adsabs/SciX_UAT_keywords huggingface dataset:
Weak-lensing Mass Bias in Merging Galaxy Clusters

Although weak lensing (WL) is a powerful method to estimate a galaxy cluster mass without any dynamical assumptions, a model bias can arise when the cluster density profile departs from the assumed model profile. In a merging system, the bias is expected to become most severe because the constituent halos undergo significant structural changes. In this study, we investigate WL mass bias in binary cluster mergers using a suite of idealized hydrodynamical simulations. Realistic WL shear catalogs are generated by matching the source galaxy properties, such as intrinsic shape dispersion, measurement noise, source densities, etc., to those from Subaru and Hubble Space Telescope observations. We find that, with the typical mass-concentration (M-c) relation and the Navarro-Frenk-White profile, the halo mass bias depends on the time since the first pericenter passage and increases with the mass of the companion cluster. The time evolution of the mass bias is similar to that of the concentration, indicating that, to first order, the mass bias is modulated by the concentration change. For a collision between two ~1015 M ⊙ clusters, the maximum bias amounts to ~60%. This suggests that previous WL studies may have significantly overestimated the mass of the clusters in some of the most massive mergers. Finally, we apply our results to three merger cases: A2034, MACS J1752.0 + 4440, and ZwCl 1856.8 + 6616, and report their mass biases at the observed epoch, as well as their pre-merger masses, utilizing their merger shock locations as tracers of the merger phases.

Keywords: galaxy clusters; weak gravitational lensing
Parker Solar Probe Observations of Near-f Ce Harmonic Emissions in the Near-Sun Solar Wind and Their Dependence on the Magnetic Field Direction

Wave emissions at frequencies near electron gyrofrequency harmonics are observed at small heliocentric distances below about 40 R ⊙ and are known to occur in regions with quiescent magnetic fields. We show the close connection of these waves to the large-scale properties of the magnetic field. Near electron gyrofrequency harmonic emissions occur only when the ambient magnetic field points to a narrow range of directions bounded by polar and azimuthal angular ranges in the RTN coordinate system of correspondingly 80° ≲ θ B ≲ 100° and 10° ≲ ϕ B ≲ 30°. We show that the amplitudes of wave emissions are highest when both angles are close to the center of their respective angular interval favorable to wave emissions. The intensity of wave emissions correlates with the magnetic field angular changes at both large and small timescales. Wave emissions intervals correlate with intervals of decreases in the amplitudes of broadband magnetic fluctuations at low frequencies of 10-100 Hz. We discuss possible generation mechanisms of the waves.

Keywords: space plasmas; plasma physics; solar wind
Multi-orbital-phase and Multiband Characterization of Exoplanetary Atmospheres with Reflected Light Spectra

Direct imaging of widely separated exoplanets from space will obtain their reflected light spectra and measure atmospheric properties. Previous calculations have shown that a change in the orbital phase would cause a spectral signal, but whether this signal may be used to characterize the atmosphere has not been shown. We simulate starshade-enabled observations of the planet 47 UMa b, using the present most realistic simulator Starshade Imaging Simulation Toolkit for Exoplanet Reconnaissance to estimate the uncertainties due to residual starlight, solar glint, and exozodiacal light. We then use the Bayesian retrieval algorithm EXOREL ${}^{{\mathfrak{R}}}$ to determine the constraints on the atmospheric properties from observations using a Roman- or Habitable Exoplanet Observatory (HabEx)-like telescope, comparing the strategies to observe at multiple orbital phases or in multiple wavelength bands. With a ∼20% bandwidth in 600-800 nm on a Roman-like telescope, the retrieval finds a degenerate scenario with a lower gas abundance and a deeper or absent cloud than the truth. Repeating the observation at a different orbital phase or at a second 20% wavelength band in 800-1000 nm, with the same integration time and thus degraded signal-to-noise ratio (S/N), would effectively eliminate this degenerate solution. Single observation with a HabEx-like telescope would yield high-precision constraints on the gas abundances and cloud properties, without the degenerate scenario. These results are also generally applicable to high-contrast spectroscopy with a coronagraph with a similar wavelength coverage and S/N, and can help design the wavelength bandwidth and the observation plan of exoplanet direct-imaging experiments in the future.

