adsabs/SciX_UAT_keywords huggingface dataset:
Core Mass Estimates in Strong Lensing Galaxy Clusters Using a Single-halo Lens Model

The core mass of galaxy clusters is an important probe of structure formation. Here we evaluate the use of a single-halo model (SHM) as an efficient method to estimate the strong lensing cluster core mass, testing it with ray-traced images from the Outer Rim simulation. Unlike detailed lens models, the SHM represents the cluster mass distribution with a single halo and can be automatically generated from the measured lensing constraints. We find that the projected core mass estimated with this method, MSHM, has a scatter of 8.52% and a bias of 0.90% compared to the "true" mass within the same aperture. Our analysis shows no systematic correlation between the scatter or bias and the lens-source system properties. The bias and scatter can be reduced to 3.26% and 0.34%, respectively, by excluding models that fail a visual inspection test. We find that the SHM success depends on the lensing geometry, with single giant arc configurations accounting for most of the failed cases due to their limiting constraining power. When excluding such cases, we measure a scatter and bias of 3.88% and 0.84%, respectively. Finally, we find that when the source redshift is unknown, the model-predicted redshifts are overestimated, and the MSHM is underestimated by a few percent, highlighting the importance of securing spectroscopic redshifts of background sources. Our analysis provides a quantitative characterization of MSHM, enabling its efficient use as a tool to estimate the strong lensing cluster core masses in the large samples, expected from current and future surveys.

Keywords: galaxy clusters; strong gravitational lensing
EvryFlare. IV. Detection of Periodicity in Flare Occurrence from Cool Stars with TESS

Phased flaring, or the periodic occurrence of stellar flares, may probe electromagnetic star-planet interaction (SPI), binary interaction, or magnetic conditions in spots. For the first time, we explore flare periodograms for a large sample of flare stars to identify periodicity due to magnetic interactions with orbiting companions, magnetic reservoirs, or rotational phase. Previous large surveys have explored periodicity at the stellar rotation period, but we do not assume periods must correspond with rotation in this work. Two-minute TESS light curves of 284 cool stars are searched for periods of 1-10 days using two newly developed periodograms. Because flares are discrete events in noisy and incomplete data, typical periodograms are not well suited to detect phased flaring. We construct and test a new Bayesian likelihood periodogram and a modified Lomb-Scargle periodogram. We find six candidates with a false-alarm probability below 1%. Three targets are ≥3σ detections of flare periodicity; the others are plausible candidates that cannot be individually confirmed. Periods range from 1.35 to 6.7 days and some, but not all, correlate with the stellar rotation period or its 1/2 alias. Periodicity from two targets may persist from TESS Cycle 1 into Cycle 3. The periodicity does not appear to persist for the others. Long-term changes in periodicity may result from the spot evolution observed from each candidate, which suggests magnetic conditions play an important role in sustaining periodicity.

Keywords: stellar rotation; stellar flares; stellar magnetic fields; star-planet interactions; starspots; wide-field telescopes
UV/Optical Disk Thermal Reverberation in Active Galactic Nuclei: An In-depth Study with an Analytic Prescription for Time-lag Spectra

Several active galactic nuclei show correlated variations in the UV/optical range, with time delays increasing at longer wavelengths. Thermal reprocessing of the X-rays illuminating the accretion disk has been proposed as a viable explanation. In this scenario, the variable X-ray flux irradiating the accretion disk is partially reflected in X-rays and partially absorbed, thermalized, and reemitted with some delay by the accretion disk at longer wavelengths. We investigate this scenario assuming an X-ray pointlike source illuminating a standard Novikov-Thorne accretion disk around a rotating black hole. We consider all special and general relativistic effects to determine the incident X-ray flux on the disk and in propagating light from the source to the disk and to the observer. We also compute the disk reflection flux, taking into consideration the disk ionization. We investigate the dependence of the disk response function and time lags on various physical parameters, such as the black hole mass and spin; X-ray corona height, luminosity, and photon index; accretion rate; inclination; and inner/outer disk radii. We find it is important to consider relativistic effects and the disk ionization in estimating the disk response. We also find a strong nonlinearity between the X-ray luminosity and the disk response. We present an analytic function for the time-lag dependence on wavelength, which can be used to fit observed time-lag spectra. We also estimate the fraction of the reverberation signal with respect to the total flux, and we suggest possible explanations for the lack of X-ray-UV/optical correlated variations in a few sources.

