adsabs/SciX_UAT_keywords huggingface dataset:
The Beautiful Mess in Abell 2255

We present LOFAR observations of one of the most spectacular objects in the radio sky: Abell 2255. This is a nearby (z = 0.0806) merging galaxy cluster hosting one of the first radio halos ever detected in the intracluster medium (ICM). The deep LOFAR images at 144 MHz of the central ∼10 Mpc2 region show a plethora of emission on different scales, from tens of kiloparsecs to above megaparsec sizes. In this work, we focus on the innermost region of the cluster. Among the numerous interesting features observed, we discover remarkable bright and filamentary structures embedded in the radio halo. We incorporate archival WSRT 1.2 GHz data to study the spectral properties of the diffuse synchrotron emission and find a very complex spectral index distribution in the halo spanning a wide range of values. We combine the radio data with Chandra observations to investigate the connection between the thermal and nonthermal components by quantitatively comparing the radio and X-ray surface brightness and the spectral index of the radio emission with the thermodynamical quantities of the ICM. Despite the multitude of structures observed in the radio halo, we find that the X-ray and radio emission are overall well correlated. The fact that the steepest spectrum emission is located in the cluster center and traces regions with high entropy possibly suggests the presence of seed particles injected by radio galaxies that are spread in the ICM by the turbulence generating the extended radio halo.

Keywords: radio interferometry; intracluster medium; extended radiation sources; galaxy clusters; non-thermal radiation sources; x-ray astronomy; tailed radio galaxies; extragalactic radio sources; radio astronomy; abell clusters
Chronicling the Reionization History at 6 ≲ z ≲ 7 with Emergent Quasar Damping Wings

The spectra of high-redshift (z ≳ 6) quasars contain valuable information on the progression of the Epoch of Reionization. At redshifts z < 6, the observed Lyman-series forest shows that the intergalactic medium is nearly ionized, while at z > 7 the observed quasar damping wings indicate high neutral gas fractions. However, there remains a gap in neutral gas fraction constraints at 6 ≲ z ≲ 7 where the Lyman-series forest becomes saturated but damping wings have yet to fully emerge. In this work, we use a sample of 18 quasar spectra at redshifts 6.0 < z < 7.1 to close this gap. We apply neural networks to reconstruct the quasars' continuum emission around the partially absorbed Lyα line to normalize their spectra, and stack these continuum-normalized spectra in three redshift bins. To increase the robustness of our results, we compare the stacks to a grid of models from two hydrodynamical simulations, ATON and CROC, and we measure the volume-averaged neutral gas fraction, , while jointly fitting for the mean quasar lifetime, t Q, for each stacked spectrum. We chronicle the evolution of neutral gas fraction using the ATON (CROC) models as follows: ( ) at <z> = 6.10, ( ) at <z> = 6.46, and ( ) at <z> = 6.87. At the same time, we constrain the average quasar lifetime to be t Q ≲ 7 Myr across all redshift bins, in good agreement with previous studies.

Keywords: quasars; supermassive black holes; reionization; intergalactic medium; intergalactic gas
An Efficient Tidal Dissipation Mechanism via Stellar Magnetic Fields

Recent work suggests that inwardly propagating internal gravity waves (IGWs) within a star can be fully converted to outward magnetic waves if they encounter a sufficiently strong magnetic field. The resulting magnetic waves dissipate as they propagate outward to regions with lower Alfvén velocity. While tidal forcing is known to excite IGWs, this conversion and subsequent damping of magnetic waves have not been explored as a tidal dissipation mechanism. In particular, stars with sufficiently strong magnetic fields could fully dissipate tidally excited waves, yielding the same tidal evolution as the previously studied "traveling wave regime." Here, we evaluate the viability of this mechanism using stellar models of stars with convective cores (F-type stars in the mass range of 1.2–1.6 M ⊙), which were previously thought to be weakly tidally dissipative (due to the absence of nonlinear gravity-wave breaking). The criterion for wave conversion to operate is evaluated for each stellar mass using the properties of each star's interior along with estimates of the magnetic field produced by a convective core dynamo under the assumption of equipartition between kinetic (convective) and magnetic energies. Our main result is that this previously unexplored source of efficient tidal dissipation can operate in stars within this mass range for significant fractions of their lifetimes. This tidal dissipation mechanism appears to be consistent with the observed inspiral of WASP-12b and more generally could play an important role in the orbital evolution of hot Jupiters—and to lower-mass ultra-short-period planets—orbiting F-type stars.

