Sazuna/UAT_keywords huggingface dataset:
Reliable Detections of Atmospheres on Rocky Exoplanets with Photometric JWST Phase Curves. The prevalence of atmospheres on rocky planets is one of the major questions in exoplanet astronomy, but there are currently no published unambiguous detections of atmospheres on any rocky exoplanets. The MIRI instrument on JWST can measure thermal emission from tidally locked rocky exoplanets orbiting small, cool stars. This emission is a function of their surface and atmospheric properties, potentially allowing detections of atmospheres. One way to find atmospheres is to search for lower dayside emission than would be expected for a blackbody planet. Another technique is to measure phase curves of thermal emission to search for nightside emission due to atmospheric heat redistribution. Here, we compare strategies for detecting atmospheres on rocky exoplanets. We simulate secondary eclipse and phase curve observations in the MIRI F1500W and F1280W filters for a range of surfaces (providing our open-access albedo data) and atmospheres on 30 exoplanets selected for their F1500W signal-to-noise ratio. We show that secondary eclipse observations are more degenerate between surfaces and atmospheres than suggested in previous work, and that thick atmospheres can support emission consistent with a blackbody planet in these filters. These results make it difficult to unambiguously detect or rule out atmospheres using their photometric dayside emission alone. We suggest that an F1500W phase curve could instead be observed for a similar sample of planets. While phase curves are time-consuming and their instrumental systematics can be challenging, we suggest that they allow the only unambiguous detections of atmospheres by nightside thermal emission.

Keywords: Extrasolar rocky planets
Most High-density Exoplanets Are Unlikely to Be Remnant Giant Planet's Cores. Some exoplanets have much higher densities than expected from stellar abundances of planet-forming elements. There are two theories—metal-rich formation hypothesis and naked core hypothesis—that explain how formation and evolution can alter the compositions and structures of rocky planets to diverge from their primordial building blocks. Here we revisit the naked core hypothesis, which states that high-density planets are remnant cores of giant planets that remain in a fossil-compressed state, even after envelope loss. Using a planetary interior model and assuming energy-limited atmospheric escape, we show that a large fraction, if not all, of the iron–silicate core of a giant planet is molten during the planet's early evolution. Upon envelope loss, the molten part of the planets can rapidly rebound owing to low viscosity, resulting in a decrease in radius by at most 0.06%, if they had hydrogen/helium envelopes, or by at most 7%, if they had H2O envelopes, compared to self-compressed counterparts with the same core mass fraction. Based on our findings, we reject the hypothesis that all high-density exoplanets are naked cores with Kolmogorov–Smirnov p-value ≪0.05 for both envelope compositions. We find that some high-density exoplanets can still possibly be naked cores, but the probabilities are lower than ∼1/2 and ∼1/3 for the ice giant and gas giant scenario, respectively, in 95% of the cases. We conclude that most high-density exoplanets are unlikely to be remnant giant planet cores.

Keywords: Exoplanet structure, Exoplanet evolution, Planetary interior, Planetary structure
High-z Stellar Masses Can Be Recovered Robustly with JWST Photometry. Robust inference of galaxy stellar masses from photometry is crucial for constraints on galaxy assembly across cosmic time. Here, we test a commonly used spectral energy distribution (SED) fitting code using simulated galaxies from the SPHINX20 cosmological radiation hydrodynamics simulation with JWST NIRCam photometry forward-modeled with radiative transfer. Fitting the synthetic photometry with various star formation history models, we show that recovered stellar masses are, encouragingly, generally robust to within a factor of ∼3 for galaxies in the range M⋆ ∼ 107‑109 M⊙ at z = 5‑10. These results are in stark contrast to recent work claiming that stellar masses can be underestimated by as much as an order of magnitude in these mass and redshift ranges. However, while &gt;90% of masses are recovered to within 0.5 dex, there are notable systematic trends, with stellar masses typically overestimated for low-mass galaxies (M⋆ ≲ 108 M⊙) and slightly underestimated for high-mass galaxies (M⋆ ≳ 109 M⊙). We demonstrate that these trends arise due to the SED fitting code poorly modeling the impact of strong emission lines on broadband photometry. These systematic trends, which exist for all star formation history parameterizations tested, have a tilting effect on the inferred stellar mass function, with the number densities of massive galaxies underestimated (particularly at the lowest redshifts studied) and the number densities of lower-mass galaxies typically overestimated. Overall, this work suggests that we should be optimistic about our ability to infer the masses of high-z galaxies observed with JWST (notwithstanding contamination from active galactic nuclei) but careful when modeling the impact of strong emission lines on broadband photometry.