Keywords: x-ray active galactic nuclei; accretion; seyfert galaxies; active galactic nuclei
Recent Star Formation in a Massive Slowly Quenched Lensed Quiescent Galaxy at z = 1.88

In this Letter, we reconstruct the formation pathway of MRG-S0851, a massive, $\mathrm{log}{M}_{* }/{M}_{\odot }=11.02\pm 0.04$ , strongly lensed, red galaxy at z = 1.883 ± 0.001. While the global photometry and spatially resolved outskirts of MRG-S0851 imply an early formation scenario with a slowly decreasing or constant star formation history, a joint fit of 2D grism spectroscopy and photometry reveals a more complex scenario: MRG-S0851 is likely to be experiencing a centrally concentrated rejuvenation in the inner ∼1 kpc in the last ∼100 Myr of evolution. We estimate 0.5 ± 0.1% of the total stellar mass is formed in this phase. Rejuvenation episodes are suggested to be infrequent for massive galaxies at z ∼ 2, but as our analyses indicate, more examples of complex star formation histories may yet be hidden within existing data. By adding an FUV color criterion to the standard U-V/V-J diagnostic—thereby heightening our sensitivity to recent star formation—we show that we can select populations of galaxies with similar spectral energy distributions to that of MRG-S0851, but note that deep follow-up spectroscopic observations and/or spatially resolved analyses are necessary to robustly confirm the rejuvenation of these candidates. Using our criteria with MRG-S0851 as a prototype, we estimate that ∼1% of massive quiescent galaxies at 1 < z < 2 are potentially rejuvenating.

Keywords: galaxy formation; high-redshift galaxies; galaxy stellar content; galaxy quenching
A Stochastic Theory of the Hierarchical Clustering. III. The Nonuniversality and Nonstationarity of the Halo Mass Function

In the framework of the stochastic theory for hierarchical clustering, we investigate the time-dependent solutions of the Fokker-Planck equation describing the statistics of dark matter halos, and discuss the typical timescales needed for these to converge toward stationary states, far away enough from initial conditions. Although we show that the stationary solutions can reproduce the outcomes of state-of-the-art N-body simulations at z ≈ 0 to great accuracy, one needs to go beyond to fully account for the cosmic evolution of the simulated halo mass function toward high redshift. Specifically, we demonstrate that the time-dependent solutions of the Fokker-Planck equation can describe, for reasonable initial conditions, the nonuniversal evolution of the simulated halo mass functions. Compared to standard theoretical estimates, our stochastic theory predicts a halo number density higher by a factor of several toward z ≳ 10, an outcome that can be helpful in elucidating early and upcoming data from JWST. Finally, we point out the relevance of our approach in designing, interpreting, and emulating present and future N-body experiments.

Keywords: cosmology; dark matter
Elemental Abundances in M31: [Fe/H] and [α/Fe] in M31 Dwarf Galaxies Using Coadded Spectra

We present chemical abundances of red giant branch (RGB) stars in the dwarf spheroidal (dSph) satellite system of Andromeda (M31), using spectral synthesis of medium-resolution (R ∼ 6000) spectra obtained with the Keck II telescope and Deep Imaging Multi-Object Spectrometer spectrograph via the Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo survey. We coadd stars according to their similarity in photometric metallicity or effective temperature to obtain a signal-to-noise ratio (S/N) high enough to measure average [Fe/H] and [α/Fe] abundances. We validate our method using high S/N spectra of RGB stars in Milky Way globular clusters, as well as deep observations for a subset of the M31 dSphs in our sample. For this set of validation coadds, we compare the weighted average abundance of the individual stars with the abundance determined from the coadd. We present individual and coadded measurements of [Fe/H] and [α/Fe] for stars in 10 M31 dSphs, including the first [α/Fe] measurements for And IX, XIV, XV, and XVIII. These fainter, less massive dSphs show declining [α/Fe] relative to [Fe/H], implying an extended star formation history (SFH). In addition, these dSphs also follow the same mass-metallicity relation found in other Local Group satellites. The conclusions we infer from coadded spectra agree with those from previous measurements in brighter M31 dSphs with individual abundance measurements, as well as conclusions from photometric studies. These abundances greatly increase the number of spectroscopic measurements of the chemical composition of M31's less massive dwarf satellites, which are crucial to understanding their SFH and interaction with the M31 system.

