adsabs/SciX_UAT_keywords huggingface dataset:
Self-consistent Color-Stellar Mass-to-light Ratio Relations for Low Surface Brightness Galaxies

The color-stellar mass-to-light ratio relation (CMLR) is a widely accepted tool for estimating the stellar mass (M*) of a galaxy. However, an individual CMLR tends to give distinct M* for a same galaxy when it is applied in different bands. Examining five representative CMLRs from the literature, we find that the difference in M* predicted in different bands from optical to near-infrared by a CMLR is 0.1 ∼ 0.3 dex. Based on a sample of low surface brightness galaxies that covers a wide range of color and luminosity, we therefore recalibrated each original CMLR in r, i, z, J, H, and K bands to give internally self-consistent M* for a same galaxy. The g-r is the primary color indicator in the recalibrated relations, which show little dependence on red (r-z) or near-infrared (J-K) colors. Additionally, the external discrepancies in the originally predicted γ* by the five independent CMLRs have been greatly reduced after recalibration, especially in the near-infrared bands, implying that the near-infrared luminosities are more robust in predicting γ*. For each CMLR, the recalibrated relations provided in this work could produce internally self-consistent M* from divergent photometric bands, and are extensions of the recalibrations from the Johnson-Cousin filter system by the pioneering work of McGaugh & Schombert to the filter system of the Sloan Digital Sky Survey.

Keywords: low surface brightness galaxies; galaxy stellar content; photometry; galaxy properties; scaling relations
Galactic Cosmic-Ray Propagation in the Inner Heliosphere: Improved Force-field Model

A key goal of heliophysics is to understand how cosmic rays propagate in the solar system's complex, dynamic environment. One observable is solar modulation, i.e., how the flux and spectrum of cosmic rays change as they propagate inward. We construct an improved force-field model, taking advantage of new measurements of magnetic power spectral density by Parker Solar Probe to predict solar modulation within the Earth's orbit. We find that modulation of cosmic rays between the Earth and Sun is modest, at least at solar minimum and in the ecliptic plane. Our results agree much better with the limited data on cosmic-ray radial gradients within Earth's orbit than past treatments of the force-field model. Our predictions can be tested with forthcoming direct cosmic-ray measurements in the inner heliosphere by Parker Solar Probe and Solar Orbiter. They are also important for interpreting the gamma-ray emission from the Sun due to scattering of cosmic rays with solar matter and photons.

Keywords: cosmic rays; galactic cosmic rays; gamma-ray astronomy; gamma-ray observatories; magnetohydrodynamics; plasma astrophysics; particle astrophysics; high energy astrophysics; solar physics; interplanetary turbulence
Seasonal Thaws under Mid- to Low-pressure Atmospheres on Early Mars

Despite decades of scientific research on the subject, the climate of the first 1.5 Gyr of Mars' history has not been fully understood yet. Especially challenging is the need to reconcile the presence of liquid water for extended periods of time on the Martian surface with the comparatively low insolation received by the planet, a problem which is known as the Faint Young Sun paradox. In this paper, we use the Earth-like planet surface-temperature model (or ESTM), a latitudinal energy-balance model with enhanced prescriptions for meridional heat diffusion, and the radiative-transfer code EOS to investigate how seasonal variations of temperature can give rise to local conditions which are conducive to liquid-water runoffs. We include the effects of the Martian dichotomy, a northern ocean with either 150 or 550 m of global equivalent layer, and simplified CO2 or H2O clouds. We find that 1.3-2.0 bar CO2-dominated atmospheres can produce seasonal thaws due to inefficient heat redistribution, provided that the eccentricity and the obliquity of the planet are sufficiently different from zero. We also studied the impact of different values for the argument of perihelion. When local favorable conditions exist, they nearly always persist for >15% of the Martian year. These results are obtained without the need for additional greenhouse gases (e.g., H2, CH4) or transient heat-injecting phenomena (e.g., asteroid impacts, volcanic eruptions). A moderate amount (0.1%-1%) of CH4 significantly widens the parameter space region in which seasonal thaws are possible.

