adsabs/SciX_UAT_keywords huggingface dataset:
Compositional Maps of the Lunar Polar Regions Derived from the Kaguya Spectral Profiler and the Lunar Orbiter Laser Altimeter Data

Due to the challenging illumination conditions of the lunar polar regions, mineralogic maps have generally been constrained to within 0°-70°N/S. Here we generate a gridded reflectance data cube from the Kaguya Spectral Profiler measurements for each polar region and calibrate it to absolute reflectance using data from the Lunar Orbiter Laser Altimeter. We use this data set to derive the first quantitative mineral maps of iron oxide (FeO), the optical maturity parameter (OMAT), and nanophase iron poleward of 50°N/S at a spatial resolution of 1 km pixel-1. We evaluate potential latitudinal trends in space weathering and optical maturity and characterize the polar geology, with an emphasis on the Artemis region (84°-90°S). The maps of FeO are in excellent agreement with the abundances measured by the Lunar Prospector and provide an increased level of detail, such as the excavation of high- and low-FeO material by De Forest crater. The OMAT maps offer a fantastic view of both polar regions. They highlight small fresh craters, walls, and central peaks, as well as rays extending through multiple degrees of latitude, such as those from Tycho and De Forest, which extend into the Artemis region. Both polar regions are characterized by the ubiquitous presence of noritic anorthosites and anorthositic norite. Low-calcium pyroxene is largely the dominant mafic mineral present. The Artemis region has relatively homogeneous FeO and plagioclase content at the observed spatial resolution. The lowest FeO values are found near Shackleton, between Shoemaker and Faustini, and on the central peak of Amundsen crater.

Keywords: planetary science; lunar surface; lunar mineralogy
Disentangling Modified Gravity and Massive Neutrinos with Intrinsic Shape Alignments of Massive Halos

We present two new diagnostics based on the intrinsic shape alignments of group/cluster size dark matter halos to disentangle the effect of f(R) gravity from that of massive neutrinos. Using snapshot data from a series of the DUSTGRAIN-pathfinder N-body simulations for a Planck ΛCDM cosmology and three f(R) gravity models with massive neutrinos (ν), we first determine the probability density functions of the alignment angles between the shape orientations of massive halos and the minor principal axes of the local tidal fields. The numerically obtained results turn out to agree very well with the analytic formula derived under the assumption that the anisotropic merging along the cosmic web induces the halo shape alignments. The four cosmologies, which several standard diagnostics failed to discriminate, are found to yield significantly different best-fit values of the single parameter that characterizes their analytic formulae. We also numerically determine the spatial cross-correlations between the shape orientations of neighbor group/cluster halos, and find them to be in good agreements with a fitting formula characterized by two parameters, whose best-fit values are found to differ substantially among the four models. We also discuss the limitations and caveats of these new diagnostics that must be overcome for their application to real observational data.

Keywords: large-scale structure of the universe; cosmology
Light Curves of Tidal Disruption Events in Active Galactic Nuclei

The black hole of an active galactic nucleus is encircled by an accretion disk. The surface density of the disk is always too low to affect the tidal disruption of a star, but it can be high enough that a vigorous interaction results when the debris stream returns to pericenter and punches through the disk. Shocks excited in the disk dissipate the kinetic energy of the disk interior to the impact point and expedite inflow toward the black hole. Radiatively efficient disks with luminosity $\gtrsim {10}^{-3}$ Eddington have a high enough surface density that the initial stream-disk interaction leads to energy dissipation at a super-Eddington rate. Because of the rapid inflow, only part of this dissipated energy emerges as radiation, while the rest is advected into the black hole. Dissipation, inflow, and cooling balance to keep the bolometric luminosity at an Eddington-level plateau whose duration is tens of days, with an almost linear dependence on stellar mass. After the plateau, the luminosity decreases in proportion to the disk surface density, with a power-law index between -3 and -2 at earlier times, and possibly a steeper index at later times.