Keywords: andromeda galaxy; chemical abundances; dwarf galaxies
Neutrino-driven Winds in Three-dimensional Core-collapse Supernova Simulations

In this paper, we analyze the neutrino-driven winds that emerge in 12 unprecedentedly long-duration 3D core-collapse supernova simulations done using the code FORNAX. The 12 models cover progenitors with zero-age main-sequence mass between 9 and 60 solar masses. In all our models, we see transonic outflows that are at least 2 times as fast as the surrounding ejecta and that originate generically from a proto-neutron star surface atmosphere that is turbulent and rotating. We find that winds are common features of 3D simulations, even if there is anisotropic early infall. We find that the basic dynamical properties of 3D winds behave qualitatively similarly to those inferred in the past using simpler 1D models, but that the shape of the emergent wind can be deformed, very aspherical, and channeled by its environment. The thermal properties of winds for less massive progenitors very approximately recapitulate the 1D stationary solutions, while for more massive progenitors they deviate significantly owing to aspherical accretion. The Y e temporal evolution in winds is stochastic, and there can be some neutron-rich phases. Though no strong r-process is seen in any model, a weak r-process can be produced, and isotopes up to 90Zr are synthesized in some models. Finally, we find that there is at most a few percent of a solar mass in the integrated wind component, while the energy carried by the wind itself can be as much as 10%-20% of the total explosion energy.

Keywords: core-collapse supernovae; supernova dynamics; nucleosynthesis
Spectral Hardness and Evolution of Swift Gamma-Ray Bursts and X-Ray Afterglows

Spectral hardness of gamma-ray bursts can be characterized by either hardness ratio or peak energy, and the inconsistency of these parameters can reflect spectral diversity and complexity. We have chosen 310 Swift bursts with well-measured X-ray afterglows to analyze the distributions of their peak energies and hardness ratios before and after absorption of neutral hydrogen. We categorize them into four types according to X-ray temporal patterns and calculate the hardness ratios of both γ-rays and X-rays. It is found that the hardness ratios of X-rays are systematically smaller than those of γ-rays. We also find that both γ-ray hardness ratios and peak energies of bursts of types I, II, and III are identically distributed and are significantly lower than the corresponding measurements of type IV bursts in statistics, which hints that the evolving spectra of type IV bursts are most probably affected by the geometry of outflows. This proves that the influence of neutral hydrogen absorption on the estimation of hardness ratio is negligible even though it can reduce the brightness of γ/X-rays somewhat. Furthermore, we verify that almost all the observed spectra of gamma-ray bursts can be described by a broken power-law function and confirm a magnetar origin for the bursts with internal X-ray plateaus.

Keywords: gamma-ray bursts
Deep Synoptic Array Science: First FRB and Host Galaxy Catalog