Keywords: mars; astrobiology; planetary climates; planetary atmospheres; computational methods
Systematic KMTNet Planetary Anomaly Search. VI. Complete Sample of 2018 Sub-prime-field Planets

We complete the analysis of all 2018 sub-prime-field microlensing planets identified by the KMTNet AnomalyFinder. Among the 9 previously unpublished events with clear planetary solutions, 6 are clearly planetary (OGLE-2018-BLG-0298, KMT-2018-BLG-0087, KMT-2018-BLG-0247, KMT-2018-BLG-0030, OGLE-2018-BLG-1119, and KMT-2018-BLG-2602), while the remaining 3 are ambiguous in nature. The above ordering of these events is made to facilitate grouping of their Bayesian estimates: the first two are lower-mass gas giants while the last four are Jovian-class planets; the first three most likely lie in the bulge, the last in the disk, and the remaining two are equally likely to be in either population. More specifically, these six planets have host masses ${M}_{\mathrm{host}}=({0.69}_{-0.30}^{+0.34},{0.10}_{-0.05}^{+0.14},{0.29}_{-0.14}^{+0.28},{0.51}_{-0.31}^{+0.43},{0.48}_{-0.28}^{+0.35},{0.66}_{-0.36}^{+0.42}){M}_{\odot }$ , planet masses ${M}_{\mathrm{planet}}=({0.14}_{-0.06}^{+0.07},{0.23}_{-0.12}^{+0.32},{2.11}_{-1.04}^{+2.09},{1.45}_{-0.88}^{+1.23},{0.91}_{-0.52}^{+0.66},{1.15}_{-0.63}^{+0.73}){M}_{\mathrm{Jup}}$ , and distances ${D}_{L}=({6.54}_{-1.23}^{+0.95},{7.02}_{-1.15}^{+1.03},{6.76}_{-1.24}^{+0.99},{6.48}_{-1.96}^{+1.28},{5.76}_{-2.48}^{+1.43},{4.31}_{-1.84}^{+1.97})\mathrm{kpc}$ . In addition, there are 8 previously published sub-prime-field planets that were selected by the AnomalyFinder algorithm. Together with a companion paper on 2018 prime-field planets, this work lays the basis for comprehensive statistical studies. We carry out two such studies, one on caustic topologies and the other on the role of Gaia data. From the first, as expected, half (17/33) of the 2018 planets likely to enter the mass-ratio analysis have non-caustic-crossing anomalies. However, only 1 of the 5 noncaustic anomalies with planet-host mass ratio q < 10-3 was discovered by eye (compared to 7 of the 12 with q > 10-3), showing the importance of the semiautomated AnomalyFinder search. From the second, we find that Gaia has played a major role in the interpretation of 16% of the sample and a supplementary role in 6%.

Keywords: gravitational microlensing exoplanet detection; gravitational microlensing; exoplanet detection methods
A Multiparameter Degeneracy in Microlensing Events with Extreme Finite Source Effects

For microlenses with sufficiently low mass, the angular radius of the source star can be much larger than the angular Einstein ring radius of the lens. For such extreme finite source effect (EFSE) events, finite source effects dominate throughout the duration of the event. Here, we demonstrate and explore a continuous degeneracy between multiple parameters of such EFSE events. The first component in the degeneracy arises from the fact that the directly observable peak change of the flux depends on both the ratio of the angular source radius to the angular Einstein ring radius and the fraction of the baseline flux that is attributable to the lensed source star. The second component arises because the directly observable duration of the event depends on both the impact parameter of the event and the relative lens-source proper motion. These two pairwise degeneracies become coupled when the detailed morphology of the light curve is considered, especially when including a limb-darkening profile of the source star. We derive these degeneracies mathematically through analytic approximations and investigate them further numerically with no approximations. We explore the likely physical situations in which these mathematical degeneracies may be realized and potentially broken. As more and more low-mass lensing events (with ever decreasing Einstein ring radii) are detected with improving precision and increasing cadence from microlensing surveys, one can expect that more of these EFSE events will be discovered. In particular, the detection of EFSE microlensing events could increase dramatically with the Roman Space Telescope Galactic Bulge Time Domain Survey.

Keywords: gravitational microlensing; finite-source photometric effect; free floating planets; primordial black holes
Subaru Suprime-Cam Wide-field BVI Stellar Photometry of the M33 Galaxy

We have surveyed the complete extent of the disk of M33—a gas-rich low-mass dwarf spiral galaxy in the Local Group. The B-, V-, and I-passband (the Johnson–Cousins system) CCD images (typical seeing ∼0.″8) were obtained with the Subaru Telescope equipped with the Suprime-Cam mosaic camera. The wide-field (∼1.°0 × 1.°5) catalog of 803,095 (15 ≤ V ≤ 25) starlike objects, measured using the point-spread function and aperture photometry techniques, is presented. We determined the distance modulus of M33 using the tip of the red giant branch (I TRGB = 20.64 ± 0.02) as a reference point of (m ‑ M)0 = 24.63 ± 0.02stat ± 0.06syst (843 kpc). We found young (≲100 Myr) stellar populations residing up to the deprojected radius of ∼10 kpc. The scale length of the young main-sequence (MS) star surface-number density in the range of radial distances from 7 to 9 kpc is 0.53 ± 0.03 kpc. The youngest MS stars (≲15 Myr) reside up to the radius of ∼8 kpc. This distribution of stellar populations may suggest an outside-in scenario of recent star formation in the disk of M33.

