adsabs/SciX_UAT_keywords huggingface dataset:
JWST NIRCam Photometry: A Study of Globular Clusters Surrounding Bright Elliptical Galaxy VV 191a at z = 0.0513

James Webb Space Telescope NIRCam images have revealed 154 reliable globular cluster (GC) candidates around the z = 0.0513 elliptical galaxy VV 191a after subtracting 34 likely interlopers from background galaxies inside our search area. NIRCam broadband observations are made at 0.9–4.5 μm using the F090W, F150W, F356W, and F444W filters. Using point-spread-function-matched photometry, the data are analyzed to present color–magnitude diagrams and color distributions that suggest a relatively uniform population of GCs, except for small fractions of reddest (5%–8%) and bluest (2%–4%) outliers. GC models in the F090W versus (F090W–F150W) diagram fit the NIRCam data well and show that the majority of GCs detected have a mass of ∼106.5 M ⊙, with metallicities [Fe/H] spanning the typical range expected for GCs (‑2.5 ≲ [Fe/H]≲ 0.5). However, the models predict ∼0.3–0.4 mag bluer (F356W–F444W) colors than the NIRCam data for a reasonable range of GC ages, metallicities, and reddening. Although our data do not quite reach the luminosity function turnover, the measured luminosity function is consistent with previous measurements, suggesting an estimated peak at m AB ∼ ‑9.4 ± 0.2 mag in the F090W filter.

Keywords: elliptical galaxies; globular star clusters; photometry; james webb space telescope
On the Hunt for the Origins of the Orphan-Chenab Stream: Detailed Element Abundances with APOGEE and Gaia

Stellar streams in the Galactic halo are useful probes of the assembly of galaxies like the Milky Way. Many tidal stellar streams that have been found in recent years are accompanied by a known progenitor globular cluster or dwarf galaxy. However, the Orphan-Chenab (OC) stream is one case where a relatively narrow stream of stars has been found without a known progenitor. In an effort to find the parent of the OC stream, we use astrometry from the early third data release of ESA's Gaia mission (Gaia EDR3) and radial velocity information from the Sloan Digital Sky Survey (SDSS)-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey to find up to 13 stars that are likely members of the OC stream. We use the APOGEE survey to study the chemical nature (for up to 10 stars) of the OC stream in the α (O, Mg, Ca, Si, Ti, and S), odd-Z (Al, K, and V), Fe-peak (Fe, Ni, Mn, Co, and Cr), and neutron-capture (Ce) elemental groups. We find that the stars that make up the OC stream are not consistent with a monometallic population and have a median metallicity of -1.92 dex with a dispersion of 0.28 dex. Our results also indicate that the α elements are depleted compared to the known Milky Way populations and that its [Mg/Al] abundance ratio is not consistent with second-generation stars from globular clusters. The detailed chemical pattern of these stars, namely the [α/Fe]-[Fe/H] plane and the metallicity distribution, indicates that the OC stream progenitor is very likely to be a dwarf spheroidal galaxy with a mass of ~106 M ⊙.

Keywords: stellar streams; chemical abundances; stellar abundances
A Spatially Resolved X-Ray Polarization Map of the Vela Pulsar Wind Nebula

In this paper, we present a full spatially resolved polarization map for the Vela pulsar wind nebula (PWN) observed by IXPE. By employing effective background discrimination techniques, our results show a remarkably high degree of local polarization in the outskirt region, exceeding 60% (55%) with a probability of 95% (99%), which approaches the upper limit predicted by the synchrotron emission mechanism. The high degree of polarization suggests that the turbulent magnetic energy is at most 33% of the ordered one. In addition, the X-ray polarization map exhibits a toroidal magnetic field pattern that is consistent with the field revealed by radio observations across the entire nebula. This consistency reveals that the observed X-ray and radio emissions are radiated by electrons from the same magnetic field. Different from the Crab PWN, the consistency observed in the Vela PWN may be attributed to the interaction between the reverse shock of the supernova blast wave and the PWN, which leads to a displacement between the synchrotron-cooled nebula and the fresh nebula close to the pulsar. These findings deepen our understanding of the structure and evolution of the Vela PWN and the magnetohydrodynamic interaction in PWNe.

