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The Arecibo Galaxy Environment Survey. XII. Optically Dark H I Clouds in the Leo I Group

Using data from the Arecibo Galaxy Environment Survey, we report the discovery of five H I clouds in the Leo I group without detected optical counterparts. Three of the clouds are found midway between M96 and M95, one is only ${10}^{{\prime} }$ from the southeast side of the well-known Leo Ring, and the fifth is relatively isolated. H I masses range from 2.6 × 106 M ⊙ to 9.0 × 106 M ⊙, and velocity widths (W50) range from 16 to 42 km s-1. Although a tidal origin is the most obvious explanation, this formation mechanism faces several challenges. For the most isolated cloud, the difficulties are its distance from neighboring galaxies and the lack of any signs of disturbance in the H I disks of those systems. Some of the clouds also appear to follow the baryonic Tully-Fisher relation between mass and velocity width for normal, stable galaxies, which is not expected if they are tidal in origin. Three clouds are found between M96 and M95 that have no optical counterparts but have otherwise similar properties and locations to the optically detected galaxy LeG 13. While overall we favor a tidal debris scenario to explain the clouds, we cannot rule out a primordial origin. If the clouds were produced in the same event that gave rise to the Leo Ring, they may provide important constraints on any model attempting to explain that structure.

Keywords: galaxies; circumgalactic medium; galaxy environments; galaxy encounters; galaxy groups; galaxy dynamics; galaxy kinematics; galaxy evolution
The JWST Resolved Stellar Populations Early Release Science Program. I. NIRCam Flux Calibration

We use globular cluster data from the Resolved Stellar Populations Early Release Science (ERS) program to validate the flux calibration for the Near Infrared Camera (NIRCam) on the James Webb Space Telescope. We find a significant flux offset between the eight short wavelength detectors, ranging from 1% to 23% (~0.01-0.2 mag) that affects all NIRCam imaging observations. We deliver improved zero-points for the ERS filters and show that alternate zero-points derived by the community also improve the calibration significantly. We also find that the detector offsets appear to be time variable by up to at least 0.1 mag.

Keywords: flux calibration; james webb space telescope; globular star clusters
Ram Pressure Stripping of the Multiphase ISM: A Detailed View from TIGRESS Simulations

Ram pressure stripping (RPS) is a process that removes the interstellar medium (ISM) quickly, playing a vital role in galaxy evolution. Previous RPS studies have treated the ISM as single-phase or lack the resolution and physical processes to properly capture the full multiphase ISM. To improve this simplification, we introduce an inflowing, hot intracluster medium (ICM) into a self-consistently modeled ISM in a local patch of star-forming galactic disks using the TIGRESS framework. Our simulations reveal that the workings of RPS are not only direct acceleration of the ISM by ICM ram pressure but also mixing-driven momentum transfer involving significant phase transition and radiative cooling. The hot ICM passes through the low-density channels of the porous, multiphase ISM; shreds the cool ISM; and creates mixing layers. The ICM momentum is transferred through the mixing layers while populating the intermediate-temperature gas and radiating thermal energy away. The mixed gas extends beyond galactic disks and forms stripped tails that cool back unless the ICM fluxes are large enough to prevent cooling until they escape the simulation domain. The mixing-driven momentum transfer predicts that the more ICM mixes in, the faster the ISM moves, resulting in the anticorrelation of outflow velocity and gas metallicity of the stripped ISM. The compression of the ISM disks due to the ICM ram pressure enhances star formation rates up to 50% compared to the model without ICM. With the ICM ram pressure higher than the disk anchoring pressure, star formation is quenched within ~100 Myr.