Keywords: spiral galaxies; triangulum galaxy; stellar photometry
New Insights into the Chemical Composition of Five Oort Cloud Comets after Re-analysis of Their Infrared Spectra

We present revised results for the main molecular species in five Oort Cloud comets observed with near-infrared echelle grating spectrometer (NIRSPEC) at the Keck Observatory between 1999 and 2012 (C/1999 S4 (LINEAR), C/2001 A2 (LINEAR), C/2007 W1 (Boattini), C/2012 F6 (Lemmon), and C/2012 S1 (ISON)). The re-evaluation of these data shows the improvement of results in some of the data sets, in particular for comets observed and analyzed before the advent of new and revised fluorescence models and terrestrial retrieval methods introduced since 2011. We observe significant improvements in the resulting rotational temperatures and the production rates for all species, and in mixing ratios of minor species (relative to water). The re-analysis also allowed us to quantify species not analyzed previously, mostly due to the lack of molecular models (e.g., ammonia and formaldehyde). We note, however, that the improvement of these revised values is less substantial for comets observed (and/or analyzed) since 2010.

Keywords: comets; astrobiology; solar system formation
Toward a Physical Understanding of Galaxy-Halo Alignment

We investigate the alignment of galaxy and halo orientations using the TNG300-1 hydrodynamical simulation. Our analysis reveals that the distribution of the 2D misalignment angle θ 2D can be well described by a truncated shifted exponential distribution with only one free parameter across different redshifts and galaxy/halo properties. We demonstrate that the galaxy-ellipticity (GI) correlations of galaxies can be reproduced by perturbing halo orientations with the obtained θ 2D distribution, with only a small bias (<3°) possibly arising from unaccounted for couplings between θ 2D and other factors. We find that both the 2D and 3D misalignment angles θ 2D and θ 3D decrease with ex situ stellar mass fraction F acc, halo mass M vir, and stellar mass M *, while increasing with the disk-to-total stellar mass fraction F disk and redshift. These dependences are in good agreement with our recent observational study based on BOSS galaxy samples. Our results suggest that F acc is a key factor in determining galaxy-halo alignment. Grouping galaxies by F acc nearly eliminates the dependence of θ 3D on M vir for all three principle axes, and also reduces the redshift dependence. For θ 2D, we find a more significant redshift dependence than for θ 3D even after controlling F acc, which may be attributed to the evolution of galaxy and halo shapes. Our findings present a valuable model for observational studies and enhance our understanding of galaxy-halo alignment.

Keywords: galaxy properties; hydrodynamical simulations; weak gravitational lensing; galaxy dark matter halos
Evidence for Two Distinct Broad-line Regions from Reverberation Mapping of PG 0026+129

We report on the results of a new spectroscopic monitoring campaign of the quasar PG 0026+129 at the Calar Alto Observatory 2.2 m telescope from 2017 July to 2020 February. Significant variations in the fluxes of the continuum and broad emission lines, including Hβ and He II, were observed in the first and third years, and clear time lags between them are measured. The broad Hβ line profile consists of two Gaussian components: an intermediate-width H ${\beta }_{\mathrm{IC}}$ with an FWHM of 1964 ± 18 $\mathrm{km}\,{{\rm{s}}}^{-1}$ and another very broad H ${\beta }_{\mathrm{VBC}}$ with an FWHM of 7570 ± 83 $\mathrm{km}\,{{\rm{s}}}^{-1}$ . H ${\beta }_{\mathrm{IC}}$ has long time lags of ∼40-60 days in the rest frame, while H ${\beta }_{\mathrm{VBC}}$ shows nearly zero time delay with respect to the optical continuum at 5100 Å. The velocity-resolved delays show consistent results: lags of ∼30-50 days at the core of the broad Hβ line and roughly zero lags at the wings. H ${\beta }_{\mathrm{IC}}$ has a redshift of ∼400 $\mathrm{km}\,{{\rm{s}}}^{-1}$ , which seems to be stable for nearly 30 yr by comparing with archived spectra, and may originate from an infall. The rms spectrum of H ${\beta }_{\mathrm{VBC}}$ shows a double-peaked profile with brighter blue peak and extended red wing in the first year, which matches the signature of a thin disk. Both the double-peaked profile and the near-zero lag suggest that H ${\beta }_{\mathrm{VBC}}$ comes from a region associated with the part of the accretion disk that emits the optical continuum. Adopting the FWHM (in the rms spectrum) and the time lag measured for the total Hβ line, and a virial factor of 1.5, we obtain a virial mass of ${2.89}_{-0.69}^{+0.60}\times {10}^{7}\,{M}_{\odot }$ for the central black hole in this quasar.