Keywords: tides; internal waves; f stars; magnetic fields; orbital evolution; tidal friction; exoplanet migration
BVRcIc Observations, Third-body Orbital Study, and Analysis of the UV Leo-type, Pre-W UMA Binary V642 Virginis

V642 Vir is a polar spotted, well-detached, UV Leo-type, low-mass, pre-WUMa (T1 ∼ 4250K, ∼K6V) eclipsing binary. It was observed in 2020 April, May, and June at the Dark Sky Observatory in North Carolina, USA with the 0.81 m reflector of Appalachian State University. A total of 88 timings were used in our 22-year period study which included 12 Transiting Exoplanet Survey Satellite (TESS) timings. The O - C plots show a low-amplitude oscillation of residuals that points to the existence of an orbiting third body, a dwarf of minimum mass, 0.15 M⊙ in an eccentric orbit (e = 0.41), with an orbital period of 20.07 yr. The odd light curves of V642 Virginis indicate that it has polar spots similar to UV Leo and the recently published V1023 Per. Its present large polar spot region indicates that it must have a strong magnetic field and that it is synchronously rotating. The BVRcIc simultaneous Wilson-Devinney Program solution gives a detached binary (primary and secondary components are underfilling their respective Roche Lobes, with 76% and 78% fill outs respectively). The cool spot region models near the pole of the primary component (centered at 10° colatitude) and is angled toward the secondary component. Its large radius (68°) and T-fact (Tspot/Tsurface = 0.69) also attest to the conclusion of the strength of the magnetic field. The small ΔT in the components (∼318 K) and mass ratio near unity (0.9542 ± 0.0005) show that the stars are similar in spectral type (secondary ∼K9V). The inclination is high, ∼86.87 ± 0.04°, yet there is no time of constant light due to the two stars' essentially equal radii.

Keywords: eclipsing binary stars; detached binary stars; rs canum venaticorum variable stars
Speed and Acceleration of Coronal Mass Ejections Associated with Sustained Gamma-Ray Emission Events Observed by Fermi/LAT

The sustained gamma-ray emission (SGRE) from the Sun is a prolonged enhancement of >100 MeV gamma-ray emission that extends beyond the flare impulsive phase. The origin of the >300 MeV protons resulting in SGRE is debated, with both flares and shocks driven by coronal mass ejections (CMEs) being the suggested sites of proton acceleration. We compared the near-Sun acceleration and space speed of CMEs with "Prompt" and "Delayed" (SGRE) gamma-ray components. We found that "Delayed"-component-associated CMEs have higher initial accelerations and space speeds than "Prompt Only"-component-associated CMEs. We selected halo CMEs (HCMEs) associated with type II radio bursts (shock-driving HCMEs) and compared the average acceleration and space speed between HCME populations with or without SGRE events, major solar energetic particle (SEP) events, metric, or decameter-hectometric (DH) type II radio bursts. We found that the SGRE-producing HCMEs associated with a DH type II radio burst and/or a major SEP event have higher space speeds and especially initial accelerations than those without an SGRE event. We estimated the radial distances and speeds of the CME-driven shocks at the end time of the 2012 January 23 and March 7 SGRE events using white-light images of STEREO Heliospheric Imagers and radio dynamic spectra of Wind WAVES. The shocks were at the radial distances of 0.6-0.8 au and their speeds were high enough (≈975 km s-1 and ≈750 km s-1, respectively) for high-energy particle acceleration. Therefore, we conclude that our findings support the CME-driven shock as the source of >300 MeV protons.

Keywords: solar gamma-ray emission; solar coronal mass ejections; solar energetic particles
Oxygen Isotopic Variations in the Calcium, Aluminum-rich Inclusion–forming Region Recorded by a Single Refractory Inclusion from the CO3.1 Carbonaceous Chondrite Dar al Gani 083