Keywords: astronomical techniques; direct imaging; spectroscopy; exoplanet atmospheres; exoplanet atmospheric composition; bayesian statistics; posterior distribution
Formation of Complex Organic Molecules in Cold Interstellar Environments through Nondiffusive Grain-surface and Ice-mantle Chemistry

A prevailing theory for the interstellar production of complex organic molecules (COMs) involves formation on warm dust-grain surfaces, via the diffusion and reaction of radicals produced through grain-surface photodissociation of stable molecules. However, some gas-phase O-bearing COMs, notably acetaldehyde (CH3CHO), methyl formate (CH3OCHO), and dimethyl ether (CH3OCH3), are now observed at very low temperatures, challenging the warm scenario. Here, we introduce a selection of new nondiffusive mechanisms into an astrochemical model to account for the failure of the standard diffusive picture and to provide a more generalized scenario of COM formation on interstellar grains. New generic rate formulations are provided for cases where (i) radicals are formed by reactions occurring close to another reactant, producing an immediate follow-on reaction; (ii) radicals are formed in an excited state, allowing them to overcome activation barriers to react with nearby stable molecules; and (iii) radicals are formed through photodissociation close to a reaction partner, followed by immediate reaction. Each process occurs without thermal diffusion of large radicals. The new mechanisms significantly enhance cold COM abundances, successfully reproducing key observational results for prestellar core L1544. H abstraction from grain-surface COMs, followed by recombination, plays a crucial role in amplifying chemical desorption into the gas phase. The ultraviolet-induced chemistry produces significant COM abundances in the bulk ices, which are retained on the grains and may persist to later stages. O2 is also formed strongly in the mantle though photolysis, suggesting cometary O2 could indeed be interstellar.

Keywords: astrochemistry; interstellar dust processes; star formation; molecule formation
Testing Einstein's Equivalence Principle and Its Cosmological Evolution from Quasar Gravitational Redshifts

We propose and apply a new test of Einstein's equivalence principle (EEP) based on the gravitational redshift induced by the central supermassive black hole of quasars in the surrounding accretion disk. Specifically, we compare the observed gravitational redshift of the Fe III λλ 2039-2113 emission line blend in quasars with the predicted values in a wide, uncharted, cosmic territory (0 ≲ zcosm ≲ 3). For the first time we measure, with statistical uncertainties comparable or better than those of other classical methods outside the solar system, the ratio between the observed gravitational redshifts and the theoretical predictions in 10 independent cosmological redshift bins in the 1 ≲ zcosm ≲ 3 range. The average of the measured over predicted gravitational redshifts ratio in this cosmological redshift interval is $\langle {z}_{g}^{m}/{z}_{g}^{p}\rangle =1.05\pm 0.06$ with scatter 0.13 ± 0.05 showing no cosmological evolution of EEP within these limits. This method can benefit from larger samples of measurements with better signal-to-noise ratios, paving the way for high-precision tests (below 1%) of EEP on cosmological scales.

Keywords: cosmology; quasars; general relativity
KIC 12268220: A δ Scuti Pulsating Star and an Active Protohelium White Dwarf in an Eclipsing Binary System

We present a photometric, spectroscopic, asteroseismic, and evolutionary analysis of the Algol-type eclipsing binary KIC 12268220. We find the O'Connell effect and anticorrelated eclipse timing variations in the Kepler light curve, revealing the presence of large starspots. Radial velocities and atmospheric parameters are obtained from ground-based spectroscopic observations. Combined with the radial velocity measurements and Gaia-derived total luminosity, our light-curve modeling yields the solution of the physical parameters for both the primary and secondary components. We find 14 independent frequencies arising from the δ Scuti primary, and the observed frequencies agree with the frequency range of unstable modes from nonadiabatic calculations. Based on the conclusion from previous literature, we run a grid of models to study the evolution process of our system. The evolutionary tracks of our model suggest that the low-mass ( $\sim 0.23\,{M}_{\odot }$ ) evolved secondary shows a similar evolutionary state to the R CMa-type system, which might evolve to an EL CVn system.