Keywords: pulsar wind nebulae; magnetic fields; polarimetry
Utilizing a Database of Simulated Geometric Albedo Spectra for Photometric Characterization of Rocky Exoplanet Atmospheres

In anticipation of future flagship missions focused on the goal of achieving direct imaging of rocky exoplanets, we have developed a database of models to help the community examine the potential spectral characteristics of a broad range of rocky planet atmospheres. Using the publicly available Planetary Spectrum Generator, we have computed a grid of 141,600 rocky exoplanet geometric albedo spectra across a seven-dimensional parameter space. Using this grid, we have performed a color-color analysis seeking to identify the most useful near-UV and red or near-infrared photometric follow-up channels to combine with a green-optical (discovery) spectral channel. We found that a combination of filters at 0.4, 0.58, and ∼0.8 μm were able to distinguish between atmospheres with moderate-to-high concentrations of four different dominant absorbing constituents, given at least 10 hr of observation on a star at 10 parsec with a 15 m class space telescope; however, more moderate abundances similar to those of solar system rocky bodies would be more challenging to detect. We recommend that future missions seeking to characterize directly imaged rocky exoplanets by colors alone further consider multiband photometry as a first discriminator for planetary characteristics.

Keywords: exoplanets; exoplanet astronomy; computational astronomy; astronomical models
Prevalence of Complex Organic Molecules in Starless and Prestellar Cores within the Taurus Molecular Cloud

The detection of complex organic molecules (COMs) toward dense, collapsing prestellar cores has sparked interest in the fields of astrochemistry and astrobiology, yet the mechanisms for COM formation are still debated. It was originally believed that COMs first form in ices, only to be irradiated by UV radiation from the surrounding interstellar radiation field as well as forming protostars, and subsequently photodesorbed into the gas phase. However, starless and prestellar cores do not have internal protostars to heat up and sublimate the ices. Alternative models using chemical energy have been developed to explain the desorption of COMs, yet in order to test these models, robust measurements of COM abundances are needed toward representative samples of cores. We have conducted a large sample survey of 31 starless and prestellar cores in the Taurus molecular cloud, detecting methanol (CH3OH) in 100% of the cores targeted and acetaldehyde (CH3CHO) in 70%. At least two transition lines of each molecule were measured, allowing us to place tight constraints on excitation temperature, column density, and abundance. Additional mapping of methanol revealed extended emission detected down to AV as low as ∼3 mag. We find that COMs are detectable in the gas phase and are being formed early, at least hundreds of thousands of years prior to star and planet formation. The precursor molecule, CH3OH, may be chemically linked to the more complex CH3CHO; however, higher spatial resolution maps are needed to further test chemical models.

Keywords: astrochemistry; star formation; dense interstellar clouds
Cosmic Distributions of Stellar Tidal Disruptions by Massive Black Holes at Galactic Centers

Stars can be consumed (either tidally disrupted or swallowed whole) by massive black holes (MBHs) at galactic centers when they move into the vicinity of the MBHs. In this study, we investigate the rates of stellar consumption by central MBHs and their cosmic distributions, including the effects of triaxial galaxy shapes in enhancing the reservoir of low-angular-momentum stars and incorporating realistic galaxy distributions. We find that the enhancement in the stellar consumption rates due to triaxial galaxy shapes can be significant, by a factor of ∼3 for MBH mass ${M}_{\mathrm{BH}}\sim {10}^{5}$ - ${10}^{6}\,{M}_{\odot }$ and up to more than one order of magnitude for ${M}_{\mathrm{BH}}\gtrsim {10}^{8}\,{M}_{\odot }$ . Only for ${M}_{\mathrm{BH}}\lesssim {10}^{7}\,{M}_{\odot }$ are the stellar consumption rates significantly higher in galaxies with steeper inner surface brightness profiles. The average (per galaxy) stellar consumption rates correlate with central MBH masses positively for ${M}_{\mathrm{BH}}\gtrsim {10}^{7}\,{M}_{\odot }$ and negatively for ${M}_{\mathrm{BH}}\lesssim {10}^{7}\,{M}_{\odot }$ . The volumetric stellar tidal disruption rates are $\sim 3\times {10}^{-5}\,{\mathrm{yr}}^{-1}\,{\mathrm{Mpc}}^{-3}$ for MBHs in the mass range 105- ${10}^{8}\,{M}_{\odot }$ at z = 0; and the volumetric stellar consumption rates by MBHs with higher masses are $\sim {10}^{-6}\,{\mathrm{yr}}^{-1}\,{\mathrm{Mpc}}^{-3}$ , which can be the stellar tidal disruption rate if the high-mass BHs are extremely spinning Kerr BHs or the rate of being swallowed if those BHs are Schwarzschild ones. The volumetric stellar consumption rates decrease with increasing redshift, and the decrease is relatively mild for ${M}_{\mathrm{BH}}\sim {10}^{5}$ - ${10}^{7}\,{M}_{\odot }$ and stronger for higher ${M}_{\mathrm{BH}}$ . Most of the stellar tidal disruption events (TDEs) at z = 0 occur in galaxies with mass ${M}_{\mathrm{gal}}\lesssim {10}^{11}\,{M}_{\odot }$ , and about 1%-2% of the TDEs can occur in high-mass galaxies with ${M}_{\mathrm{gal}}\gtrsim {10}^{11}\,{M}_{\odot }$ .