Keywords: galaxy interactions; interstellar medium; intracluster medium; magnetohydrodynamical simulations
Switchbacks in the Near-Sun Magnetic Field: Long Memory and Impact on the Turbulence Cascade

One of the most striking observations made by Parker Solar Probe during its first solar encounter is the omnipresence of rapid polarity reversals in a magnetic field that is otherwise mostly radial. These so-called switchbacks strongly affect the dynamics of the magnetic field. We concentrate here on their macroscopic properties. First, we find that these structures are self-similar, and have neither a characteristic magnitude, nor a characteristic duration. Their waiting time statistics show evidence of aggregation. The associated long memory resides in their occurrence rate, and is not inherent to the background fluctuations. Interestingly, the spectral properties of inertial range turbulence differ inside and outside of switchback structures; in the latter the 1/f range extends to higher frequencies. These results suggest that outside of these structures we are in the presence of lower-amplitude fluctuations with a shorter turbulent inertial range. We conjecture that these correspond to a pristine solar wind.

Keywords: solar wind; interplanetary turbulence; interplanetary magnetic fields
Occurrence Rate of Hot Jupiters Around Early-type M Dwarfs Based on Transiting Exoplanet Survey Satellite Data

We present an estimate of the occurrence rate of hot Jupiters (7 R ⊕ ≤ R p ≤ 2 R J, 0.8 ≤ P b ≤ 10 days) around early-type M dwarfs based on stars observed by the Transiting Exoplanet Survey Satellite (TESS) during its primary mission. We adopt stellar parameters from the TESS Input Catalog and construct a sample of 60,819 M dwarfs with 10.5 ≤ T mag ≤ 13.5, effective temperatures 2900 ≤ T eff ≤ 4000 K, and stellar masses 0.45 ≤ M * ≤ 0.65 M ⊙. We conduct a uninformed transit search using a detection pipeline based on the box least square search and characterize the searching completeness through an injection and recovery experiment. We combine a series of vetting steps including light centroid measurement, odd/even and secondary eclipse analysis, rotation and transit period synchronization tests as well as inspecting the ground-based photometric, spectroscopic, and imaging observations. Finally, we find a total of nine planet candidates, all of which are known TESS objects of interest. We obtain an occurrence rate of 0.27% ± 0.09% for hot Jupiters around early-type M dwarfs that satisfy our selection criteria. Compared with previous studies, the occurrence rate of hot Jupiters around early-type M dwarfs is smaller than all measurements for FGK stars, although they are consistent within 1σ-2σ. There is a trend that the occurrence rate of hot Jupiters has a peak at G dwarfs and falls toward both hotter and cooler stars. Combining results from transit, radial velocity, and microlensing surveys, we find that hot Jupiters around early-type M dwarfs possibly show a steeper decrease in the occurrence rate per logarithmic semimajor axis bin ( ${dN}/d{\mathrm{log}}_{10}a$ ) when compared with FGK stars.

Keywords: hot jupiters; exoplanet detection methods; extrasolar gaseous giant planets; astrostatistics
High-energy Neutrinos and Gamma Rays from Nonrelativistic Shock-powered Transients

Shock interaction has been argued to play a role in powering a range of optical transients, including supernovae, classical novae, stellar mergers, tidal disruption events, and fast blue optical transients. These same shocks can accelerate relativistic ions, generating high-energy neutrino and gamma-ray emission via hadronic pion production. The recent discovery of time-correlated optical and gamma-ray emission in classical novae has revealed the important role of radiative shocks in powering these events, enabling an unprecedented view of the properties of ion acceleration, including its efficiency and energy spectrum, under similar physical conditions to shocks in extragalactic transients. Here we introduce a model for connecting the radiated optical fluence of nonrelativistic transients to their maximal neutrino and gamma-ray fluence. We apply this technique to a wide range of extragalactic transient classes in order to place limits on their contributions to the cosmological high-energy gamma-ray and neutrino backgrounds. Based on a simple model for diffusive shock acceleration at radiative shocks, calibrated to novae, we demonstrate that several of the most luminous transients can accelerate protons up to 1016 eV, sufficient to contribute to the IceCube astrophysical background. Furthermore, several of the considered sources—particularly hydrogen-poor supernovae—may serve as "gamma-ray-hidden" neutrino sources owing to the high gamma-ray opacity of their ejecta, evading constraints imposed by the nonblazar Fermi Large Area Telescope background. However, adopting an ion acceleration efficiency of ∼0.3%-1% motivated by nova observations, we find that currently known classes of nonrelativistic, potentially shock-powered transients contribute at most a few percent of the total IceCube background.

