adsabs/SciX_UAT_keywords huggingface dataset:
The Complex Structure of the Bulge of M31

The bulge of M31 is of interest regarding the nature of galactic bulges and how their structure relates to bulge formation mechanisms and their subsequent evolution. With the UVIT instrument on AstroSat, we have observed the bulge of M31 in five far-ultraviolet (FUV) and near-ultraviolet (NUV) filters at 1″ spatial resolution. Models for the luminosity distribution of the bulge are constructed using the UVIT data and the galaxy image fitting algorithm GALFIT. We fit the bulge without the nuclear region with a Sérsic function for the five images and find Sérsic indices (≃2.1-2.5) similar to previous studies but smaller R e values (≃0.5-0.6 kpc). When fitting the images including the nuclear region, a multicomponent model is used. We use an eight-component model for the FUV 148 nm image, which has the highest sensitivity. The other images (169-279 nm) are fit with four-component models. The dust lanes in the bulge region are recovered in the residual images, which have subtraction of the bright bulge light using the multicomponent models. The dust lanes show that M31's nuclear spiral is visible in absorption at NUV and FUV wavelengths. The bulge images show boxy contours in all five UVIT wave bands, which is confirmed by fitting using GALFIT. The Sérsic indices of ~2.1-2.5 are intermediate between the expected values for a classical bulge and for a pseudobulge. The boxiness of the bulge provides further evidence that M31's bulge has contributions from a classical bulge and a pseudobulge.

Keywords: andromeda galaxy; galaxy bulges; galaxy structure; ultraviolet astronomy
JWST Photometric Time-delay and Magnification Measurements for the Triply Imaged Type Ia "SN H0pe" at z = 1.78

Supernova (SN) SN H0pe is a gravitationally lensed, triply imaged, Type Ia SN (SN Ia) discovered in James Webb Space Telescope imaging of the PLCK G165.7+67.0 cluster of galaxies. Well-observed multiply imaged SNe provide a rare opportunity to constrain the Hubble constant (H 0), by measuring the relative time delay between the images and modeling the foreground mass distribution. SN H0pe is located at z = 1.783 and is the first SN Ia with sufficient light-curve sampling and long enough time delays for an H 0 inference. Here we present photometric time-delay measurements and SN properties of SN H0pe. Using JWST/NIRCam photometry, we measure time delays of Δt ab = $-{116.6}_{-9.3}^{+10.8}$ observer-frame days and Δt cb = $-{48.6}_{-4.0}^{+3.6}$ observer-frame days relative to the last image to arrive (image 2b; all uncertainties are 1σ), which corresponds to a ∼5.6% uncertainty contribution for H 0 assuming 70 km s‑1 Mpc‑1. We also constrain the absolute magnification of each image to μ a = ${4.3}_{-1.8}^{+1.6}$ , μ b = ${7.6}_{-2.6}^{+3.6}$ , μ c = ${6.4}_{-1.5}^{+1.6}$ by comparing the observed peak near-IR magnitude of SN H0pe to the nonlensed population of SNe Ia.

Keywords: cosmology; type ia supernovae; gravitational lensing; galaxy clusters
Direct T e-based Metallicities of z = 2–9 Galaxies with JWST/NIRSpec: Empirical Metallicity Calibrations Applicable from Reionization to Cosmic Noon

We report detections of the [O III]λ4364 auroral emission line for 16 galaxies at z = 2.1–8.7, measured from JWST/NIRSpec observations obtained as part of the Cosmic Evolution Early Release Science (CEERS) survey program. We combine this CEERS sample with 9 objects from the literature at z = 4‑9 with auroral-line detections from JWST/NIRSpec and 21 galaxies at z = 1.4‑3.7 with auroral-line detections from ground-based spectroscopy. We derive electron temperature (T e) and direct-method oxygen abundances for the combined sample of 46 star-forming galaxies at z = 1.4‑8.7. We use these measurements to construct the first high-redshift empirical T e-based metallicity calibrations for the strong-line ratios [O III]/Hβ, [O II]/Hβ, R23 = ([O III]+[O II])/Hβ, [O III]/[O II], and [Ne III]/[O II]. These new calibrations are valid over 12+log(O/H) = 7.4‑8.3 and can be applied to samples of star-forming galaxies at z = 2‑9, leading to an improvement in the accuracy of metallicity determinations at Cosmic Noon and in the Epoch of Reionization. The high-redshift strong-line relations are offset from calibrations based on typical z ∼ 0 galaxies or H II regions, reflecting the known evolution of ionization conditions between z ∼ 0 and z ∼ 2. Deep spectroscopic programs with JWST/NIRSpec promise to improve statistics at the low and high ends of the metallicity range covered by the current sample, as well as to improve the detection rate of [N II]λ6585 and thus allow the future assessment of N-based indicators. These new high-redshift calibrations will enable accurate characterizations of metallicity scaling relations at high redshift, improving our understanding of feedback and baryon cycling in the early Universe.