Keywords: Observational astronomy, High-redshift galaxies, Galaxy evolution, Radiative transfer
Evaluating the Potential to Constrain Dark Matter Annihilation with Fermi-LAT Observations of Ultrafaint Compact Stellar Systems. Recent results from numerical simulations and models of galaxy formation suggest that recently discovered ultrafaint compact stellar systems (UFCSs) in the halo of the Milky Way (MW) may be some of the smallest and faintest galaxies. If this is the case, these systems would be attractive targets for indirect searches of weakly interacting massive particle dark matter (DM) annihilation due to their relative proximity and high expected DM content. In this study, we analyze 14.3 yr of γ-ray data collected by the Fermi-Large Area Telescope coincident with 26 UFCSs. No significant excess γ-ray emission is detected, and we present γ-ray flux upper limits for these systems. Assuming that the UFCSs are DM-dominated galaxies consistent with being among the faintest and least massive MW dwarf spheroidal (dSph) satellite galaxies, we derive the projected sensitivity for a DM annihilation signal. We find that observations of UFCSs have the potential to yield some of the most powerful constraints on DM annihilation, with sensitivity comparable to observations of known dSphs and the Galactic center. This result emphasizes the importance of precise kinematic studies of UFCSs to empirically determine their DM content.

Keywords: Gamma-ray astronomy, Dark matter
Ultradiffuse Dwarf Galaxies Hosting Pseudobulges. By analyzing data from DESI Legacy Imaging Survey of the dwarf galaxies in the Arecibo Legacy Fast Alfa Survey, we have identified five ultradiffuse galaxies (UDGs) featuring central pseudobulges. These UDGs display blue pseudobulges with Sérsic indices n &lt; 2.5 and effective radii spanning 300–700 pc, along with bluer thin stellar disks exhibiting low surface brightness and expansive effective radii that align with the UDG definition. The rotation velocities of these UDGs, determined using H I line widths and optical inclinations, exceed those of most dwarf galaxies of similar mass, suggesting the high halo spins or substantial dark matter halos. We propose that these UDGs likely formed through mergers of dwarf galaxies lacking old stars in their progenitors, resulting in the development of central bulge-like structures during starbursts triggered by the mergers while also enhancing their halo spin. Subsequent gas accretion facilitated the formation of extended stellar disks. It is also worth noting the possibility that these UDGs could alternatively represent "failed L⋆ galaxies" with massive dark matter halos but reduced star formation efficiencies. If future high-resolution H I observations confirm the presence of massive halos around these UDGs, they may have formed due to intense AGN feedback in the early Universe and may be the descendants of "little red dots" observed by the James Webb Space Telescope, which are characterized by heightened central black hole masses and intensified accretion and feedback processes in the early Universe.

Keywords: Galaxy formation, Dwarf galaxies, Galaxy evolution, Photometry
Effective Resistivity in Relativistic Reconnection: A Prescription Based on Fully Kinetic Simulations. A variety of high-energy astrophysical phenomena are powered by the release—via magnetic reconnection—of the energy stored in oppositely directed fields. Single-fluid resistive magnetohydrodynamic (MHD) simulations with uniform resistivity yield dissipation rates that are much lower (by nearly 1 order of magnitude) than equivalent kinetic calculations. Reconnection-driven phenomena could be accordingly modeled in resistive MHD employing a nonuniform, "effective" resistivity informed by kinetic calculations. In this work, we analyze a suite of fully kinetic particle-in-cell (PIC) simulations of relativistic pair-plasma reconnection—where the magnetic energy is greater than the rest mass energy—for different strengths of the guide field orthogonal to the alternating component. We extract an empirical prescription for the effective resistivity,  ηeff=αB0∣J∣p/∣J∣p+1+entcp+1 , where B0 is the reconnecting magnetic field strength, J is the current density, nt is the lab-frame total number density, e is the elementary charge, and c is the speed of light. The guide field dependence is encoded in α and p, which we fit to PIC data. This resistivity formulation—which relies only on single-fluid MHD quantities—successfully reproduces the spatial structure and strength of nonideal electric fields and thus provides a promising strategy for enhancing the reconnection rate in resistive MHD simulations.