Keywords: astrodynamics; galaxy dynamics; gravitational wave astronomy; high energy astrophysics; supermassive black holes; tidal disruption; transient sources; time domain astronomy
A Catalog of Quasar Properties from Sloan Digital Sky Survey Data Release 16

We present a catalog of continuum and emission-line properties for 750,414 broad-line quasars included in the Sloan Digital Sky Survey Data Release 16 quasar catalog (DR16Q), measured from optical spectroscopy. These quasars cover broad ranges in redshift (0.1 ≲ z ≲ 6) and luminosity (44 ≲ log(L bol/erg s-1) ≲ 48), and probe lower luminosities than an earlier compilation of SDSS DR7 quasars. Derived physical quantities such as single-epoch virial black hole masses and bolometric luminosities are also included in this catalog. We present improved systemic redshifts and realistic redshift uncertainties for DR16Q quasars using the measured line peaks and correcting for velocity shifts of various lines with respect to the systemic velocity. About 1%, 1.4%, and 11% of the original DR16Q redshifts deviate from the systemic redshifts by ∣ΔV∣ > 1500 km s-1, ∣ΔV∣ ∈ [1000, 1500] km s-1, and ∣ΔV∣ ∈ [500, 1000] km s-1, respectively; about 1900 DR16Q redshifts were catastrophically wrong (∣ΔV∣ > 10,000 km s-1). We demonstrate the utility of this data product in quantifying the spectral diversity and correlations among physical properties of quasars with large statistical samples.

Keywords: quasars; surveys
From Nuclear to Circumgalactic: Zooming in on AGN-driven Outflows at z ∼ 2.2 with SINFONI

We use deep adaptive optics assisted integral field spectroscopy from SINFONI on the VLT to study the spatially resolved properties of ionized gas outflows driven by active galactic nuclei (AGNs) in three galaxies at z ∼ 2.2—K20-ID5, COS4-11337, and J0901 + 1814. These systems probe AGN feedback from nuclear to circumgalactic scales and provide unique insights into the different mechanisms by which AGN-driven outflows interact with their host galaxies. K20-ID5 and COS4-11337 are compact star-forming galaxies with powerful ∼1500 km s-1 AGN-driven outflows that dominate their nuclear Hα emission. The outflows do not appear to have any impact on the instantaneous star formation activity of the host galaxies, but they carry a significant amount of kinetic energy that could heat the halo gas and potentially lead to a reduction in the rate of cold gas accretion onto the galaxies. The outflow from COS4-11337 is propagating directly toward its companion galaxy COS4-11363, at a projected separation of 5.4 kpc. COS4-11363 shows signs of shock excitation and recent truncation of star formation activity, which could plausibly have been induced by the outflow from COS4-11337. J0901 + 1814 is gravitationally lensed, giving us a unique view of a compact (R = 470 ± 70 pc), relatively low-velocity (∼650 km s-1) AGN-driven outflow. J0901 + 1814 has a similar AGN luminosity to COS4-11337, suggesting that the difference in outflow properties is not related to the current AGN luminosity and may instead reflect a difference in the evolutionary stage of the outflow and/or the coupling efficiency between the AGN ionizing radiation field and the gas in the nuclear regions.