Keywords: high-redshift galaxies; chemical abundances; galaxy evolution; emission line galaxies
An Efficient Numerical Approach to Modeling the Effects of Particle Shape on Rubble-pile Dynamics

We present an approach for the inclusion of nonspherical constituents in high-resolution N-body discrete element method (DEM) simulations. We use aggregates composed of bonded spheres to model nonspherical components. Though the method may be applied more generally, we detail our implementation in the existing N-body code pkdgrav. It has long been acknowledged that nonspherical grains confer additional shear strength and resistance to flow when compared with spheres. As a result, we expect that rubble-pile asteroids will also exhibit these properties and may behave differently than comparable rubble piles composed of idealized spheres. Since spherical particles avoid some significant technical challenges, most DEM gravity codes have used only spherical particles or have been confined to relatively low resolutions. We also discuss the work that has gone into improving performance with nonspherical grains, building on pkdgrav's existing leading-edge computational efficiency among DEM gravity codes. This allows for the addition of nonspherical shapes while maintaining the efficiencies afforded by pkdgrav's tree implementation and parallelization. As a test, we simulated the gravitational collapse of 25,000 nonspherical bodies in parallel. In this case, the efficiency improvements allowed for an increase in speed by nearly a factor of 3 when compared with the naive implementation. Without these enhancements, large runs with nonspherical components would remain prohibitively expensive. Finally, we present the results of several small-scale tests: spin-up due to the YORP effect, tidal encounters, and the Brazil nut effect. In all cases, we find that the inclusion of nonspherical constituents has a measurable impact on simulation outcomes.

Keywords: trans-neptunian objects; asteroid surfaces; near-earth objects; asteroid dynamics; asteroid rotation; asteroids; planetary science; astronomical simulations; theoretical models; n-body simulations
Measuring Tracers of Planet Formation in the Atmosphere of WASP-77A b: Substellar O/H and C/H Ratios, with a Stellar C/O Ratio and a Potentially Superstellar Ti/H Ratio

We present a comprehensive atmospheric retrieval study of the hot Jupiter WASP-77A b using eclipse observations from the Hubble Space Telescope (HST) and JWST. Using atmospheric retrievals, the spectral features of H2O, CO, and TiO are identified, with volume mixing ratios estimated at log10(VMR) = ‑4.40 ${}_{-0.11}^{+0.14}$ , ‑4.44 ${}_{-0.28}^{+0.34}$ , and ‑6.40 ${}_{-0.23}^{+0.22}$ , respectively. We derive the atmospheric C-to-O ratio—a key planetary formation tracer—to be C/O = 0.54 ± 0.12, which is consistent with both the stellar host value and previous studies of the planet's atmosphere, suggesting a relatively close-in formation. Computing other elemental ratios (i.e., C/H, O/H, and Ti/H), we conclude that the general enrichment of the atmosphere (i.e., metallicity) is substellar, depleted in C and O, but that Ti appears slightly superstellar. A low C and O content could be obtained, in combination with a stellar C/O ratio if the planet formed outside of the CO2 snow line before migrating inwards. Meanwhile, a superstellar Ti/H could be obtained by late contamination from refractory rich planetesimals. While broadly in agreement with previous works, we do find some differences and discuss these while also highlighting the need for homogeneous analyses when comparative exoplanetology is conducted.

Keywords: exoplanet atmospheres; hot jupiters; hubble space telescope; james webb space telescope; exoplanet formation
Early Results from GLASS-JWST. XV. Properties of the Faintest Red Sources in the NIRCAM Deep Fields