Keywords: tidal disruption; hydrodynamical simulations; active galactic nuclei; accretion; gravitation; black hole physics
Imaging Polarization of the Blue-excess Hot Dust-obscured Galaxy WISE J011601.41-050504.0

We report on VLT/FORS2 imaging polarimetry observations in the R Special band of WISE J011601.41-050504.0 (W0116-0505), a heavily obscured hyperluminous quasar at z = 3.173 classified as a Hot Dust-obscured Galaxy (Hot DOG) based on its mid-IR colors. Recently, Assef et al. identified W0116-0505 as having excess rest-frame optical/UV emission and concluded that this excess emission is most likely scattered light from the heavily obscured AGN. We find that the broadband rest-frame UV flux is strongly linearly polarized (10.8% ± 1.9%, with a polarization angle of 74° ± 9°), confirming this conclusion. We analyze these observations in the context of a simple model based on scattering either by free electrons or by optically thin dust, assuming a classical dust torus with polar openings. Both can replicate the degree of polarization and the luminosity of the scattered component for a range of geometries and column densities, but we argue that optically thin dust in the ISM is the more likely scenario. We also explore the possibility that the scattering medium corresponds to an outflow recently identified for W0116-0505. This is a feasible option if the outflow component is biconical with most of the scattering occurring at the base of the receding outflow. In this scenario, the quasar would still be obscured even if viewed face-on but might appear as a reddened type 1 quasar once the outflow has expanded. We discuss a possible connection between blue-excess Hot DOGs, extremely red quasars, reddened type 1 quasars, and unreddened quasars that depends on a combination of evolution and viewing geometry.

Keywords: active galaxies; galaxy evolution; high-redshift galaxies; quasars; polarimetry
The Young Planet DS Tuc Ab Has a Low Obliquity

The abundance of short-period planetary systems with high orbital obliquities relative to the spin of their host stars is often taken as evidence that scattering processes play important roles in the formation and evolution of these systems. More recent studies have suggested that wide binary companions can tilt protoplanetary disks, inducing a high stellar obliquity that form through smooth processes like disk migration. DS Tuc Ab, a transiting planet with an 8.138 day period in the 40 Myr Tucana-Horologium association, likely orbits in the same plane as its now-dissipated protoplanetary disk, enabling us to test these theories of disk physics. Here, we report on Rossiter-McLaughlin observations of one transit of DS Tuc Ab with the Planet Finder Spectrograph on the Magellan Clay Telescope at Las Campanas Observatory. We confirm the previously detected planet by modeling the planet transit and stellar activity signals simultaneously. We test multiple models to describe the stellar activity-induced radial velocity variations over the night of the transit, finding the obliquity to be low: λ = 12° ± 13°, which suggests that this planet likely formed through smooth disk processes and its protoplanetary disk was not significantly torqued by DS Tuc B. The specific stellar activity model chosen affects the results at the ≈5° level. This is the youngest planet to be observed using this technique; we provide a discussion on best practices to accurately measure the observed signal of similar young planets.

Keywords: exoplanets; exoplanet dynamics; high resolution spectroscopy; starspots
The Asteroseismological Richness of RCB and dLHdC Stars

RCB stars are L ≈ 104 L ⊙ solar-mass objects that can exhibit large periods of extinction from dust ejection episodes. Many exhibit semi-regular pulsations in the range of 30–50 days with semi-amplitudes of 0.05–0.3 mag. Space-based photometry has discovered that solar-like oscillations are ubiquitous in hydrogen-dominated stars that have substantial outer convective envelopes, so we explore the hypothesis that the pulsations in RCB stars and the closely related dustless hydrogen-deficient carbon (dLHdC) stars, which have large convective outer envelopes of nearly pure helium, have a similar origin. Through stellar modeling and pulsation calculations, we find that the observed periods and amplitudes of these pulsations follows the well-measured phenomenology of their H-rich brethren. In particular, we show that the observed modes are likely of angular orders l = 0, 1, and 2 and predominantly of an acoustic nature (i.e., p-modes with low radial order). The modes with largest amplitude are near the acoustic cutoff frequency appropriately rescaled to the helium-dominated envelope, and the observed amplitudes are consistent with that seen in high-luminosity (L > 103 L ⊙) H-rich giants. We also find that for T eff ≳ 5400 K, an hydrogen-deficient carbon stellar model exhibits a radiative layer between two outer convective zones, creating a g-mode cavity that supports much longer period (≈100 days) oscillations. Our initial work was focused primarily on the adiabatic modes, but we expect that subsequent space-based observations of these targets (e.g., with TESS or Plato) are likely to lead to a larger set of detected frequencies that would allow for a deeper study of the interiors of these rare stars.