Calcium, aluminum-rich inclusions (CAIs) are the oldest solids dated that formed in the solar system. Most CAIs in unmetamorphosed chondritic meteorites (chondrites; petrologic type ≤3.0) have uniform solar-like 16O-rich compositions (Δ17O ∼ ‑24‰) and a high initial 26Al/27Al ratio [(26Al/27Al)0] of ∼(4–5) × 10‑5, consistent with their origin in a gas of approximately solar composition during a brief (<0.3 Ma) epoch at the earliest stage of our solar system. The nature of O-isotope heterogeneity in CAIs (Δ17O range from ∼‑24 up to ∼+5‰) from weakly metamorphosed chondrites (petrologic type >3.0) remains an open issue. This heterogeneity could have recorded fluctuations of O-isotope composition of nebular gas in the CAI-forming region and/or postcrystallization O-isotope exchange of CAI minerals with aqueous fluids on the chondrite parent asteroids. To obtain insights into possible processes resulting in this heterogeneity, we investigated the mineralogy, rare-earth element abundances, and O- and Mg-isotope compositions of a CAI from the CO3.1 chondrite Dar al Gani 083. This concentrically zoned inclusion has a Zn-hercynite core surrounded by layers of (from core to edge) grossite, spinel, melilite, and Al-diopside. The various phases have heterogeneous Δ17O (from core to edge): ‑2.2 ± 0.6‰, ‑0.9 ± 2.1‰, ‑13.7 ± 2.1‰, ‑2.6 ± 2.3‰, and ‑22.6 ± 2.1‰, respectively. Magnesium-isotope compositions of grossite, spinel, melilite, and Al-diopside define an undisturbed internal Al–Mg isochron with (26Al/27Al)0 of (2.60 ± 0.29) × 10‑6. We conclude that the variations in Δ17O of spinel and diopside recorded fluctuations in O-isotope composition of nebular gas in the CAI-forming region prior to injection and/or homogenization of 26Al at the canonical level. The 16O depletion of grossite and melilite resulted from O-isotope exchange with asteroidal fluid, which did not disturb Al–Mg isotope systematics of the CAI primary minerals.

Keywords: meteorite composition; planetary-disk interactions; meteorites; chondrites; carbonaceous chondrites; protoplanetary nebulae; protoplanetary disks
Peas-in-a-pod across the Radius Valley: Rocky Systems Are Less Uniform in Mass but More Uniform in Size and Spacing

The ubiquity of "peas-in-a-pod" architectural patterns and the existence of the radius valley each presents a striking population-level trend for planets with R p ≤ 4 R ⊕ that serves to place powerful constraints on the formation and evolution of these subgiant worlds. As it has yet to be determined whether the strength of this peas-in-a-pod uniformity differs on either side of the radius valley, we separately assess the architectures of systems containing only small (R p ≤ 1.6 R ⊕), rocky planets from those harboring only intermediate-sized (1.6 R ⊕ < R p ≤ 4 R ⊕), volatile-rich worlds to perform a novel statistical comparison of intra-system planetary uniformity across compositionally distinct regimes. We find that, compared to their volatile-rich counterparts, rocky systems are less uniform in mass (2.6σ) but more uniform in size (4.0σ) and spacing (3.0σ). We provide further statistical validation for these results, demonstrating that they are not substantially influenced by the presence of mean-motion resonances, low-mass host stars, alternative bulk compositional assumptions, sample size effects, or detection biases. We also obtain tentative evidence (>2σ significance) that the enhanced size uniformity of rocky systems is dominated by the presence of super-Earths (1 R ⊕ ≤ R p ≤ 1.6 R ⊕), while their enhanced mass diversity is driven by the presence of sub-Earth (R p < 1 R ⊕) worlds.

Keywords: exoplanet astronomy; exoplanet evolution; exoplanet formation; exoplanet structure; exoplanets; exoplanet systems; super earths; mini neptunes; planetary system evolution
A Survey of Lyα Emission around Damped Lyα Absorbers at z ≈ 2 with the Keck Cosmic Web Imager

We present Keck Cosmic Web Imager Lyα integral field spectroscopy of the fields surrounding 14 damped Lyα absorbers (DLAs) at z ≈ 2. Of these 14 DLAs, nine have high metallicities ([M/H] > ‑ 0.3), and four of those nine feature a CO-emitting galaxy at an impact parameter ≲30 kpc. Our search reaches median Lyα line flux sensitivities of ∼2 × 10‑17 erg s‑1 cm‑2 over apertures of ∼6 kpc and out to impact parameters of ∼50 kpc. We recover the Lyα flux of three known Lyα-emitting H I-selected galaxies in our sample. In addition, we find two Lyα emitters at impact parameters of ≈50–70 kpc from the high-metallicity DLA at z ≈ 1.96 toward QSO B0551-366. This field also contains a massive CO-emitting galaxy at an impact parameter of ≈15 kpc. Apart from the field with QSO B0551-366, we do not detect significant Lyα emission in any of the remaining eight high-metallicity DLA fields. Considering the depth of our observations and our ability to recover previously known Lyα emitters, we conclude that H I-selected galaxies associated with high-metallicity DLAs at z ≈ 2 are dusty and therefore might feature low Lyα escape fractions. Our results indicate that complementary approaches—using Lyα, CO, Hα, and [C II] 158 μm emission—are necessary to identify the wide range of galaxy types associated with z ≈ 2 DLAs.