We present a first look at the reddest 2-5 μm sources found in deep images from the GLASS Early Release Science program. We undertake a general search, i.e., not looking for any particular spectral signatures, for sources detected only in bands redder than is reachable with the Hubble Space Telescope, and which would likely not have been identified in pre-JWST surveys. We search for sources down to AB ~27 (corresponding to >10σ detection threshold) in any of the F200W to F444W filters, with a >1 magnitude excess relative to F090W to F150W bands. Fainter than F444W >25 we find 56 such sources of which 37 have reasonably constrained spectral energy distributions to which we can fit photometric redshifts. We find the majority of this population (~65%) as 2 < z < 6 star-forming low-attenuation galaxies that are faint at rest-frame ultraviolet-optical wavelengths, have stellar masses 108.5-109.5 M ⊙, and have observed fluxes at >2 μm boosted by a combination of the Balmer break and emission lines. The typical implied rest equivalent widths are ~200 Å with some extreme objects up to ~1000 Å. This is in contrast with brighter magnitudes where the red sources tend to be z < 3 quiescent galaxies and dusty star-forming objects. Our general selection criteria for red sources allow us to independently identify other phenomena as diverse as extremely low-mass (~108 M ⊙) quiescent galaxies at z < 1, recovering recently identified z > 11 galaxies and a very cool brown dwarf.

Keywords: high-redshift galaxies
Connection between Emission and Absorption Outflows through the Study of Quasars with Extremely High Velocity Outflows

A recently discovered class of outflows, extremely high velocity outflows (EHVOs), may be key to understanding feedback processes, as it is likely the most powerful in terms of mass energy. These EHVOs have been observed at redshifts 1.052 < z em < 7.641, but the potential connection with outflows in emission has not been studied. We find that EHVOs, albeit their small numbers at the moment, appear to show distinct C IV and He II properties. In particular, EHVOs are more predominant in quasars with large blueshifts of the C IV emission line, suggesting a connection between emission and absorption outflowing signatures for these extreme outflows. We also find incipient trends with the maximum velocity of the outflows, which is similar to what has been previously found in BALQSOs but now extending previous studies to speeds up to ~0.2c. We find that the bolometric luminosities, Eddington ratios, and black hole masses of our sample are overall very similar to the general quasar population upon considering their C IV emission properties. This is close to the case for He II EW, as we observe a tentative upper limit to the He II strength for a quasar to host an EHVO. This study shows that extreme outflows such as EHVOs appear in quasars that are clearly a distinct class from the overall BALQSO population and solidify the relation between outflows observed in emission and absorption.

Keywords: quasars; active galactic nuclei; broad-absorption line quasar; quasar absorption line spectroscopy
Model-independently Calibrating the Luminosity Correlations of Gamma-Ray Bursts Using Deep Learning

Gamma-ray bursts (GRBs) detected at high redshift can be used to trace the Hubble diagram of the universe. However, the distance calibration of GRBs is not as easy as that of SNe Ia. For the calibration method based on the empirical luminosity correlations, there is an underlying assumption that the correlations should be universal over the whole redshift range. In this paper, we investigate the possible redshift dependence of six luminosity correlations with a completely model-independent deep-learning method. We construct a network combining the recurrent neural networks (RNN) and the Bayesian neural networks (BNN), where RNN is used to reconstruct the distance-redshift relation by training the network with the Pantheon compilation, and BNN is used to calculate the uncertainty of the reconstruction. Using the reconstructed distance-redshift relation of Pantheon, we test the redshift dependence of six luminosity correlations by dividing the full GRB sample into two subsamples (low-z and high-z subsamples), and find that only the Ep - Eγ relation has no evidence for redshift dependence. We use the Ep - Eγ relation to calibrate GRBs, and the calibrated GRBs give tight constraints on the flat ΛCDM model, with the best-fitting parameter ${{\rm{\Omega }}}_{{\rm{M}}}={0.307}_{-0.073}^{+0.065}$ .

Keywords: gamma-ray bursts; cosmology; distance measure
X-Ray AGB Stars in the 4XMM-DR9 Catalog: Further Evidence for Companions

Single AGB stars are not normally expected to be X-ray emitters due to the lack of a corona capable of powering a hot plasma. Therefore, the detection of X-ray emission in AGB stars by the ROSAT, Chandra, and XMM-Newton observatories has been interpreted as evidence for binarity. The number of X-ray-emitting AGB stars is, however, very small, and statistically sound conclusions shall be considered tentative. In this paper we aim at increasing the number of X-ray-emitting AGB stars and at providing a consistent analysis of their X-ray emission to be compared to their UV and optical properties. The XMM-Newton 4XMM-DR9 catalog has been searched for X-ray counterparts of various types of AGB stars: nearby (i.e., listed in Hipparcos), mass-losing, and S- and C-types. Seventeen X-ray counterparts of AGB stars have been found in the 4XMM-DR9. Nine of them have pointed XMM-Newton observations, whereas eight are genuine serendipitous discoveries. Together with the AGB stars detected by ROSAT, this increases the number of X-ray AGB stars to 26. Most of their X-ray spectra can be fit by the emission from an optically thin single-temperature thermal plasma with temperatures typically larger than 107 K. There is no obvious correlation between the X-ray and bolometric luminosity of these stars, but the X-ray luminosity generally increases with the amount of far-UV excess. The high temperature of some X-ray-emitting plasma in AGB stars and the correlation of their X-ray luminosity with the far-UV emission supports the origin of this X-ray emission from accretion disks around unseen companions.