Keywords: Magnetohydrodynamics, Magnetic fields, Plasma astrophysics, High energy astrophysics
Solid and Gaseous Methane in IRAS 23385+6053 as Seen with Open JWST Data. We present a new description of the 7.7 μm region towards the high-mass star-forming region IRAS 23385+6053 taken from the open James Webb Space Telescope Mid-Infrared Instrument Medium Resolution Spectrometer data. This area is commonly attributed to the ν4 deformation mode of methane ice. For the first time, gaseous and solid methane were analyzed simultaneously in IRAS 23385+6053. The band at 7.58–7.8 μm (1320–1280 cm‑1) is interpreted as a wide solid absorption methane feature overlapped by the sharp features of the methane emission. We report the detection of gaseous methane and estimate its emitting area radius R, temperature T, and column density N as R = 2940 au,  T=103‑11+13  K, and  N=0.78+6.18‑0.64×1017  cm‑2, correspondingly. The ice content was analyzed with the laboratory spectra data set of methane in different molecular environments obtained on the Ice Spectroscopy Experimental Aggregate. We were able to describe the wide feature of solid methane with the following laboratory spectra: CH4 : CO2 = 1 : 5 (at  27.4‑10.8+6.0  K) and CH4 : H2O = 1 : 10 (at  8.4‑1.7+16.4  K) deposited at 6.7 K and warmed up at a rate of 0.5 K per minute. The derived column densities are  NCH4 (CO2) =  2.97‑0.57+0.37×1017  cm‑2 and  NCH4 (H2O) =  1.02‑0.27+0.46×1017  cm‑2. According to the best fit, solid methane is mostly surrounded by CO2 rather than H2O. The residual analysis reveals the unassigned region at 1283–1297 cm‑1 (7.71–7.79 μm), which is tentatively assigned to nitrous oxide (N2O) in various environments.

Keywords: Ice spectroscopy, Laboratory astrophysics, Interstellar clouds, Astrochemistry
Detection of a New GeV Source in the Outer Region of the Coma Cluster: A Signature of External Accretion Shock?. The supersonic flow motions associated with infall of baryonic gas toward sheets and filaments, as well as cluster mergers, produces large-scale shock waves. The shocks associated with galaxy clusters can be classified mainly into two categories: internal shocks appearing in the hot intracluster medium within the viral radius and external accretion shocks forming in the outer cold region well outside of the virial radius. Cosmic-ray (CR) electrons and/or protons accelerated by these shocks are expected to produce gamma rays through inverse-Compton scattering (ICS) or inelastic pp collisions, respectively. Recent studies have found a spatially extended GeV source within the virial radius, consistent with the internal shock origin. Here, we report the detection of a new GeV source at a distance of about 2 .° 8 from the center of the Coma cluster through the analysis of 16.2 yr of Fermi-LAT data. The hard spectrum of the source, in agreement with the ICS origin, and its location in a large-scale filament of galaxies points to the external accretion shock origin. The gamma-ray (0.1‑103 GeV) luminosity of the source, 1.4 × 1042 erg s‑1, suggests that a fraction ~10‑3 of the kinetic energy flux through the shock surface is transferred to relativistic CR electrons.

Keywords: Galaxy clusters, Shocks, Cosmic rays
PKS 2332–017 and PMN J1916–1519: Candidate Blazar Counterparts to Two High-energy Neutrino Events. We report our counterpart identification study for two high-energy neutrino events IC-130127A and IC-131204A listed in the IceCube Event Catalog of Alert Tracks. These two events belong to Gold alerts, which have a significant probability of being of astrophysical origin. Within the events' 90% positional uncertainty regions, we, respectively, find PKS 2332–017 and PMN J1916–1519. The first source is a flat-spectrum radio quasar at redshift z = 1.18, and the second is a blazar of an uncertain type with photometric z = 0.968. As they correspondingly had a γ-ray flare temporally coincident with the arrival times of IC-130127A and IC-131204A, we identify them as the respective neutrino emitters. Detailed analysis of the γ-ray data for the two blazars, obtained with the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope, is conducted. The two flares, respectively, from PKS 2332–017 and PMN J1916–1519 lasted ~4 yr and ~4 months and showed possible emission hardening by containing high-energy ~2–10 GeV photons in the emissions. Accompanying the flare of PKS 2332–017, optical and mid-infrared brightening variations were also observed. We discuss the properties of the two sources and compare the properties with those of the previously reported (candidate) neutrino-emitting blazars.