Keywords: eclipsing binary stars; delta scuti variable stars; white dwarf stars; stellar evolution
Discovery and Timing of Millisecond Pulsars with the Arecibo 327 MHz Drift-scan Survey

We present the discovery and timing solutions of four millisecond pulsars (MSPs) discovered in the Arecibo 327 MHz Drift-Scan Pulsar Survey. Three of these pulsars are in binary systems, consisting of a redback (PSR J2055+1545), a black widow (PSR J1630+3550), and a neutron star-white dwarf binary (PSR J2116+1345). The fourth MSP, PSR J2212+2450, is isolated. We present the multiyear timing solutions as well as polarization properties across a range of radio frequencies for each pulsar. We perform a multiwavelength search for emission from these systems and find an optical counterpart for PSR J2055+1545 in Gaia DR3, as well as a gamma-ray counterpart for PSR J2116+1345 with the Fermi-LAT telescope. Despite the close colocation of PSR J2055+1545 with a Fermi source, we are unable to detect gamma-ray pulsations, likely due to the large orbital variability of the system. This work presents the first two binaries found by this survey with orbital periods shorter than a day; we expect to find more in the 40% of the survey data that have yet to be searched.

Keywords: millisecond pulsars; binary pulsars; gamma-ray sources
Multispacecraft Energetic Particle Enhancements Associated with a Single Corotating Interaction Region

The radial evolution of particles accelerated at corotating interaction regions (CIRs) is not fully understood, particularly the distance range over which this particle acceleration occurs and how the energy spectra are modulated by transport through the inner heliosphere. Here, we present observations of energetic proton enhancements associated with a CIR observed by Parker Solar Probe on 2021 April 25 during the inbound leg of its orbit near ∼46 R s (∼0.21 au). The CIR is identified at additional spacecraft (Solar Terrestrial Relations Observatory, STEREO-A; Solar Orbiter, SolO; and Advanced Composition Explorer, ACE) using a corotation time delay estimation, and energetic proton spectra from each spacecraft are compared. We find that (1) energetic protons are observed near 46 R s streaming sunward ahead of the CIR; (2) the CIR persists for at least one solar rotation and the corresponding energetic proton enhancements are observed at STEREO-A, SolO, and ACE; and (3) the proton energy spectrum is steeper near the Sun and hardens near 1 au. This observation presents the closest in situ energetic particle observation of a CIR to the Sun ever recorded. Results presented here suggest that particles can be accelerated by CIR structures within 1 au and these particles can penetrate very deep into the inner heliosphere.

Keywords: corotating streams; interplanetary particle acceleration
Investigation of Important Weak Interaction Nuclei in Presupernova Evolution

This project aims to investigate the most important weak interaction nuclei in the presupernova evolution of massive stars. To achieve this goal, an ensemble containing 728 nuclei in the mass range of A = 1-100 was considered. We computed the mass fractions of these nuclei using Saha's equation for predetermined values of T, ρ, and Ye and assuming nuclear statistical equilibrium. The nuclear partition functions were obtained using a newly introduced recipe where excited states, up to 10 MeV, were treated as discrete. The weak interaction rates (electron capture (ec) and β-decay (bd)) were calculated in a totally microscopic fashion using the proton-neutron quasiparticle random phase approximation model and without assuming the Brink-Axel hypothesis. The calculated rates were coupled with the computed mass fractions to investigate the time rate of change of lepton to baryon fraction of the stellar matter. We compare our results with the previous calculations reported in the literature. Noticeable differences up to orders of magnitude are reported with previous calculations. These differences may influence the evolution of the star in the later stages of presupernova. We present a list of the top 50 ec and bd nuclei, which have the largest effect on Ye for conditions after silicon core burning. The competition between the ec and bd rates in the stellar core was investigated and it was found that Ye = 0.424-0.455 is the interval where the bd results are bigger than the ec rates.

Keywords: nuclear astrophysics; nucleosynthesis; stellar physics; stellar evolution; stellar abundances; stellar dynamics; isotopic abundances
Exploring Primordial Curvature Perturbation on Small Scales with the Lensing Effect of Fast Radio Bursts

Cosmological observations, e.g., cosmic microwave background, have precisely measured the spectrum of primordial curvature perturbation on larger scales, but smaller scales are still poorly constrained. Since primordial black holes (PBHs) could form in the very early Universe through the gravitational collapse of primordial density perturbations, constraints on the PBH could encode much information on primordial fluctuations. In this work, we first derive a simple formula for the lensing effect to apply PBH constraints with the monochromatic mass distribution to an extended mass distribution. Then, we investigate the latest fast radio burst observations with this relationship to constrain two kinds of primordial curvature perturbation models on small scales. This suggests that, from the null search result of lensed fast radio bursts in currently available observations, the amplitude of primordial curvature perturbation should be less than 8 × 10‑2 at the scale region of 105–106 Mpc‑1. This corresponds to an interesting mass range relating to binary black holes detected by LIGO–Virgo–KAGRA and future Einstein Telescope or Cosmic Explorer.