Keywords: hydrogen deficient stars; helium-rich stars; stellar mergers; white dwarf stars
All Comets are Somewhat Hyperactive and the Implications Thereof

We critically examine what hyperactivity on a comet entails, fully develop the A'Hearn Model for Hyperactivity based on the analyses of data collected for the Deep Impact encounter of comet 103P/Hartley 2, describe manifestations of hyperactivity suggested on many, if not all, comets, and give implications of hyperactivity for future cometary exploration. The A'Hearn model requires a highly volatile ice reservoir within a comet to undergo sublimation, escape the nucleus, and drive out less volatile ices along its path to the surface. Once in the coma, the less volatile ice eventually sublimates, creating a secondary source of that gas in the coma, which is generally displaced anti-sunward and not distributed symmetrically about the nucleus. The secondary source of gas increases the total production of the less volatile species in the coma, sometimes well above that expected if the total surface was undergoing sublimation. We argue that based on the simple assumptions of the A'Hearn model and the fact that several comets display one or more of the characteristics of hyperactivity detailed here, it is probable that nearly all comets experience some degree of hyperactivity. Of significance, the ice that is brought from deep within the nucleus into the coma via the process described by the A'Hearn model is the least thermally altered and is thus the most pristine ice in the comet. Therefore, it behooves future mission teams to consider cryogenically sampling coma ice, rather than or in addition to attempting a direct nucleus sample, for a better understanding of the unaltered ices and conditions present in the protoplanetary disk.

Keywords: comets; comet origins; comet volatiles; comae; dirty snowball model
Observations of the Quiet Sun during the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM: Elemental Abundances in the Quiescent Corona

Elements with low first ionization potential (FIP) are known to be 3-4 times more abundant in active region loops of the solar corona than in the photosphere. There have been observations suggesting that this observed "FIP bias" may be different in other parts of the solar corona and such observations are thus important in understanding the underlying mechanism. The Solar X-ray Monitor (XSM) on board the Chandrayaan-2 mission carried out spectroscopic observations of the Sun in soft X-rays during the 2019-2020 solar minimum, considered to be the quietest solar minimum of the past century. These observations provided a unique opportunity to study soft X-ray spectra of the quiescent solar corona in the absence of any active regions. By modeling high-resolution broadband X-ray spectra from XSM, we estimate the temperature and emission measure during periods of possibly the lowest solar X-ray intensity. We find that the derived parameters remain nearly constant over time with a temperature around 2 MK, suggesting the emission is dominated by X-ray bright points. We also obtain the abundances of Mg, Al, and Si relative to H, and find that the FIP bias is ∼2, lower than the values observed in active regions.

Keywords: quiet sun; solar abundances
Templates for Fitting Photometry of Ultra-high-redshift Galaxies

Recent data from the James Webb Space Telescope allow a first glimpse of galaxies at z ≳ 11. The most successful tool for identifying ultra-high-redshift candidates and inferring their properties is photometric template fitting. However, current methods rely on templates derived from much lower-redshift conditions, including stellar populations older than the age of the Universe at z > 12, a stellar initial mass function that is physically disallowed at z > 6, and weaker emission lines than currently observed at z > 7.5. Here, two sets of synthetic templates, optimized for the expected astrophysics of galaxies at 8 < z < 12 and z > 12, are developed and used to fit three galaxies at z > 12 from the SMACS0723 field. Using these improved templates, quantitative estimates are produced of the bias in inferred properties from JWST observations at z > 8 due to these effects. The best-fit redshifts are similar to those found with previous template sets, but the inferred stellar masses drop by as much as 1-1.6 dex, such that stellar masses are no longer seemingly inconsistent with ΛCDM. The two new template sets are released in formats compatible with EAZY and LEPHARE.