Keywords: Gamma-ray sources, Blazars, Neutrino astronomy
Testing the Cosmic Distance Duality Relation Using Strong Gravitational Lensing Time Delays and Type Ia Supernovae. We present a comprehensive test of the cosmic distance duality relation (DDR) using a combination of strong gravitational lensing (SGL) time delay measurements and Type Ia supernovae (SNe Ia) data. We investigate three different parameterizations of potential DDR violations. To bridge the gap between SGL and SNe Ia data sets, we implement an artificial neural network approach to reconstruct the distance modulus of SNe Ia. Our analysis uniquely considers both scenarios where the absolute magnitude of SNe Ia (MB) is treated as a free parameter and where it is fixed to a Cepheid-calibrated value. Using a sample of six SGL systems and the Pantheon+ SNe Ia data set, we find no statistically significant evidence for DDR violations across all parameterizations. The consistency of our findings across different parameterizations not only reinforces confidence in the standard DDR but also demonstrates the robustness of our analytical approach.

Keywords: Cosmology, Strong gravitational lensing, Cosmological parameters
Probing Cosmic Isotropy with the FAST All Sky H I Survey. This paper leverages the first released catalog from the FAST All Sky H I Survey (FASHI) to examine the hypothesis of cosmic isotropy in the local Universe. Given the design of the overall FAST survey, the inhomogeneous detection sensitivity of FASHI is likely to introduce significant biases in the statistical properties of the catalog. To mitigate the potential influence of spurious clustering effects due to these sensitivity variations, we focus on extragalactic H I sources within the sensitivity range of [0.65, 1.0]. This refined subsample is divided into 10 distinct sky regions, for which we compute the two-point angular correlation functions (2PACF) over angular scales of 0 5 &lt; θ &lt; 10°. We apply the Markov Chain Monte Carlo method to fit these 2PACFs with a power-law model and assess the statistical significance of the best-fit parameters for the 10 FASHI sky regions by comparing them against results from mock catalogs generated under the assumptions of homogeneity and isotropy. Our findings indicate that the local Universe, as traced by the H I sources in the FASHI survey, aligns with the cosmic isotropy hypothesis within a 2σ confidence level. We do not detect any statistically significant deviations from cosmic isotropy in the FASHI survey data.

Keywords: Cosmic isotropy, Observational cosmology, Large-scale structure of the universe
A uGMRT and MeerKAT Study of Radio Relics in the Low-mass Merging Cluster PSZ2 G200.95‑28.16. Diffuse radio sources known as radio relics are direct tracers of shocks in the outskirts of merging galaxy clusters. PSZ2 G200.95–28.16, a low-mass merging cluster (M500 = (2.7 ± 0.2) × 1014M⊙), features a prominent radio relic, first identified by R. Kale et al. We name this relic as the Seahorse. The MeerKAT Galaxy Cluster Legacy Survey has confirmed two additional radio relics, R2 and R3, in this cluster. We present new observations of this cluster with the upgraded Giant Metrewave Radio Telescope (uGMRT) at 400 and 650 MHz, paired with Chandra X-ray data. The largest linear sizes for the three relics are 1.53 Mpc, 1.12 kpc, and 340 kpc. All three radio relics are polarized at 1283 MHz. Assuming the diffusive shock acceleration model, the spectral indices of the relics imply shock Mach Numbers of 3.1 ± 0.8 and 2.8 ± 0.9 for the Seahorse and R2, respectively. The Chandra X-ray surface brightness map shows two prominent subclusters, but the relics are not perpendicular to the likely merger axis, as typically observed; no shocks are detected at the locations of the relics. We discuss possible merger scenarios in light of the low mass of the cluster and the radio and X-ray properties of the relics. The relic R2 follows the correlation known in the radio relic power and cluster-mass plane, but the Seahorse and R3 relics are outliers. We have also discovered a radio ring in our 650 MHz uGMRT image that could be an Odd Radio Circle candidate.

