic measurements rule out the earlier suggestion that X7 is associated with the stellar source S0-73 or with any other point source that has overlapped with X7 during our monitoring period. Over the course of our observations, X7 has (1) become more elongated, with a current length-to-width ratio of 9, (2) maintained a very consistent long-axis orientation (position angle of 50°), (3) inverted its radial velocity differential from tip to tail from -50 to +80 km s-1, and (4) sustained its total brightness (12.8 Lp magnitudes at the leading edge) and color temperature (425 K), which suggest a constant mass of ~50 M Earth. We present a simple model showing that these results are compatible with the expected effect of tidal forces exerted on it by the central black hole, and we propose that X7 is the gas and dust recently ejected from a grazing collision in a binary system.

Keywords: Tidal interaction, Galactic center, Interstellar medium, Supermassive black holes
GALFIT-ing AGN Host Galaxies in COSMOS: HST versus Subaru. The COSMOS field has been extensively observed by most major telescopes, including Chandra, HST, and Subaru. HST imaging boasts very high spatial resolution and is used extensively in morphological studies of distant galaxies. Subaru provides lower spatial resolution imaging than HST but a substantially wider field of view with greater sensitivity. Both telescopes provide near-infrared imaging of COSMOS. Successful morphological fitting of Subaru data would allow us to measure morphologies of over 104 known active galactic nucleus (AGN) hosts, accessible through Subaru wide-field surveys, currently not covered by HST. The morphological parameters indicate the types of galaxies that host AGNs. For 4016 AGNs between 0.03 &lt; z &lt; 6.5, we study the morphology of their galaxy hosts using GALFIT, fitting components representing the AGN and host galaxy simultaneously using the i-band imaging from both HST and Subaru. Comparing the fits for the differing telescope spatial resolutions and image signal-to-noise ratios, we identify parameter regimes for which there is strong disagreement between distributions of fitted parameters for HST and Subaru. In particular, the Sérsic index values strongly disagree between the two sets of data, including sources at lower redshifts. In contrast, the measured magnitude and radius parameters show reasonable agreement. Additionally, large variations in the Sérsic index have little effect on the ${\chi }_{\nu }^{2}$ of each fit, whereas variations in other parameters have a more significant effect. These results indicate that the Sérsic index distributions of high-redshift galaxies that host AGNs imaged at ground-based spatial resolution are not reliable indicators of galaxy type and should be interpreted with caution.

Keywords: AGN host galaxies, Active galactic nuclei, Galaxy classification systems, Surveys
Patchy Forsterite Clouds in the Atmospheres of Two Highly Variable Exoplanet Analogs. We present an atmospheric retrieval analysis of a pair of highly variable, ~200 Myr old, early T type planetary-mass exoplanet analogs SIMP J01365662+0933473 and 2MASS J21392676+0220226 using the Brewster retrieval framework. Our analysis, which makes use of archival 1-15 μm spectra, finds almost identical atmospheres for both objects. For both targets, we find that the data is best described by a patchy, high-altitude forsterite (Mg2SiO4) cloud above a deeper, optically thick iron (Fe) cloud. Our model constrains the cloud properties well, including the cloud locations and cloud particle sizes. We find that the patchy forsterite slab cloud inferred from our retrieval may be responsible for the spectral behavior of the observed variability. Our retrieved cloud structure is consistent with the atmospheric structure previously inferred from spectroscopic variability measurements, but clarifies this picture significantly. We find consistent C/O ratios for both objects, which supports their formation within the same molecular cloud in the Carina-Near moving group. Finally, we note some differences in the constrained abundances of H2O and CO, which may be caused by data quality and/or astrophysical processes such as auroral activity and their differing rotation rates. The results presented in this work provide a promising preview of the detail with which we will characterize extrasolar atmospheres with JWST, which will yield higher-quality spectra across a wider wavelength range.

Keywords: Exoplanet atmospheric composition , Brown dwarfs, Exoplanet atmospheric variability, Exoplanet astronomy, Exoplanet atmospheres, T dwarfs
JCMT BISTRO Observations: Magnetic Field Morphology of Bubbles Associated with NGC 6334. We study the HII regions associated with the NGC 6334 molecular cloud observed in the submillimeter and taken as part of the B-fields In STar-forming Region Observations Survey. In particular, we investigate the polarization patterns and magnetic field morphologies associated with these HII regions. Through polarization pattern and pressure calculation analyses, several of these bubbles indicate that the gas and magnetic field lines have been pushed away from the bubble, toward an almost tangential (to the bubble) magnetic field morphology. In the densest part of NGC 6334, where the magnetic field morphology is similar to an hourglass, the polarization observations do not exhibit observable impact from HII regions. We detect two nested radial polarization patterns in a bubble to the south of NGC 6334 that correspond to the previously observed bipolar structure in this bubble. Finally, using the results of this study, we present steps (incorporating computer vision; circular Hough transform) that can be used in future studies to identify bubbles that have physically impacted magnetic field lines.

Keywords: Molecular clouds, Interstellar magnetic fields, Dust continuum emission, Star formation, H II regions