adsabs/SciX_UAT_keywords huggingface dataset:
Statistical Relationship between Long-duration High-energy Gamma-Ray Emission and Solar Energetic Particles

Large solar eruptions are often associated with long-duration γ-ray emission extending well above 100 MeV. While this phenomenon is known to be caused by high-energy ions interacting with the solar atmosphere, the underlying dominant acceleration process remains under debate. Potential mechanisms include continuous acceleration of particles trapped within large coronal loops or acceleration at coronal mass ejection (CME)-driven shocks, with subsequent back-propagation toward the Sun. As a test of the latter scenario, previous studies have explored the relationship between the inferred particle population producing the high-energy γ-rays and the population of solar energetic particles (SEPs) measured in situ. However, given the significant limitations on available observations, these estimates unavoidably rely on a number of assumptions. In an effort to better constrain theories of the γ-ray emission origin, we reexamine the calculation uncertainties and how they influence the comparison of these two proton populations. We show that, even accounting for conservative assumptions related to the γ-ray flare, SEP event, and interplanetary scattering modeling, their statistical relationship is only poorly/moderately significant. However, though the level of correlation is of interest, it does not provide conclusive evidence for or against a causal connection. The main result of this investigation is that the fraction of the shock-accelerated protons required to account for the γ-ray observations is >20%-40% for six of the 14 eruptions analyzed. Such high values argue against current CME-shock origin models, predicting a <2% back-precipitation; hence, the computed number of high-energy SEPs appears to be greatly insufficient to sustain the measured γ-ray emission.

Keywords: solar energetic particles; solar gamma-ray emission
KELT-11 b: Abundances of Water and Constraints on Carbon-bearing Molecules from the Hubble Transmission Spectrum

In the past decade, the analysis of exoplanet atmospheric spectra has revealed the presence of water vapor in almost all the planets observed, with the exception of a fraction of overcast planets. Indeed, water vapor presents a large absorption signature in the wavelength coverage of the Hubble Space Telescope's (HST) Wide Field Camera 3 (WFC3), which is the main space-based observatory for atmospheric studies of exoplanets, making its detection very robust. However, while carbon-bearing species such as methane, carbon monoxide, and carbon dioxide are also predicted from current chemical models, their direct detection and abundance characterization has remained a challenge. Here we analyze the transmission spectrum of the puffy, clear hot-Jupiter KELT-11 b from the HST WFC3 camera. We find that the spectrum is consistent with the presence of water vapor and an additional absorption at longer wavelengths than 1.5 μm, which could well be explained by a mix of carbon bearing molecules. CO2, when included is systematically detected. One of the main difficulties to constrain the abundance of those molecules is their weak signatures across the HST WFC3 wavelength coverage, particularly when compared to those of water. Through a comprehensive retrieval analysis, we attempt to explain the main degeneracies present in this data set and explore some of the recurrent challenges that are occurring in retrieval studies (e.g., the impact of model selection, the use of free versus self-consistent chemistry, and the combination of instrument observations). Our results make this planet an exceptional example of a chemical laboratory to test current physical and chemical models of the atmospheres of hot Jupiters.

Keywords: exoplanet atmospheres; extrasolar gaseous giant planets; bayesian statistics; exoplanet atmospheric composition
High-redshift JWST Observations and Primordial Non-Gaussianity

Several bright and massive galaxy candidates at high redshifts have been recently observed by the James Webb Space Telescope. Such early massive galaxies seem difficult to reconcile with standard Λ cold dark matter model predictions. We discuss under which circumstances such observed massive galaxy candidates can be explained by introducing primordial non-Gaussianity in the initial conditions of cosmological perturbations.

Keywords: galaxy dark matter halos; high-redshift galaxy clusters; primordial galaxies
Population Modeling of Fast Radio Bursts from Source Properties