Keywords: supermassive black holes; seyfert galaxies; active galactic nuclei; quasars; reverberation mapping; time domain astronomy
Galaxy Clusters Selected via the Sunyaev-Zel'dovich Effect in the SPTpol 100-square-degree Survey

We present a catalog of galaxy cluster candidates detected in 100 square degrees surveyed with the SPTpol receiver on the South Pole Telescope. The catalog contains 89 candidates detected with a signal-to-noise ratio greater than 4.6. The candidates are selected using the Sunyaev-Zel'dovich effect at 95 and 150 GHz. Using both space- and ground-based optical and infrared telescopes, we have confirmed 81 candidates as galaxy clusters. We use these follow-up images and archival images to estimate photometric redshifts for 66 galaxy clusters and spectroscopic observations to obtain redshifts for 13 systems. An additional two galaxy clusters are confirmed using the overdensity of near-infrared galaxies only and are presented without redshifts. We find that 15 candidates (18% of the total sample) are at redshift z ≥ 1.0, with a maximum confirmed redshift of ${z}_{\max }=1.38\pm 0.10$ . We expect this catalog to contain every galaxy cluster with ${M}_{500c}\gt 2.6\times {10}^{14}{M}_{\odot }{{h}}_{70}^{-1}$ and z > 0.25 in the survey area. The mass threshold is approximately constant above z = 0.25, and the complete catalog has a median mass of approximately ${M}_{500c}=2.7\times {10}^{14}{M}_{\odot }{{h}}_{70}^{-1}$ . Compared to previous SPT works, the increased depth of the millimeter-wave data (11.2 and 6.5 μK-arcmin at 95 and 150 GHz, respectively) makes it possible to find more galaxy clusters at high redshift and lower mass.

Keywords: galaxy clusters; observational cosmology; large-scale structure of the universe
Chandra Observation of NGC 1559: Eight Ultraluminous X-Ray Sources Including a Compact Binary Candidate

Despite the 30 yr history of ultraluminous X-ray sources (ULXs) studies, issues such as the majority of their physical natures (i.e., neutron stars, stellar-mass black holes, or intermediate black holes) as well as the accretion mechanisms are still under debate. Expanding the ULX sample size in the literature is clearly a way to help. To this end, we investigated the X-ray source population, ULXs in particular, in the barred spiral galaxy NGC 1559 using a Chandra observation made in 2016. In this 45 ks exposure, 33 X-ray point sources were detected within the 2.'7 isophotal radius of the galaxy. Among them, eight ULXs were identified with the criterion of the X-ray luminosity L x > 1039 erg s-1 (0.3-7 keV). Both X-ray light curves and spectra of all the sources were examined. Except for some low-count spectra that only provide ambiguous spectral fitting results, all the X-ray sources were basically spectrally hard and therefore likely have nonthermal origins. While no strong X-ray variability was present in most of the sources owing to the relatively short exposure of the observation, we found an intriguing ULX, named X-24, exhibiting a periodicity of ~7500 s with a detection significance of 2.7σ. We speculate that it is the orbital period of the system. Roche-lobe overflow and Roche limit are consistent with the speculation. Thus, we suggest that X-24 may be one of the rare compact binary ULXs, and hence, a good candidate as a stellar-mass black hole.

Keywords: ultraluminous x-ray sources; stellar mass black holes; roche lobe overflow; roche limit
Searching for Black Holes in the Outer Solar System with LSST

Planet Nine has been proposed to potentially be a black hole (BH) in the outer solar system. We investigate the accretion flares that would result from impacts of small Oort Cloud objects, and find that the upcoming Legacy Survey of Space and Time (LSST) observing program will be able to either rule out or confirm Planet Nine as a BH within a year. We also find that LSST could rule out or confirm the existence of trapped planet-mass BHs out to the edge of the Oort Cloud, indirectly probing the dark matter fraction in subsolar mass BHs and potentially improving upon current limits by orders of magnitude.