Keywords: high-redshift galaxies; photometry; astronomical techniques; galaxy photometry; stellar populations; initial mass function
The Diversity of Environments around Luminous Quasars at Redshift z 6

Significant clustering around the rarest luminous quasars is a feature predicted by dark matter theory combined with number density matching arguments. However, this expectation is not reflected by observations of quasars residing in a diverse range of environments. Here we assess the tension in the diverse clustering of visible i-band dropout galaxies around luminous z ~ 6 quasars. Our approach uses a simple empirical method to derive the median luminosity-to-halo mass relation, Lc(Mh), for both quasars and galaxies under the assumption of lognormal luminosity scatter, ΣQ and ΣG. We show that higher ΣQ reduces the average halo mass hosting a quasar of a given luminosity, thus introducing at least a partial reversion to the mean in the number count distribution of nearby Lyman-break galaxies. We generate a large sample of mock Hubble Space Telescope fields of view centered across rare z ~ 6 quasars by resampling pencil beams traced through the dark matter component of the BlueTides cosmological simulation. We find that diverse quasar environments are expected for ΣQ > 0.4, consistent with numerous observations and theoretical studies. However, we note that the average number of galaxies around the central quasar is primarily driven by galaxy evolutionary processes in neighboring halos, as embodied by our parameter ΣG, instead of a difference in the large-scale structure around the central quasar host, embodied by ΣQ. We conclude that models with ΣG > 0.3 are consistent with current observational constraints on high-z quasars, and that such a value is comparable to the scatter estimated from hydrodynamical simulations of galaxy formation.

Keywords: quasars; supermassive black holes; clustering
Volatile Composition and Outgassing in C/2018 Y1 (Iwamoto): Extending Limits for High-resolution Infrared Cometary Spectroscopy between 2.8 and 5.0 μm

We used the powerful high spectral resolution cross-dispersed facility spectrograph, iSHELL, at the NASA Infrared Telescope Facility (IRTF) to observe C/2018 Y1 (Iwamoto), a long-period comet from the Oort cloud. We report production rates for water and eight other parent molecules (native ices), C2H6, CO, CH4, H2CO, CH3OH, HCN, NH3, and C2H2, on three preperihelion UT dates, 2019 January 13 and (near perihelion) February 4-5. We present abundance ratios relative to both C2H6 (a nonpolar molecule) and H2O (a polar molecule), thereby providing a more complete picture of the parent volatile composition of C/2018 Y1 and potential associations of ices in its nucleus. Overall, the measured spatial distributions for polar molecules (in particular, H2O and CH3OH) were broader, exhibiting more complex structure compared with nonpolar or weakly polar species (CH4, C2H6, and CO). Our January 13 results permitted quantitatively assessing the significant improvement in sensitivity delivered by iSHELL compared with previous capabilities at the IRTF. The efficient spectral coverage of iSHELL plus the favorable geocentric Doppler shift of C/2018 Y1 allowed for measuring >50% of CH4 ν3-band emission intensity on both January 13 and February 5. Compositionally, compared to their respective mean abundances among comets from the Oort cloud, C2H6 and CH3OH were enriched, CH4 and HCN were near normal, and all other species were depleted. The abundance ratio CH3OH/C2H6 was higher by 45% ± 8% on January 13 versus February 5, whereas CH4/C2H6 was unchanged within the uncertainty, suggesting nonhomogeneous composition among regions of the nucleus dominating activity on these dates.

Keywords: comet volatiles; comae
Light Curve Test of GRB 200716C as a Gravitationally Lensed Echo

A gravitational lens can imprint distinct features on the light curve of a gamma-ray burst (GRB). Most prominently, when creating multiple images, the light curves for all images should be identical, within a scale factor in amplitude. For GRB images that are bright enough to have significant counts in multiple time bins, the similarity of the light curves can be assessed with a straightforward χ 2 test. In response to a recent claim that the two pulses in GRB 200716C are lensed images of the same pulse, such a χ 2 test was computed. The test indicated that the likelihood that the two pulses are images of the same parent pulse is less than 0.218%, differing at about the 3.1σ confidence level. Therefore, under the given assumptions, GRB 200716C is not a compelling example of gravitational lensing.