We present a method to estimate the source properties of Fast Radio Bursts (FRBs) from observations by assuming a fixed dispersion measure contribution from a Milky Way-like host galaxy, pulse temporal broadening models for turbulent plasma, and a flat FRB energy spectrum. Then we perform Monte Carlo simulations to constrain the properties of the FRB source, its host galaxy, and scattering in the intervening plasma from the observational data of FRBs detected with Parkes. The typical scatter broadening of the intrinsic pulse is found to be considerably small, ≲ 10-2 - 1 ms, from physical models, with the interstellar medium contribution suppressed significantly relative to that of the intergalactic medium. The intrinsic width for nonrepeating FRBs is broadened by a factor of ∼2-3 on average, primarily due to dispersive smearing. From the simulations, we find that the host galaxy dispersion measure contribution is likely to be comparable to the Galactic contribution and the FRB energy decreases significantly at high frequencies with a negative spectral index. The FRB spatial density is found to increase up to redshift ∼2.0 and then drops significantly at larger distances. We obtain the energy distribution for FRB 121102 with repetition rate ∼0.1-0.3 hr-1 and exponential energy cutoff that is significantly smaller compared to typical FRB energies. We find that the probability of observing none of the other FRBs to be repeating at Parkes is ∼0.8-0.9 with the current follow-up data insufficient to suggest more than one class of FRB progenitors.

Keywords: radio astronomy; radio transient sources; interstellar scattering; astronomical simulations; cosmological models; intergalactic medium; neutron stars
The Nebular Properties of Star-forming Galaxies at Intermediate Redshift from the Large Early Galaxy Astrophysics Census

We present a detailed study of the partial rest-optical (λ obs ≈ 3600-5600 Å) spectra of N = 767 star-forming galaxies at 0.6 < z < 1.0 from the Large Early Galaxy Astrophysics Census (LEGA-C). We compare this sample with low-redshift (z ~ 0) galaxies from the Sloan Digital Sky Survey (SDSS), intermediate-redshift (z ~ 1.6) galaxies from the Fiber Multi-Object Spectrograph (FMOS)-COSMOS Survey, and high-redshift (z ~ 2) galaxies from the Keck Baryonic Structure Survey (KBSS). At a look-back time of 6-8 Gyr, galaxies with stellar masses $\mathrm{log}({M}_{* }/{M}_{\odot })\gt 10.50$ appear remarkably similar to z ~ 0 galaxies in terms of their nebular excitation, as measured using [O III] λ5008/Hβ. There is some evidence that 0.6 < z < 1.0 galaxies with lower M * have higher [O III] λ5008/Hβ than z ~ 0 galaxies and are more similar to less evolved z ~ 1.6 and z ~ 2 galaxies, which are offset from the z ~ 0 locus at all M *. We explore the impact of selection effects, contributions from active galactic nuclei, and variations in physical conditions (ionization parameter and gas-phase oxygen abundance) on the apparent distribution of [O III] λ5008/Hβ and find somewhat higher ionization in 0.6 < z < 1.0 galaxies with lower M * relative to z ~ 0 galaxies. We use new near-infrared spectroscopic observations of a subsample of LEGA-C galaxies to investigate other probes of enrichment and excitation. Our analysis demonstrates the importance of obtaining complete rest-optical spectra of galaxies in order to disentangle these effects.

Keywords: galaxies; galaxy evolution; interstellar medium
Porous Dust Particles in Protoplanetary Disks: Application to the HL Tau Disk

Dust particle sizes constrained from dust continuum and polarization observations by radio interferometry are inconsistent by at least an order of magnitude. Motivated by porous dust observed in small solar system bodies (e.g., from the Rosetta mission), we explore how the dust particle's porosity affects the estimated particle sizes from these two methods. Porous particles have lower refractive indices, which affect both opacity and polarization fraction. With weaker Mie interference patterns, the porous particles have lower opacity at millimeter wavelengths than the compact particles if the particle size exceeds several hundred microns. Consequently, the inferred dust mass using porous particles can be up to a factor of six higher. The most significant difference between compact and porous particles is their scattering properties. The porous particles have a wider range of particle sizes with high linear polarization from dust self-scattering, allowing millimeter- to centimeter-sized particles to explain polarization observations. With a Bayesian approach, we use porous particles to fit HL Tau disk's multiwavelength continuum and millimeter-polarization observations from the Atacama Large Millimeter/submillimeter Array (ALMA) and the Very Large Array (VLA). The moderately porous particles with sizes from 1 mm-1 m can explain both continuum and polarization observations, especially in the region between 20 and 60 au. If the particles in HL Tau are porous, the porosity should be from 70%-97% from current polarization observations. We also predict that future observations of the self-scattering linear polarization at longer wavelengths (e.g., ALMA B1 and ngVLA) have the potential to further constrain the particle's porosity and size.