Keywords: galaxy evolution; galaxy formation; galaxies; quasars; circumgalactic medium; intergalactic clouds; neutral hydrogen clouds; intergalactic gas; intergalactic medium; quasar-galaxy pairs
A Semianalytical Line Transfer Model. III. Galactic Inflows

We present calculations of ultraviolet spectra resulting from the scattering of photons by gas infalling onto an isotropically emitting source of radiation. The model is based on an adaptation of the semianalytical line transfer (SALT) code of Scarlata & Panagia, and designed to interpret the inverse P Cygni profiles observed in the spectra of partially ionized galactic inflows. In addition to presenting the model, we explore the parameter space of the inflowing SALT model and recreate various physically motivated scenarios including spherical inflows, inflows with covering fractions less than unity, and galactic fountains (i.e., galactic systems with both an inflowing and outflowing component). The resulting spectra from inflowing gas show spectral features that could be misinterpreted as interstellar medium features in low resolution spectroscopy (σ ≈ 120 km s-1), suggesting that the total number of galactic systems with inflows is undercounted. Our models suggest that observations at medium resolution (R = 6000 or σ ≈ 50 km s-1) that can be obtained with 8 m class telescopes will be able to resolve the characteristic inverse P Cygni profiles necessary to identify inflows.

Keywords: radiative transfer; galaxy infall; ultraviolet astronomy; circumgalactic medium; galaxy spectroscopy; galaxy fountains; galaxy kinematics; galaxy evolution
Reinterpreting the Polluted White Dwarf SDSS J122859.93+104032.9 in Light of Thermohaline Mixing Models: More Polluting Material from a Larger Orbiting Solid Body

The polluted white dwarf (WD) system SDSS J122859.93+104032.9 (SDSS J1228) shows variable emission features interpreted as originating from a solid core fragment held together against tidal forces by its own internal strength, orbiting within its surrounding debris disk. Estimating the size of this orbiting solid body requires modeling the accretion rate of the polluting material that is observed mixing into the WD surface. That material is supplied via sublimation from the surface of the orbiting solid body. The sublimation rate can be estimated as a simple function of the surface area of the solid body and the incident flux from the nearby hot WD. On the other hand, estimating the accretion rate requires detailed modeling of the surface structure and mixing in the accreting WD. In this work, we present MESA WD models for SDSS J1228 that account for the thermohaline instability and mixing in addition to heavy element sedimentation to constrain accurately the sublimation and accretion rate necessary to supply the observed pollution. We derive a total accretion rate of ${\dot{M}}_{\mathrm{acc}}=1.8\times {10}^{11}\,{\rm{g}}\,{{\rm{s}}}^{-1}$ , several orders of magnitude higher than the ${\dot{M}}_{\mathrm{acc}}=5.6\times {10}^{8}\,{\rm{g}}\,{{\rm{s}}}^{-1}$ estimate obtained in earlier efforts. The larger mass accretion rate implies that the minimum estimated radius of the orbiting solid body is ${r}_{\min }$ = 72 km, which, although significantly larger than prior estimates, still lies within the upper bounds (a few hundred kilometers) for which the internal strength could no longer withstand the tidal forces from the gravity of the WD.

Keywords: white dwarf stars; stellar accretion disks; stellar diffusion; planetary system evolution
A Survey of Galaxy Pairs in the SDSS Photometric Images based on Faster-RCNN

Galaxy pairs hold significant importance in understanding the evolution of galaxies, and the extensive search for a large sample of galaxy pairs is meaningful. In this article, we develop a deep learning-based approach for the search of galaxy pairs and conduct a comprehensive search on Sloan Digital Sky Survey (SDSS) images. In nine million photometric images, 17,965 physical galaxy pairs with spectral or photometric redshifts are detected. Four sets of results are provided, including physical pairs determined by two spectral redshifts, two photometric redshifts, one spectral redshift, and one photometric redshift, and visual irregular pairs that have no precise redshift information but can be inferred as physical galaxy pairs based on the morphological changes. Then their morphological and physical characteristics are explored, the redshifts of most targets are around 0.1, and as the redshift difference between two galaxies increases, the number of galaxy pairs gradually reduces. The distributions of star formation rate (SFR) are not the same for different morphologies of galaxy pairs, irregular pairs have higher SFR than the other three types, and statistics indicate that the SFR of galaxies depends on both nearby galaxies and internal properties. Color and stellar mass are also key properties of galaxies which can reflect the status of galaxy pairs. Compared to other surveys, a greater number of galaxy pair targets are detected, and this is also the first extensive detection of galaxy pairs in SDSS images using photometric redshifts. These galaxy pair samples can greatly aid in the study of galaxy evolution.