Keywords: gamma-rays; novae; supernovae; neutrino astronomy
The Possible Formation of Jupiter from Supersolar Gas

More than two decades ago, the Galileo probe performed in situ measurements of the composition of Jupiter's atmosphere and found that the abundances of C, N, S, P, Ar, Kr, and Xe were all enriched by factors of 1.5-5.4 times their protosolar value. Juno's measurements recently confirmed the supersolar N abundance and also found that the O abundance was enriched by a factor 1-5 compared with its protosolar value. Here, we aim at determining the radial and temporal evolution of the composition of gases and solids in the protosolar nebula (PSN) to assess the possibility that Jupiter's current composition was acquired via the direct accretion of supersolar gases. To do so, we model the evolution of a 1D α-viscous accretion disk that includes the radial transport of dust and ice particles and their vapors, with their sublimation and condensation rates, to compute the composition of the PSN. We find that the composition of Jupiter's envelope can be explained only from its accretion from PSN gas (α ≤ 10-3), or from a mixture of vapors and solids (α > 10-3). The composition of the PSN at 4 au, namely between the locations of the H2O and CO2 icelines, reproduces the one measured in Jupiter between 100 and 300 kyr of disk evolution. Our results are found to be compatible with both the core accretion model, where Jupiter would acquire its metallicity by late accretion of volatile-rich planetesimals, and the gravitational collapse scenario, where the composition of proto-Jupiter would be similar to that of the PSN.

Keywords: protoplanetary disks; jupiter; planetary interior; solar system gas giant planets; planet formation
Grain Size Effects on Visible and Near-infrared (0.35-2.5 μm) Laboratory Spectra of Ordinary Chondrite and HED Meteorites

Remote spectral characterization of near-Earth asteroids (NEAs) relies on laboratory spectral calibration to constrain their surface composition, including mineral chemistry and relative mineral abundances. Often these calibrations are based on fine meteorite powders that are representative of regolith observed on large NEAs such as (433) Eros. However, spacecraft observations of smaller NEAs such as (25143) Itokawa, (101955) Bennu, and (162173) Ryugu show surfaces devoid of a thick layer of regolith and instead find variegated landscapes with millimeter-sized particles to meter-scale boulders. Here we present the results of a laboratory study to understand the effects of grain size on the spectral properties of meteorites and how this can impact ground-based characterization of NEAs. Our study focuses on ordinary chondrites (H, L, LL) and HED meteorites, as they comprise ~90% of all meteorites that fall on Earth. Compared to ordinary chondrites, the spectral band parameters of HED meteorites are less affected by changing grain size. Among the ordinary chondrites, LL chondrites are least affected, but the spectral band parameters and mineral chemistries and abundances for H and L chondrites are most affected by changing grain size. Grain size does not seem to have any significant effect on the taxonomic classification of our meteorite spectra. We also used the Hapke model to investigate trends in single-scattering albedo as a function of grain size and present equations to recover the grain size from a spectrum.

Keywords: meteorites
The Coronal Global Evolutionary Model: Using HMI Vector Magnetogram and Doppler Data to Determine Coronal Magnetic Field Evolution

The Coronal Global Evolutionary Model (CGEM) provides data-driven simulations of the magnetic field in the solar corona to better understand the build-up of magnetic energy that leads to eruptive events. The CGEM project has developed six capabilities. CGEM modules (1) prepare time series of full-disk vector magnetic field observations to (2) derive the changing electric field in the solar photosphere over active-region scales. This local electric field is (3) incorporated into a surface flux transport model that reconstructs a global electric field that evolves magnetic flux in a consistent way. These electric fields drive a (4) 3D spherical magnetofrictional (SMF) model, either at high resolution over a restricted range of solid angles or at lower resolution over a global domain to determine the magnetic field and current density in the low corona. An SMF-generated initial field above an active region and the evolving electric field at the photosphere are used to drive (5) detailed magnetohydrodynamic (MHD) simulations of active regions in the low corona. SMF or MHD solutions are then used to compute emissivity proxies that can be compared with coronal observations. Finally, a lower-resolution SMF magnetic field is used to initialize (6) a global MHD model that is driven by an SMF electric field time series to simulate the outer corona and heliosphere, ultimately connecting Sun to Earth. As a demonstration, this report features results of CGEM applied to observations of the evolution of NOAA Active Region 11158 in 2011 February.