Keywords: interstellar dust extinction; planet formation; protoplanetary disks; millimeter astronomy; optical constants (dust); submillimeter astronomy; spectral index; radio astronomy; polarimetry; astrophysical dust processes; dust composition; dust continuum emission
Transmission Electron Microscopy Study of the Morphology of Ices Composed of H2O, CO2, and CO on Refractory Grains

It has been implicitly assumed that ices on grains in molecular clouds and protoplanetary disks are formed by homogeneous layers regardless of their composition or crystallinity. To verify this assumption, we observed the H2O deposition onto refractory substrates and the crystallization of amorphous ices (H2O, CO2, and CO) using an ultra-high-vacuum transmission electron microscope. In the H2O-deposition experiments, we found that three-dimensional islands of crystalline ice (Ic) were formed at temperatures above 130 K. The crystallization experiments showed that uniform thin films of amorphous CO and H2O became three-dimensional islands of polyhedral crystals; amorphous CO2, on the other hand, became a thin film of nano-crystalline CO2 covering the amorphous H2O. Our observations show that crystal morphologies strongly depend not only on the ice composition but also on the substrate. Using experimental data concerning the crystallinity of deposited ices and the crystallization timescale of amorphous ices, we illustrated the criteria for ice crystallinity in space and outlined the macroscopic morphology of icy grains in molecular clouds as follows: amorphous H2O covered the refractory grain uniformly, CO2 nano-crystals were embedded in the amorphous H2O, and a polyhedral CO crystal was attached to the amorphous H2O. Furthermore, a change in the grain morphology in a protoplanetary disk is shown. These results have important implications for the chemical evolution of molecules, nonthermal desorption, collision of icy grains, and sintering.

Keywords: experimental techniques; ice formation; laboratory astrophysics
Ion Loss within a Reconnection Exhaust near Mars: MAVEN Observations

We present observations from Mars Atmosphere and Volatile EvolutioN of a reconnection exhaust, which was probably not ongoing, in the Martian magnetosheath. The reconnection jet with abundant heavy ions is directed outward to space. The magnetic field lines within the exhaust are found to be draped, suggesting that the reconnection exhaust was detached from the ionosphere and the heavy ions within it escaped from Mars. The dimensionless reconnection rate estimated from proton measurements is about 5.56%. The total oxygen loss rate via the reconnection exhaust is calculated to be 1.3 × 1021 s-1. This much lower ion loss rate than that estimated in active magnetic reconnection at the ionopause suggests that the reconnection associated with the reconnection exhaust is not ongoing, so most of the heavy ions have already escaped. Our results demonstrate that magnetic reconnection can directly contribute to the ion loss of Mars. Due to the participation of multiple heavy ions, the characteristics of magnetic reconnection could be very different.

Keywords: solar wind; mars; solar-planetary interactions; planetary ionospheres
The Birth of Binary Direct-collapse Black Holes

Supermassive primordial stars forming during catastrophic baryon collapse in atomically cooling halos at z ∼ 15-20 may be the origin of the first quasars in the universe. However, no simulation to date has followed the evolution of these halos at resolutions that are high enough or for times that are long enough to determine if collapse actually produces supermassive stars (SMSs). Here we report new cosmological simulations of baryon collapse in atomically cooled halos for times that are long enough for SMSs to form and die as direct-collapse black holes (DCBHs). We find that the high infall rates required to build up such stars persist until the end of their lives and could fuel the rapid growth of their BHs thereafter. Our simulations also demonstrate that binary and even small multiples of SMSs can form in low-spin and high-spin halos, respectively. This discovery raises the exciting possibility of detecting gravitational waves from DCBH mergers with LISA and tidal disruption events in the near-infrared with the James Webb Space Telescope and ground-based telescopes in the coming decade.