Keywords: transient sources; primordial black holes; oort cloud objects; dark matter; accretion
Magnetohydrodynamic Turbulence Formation in Solar Flares: 3D Simulation and Synthetic Observations

Turbulent plasma motion is common in the universe and invoked in solar flares to drive effective acceleration leading to high-energy electrons. Unresolved mass motions are frequently detected in flares from extreme ultraviolet (EUV) observations, which are often regarded as turbulence. However, how this plasma turbulence forms during the flare is still largely a mystery. Here we successfully reproduce observed turbulence in our 3D magnetohydrodynamic simulation where the magnetic reconnection process is included. The turbulence forms as a result of an intricate nonlinear interaction between the reconnection outflows and the magnetic arcades below the reconnection site, in which the shear-flow-driven Kelvin-Helmholtz instability (KHI) plays a key role in generating turbulent vortices. The turbulence is produced above high-density flare loops and then propagates to chromospheric footpoints along the magnetic field as Alfvénic perturbations. High turbulent velocities above 200 km s-1 can be found around the termination shock, while the low atmosphere reaches turbulent velocities of 10 km s-1 at a layer where the number density is about 1011 cm-3. The turbulent region with maximum nonthermal velocity coincides with the region where the observed high-energy electrons are concentrated, demonstrating the potential role of turbulence in acceleration. Synthetic views in EUV and fitted Hinode-EUV Imaging Spectrometer spectra show excellent agreement with observational results. An energy analysis demonstrates that more than 10% of the reconnection-downflow kinetic energy can be converted to turbulent energy via KHI.

Keywords: magnetohydrodynamics; solar flares; solar physics
Taking Titan's Boreal Pole Temperature: Evidence for Evaporative Cooling in Ligeia Mare

From 2004 to 2017, the Cassini RADAR recorded the 2.2 cm thermal emission from Titan's surface in its passive (radiometry) mode of operation. We use this data set to investigate the seasonal evolution of the effective temperature sensed by the microwave radiometer in two regions in the northern pole of the satellite: the sea Ligeia Mare, and its nearby solid terrains. We find that despite the arrival of summer at the end of the mission, the effective temperature of Ligeia Mare decreased by almost 1 K, while that of the solid region slowly increased until 2017 by 1.4 ± 0.3 K. These observations, as well as the lag in summer warming observed by Cassini's Composite Infrared Spectrometer, can be explained by evaporative cooling in both the solid and liquid surfaces after the vernal equinox. It therefore supports the idea that the northern polar terrains are wet. Using an ocean circulation model, we show that the cooling of the sea surface should initiate convection in the sea's interior, ultimately cooling the whole liquid column sensed by the Cassini radiometer and thus decreasing the temperature at depths even long after the evaporation period has ceased. Overall, this work highlights the key role of methane hydrology in controlling the surface and submarine temperatures in the boreal polar regions of Titan.

Keywords: titan; radar observations; effective temperature; brightness temperature; astronomy data analysis; planetary polar regions
A Comparison of Outflow Properties in AGN Dwarfs versus Star-forming Dwarfs

Feedback likely plays a crucial role in resolving discrepancies between observations and theoretical predictions of dwarf galaxy properties. Stellar feedback was once believed to be sufficient to explain these discrepancies, but it has thus far failed to fully reconcile theory and observations. The recent discovery of energetic galaxy-wide outflows in dwarf galaxies hosting active galactic nuclei (AGNs) suggests that AGN feedback may have a larger role in the evolution of dwarf galaxies than previously suspected. In order to assess the relative importance of stellar versus AGN feedback in these galaxies, we perform a detailed Keck/KCWI optical integral field spectroscopic study of a sample of low-redshift star-forming (SF) dwarf galaxies that show outflows in ionized gas in their Sloan Digital Sky Survey spectra. We characterize the outflows and compare them to observations of AGN-driven outflows in dwarfs. We find that SF dwarfs have outflow components that have comparable widths (W 80) to those of outflows in AGN dwarfs, but are much less blueshifted, indicating that SF dwarfs have significantly slower outflows than their AGN counterparts. Outflows in SF dwarfs are spatially resolved and significantly more extended than those in AGN dwarfs. The mass-loss, momentum, and energy rates of star-formation-driven outflows are much lower than those of AGN-driven outflows. Our results indicate that AGN feedback in the form of gas outflows may play an important role in dwarf galaxies and should be considered along with SF feedback in models of dwarf galaxy evolution.

Keywords: dwarf galaxies; extragalactic astronomy; stellar winds; active galactic nuclei; galaxy evolution; star formation