Keywords: Galaxy clusters, Extragalactic radio sources, Intracluster medium, Radio continuum emission
Closing the Stellar Labels Gap: Stellar Label independent Evidence for [α/M] Information in Gaia BP/RP Spectra. Data-driven models for stellar spectra that depend on stellar labels suffer from label systematics which decrease model performance: the stellar labels gap. To close the stellar labels gap, we present a stellar label independent model for Gaia BP/RP spectra. We develop a novel implementation of a variational auto-encoder, which learns to generate an XP spectrum and accompanying scatter without relying on stellar labels. We demonstrate that our model achieves competitive XP spectra reconstructions in comparison to stellar label dependent models. We find that our model learns stellar properties directly from the data itself. We then apply our model to XP/APOGEE giant stars to study the [α/M] information in Gaia XP. We provide strong evidence that the XP spectra contain meaningful [α/M] information by demonstrating that our model learns the α-bimodality, without relying on stellar label correlations for stars with Teff &lt; 5000 K, while also being sensitive to the anomalous abundances of Gaia-Enceladus stars. We have publicly released our trained model, codebase and data. Importantly, our stellar label independent model can be implemented for any and all XP spectra because our model's performance scales with training object density, not training label density.

Keywords: Fundamental parameters of stars, Stellar abundances, Astrostatistics techniques, Astronomy data analysis
On the Existence of Long-period Decayless Oscillations in Short Active Region Loops. Decayless kink oscillations, characterized by their lack of decay in amplitude, have been detected in coronal loops of varying scales in active regions, the quiet Sun, and coronal holes. Short-period (&lt;50 s) decayless oscillations have been detected in short loops (&lt; 50 Mm) within active regions. Nevertheless, long-period decayless oscillations in these loops remain relatively unexplored and crucial for understanding the wave modes and excitation mechanisms of decayless oscillations. We present the statistical analysis of decayless oscillations from two active regions observed by the Extreme Ultraviolet Imager onboard Solar Orbiter. The average loop length and period of the detected oscillations are 19 Mm and 151 s, respectively. We find 82 long-period and 23 short-period oscillations in these loops. We do not obtain a significant correlation between loop length and period. We discuss the possibility of different wave modes in short loops, although standing waves cannot be excluded from possible wave modes. Furthermore, a different branch exists for active region short loops in the loop length versus period relation, similar to decayless waves in short loops in the quiet Sun and coronal holes. The magnetic fields derived from MHD seismology, based on standing kink modes, show lower values for multiple oscillations compared to previous estimates for long loops in active regions. Additionally, the comparison of period distributions in short loops across different coronal regions indicates that different excitation mechanisms may trigger short-period kink oscillations in active regions compared to the quiet Sun and coronal holes.

Keywords: Solar coronal seismology, Solar coronal waves, Solar corona
The Effect of Galaxy Interactions on Starbursts in Milky Way-mass Galaxies in FIRE Simulations. Simulations and observations suggest that galaxy interactions may enhance the star formation rate (SFR) in merging galaxies. One proposed mechanism is the torque exerted on the gas and stars in the larger galaxy by the smaller galaxy. We analyze the interaction torques and star formation activity on six galaxies from the FIRE-2 simulation suite with masses comparable to the Milky Way galaxy at redshift z = 0. We trace the halos from z = 3.6 to z = 0, calculating the torque exerted by the nearby galaxies on the gas in the central galaxy. We calculate the correlation between the torque and the SFR across the simulations for various mass ratios. For near-equal-stellar-mass-ratio interactions in the galaxy sample, occurring between z = 1.2‑3.6, there is a positive and statistically significant correlation between the torque from nearby galaxies on the gas of the central galaxies and the SFR. For all other samples, no statistically significant correlation is found between the torque and the SFR. Our analysis shows that some, but not all, major interactions cause starbursts in the simulated Milky Way-mass galaxies, and that most starbursts are not caused by galaxy interactions. The transition from "bursty" at high redshift (z ≳ 1) to "steady" star formation state at later times is independent of the interaction history of the galaxies, and most of the interactions do not leave significant imprints on the overall trend of the star formation history of the galaxies.

Keywords: Galaxy interactions, Galaxy evolution