Keywords: high-redshift galaxies; galaxy evolution; galaxy kinematics
The Coherent Differential Imaging on Speckle Area Nulling (CDI-SAN) Method for High-contrast Imaging under Speckle Variation

Differential imaging is a postprocessing method to obtain high contrast, often used for exoplanet searches. The coherent differential imaging on speckle area nulling (CDI-SAN) method was developed to detect a faint exoplanet lying beneath residual speckles of a host star. It utilizes image acquisitions faster than the stellar speckle variation synchronized with five shapes of a deformable mirror repeatedly. By using only the integrated values of each of the five images and square differences for a long interval of observations, the light of the exoplanet could be separated from the stellar light. The achievable contrast would reach almost the photon-noise limit of the residual speckle intensities under appropriate conditions. CDI-SAN can be applied to both ground-based and space telescopes.

Keywords: exoplanet detection methods; direct imaging; coronagraphic imaging; exoplanets
Diagnosing FU Ori-like Sources: The Parameter Space of Viscously Heated Disks in the Optical and Near-infrared

FU Ori-type objects (FUors) are decades-long outbursts of accretion onto young stars that are strong enough to viscously heat disks so that the disk outshines the central star. We construct models for FUor objects by calculating emission components from a steady-state viscous accretion disk, a passively-heated dusty disk, magnetospheric accretion columns, and the stellar photosphere. We explore the parameter space of the accretion rate $\dot{M}$ and stellar mass M * to investigate implications on the optical and near-infrared spectral energy distribution and spectral lines. The models are validated by fitting to multiwavelength photometry of three confirmed FUor objects, FU Ori, V883 Ori, and HBC 722, and then comparing the predicted spectra to the observed optical and infrared spectra. The brightness ratio between the viscous disk and the stellar photosphere, η, provides an important guide for identifying viscous accretion disks, with η = 1 ("transition line") and η = 5 ("sufficient dominance line") marking turning points in diagnostics, evaluated here in the near-infrared. These turning points indicate the emergence and complete development of FUor-characteristic strong CO absorption, weak metallic absorption, the triangular spectral continuum shape in the H band, and location in color-magnitude diagrams. Lower M * and higher $\dot{M}$ imply larger η; for M * = 0.3 M ⊙, η = 1 corresponds to $\dot{M}=2\,\times \,{10}^{-7}\,{M}_{\odot }$ yr-1 and η = 5 to $\dot{M}=6\,\times \,{10}^{-7}\,{M}_{\odot }$ yr-1. The "sufficient dominance line" also coincides with the expected accretion rate where accreting material directly reaches the star. We discuss implications of the models on extinction diagnostics, FUor brightening timescales, viscous disks during initial protostellar growth, and eruptive young stellar objects associated with FUors.

Keywords: protoplanetary disks; stellar accretion disks
Optical Imaging Polarimetry of Comet 21P/Giacobini-Zinner during Its 2018 Apparition

We conducted polarimetric observations of comet 21P/Giacobini-Zinner in the optical wavelength region using the polarimetric imager PICO equipped with the 50 cm telescope for Public Outreach at the Mitaka Campus of the National Astronomical Observatory of Japan on UT 2018 September 16, at a solar phase angle of 77° for the comet. We used Gunn's i'-band filter to cover the wavelength region where sunlight reflected by dust grains dominates cometary spectra. The intensity map of comet 21P/Giacobini-Zinner showed an elongated coma structure along the east-west direction. The linear polarization degree map was almost uniform and showed no evidence of jet or arc structures in the inner coma. The linear polarization degree was 22% in the coma, which is consistent with other optical polarization observations of 21P/Giacobini-Zinner for this and previous apparitions reported in the literature. The measured polarization angles (179°) were nearly perpendicular to the position angle of the scattering plane of 271°. There is no evidence of significant changes in the dust properties (composition, porosity, and size distribution) in the comet from its 1985 to 2018 apparitions. The spectral gradient of the linear polarization degree for the comet was nearly flat in the wavelength range of ~510-830 nm at a solar phase angle of ~77° during the 2018 apparition.