Keywords: close binary stars; asymptotic giant branch stars; late-type giant stars; single x-ray stars; symbiotic binary stars; x-ray binary stars
An M Dwarf's Chromosphere, Corona, and Wind Connection via Nonlinear Alfvén Waves

An M dwarf's atmosphere is expected to be highly magnetized. The magnetic energy can be responsible for heating the stellar chromosphere and corona and driving the stellar wind. The nonlinear propagation of Alfvén waves is a promising mechanism for both heating the stellar atmosphere and driving the stellar wind. Based on this Alfvén wave scenario, we carried out a 1D compressive magnetohydrodynamic simulation to reproduce the stellar atmospheres and winds of TRAPPIST-1, Proxima Centauri, YZ CMi, AD Leo, AX Mic, and the Sun. The nonlinear propagation of Alfvén waves from the stellar photosphere to the chromosphere, corona, and interplanetary space is directly resolved in our study. The simulation result particularly shows that the slow shock generated through the nonlinear mode coupling of Alfvén waves is crucially involved in both the dynamics of the stellar chromosphere (stellar spicule) and stellar wind acceleration. Our parameter survey further revealed the following general trends of the physical quantities of the stellar atmosphere and wind. (1) The M dwarf coronae tend to be cooler and denser than the solar corona. (2) The M dwarf stellar winds can be characterized by a relatively faster velocity and much smaller mass-loss rate compared to those of the solar wind. The physical mechanisms behind these tendencies are clarified in this paper, where the stronger stratification of the M dwarf's atmosphere and relatively smaller Alfvén wave energy input from the M dwarf's photosphere are remarkable.

Keywords: stellar winds; stellar coronae; stellar chromospheres; m dwarf stars; alfven waves; magnetohydrodynamics
A Homogeneous Comparison between the Chemical Composition of the Large Magellanic Cloud and the Sagittarius Dwarf Galaxy

Similarities in the chemical composition of two of the closest Milky Way satellites, namely, the Large Magellanic Cloud (LMC) and the Sagittarius (Sgr) dwarf galaxy, have been proposed in the literature, suggesting similar chemical enrichment histories between the two galaxies. This proposition, however, rests on different abundance analyses, which likely introduce various systematics that hamper a fair comparison among the different data sets. In order to bypass this issue (and highlight real similarities and differences between their abundance patterns), we present a homogeneous chemical analysis of 30 giant stars in the LMC, 14 giant stars in Sgr, and 14 giants in the Milky Way, based on high-resolution spectra taken with the spectrograph UVES-FLAMES. The LMC and Sgr stars, in the considered metallicity range ([Fe/H] > -1.1 dex), show very similar abundance ratios for almost all the elements, with differences only in the heavy s-process elements Ba, La, and Nd, suggesting a different contribution by asymptotic giant branch stars. On the other hand, the two galaxies have chemical patterns clearly different from those measured in the Galactic stars, especially for the elements produced by massive stars. This finding suggests that the massive stars contributed less to the chemical enrichment of these galaxies with respect to the Milky Way. The derived abundances support similar chemical enrichment histories for the LMC and Sgr. * Based on observations collected at the ESO-VLT under programs 071.B-0146, 072.B-0293, 072.D-0342, 074.D-0369, 076.D-0381, 078.B-0323, 080.D-0368, 081.D-0286, 084.D-0933, 092.D-0244, 188.B-3002, 193.B-0936.