Keywords: galaxy pairs; detection; astronomy data reduction; algorithms
Magnetogenesis by Wave-driven Momentum Exchange

When multiple species interact with an electrostatic ion acoustic wave, they can exchange momentum, despite the lack of momentum in the field itself. The resulting force on the electrons can have a curl, and thus give rise to compensating electric fields with curl on magnetohydrodynamic timescales. As a result, a magnetic field can be generated. Surprisingly, in some astrophysical settings, this mechanism can seed magnetic fields with growth rates even larger than through the traditional Biermann battery.

Keywords: astrophysical magnetism; cosmic magnetic fields theory; galaxy magnetic fields; primordial magnetic fields; plasma physics; plasma astrophysics; interstellar magnetic fields
The Behavior of Bp He-weak Stars in the far-UV-Paper XI: HD 35456

The analysis of four spectra of the B7 He-weak star HD 35456 recorded by the SWP camera on board the International Ultraviolet Explorer does not reveal any variations of the far-ultraviolet spectral energy distribution shortwards of 1700 Å over slightly more than one rotational period. There is no sign of variability in the numerous Si II, Si III and Si IV lines present in the far-ultraviolet. The profile of the resonance line of C II at 1335 Å remains constant too.

Keywords: chemically peculiar stars; helium-weak stars
Spin Parity of Spiral Galaxies. III. Dipole Analysis of the Distribution of SDSS Spirals with 3D Random Walk Simulations

Observation has not yet determined whether the distribution of spin vectors of galaxies is truly random. It is unclear whether is there any large-scale symmetry-breaking in the distribution of the vorticity field in the universe. Here, we present a formulation to evaluate the dipole component Dmax of the observed spin distribution, whose statistical significance σD can be calibrated by the expected amplitude for 3D random walk (random flight) simulations. We apply this formulation to evaluate the dipole component in the distribution of Sloan Digital Sky Survey (SDSS) spirals. Shamir published a catalog of spiral galaxies from the SDSS DR8, classifying them with his pattern recognition tool into clockwise and counterclockwise (Z-spiral and S-spiral, respectively). He found significant photometric asymmetry in their distribution. We have confirmed that this sample provides dipole asymmetry up to a level of σD = 4.00. However, we also found that the catalog contains a significant number of multiple entries of the same galaxies. After removing the duplicated entries, the number of samples shrunk considerably to 45%. The actual dipole asymmetry observed for the "cleaned" catalog is quite modest, σD = 0.29. We conclude that SDSS data alone do not support the presence of a large-scale symmetry-breaking in the spin vector distribution of galaxies in the local universe. The data are compatible with a random distribution.

Keywords: cosmic anisotropy; spiral galaxies; galaxy formation; catalogs; galaxy rotation
A Close Binary Lens Revealed by the Microlensing Event Gaia20bof

During the last 25 yr, hundreds of binary stars and planets have been discovered toward the Galactic bulge by microlensing surveys. Thanks to a new generation of large-sky surveys, it is now possible to regularly detect microlensing events across the entire sky. The OMEGA Key Projet at the Las Cumbres Observatory carries out automated follow-up observations of microlensing events alerted by these surveys with the aim of identifying and characterizing exoplanets as well as stellar remnants. In this study, we present the analysis of the binary lens event Gaia20bof. By automatically requesting additional observations, the OMEGA Key Project obtained dense time coverage of an anomaly near the peak of the event, allowing characterization of the lensing system. The observed anomaly in the lightcurve is due to a binary lens. However, several models can explain the observations. Spectroscopic observations indicate that the source is located at ≤2.0 kpc, in agreement with the parallax measurements from Gaia. While the models are currently degenerate, future observations, especially the Gaia astrometric time series as well as high-resolution imaging, will provide extra constraints to distinguish between them.

Keywords: binary lens microlensing