Keywords: supermassive black holes; quasars; early universe; high-redshift galaxies
Multiphase ISM in the z = 5.7 Hyperluminous Starburst SPT 0346-52

With ΣSFR ~ 4200 M ⊙ yr-1 kpc-2, SPT 0346-52 (z = 5.7) is the most intensely star-forming galaxy discovered by the South Pole Telescope. In this paper, we expand on previous spatially resolved studies, using ALMA observations of dust continuum, [N II] 205 μm, [C II] 158 μm, [O I] 146 μm, and undetected [N II] 122 μm and [O I] 63 μm emission to study the multiphase interstellar medium (ISM) in SPT 0346-52. We use pixelated, visibility-based lens modeling to reconstruct the source-plane emission. We also model the source-plane emission using the photoionization code CLOUDY and find a supersolar metallicity system. We calculate T dust = 48.3 K and λ peak = 80 μm and see line deficits in all five lines. The ionized gas is less dense than comparable galaxies, with n e < 32 cm-3, while ~20% of the [C II] 158 μm emission originates from the ionized phase of the ISM. We also calculate the masses of several phases of the ISM. We find that molecular gas dominates the mass of the ISM in SPT 0346-52, with the molecular gas mass ~4× higher than the neutral atomic gas mass and ~100× higher than the ionized gas mass.

Keywords: high-redshift galaxies; interstellar medium; starburst galaxies
Satellite Visibility During the 2024 April Total Eclipse

On 2024 April 8, tens of millions of people across North America will be able to view a total solar eclipse. Such astronomical events have been important throughout history, but with nearly 10,000 satellites in orbit, we question whether total eclipses will now reveal a sky full of satellites, fundamentally changing this experience for humanity. Using the current population of Starlink satellites, we find that the brightest satellites would be naked-eye visible in dark skies, but the high sky brightness during totality will make them undetectable to the unaided eye. Our model does not take into account the effects of chance reflections from large, flat surfaces like solar panels, which we expect will cause glints and flares that could be visible from large satellites and abandoned rocket bodies. Time-lapse all-sky imaging might reveal satellites during the eclipse.

Keywords: artificial satellites; total eclipses
Anisotropic Satellite Galaxy Quenching: A Unique Signature of Energetic Feedback by Supermassive Black Holes?

The quenched fraction of satellite galaxies is aligned with the orientation of the halo's central galaxy, such that on average, satellites form stars at a lower rate along the major axis of the central. This effect, called anisotropic satellite galaxy quenching (ASGQ), has been found in observational data and cosmological simulations. Analyzing the IllustrisTNG simulation, Martín-Navarro et al. recently argued that ASGQ is caused by anisotropic energetic feedback and constitutes "compelling observational evidence for the role of black holes in regulating galaxy evolution." In this Letter, we study the causes of ASGQ in state-of-the-art galaxy formation simulations to evaluate this claim. We show that cosmological simulations predict that on average, satellite galaxies along the major axis of the dark matter halo tend to have been accreted at earlier cosmic times and are hosted by subhalos of larger peak halo masses. As a result, a modulation of the quenched fraction with respect to the major axis of the central galaxy is a natural prediction of hierarchical structure formation. We show that ASGQ is predicted by the UniverseMachine galaxy formation model, a model without anisotropic feedback. Furthermore, we demonstrate that even in the IllustrisTNG simulation, anisotropic satellite accretion properties are the main cause of ASGQ. Ultimately, we argue that ASGQ is not a reliable indicator of supermassive black hole feedback in galaxy formation simulations and, thus, should not be interpreted as such in observational data.

Keywords: galaxy formation; supermassive black holes; galaxy dark matter halos; galaxy quenching
The SDSS-V Black Hole Mapper Reverberation Mapping Project: Unusual Broad-line Variability in a Luminous Quasar

We present a high-cadence multiepoch analysis of dramatic variability of three broad emission lines (Mg II, Hβ, and Hα) in the spectra of the luminous quasar (λ L λ (5100 Å) = 4.7 × 1044 erg s-1) SDSS J141041.25+531849.0 at z = 0.359 with 127 spectroscopic epochs over nine years of monitoring (2013-2022). We observe anticorrelations between the broad emission-line widths and flux in all three emission lines, indicating that all three broad emission lines "breathe" in response to stochastic continuum variations. We also observe dramatic radial velocity shifts in all three broad emission lines, ranging from Δv ~ 400 km s-1 to ~800 km s-1, that vary over the course of the monitoring period. Our preferred explanation for the broad-line variability is complex kinematics in the gas in the broad-line region. We suggest a model for the broad-line variability that includes a combination of gas inflow with a radial gradient, an azimuthal asymmetry (e.g., a hot spot), superimposed on the stochastic flux-driven changes to the optimal emission region ("line breathing"). Similar instances of line-profile variability due to complex gas kinematics around quasars are likely to represent an important source of false positives in radial velocity searches for binary black holes, which typically lack the kind of high-cadence data we analyze here. The long-duration, wide-field, and many-epoch spectroscopic monitoring of SDSS-V BHM-RM provides an excellent opportunity for identifying and characterizing broad emission-line variability, and the inferred nature of the inner gas environment, of luminous quasars.