Keywords: chemical abundances; stellar abundances; large magellanic cloud; sagittarius dwarf spheroidal galaxy
PHANGS-JWST First Results: Rapid Evolution of Star Formation in the Central Molecular Gas Ring of NGC 1365

Large-scale bars can fuel galaxy centers with molecular gas, often leading to the development of dense ringlike structures where intense star formation occurs, forming a very different environment compared to galactic disks. We pair ~0.″3 (30 pc) resolution new JWST/MIRI imaging with archival ALMA CO(2-1) mapping of the central ~5 kpc of the nearby barred spiral galaxy NGC 1365 to investigate the physical mechanisms responsible for this extreme star formation. The molecular gas morphology is resolved into two well-known bright bar lanes that surround a smooth dynamically cold gas disk (R gal ~ 475 pc) reminiscent of non-star-forming disks in early-type galaxies and likely fed by gas inflow triggered by stellar feedback in the lanes. The lanes host a large number of JWST-identified massive young star clusters. We find some evidence for temporal star formation evolution along the ring. The complex kinematics in the gas lanes reveal strong streaming motions and may be consistent with convergence of gas streamlines expected there. Indeed, the extreme line widths are found to be the result of inter-"cloud" motion between gas peaks; SCOUSEPY decomposition reveals multiple components with line widths of <σ CO,scouse> ≈ 19 km s-1 and surface densities of $\langle \,{{\rm{\Sigma }}}_{{{\rm{H}}}_{2},\mathrm{scouse}}\rangle \,\approx \,800\,{M}_{\odot }\,{\mathrm{pc}}^{-2}$ , similar to the properties observed throughout the rest of the central molecular gas structure. Tailored hydrodynamical simulations exhibit many of the observed properties and imply that the observed structures are transient and highly time-variable. From our study of NGC 1365, we conclude that it is predominantly the high gas inflow triggered by the bar that is setting the star formation in its CMZ.

Keywords: barred spiral galaxies; starburst galaxies; star formation; interstellar medium
Distortion of Magnetic Fields in BHR 71

The magnetic field structure of a star-forming Bok globule BHR 71 was determined based on near-infrared polarimetric observations of background stars. The magnetic field in BHR 71 was mapped from 25 stars. By using a simple 2D parabolic function, the plane-of-sky magnetic axis of the core was found to be θmag = 125° ± 11°. The plane-of-sky mean magnetic field strength of BHR 71 was found to be Bpos = 8.8-15.0 μG, indicating that the BHR 71 core is magnetically supercritical with λ = 1.44-2.43. Taking into account the effect of thermal/turbulent pressure and the plane-of-sky magnetic field component, the critical mass of BHR 71 was Mcr = 14.5-18.7 M⊙, which is consistent with the observed core mass of Mcore ≈ 14.7 M⊙. We conclude that BHR 71 is in a condition close to a kinematically critical state, and the magnetic field direction lies close to the plane of sky. Since BHR 71 is a star-forming core, a significantly subcritical condition (I.e., the magnetic field direction deviating from the plane of sky) is unlikely, and collapsed from a condition close to a kinematically critical state. There are two possible scenarios to explain the curved magnetic fields of BHR 71, one is an hourglass-like field structure due to mass accumulation and the other is the Inoue & Fukui mechanism, which proposes the interaction of the core with a shock wave to create curved magnetic fields wrapping around the core.

Keywords: interstellar dust; interstellar magnetic fields; infrared astronomy; starlight polarization; dense interstellar clouds
Detection of Flare-induced Plasma Flows in the Corona of EV Lac with X-Ray Spectroscopy

Stellar flares are characterized by sudden enhancement of electromagnetic radiation from the atmospheres of stars. Compared to their solar counterparts, our knowledge on the coronal plasma dynamics of stellar flares and their connection to coronal mass ejections remains very limited. With time-resolved high-resolution spectroscopic observations from the Chandra X-ray Observatory, we detected noticeable coronal plasma flows during several stellar flares on a nearby dMe star EV Lac. In the observed spectra of O VIII (3 MK), Fe XVII (6 MK), Mg XII (10 MK), and Si XIV (16 MK) lines, these flare-induced upflows/downflows appear as significant Doppler shifts of several tens to 130 km s-1 , and the upflow velocity generally increases with temperature. Variable line ratios of the Si XIII triplet reveal that this plasma flows in most flares are accompanied by an increase in the coronal plasma density and temperature. We interpret these results as X-ray evidence of chromospheric evaporation on EV Lac. In two successive flares, the plasma flow pattern and a sharp increase of the measured coronal density are highly suggestive of explosive evaporation. The transition from redshifts to blueshifts in such an explosive evaporation occurs at a temperature of at least 10 MK, much higher than that observed in solar flares (~1 MK). However, in one flare the cool and warm upflows appear to be accompanied by a decreasing plasma density, which might be explained by a stellar filament/prominence eruption coupled to this flare. These results provide important clues to understanding the coronal plasma dynamics during flares on M dwarfs.

Keywords: stellar flares; stellar coronal mass ejections; stellar coronal lines; late-type stars; spectroscopy