Keywords: solar activity; solar corona; solar magnetic fields
Toward Machine-learning-based Metastudies: Applications to Cosmological Parameters

We develop a new model for automatic extraction of reported measurement values from the astrophysical literature, utilizing modern natural language processing techniques. We use this model to extract measurements present in the abstracts of the approximately 248,000 astrophysics articles from the arXiv repository, yielding a database containing over 231,000 astrophysical numerical measurements. Furthermore, we present an online interface (Numerical Atlas) to allow users to query and explore this database, based on parameter names and symbolic representations, and download the resulting data sets for their own research uses. To illustrate potential use cases, we then collect values for nine different cosmological parameters using this tool. From these results, we can clearly observe the historical trends in the reported values of these quantities over the past two decades and see the impacts of landmark publications on our understanding of cosmology.

Keywords: astronomy data analysis; cosmological parameters; astronomy databases
Selection of the Main Control Parameters for the Dst Index Prediction Model Based on a Layer-wise Relevance Propagation Method

The prediction of the Dst index is an important subject in space weather. It has significant progress with the prevalent applications of neural networks. The selection of input parameters is critical for the prediction model of the Dst index or other space-weather models. In this study, we perform a layer-wise relevance propagation (LRP) method to select the main parameters for the prediction of the Dst index and understand the physical interpretability of neural networks for the first time. Taking an hourly Dst index and 10 types of solar wind parameters as the inputs, we utilize a long short-term memory network to predict the Dst index and present the LRP method to analyze the dependence of the Dst index on these parameters. LRP defines the relevance score for each input, and a higher relevance score indicates that the corresponding input parameter contributes more to the output. The results show that Dst, E y , B z , and V are the main control parameters for Dst index prediction. In order to verify the LRP method, we design two more supplementary experiments for further confirmation. These results confirm that the LRP method can reduce the initial dimension of neural network input at the cost of minimum information loss and contribute to the understanding of physical processes in space weather.

Keywords: space weather; solar wind; solar-terrestrial interactions; geomagnetic fields
SPLUS J210428.01-004934.2: An Ultra Metal-poor Star Identified from Narrowband Photometry

We report on the discovery of SPLUS J210428.01-004934.2, an ultra metal-poor (UMP) star first identified from the narrowband photometry of the Southern Photometric Local Universe Survey (S-PLUS) Data Release 1, in the SDSS Stripe 82 region. Follow-up medium- and high-resolution spectroscopy (with Gemini South and Magellan-Clay, respectively) confirmed the effectiveness of the search for low-metallicity stars using the S-PLUS narrowband photometry. At [Fe/H] = -4.03, SPLUS J2104-0049 has the lowest detected carbon abundance, A(C) = +4.34, when compared to the 34 previously known UMP stars in the literature, which is an important constraint on its stellar progenitor and also on stellar evolution models at the lowest metallicities. Based on its chemical abundance pattern, we speculate that SPLUS J2104-0049 could be a bona fide second-generation star, formed from a gas cloud polluted by a single metal-free ∼ 30M⊙ star. This discovery opens the possibility of finding additional UMP stars directly from narrowband photometric surveys, a potentially powerful method to help complete the inventory of such peculiar objects in our Galaxy. * Based on observations gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. Based on observations obtained at the international Gemini Observatory, a program of NSF's NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea).