Keywords: comets; small solar system bodies; short period comets; comae
Dust Reverberation Mapping in Distant Quasars from Optical and Mid-infrared Imaging Surveys

The size of the dust torus in active galactic nuclei (AGNs) and their high-luminosity counterparts, quasars, can be inferred from the time delay between UV/optical accretion disk continuum variability and the response in the mid-infrared (MIR) torus emission. This dust reverberation mapping (RM) technique has been successfully applied to ∼70 z ≲ 0.3 AGNs and quasars. Here we present first results of our dust RM program for distant quasars covered in the Sloan Digital Sky Survey Stripe 82 region combining ∼20 yr ground-based optical light curves with 10 yr MIR light curves from the WISE satellite. We measure a high-fidelity lag between W1 band (3.4 μm) and g band for 587 quasars over 0.3 ≲ z ≲ 2 ( $\left\langle z\right\rangle \sim 0.8$ ) and two orders of magnitude in quasar luminosity. They tightly follow (intrinsic scatter ∼0.17 dex in lag) the IR lag-luminosity relation observed for z < 0.3 AGNs, revealing a remarkable size-luminosity relation for the dust torus over more than four decades in AGN luminosity, with little dependence on additional quasar properties such as Eddington ratio and variability amplitude. This study motivates further investigations in the utility of dust RM for cosmology and strongly endorses a compelling science case for the combined 10 yr Vera C. Rubin Observatory Legacy Survey of Space and Time (optical) and 5 yr Nancy Grace Roman Space Telescope 2 μm light curves in a deep survey for low-redshift AGN dust RM with much lower luminosities and shorter, measurable IR lags. The compiled optical and MIR light curves for 7384 quasars in our parent sample are made public with this work.

Keywords: active galactic nuclei; quasars; dust continuum emission; reverberation mapping
Gamma-Ray and Radio Background Constraints on Cosmic Rays in Milky Way Circumgalactic Medium

We study the interaction of cosmic rays (CRs) with the diffuse circumgalactic gas of the Milky Way (MW) galaxy that results in hadronic γ-ray emission and radio synchrotron emission. We aim to constrain the CR population in our circumgalactic medium (CGM) with the help of the observed isotropic γ-ray background (IGRB), its anisotropy, and radio continuum. We modify different models of CGM gas in hydrostatic equilibrium discussed in the literature by including a cosmic-ray population, parameterized by η ≡ PCR/Pth. For the simplest isothermal model, while the IGRB intensity allows η ≲ 3, the anisotropy resulting from the solar system&'s off-center position in MW rules out all values of η. For the precipitation model, in which the cooling of the CGM gas is regulated with an optimum ratio of cooling time to freefall time, while the observed IGRB intensity allows η ≲ 230, the observed anisotropy allows only very large values of η, of order ≳100. The radio continuum limits η ≲ 400 for the precipitation model and does not constrain the isothermal model; however, these constraints are mitigated by synchrotron loss time being comparable to CR diffusion timescales. These bounds are relevant for current numerical simulations that indicate a significant CR population in CGM of galaxies of MW mass.

Keywords: galactic cosmic rays; milky way galaxy physics; circumgalactic medium; radio continuum emission; diffuse radiation; gamma-rays
Flight of the Bumblebee: the Early Excess Flux of Type Ia Supernova 2023bee Revealed by TESS, Swift, and Young Supernova Experiment Observations

We present high-cadence ultraviolet through near-infrared observations of the Type Ia supernova (SN Ia) 2023bee at D = 32 ± 3 Mpc, finding excess flux in the first days after explosion, particularly in our 10 minutes cadence TESS light curve and Swift UV data. Compared to a few other normal SNe Ia with early excess flux, the excess flux in SN 2023bee is redder in the UV and less luminous. We present optical spectra of SN 2023bee, including two spectra during the period where the flux excess is dominant. At this time, the spectra are similar to those of other SNe Ia but with weaker Si II, C II, and Ca II absorption lines, perhaps because the excess flux creates a stronger continuum. We compare the data to several theoretical models on the origin of early excess flux in SNe Ia. Interaction with either the companion star or close-in circumstellar material is expected to produce a faster evolution than observed. Radioactive material in the outer layers of the ejecta, either from double detonation explosion or from a 56Ni clump near the surface, cannot fully reproduce the evolution either, likely due to the sensitivity of early UV observable to the treatment of the outer part of ejecta in simulation. We conclude that no current model can adequately explain the full set of observations. We find that a relatively large fraction of nearby, bright SNe Ia with high-cadence observations have some amount of excess flux within a few days of explosion. Considering potential asymmetric emission, the physical cause of this excess flux may be ubiquitous in normal SNe Ia.

Keywords: supernovae; type ia supernovae