Keywords: gamma-ray bursts; gravitational lensing
Rapid Growth of Seed Black Holes during Early Bulge Formation

We study the early growth of massive seed black holes (BHs) via accretion in protogalactic nuclei where the stellar bulge component is assembled, performing axisymmetric two-dimensional radiation hydrodynamical simulations. We find that when a seed BH with M • ~ 105 M ⊙ is embedded in dense metal-poor gas (Z = 0.01 Z ⊙) with a density of ≳ 100 cm-3 and bulge stars with a total mass of M ⋆ ≳ 100 M •, a massive gaseous disk feeds the BH efficiently at rates of ≳ 0.3-1 M ⊙ yr-1, and the BH mass increases nearly tenfold within ~2 Myr. This rapid accretion phase lasts until a good fraction of the gas bounded within the bulge accretes onto the BH, although the feeding rate is regulated owing to strong outflows driven by ionizing radiation emitted from the accreting BH. The transient growing mode can be triggered for seed BHs formed in massive dark-matter halos with masses of ≳ 109 M ⊙ at z ~ 15-20 (the virial temperature is T vir ≃ 105 K). The host halos are heavier and rarer than those of typical first galaxies, but are more likely to end up in quasar hosts by z ≃ 6. This mechanism naturally yields a mass ratio of M •/M ⋆ > 0.01 higher than the value seen in the local universe. The existence of such overmassive BHs provides us with a unique opportunity to detect highly accreting seed BHs at z ~ 15 with AB magnitude of m AB ~ 26-29 mag at 2 μm (rest frame 10 eV) by the upcoming observations by the James Webb Space Telescope and Nancy Grace Roman Space Telescope.

Keywords: supermassive black holes; quasars; high-redshift galaxies
Photochemical Hazes Dramatically Alter Temperature Structure and Atmospheric Circulation in 3D Simulations of Hot Jupiters

Photochemical hazes are expected to form in hot Jupiter atmospheres and may explain the strong scattering slopes and muted spectral features observed in the transmission spectra of many hot Jupiters. Absorption and scattering by photochemical hazes have the potential to drastically alter temperature structure and atmospheric circulation of these planets but have previously been neglected in general circulation models (GCMs). We present GCM simulations of the hot Jupiter HD 189733 b that include photochemical hazes as a radiatively active tracer fully coupled to atmospheric dynamics. The influence of haze radiative feedback strongly depends on the assumed haze optical properties. For soot hazes, two distinct thermal inversions form, separated by a local temperature minimum around 10-5 bar caused by upwelling on the dayside mixing air with low haze abundance upwards. The equatorial jet broadens and slows down. The horizontal distribution of hazes remains relatively similar to simulations with radiatively passive tracers. For Titan-type hazes, the equatorial jet accelerates and extends to much lower pressures, resulting in a dramatically different 3D distribution of hazes compared to radiatively passive or soot hazes. Further experimental and observational studies to constrain the optical properties of photochemical hazes will therefore be crucial for understanding the role of hazes in exoplanetary atmospheres. In the dayside emission spectrum, for both types of hazes the amplitude of near-infrared features is reduced, while the emitted flux at longer wavelengths (>4 μm) increases. Haze radiative feedback leads to increased phase-curve amplitudes in many infrared wavelength regions, mostly due to stronger dayside emission.

Keywords: exoplanet atmospheres; exoplanet atmospheric dynamics; exoplanet atmospheric structure
New Abundance Determinations for the B9 Mn Star HD 53929

Analysis of coadded high resolution spectra of the chemically peculiar star HD 53929 recorded by the SWP and LWR cameras on board the International Ultraviolet Explorer yields estimates of the abundances of silicon and manganese, respectively 1.5 and 6 times the solar abundances, in the atmosphere of this star. The synthesis of the 4400-4500 Å range allows the determination of the abundances of helium, magnesium, phosphorus and iron. Compared to solar abundances, helium is very underabundant (0.05 solar), magnesium is also underabundant by a factor of 0.20 times the solar abundances. Phosphorus is overabundant by a factor of 20.

Keywords: chemically peculiar stars; manganese stars