Keywords: high resolution spectroscopy; stellar atmospheres; narrow band photometry; chemical abundances; metallicity
Propagation of Very-high-energy γ-Rays from Distant Blazars

We rederive the possible dependence of the redshift with a very-high-energy (VHE) γ-ray photon index. The results suggest that the universe to VHE γ-rays is becoming more transparent than expected. We introduce the extragalactic background light (EBL) and photon to axion-like particle (ALP) oscillations to explain this phenomenon. We concentrate our analysis on 70 blazars up to redshift z ≃ 1. Assuming this correlation is solely the result of photon-photon absorption of VHE photons with the EBL, with deviations between the predictions and observations, especially at redshifts 0.2 < z < 1. We then discuss the implications of photon-ALP oscillations for the VHE γ-ray spectra of blazars. Strong evidence shows that (1) the results of the EBL attenuation show that the VHE γ-ray photon index increases nonlinearly at the ranges of redshift 0.03 < z < 0.2 and (2) the photon-ALP oscillation results in an attractive characteristic in the VHE γ-ray photon index at the ranges of redshift 0.2 < z < 1. We suggest that both EBL absorption and photon-ALP oscillation can influence the propagation of VHE γ-rays from distant blazars.

Keywords: blazars; bl lacertae objects; flat-spectrum radio quasars
Investigation of a Magnetic Reconnection Event with Extraordinarily High Particle Energization in Magnetotail Turbulence

Magnetic reconnection and plasma turbulence are ubiquitous and key processes in the Universe. These two processes are suggested to be intrinsically related: magnetic reconnection can develop turbulence, and, in turn, turbulence can influence or excite magnetic reconnection. In this study, we report a rare and unique electron diffusion region (EDR) observed by the Magnetospheric Multiscale mission in the Earth's magnetotail with significantly enhanced energetic particle fluxes. The EDR is in a region of strong turbulence within which the plasma density is dramatically depleted. We present three salient features. (1) Despite the turbulence, the EDR behaves nearly the same as that in 2D quasi-planar reconnection; the observations suggest that magnetic reconnection continues for several minutes. (2) The observed reconnection electric field and inferred energy transport are exceptionally large. However, the aspect ratio of the EDR (one definition of reconnection rate) is fairly typical. Instead, extraordinarily large-amplitude Hall electric fields appear to enable the strong energy transport. (3) We hypothesize that the high-energy transport rate, density depletion, and the strong particle acceleration are related to a near-runaway effect, which is due to the combination of low-plasma-density inflow (from lobes) and possible positive feedback between turbulence and reconnection. The detailed study on this EDR gives insight into the interplay between reconnection and turbulence, and the possible near-runaway effect, which may play an important role in other particle acceleration in astrophysical plasma.

Keywords: plasma physics; space plasmas
Molecules with ALMA at Planet-forming Scales (MAPS). III. Characteristics of Radial Chemical Substructures

The Molecules with ALMA at Planet-forming Scales (MAPS) Large Program provides a detailed, high-resolution (~10-20 au) view of molecular line emission in five protoplanetary disks at spatial scales relevant for planet formation. Here we present a systematic analysis of chemical substructures in 18 molecular lines toward the MAPS sources: IM Lup, GM Aur, AS 209, HD 163296, and MWC 480. We identify more than 200 chemical substructures, which are found at nearly all radii where line emission is detected. A wide diversity of radial morphologies-including rings, gaps, and plateaus-is observed both within each disk and across the MAPS sample. This diversity in line emission profiles is also present in the innermost 50 au. Overall, this suggests that planets form in varied chemical environments both across disks and at different radii within the same disk. Interior to 150 au, the majority of chemical substructures across the MAPS disks are spatially coincident with substructures in the millimeter continuum, indicative of physical and chemical links between the disk midplane and warm, elevated molecular emission layers. Some chemical substructures in the inner disk and most chemical substructures exterior to 150 au cannot be directly linked to dust substructure, however, which indicates that there are also other causes of chemical substructures, such as snowlines, gradients in UV photon fluxes, ionization, and radially varying elemental ratios. This implies that chemical substructures could be developed into powerful probes of different disk characteristics, in addition to influencing the environments within which planets assemble. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

Keywords: protoplanetary disks; planet formation; interstellar molecules; astrochemistry; high angular resolution