Fast radio bursts (FRBs) are a powerful and mysterious new class of transients that are luminous enough to be detected at cosmological distances. By associating FRBs to host galaxies, we can measure intrinsic and environmental properties that test FRB origin models, in addition to using them as precise probes of distant cosmic gas. The Deep Synoptic Array (DSA-110) is a radio interferometer built to maximize the rate at which it can simultaneously detect and localize FRBs. Here, we present the first sample of FRBs and host galaxies discovered by the DSA-110. This sample of 11 FRBs is the largest, most uniform sample of localized FRBs to date, as it is selected based on association with host galaxies identified in optical imaging by Pan-STARRS1. These FRBs have not been observed to repeat, and their radio properties (dispersion, temporal scattering, energy) are similar to that of the known nonrepeating FRB population. Most host galaxies have ongoing star formation, as has been identified before for FRB hosts. Two hosts of the new sample are massive, quiescent galaxies. The distribution of star formation history across this host-galaxy sample shows that the delay time distribution is wide, with a power-law model that spans from ∼100 Myr to ≳2 Gyr. This requires the existence of one or more progenitor formation channels associated with old stellar populations, such as the binary evolution of compact objects.

Keywords: radio transient sources; radio telescopes; galaxies
Local Limit of Nonlocal Gravity: Cosmological Perturbations

We explore the cosmological implications of the local limit of nonlocal gravity, which is a classical generalization of Einstein's theory of gravitation within the framework of teleparallelism. An appropriate solution of this theory is the modified Cartesian flat cosmological model. The main purpose of this paper is to study linear perturbations about the orthonormal tetrad frame field adapted to the standard comoving observers in this model. The observational viability of the perturbed model is examined using all available data regarding the cosmic microwave background. The implications of the linearly perturbed modified Cartesian flat model are examined and it is shown that the model is capable of alleviating the H 0 tension.

Keywords: gravitation; cosmology
Implications of Jupiter Inward Gas-driven Migration for the Inner Solar System

The migration history of Jupiter in the Sun's natal disk remains poorly constrained. Here we consider how Jupiter's migration affects small-body reservoirs and how this constrains its original orbital distance from the Sun. We study the implications of large-scale and inward radial migration of Jupiter for the inner solar system while considering the effects of collisional evolution of planetesimals. We use analytical prescriptions to simulate the growth and migration of Jupiter in the gas disk. We assume the existence of a planetesimal disk inside Jupiter's initial orbit. This planetesimal disk received an initial total mass and size-frequency distribution (SFD). Planetesimals feel the effects of aerodynamic gas drag and collide with one another, mostly while shepherded by the migrating Jupiter. Our main goal is to measure the amount of mass in planetesimals implanted into the main asteroid belt (MAB) and the SFD of the implanted population. We also monitor the amount of dust produced during planetesimal collisions. We find that the SFD of the planetesimal population implanted into the MAB tends to resemble that of the original planetesimal population interior to Jupiter. We also find that unless very little or no mass existed between 5 au and Jupiter's original orbit, it would be difficult to reconcile the current low mass of the MAB with the possibility that Jupiter migrated from distances beyond 15 au. This is because the fraction of the original disk mass that gets implanted into the MAB is very large. Finally, we discuss the implications of our results in terms of dust production to the so-called NC-CC isotopic dichotomy.

Keywords: solar system planets; main belt asteroids
Magnetically Arrested Disks in Quiescent Black Hole Binaries: Formation Scenario, Observable Signatures, and Potential PeVatrons

We propose magnetically arrested disks (MADs) in quiescent (low-luminosity) black hole (BH) binaries as the origin of multiwavelength emission, and argue that this class of sources can dominate the cosmic-ray spectrum around the knee. X-ray luminosities of Galactic BH binaries in the quiescent state are far below the Eddington luminosity, and thus radiatively inefficient accretion flows (RIAFs) are formed in the inner region. Strong thermal and turbulent pressures in RIAFs produce outflows, which can create large-scale poloidal magnetic fields. These fields are carried to the vicinity of the BH by the rapid inflow motion, forming a MAD. Inside the MAD, nonthermal protons and electrons are naturally accelerated by magnetic reconnections or stochastic acceleration by turbulence. Both thermal and nonthermal electrons emit broadband photons via synchrotron emission, which are broadly consistent with the optical and X-ray data of the quiescent BH X-ray binaries. Moreover, protons are accelerated up to PeV energies and diffusively escape from these MADs, which can account for the cosmic-ray intensity around the knee energy.