Keywords: active galactic nuclei; quasars; supermassive black holes
The Streamer Blowout Origin of a Flux Rope and Energetic Particle Event Observed by Parker Solar Probe at 0.5 au

The distribution of spacecraft in the inner heliosphere during 2019 March enabled comprehensive observations of an interplanetary coronal mass ejection (ICME) that encountered Parker Solar Probe (PSP) at 0.547 au from the Sun. This ICME originated as a slow (∼311 km s-1) streamer blowout (SBO) on the Sun as measured by the white-light coronagraphs on board the Solar TErrestrial RElations Observatory-A and the Solar and Heliospheric Observatory. Despite its low initial speed, the passage of the ICME at PSP was preceded by an anisotropic, energetic (≲100 keV/n) ion enhancement and by two interplanetary shocks. The ICME was embedded between slow (∼300 km s-1) solar wind and a following, relatively high-speed (∼500 km s-1), stream that most likely was responsible for the unexpectedly short (based on the SBO speed) ICME transit time of less than ∼56 hr between the Sun and PSP, and for the formation of the preceding shocks. By assuming a graduated cylindrical shell (GCS) model for the SBO that expands self-similarly with time, we estimate the propagation direction and morphology of the SBO near the Sun. We reconstruct the flux-rope structure of the in situ ICME assuming an elliptic-cylindrical topology and compare it with the portion of the 3D flux-rope GCS morphology intercepted by PSP. ADAPT-WSA-ENLIL-Cone magnetohydrodynamic simulations are used to illustrate the ICME propagation in a structured background solar wind and estimate the time when PSP established magnetic connection with the compressed region that formed in front of the ICME. This time is consistent with the arrival at PSP of energetic particles accelerated upstream of the ICME.

Keywords: solar coronal mass ejections; interplanetary particle acceleration; solar energetic particles; ejecta; solar coronal mass ejection shocks
AMUSE-Antlia. I. Nuclear X-Ray Properties of Early-type Galaxies in a Dynamically Young Galaxy Cluster

To understand the formation and growth of supermassive black holes (SMBHs) and their coevolution with host galaxies, it is essential to know the impact of environment on the activity of active galactic nuclei (AGNs). We present new Chandra X-ray observations of nuclear emission from member galaxies in the Antlia cluster, the nearest non-cool core and the nearest merging galaxy cluster, residing at D = 35.2 Mpc. Its inner region, centered on two dominant galaxies NGC 3268 and NGC 3258, has been mapped with three deep Chandra ACIS-I pointings. Nuclear X-ray sources are detected in 7/84 (8.3%) early-type galaxies (ETG) and 2/8 (25%) late-type galaxies with a median detection limit of 8 × 1038 erg s-1. All nuclear X-ray sources but one have a corresponding radio continuum source detected by MeerKAT at the L band. Nuclear X-ray sources detected in early-type galaxies are considered the genuine X-ray counterpart of low-luminosity AGN. When restricted to a detection limit of $\mathrm{log}({L}_{{\rm{X}}}/\mathrm{erg}\,{{\rm{s}}}^{-1})\geqslant 38.9$ and a stellar mass of $10\leqslant \mathrm{log}({M}_{\star }/{M}_{\odot })\lt 11.6$ , six of 11 ETGs are found to contain an X-ray AGN in Antlia, exceeding the AGN occupation fraction of 7/39 (18.0%) and 2/12 (16.7%) in the more relaxed, cool core clusters, Virgo and Fornax, respectively, and rivaling that of the AMUSE-Field ETG of 27/49 (55.1%). Furthermore, more than half of the X-ray AGN in Antlia is hosted by its younger subcluster, centered on NGC 3258. We believe that this is because SMBH activity is enhanced in a dynamically young cluster compared to relatively relaxed clusters.

Keywords: x-ray active galactic nuclei; low-luminosity active galactic nuclei