Keywords: primordial black holes; gravitational lensing; radio transient sources
The Predicament of Absorption-dominated Reionization: Increased Demands on Ionizing Sources

The reionization epoch concludes when ionizing photons reach every corner of the universe. Reionization has generally been assumed to be limited primarily by the rate at which galaxies produce ionizing photons, but the recent measurement of a surprisingly short ionizing photon mean free path of ${0.75}_{-0.45}^{+0.65}$ proper Mpc at z = 6 by Becker et al. suggests that absorption by residual neutral hydrogen in the otherwise ionized intergalactic medium may play a much larger role than previously expected. Here we show that consistency between this short mean free path and the coeval dark pixel fraction in the Lyα forest requires a cumulative output of ${6.1}_{-2.4}^{+11}$ ionizing photons per baryon by reionization's end, well above the typically required ~1-3. This represents a dramatic increase in the ionizing photon budget over previous estimates, greatly exacerbating the tension with measurements of the ionizing output from galaxies at later times. Translating this constraint into the instantaneous ionizing production from galaxies in our model, we find ${\mathrm{log}}_{10}{f}_{\mathrm{esc}}{\xi }_{\mathrm{ion}}/{(\mathrm{erg}/\mathrm{Hz})}^{-1}={25.02}_{-0.21}^{+0.45}$ at z ~ 6. Even with optimistic assumptions about the ionizing production efficiency of early stellar populations, and assuming the galaxy luminosity function extends to extremely faint sources (MUV ≤ - 11), complete reionization requires the escape fraction of ionizing photons to exceed 20% across the galaxy population. This is far larger than observed in any galaxy population at lower redshifts, requiring rapid evolution in galaxy properties after the first billion years of cosmic time. This tension cannot be completely relieved within existing observational constraints on the hydrogen neutral fraction and mean free path.

Keywords: reionization; high-redshift galaxies; intergalactic medium; astronomical simulations
COOL-LAMPS. VI. Lens Model and New Constraints on the Properties of COOL J1241+2219, a Bright z = 5 Lyman Break Galaxy and its z = 1 Cluster Lens

We present a strong lensing analysis of COOL J1241+2219, the brightest known gravitationally lensed galaxy at z ≥ 5, based on new multiband Hubble Space Telescope (HST) imaging data. The lensed galaxy has a redshift of z = 5.043, placing it shortly after the end of the "Epoch of Reionization," and an AB magnitude z AB = 20.47 mag (Khullar et al.). As such, it serves as a touchstone for future research of that epoch. The high spatial resolution of HST reveals internal structure in the giant arc, from which we identify 15 constraints and construct a robust lens model. We use the lens model to extract the cluster mass and lensing magnification. We find that the mass enclosed within the Einstein radius of the z = 1.001 cluster lens is $M(\lt 5\buildrel{\prime\prime}\over{.} \,77)={1.079}_{-0.007}^{+0.023}\times {10}^{13}{M}_{\odot }$ , significantly lower than other known strong lensing clusters at its redshift. The average magnification of the giant arc is <μ arc> = ${76}_{-20}^{+40}$ , a factor of ${2.4}_{-0.7}^{+1.4}$ greater than previously estimated from ground-based data; the flux-weighted average magnification is <μ arc> = ${92}_{-31}^{+37}$ . We update the current measurements of the stellar mass and star formation rate (SFR) of the source for the revised magnification to $\mathrm{log}({M}_{\star }/{M}_{\odot })\,=$ 9.7 ± 0.3 and SFR = ${10.3}_{-4.4}^{+7.0}$ M ⊙ yr‑1, respectively. The powerful lensing magnification acting upon COOL J1241+2219 resolves the source and enables future studies of the properties of its star formation on a clump-by-clump basis. The lensing analysis presented here will support upcoming multiwavelength characterization with HST and JWST data of the stellar mass assembly and physical properties of this high-redshift lensed galaxy.