Keywords: stellar mass black holes; low-mass x-ray binary stars; accretion; non-thermal radiation sources; cosmic ray sources
Solar Disk Center Shows Scattering Polarization in the Sr I 4607 Å Line

Magnetic fields in turbulent, convective high-β plasma naturally develop highly tangled and complex topologies - the solar photosphere being the paradigmatic example. These fields are mostly undetectable by standard diagnostic techniques with finite spatio-temporal resolution due to cancellations of Zeeman polarization signals. Observations of resonance scattering polarization have been considered to overcome these problems. But up to now, observations of scattering polarization lack the necessary combination of high sensitivity and high spatial resolution in order to directly infer the turbulent magnetic structure at the resolution limit of solar telescopes. Here, we report the detection of clear spatial structuring of scattering polarization in a magnetically quiet solar region at disk center in the Sr I 4607 Å spectral line on granular scales, confirming theoretical expectations. We find that the linear polarization presents a strong spatial correlation with the local quadrupole of the radiation field. The result indicates that polarization survives the dynamic and turbulent magnetic environment of the middle photosphere and is thereby usable for spatially resolved Hanle observations. This is an important step toward the long-sought goal of directly observing turbulent solar magnetic fields at the resolution limit and investigating their spatial structure.

Keywords: spectropolarimetry; quiet sun; solar photosphere; solar magnetic fields; polarimeters
Pointlike Sources among z > 11 Galaxy Candidates: Contaminants due to Supernovae at High Redshifts?

The recent searches for z > 11 galaxies using the James Webb Space Telescope have resulted in an unexpectedly high number of candidate objects, which imply at least 1 order of magnitude higher number density of z > 11 galaxies than the previously favored predictions. A question has risen whether there are some new types of contaminants among these candidates. The candidate sample of Yan et al., totaling 87 dropouts, is the largest one, and we notice that a number of these candidates are pointlike. We hypothesize that the point-source dropouts could be supernovae at high redshifts. Further investigation shows that most of their spectral energy distributions indeed can be explained by supernovae at various redshifts from z ~ 1 to 15, which lends support to this hypothesis. Attributing such point-source dropouts to supernova contamination cannot eliminate the tension, however, because they only account for ~10% of the Yan et al. sample. On the other hand, the discovery of "contaminant" supernovae at z > 3 will have a series of important implications. Ironically, the existence of supernovae at z > 10 would still imply that the previously favored picture of early galaxy formation severely underestimates the global star formation rate density such redshifts. Multiple-epoch JWST imaging will be the simplest and yet the most efficient way to further test this hypothesis.

Keywords: galaxy evolution; galaxy formation; early universe; supernovae; core-collapse supernovae; type ia supernovae
On the Triggering of Extreme Starburst Events in Low-metallicity Galaxies: A Deep Search for Companions of Green Peas

Green pea galaxies are starbursting, low-mass galaxies that are good analogues to star-forming galaxies in the early universe. We perform a survey of 23 green peas using the Multi Unit Spectroscopic Explorer (MUSE) Integral Field Unit spectrograph on the Very Large Telescope to search for companion galaxies. The survey reaches an average point-source depth of ~10-18 erg cm-2 s-1 for emission lines. The MUSE field of view allows us to probe a 1 × 1 arcmin2 field around these galaxies and to search their surroundings for faint companions that could have interacted with them and induced their starburst episodes. We search for companions using a variety of methods including template matching to emission- and absorption-line spectra. When restricting the search to the same physical area (R = 78 kpc) for all galaxies, we find that the fraction of green pea galaxies with companions is ${0.11}_{-0.05}^{+0.07}$ . We define a control sample of star-forming galaxies with the same stellar masses and redshifts as the green peas, but consistent with the star formation main sequence. We find that green pea galaxies are as likely to have companions as the control sample; for which the fraction of objects with companions is ${0.08}_{-0.03}^{+0.05}$ . Given that we do not find statistical evidence for an elevated companion fraction in the green peas in this study, we argue that the "companions" are likely unrelated to the bursts in these galaxies.

Keywords: dwarf galaxies; galaxy interactions; starburst galaxies