Keywords: strong gravitational lensing; gravitational lensing; galaxy clusters; galaxy formation
Giant Impact Events for Protoplanets: Energetics of Atmospheric Erosion by Head-on Collision

Numerous exoplanets with masses ranging from Earth to Neptune and radii larger than Earth have been found through observations. These planets possess atmospheres that range in mass fractions from 1% to 30%, reflecting the diversity of atmospheric mass fractions. Such diversities are supposed to be caused by differences in the formation processes or evolution. Here, we consider head-on giant impacts onto planets causing atmosphere losses in the later stage of their formation. We perform smoothed particle hydrodynamic simulations to study the impact-induced atmosphere loss of young super-Earths with 10%-30% initial atmospheric mass fractions. We find that the kinetic energy of the escaping atmosphere is almost proportional to the sum of the kinetic impact energy and self-gravitational energy released from the merged core. We derive the relationship between the kinetic impact energy and the escaping atmosphere mass. The giant impact events for planets of comparable masses are required in the final stage of the popular scenario of rocky planet formation. We show it results in a significant loss of the atmosphere, if the impact is a head-on collision with comparable masses. This latter fact provides a constraint on the formation scenario of rocky planets with substantial atmospheres.

Keywords: super earths; exoplanet atmospheres; impact phenomena; hydrodynamical simulations
PHANGS-JWST First Results: Interstellar Medium Structure on the Turbulent Jeans Scale in Four Disk Galaxies Observed by JWST and the Atacama Large Millimeter/submillimeter Array

JWST/Mid-Infrared Instrument imaging of the nearby galaxies IC 5332, NGC 628, NGC 1365, and NGC 7496 from PHANGS reveals a richness of gas structures that in each case form a quasi-regular network of interconnected filaments, shells, and voids. We examine whether this multiscale network of structure is consistent with the fragmentation of the gas disk through gravitational instability. We use FilFinder to detect the web of filamentary features in each galaxy and determine their characteristic radial and azimuthal spacings. These spacings are then compared to estimates of the most Toomre-unstable length (a few kiloparsecs), the turbulent Jeans length (a few hundred parsecs), and the disk scale height (tens of parsecs) reconstructed using PHANGS-Atacama Large Millimeter/submillimeter Array observations of the molecular gas as a dynamical tracer. Our analysis of the four galaxies targeted in this work indicates that Jeans-scale structure is pervasive. Future work will be essential for determining how the structure observed in gas disks impacts not only the rate and location of star formation but also how stellar feedback interacts positively or negatively with the surrounding multiphase gas reservoir.

Keywords: interstellar medium; spiral galaxies; barred spiral galaxies; gravitational instability; star formation
A First-principle Model for Polarization Swings during Reconnection-powered Flares

We show that magnetic reconnection in a magnetically dominated fast-cooling plasma can naturally produce bright flares accompanied by rotations in the synchrotron polarization vector. With particle-in-cell simulations of reconnection, we find that flares are powered by efficient particle acceleration at the interface of merging magnetic flux ropes, or "plasmoids." The accelerated particles stream through the post-merger plasmoid toward the observer, thus progressively illuminating regions with varying plane-of-sky field direction, and so leading to a rotation in the observed polarization vector. Our results provide evidence for magnetic reconnection as the physical cause of high-energy flares from the relativistic jets of blazars (which recent observations have shown to be frequently associated with polarization rotations), and provide a first-principle physical mechanism for such flares.

Keywords: blazars; relativistic jets; polarimetry
A 31.3 day Transient Quasiperiodic Oscillation in Gamma-ray Emission from Blazar S5 0716+714

We systematically search for quasiperiodic oscillatory (QPO) signals on the month timescale among the 1525 sources given in the Fermi Large Area Telescope Light Curve Repository. We find a transient QPO of 31.3 ± 1.8 days in the gamma-ray band light curve of the TeV blazar S5 0716+714, which has seven cycles (MJD 55918-56137) for the first time by weighted wavelet Z-transform and Lomb-Scargle periodogram methods. Monte Carlo simulations based on the power spectral density and probability distribution function were used to evaluate the confidence level of the QPO, and the result is ~4.1σ. Seasonal autoregressive integrated moving average modeling of the light curve revealed it is a significant physical QPO. The physical models to explain the sporadic month-timescale QPOs in the blazar were discussed. Our studies indicate that the helical jet model and blob move helically in a curved jet model to properly explain this kind of transient QPO.

Keywords: bl lacertae objects; blazars