Sazuna/UAT_keywords huggingface dataset:
Lyman Continuum Leakers at z &gt; 3 in the GOODS-S Field: Mergers Dominated. Understanding the ionizing photon escape from galaxies is essential for studying cosmic reionization. With a sample of 23 Lyman continuum (LyC) leakers (among which eight are high-confidence leakers) at 3 &lt; z &lt; 4.5 in the GOODS-S field, we investigate their morphologies using high-resolution data from the Hubble Space Telescope and the James Webb Space Telescope. We find that 20 of the 23 LyC leakers (seven out of eight high-confidence leakers) show merging signatures via visual inspection, while the remaining three are starbursts. The merger fraction of our sample is significantly higher than that of normal galaxies at similar or higher redshifts. Even when using the nonparametric method, which may miss some mergers in a sample, the merger fraction remains high, especially for the high-confidence leakers. Based on our previous finding that LyC leakers are not necessarily starbursts while some are in the star formation main sequence, we further find that those in the main sequence show merger signatures. Our results suggest that LyC leakers are either starbursts or mergers, both of which can facilitate the LyC photon escape, in addition to generating more LyC photons. Furthermore, we show that high-z LyC leakers are statistically more extended than those selected at low redshift, which exhibit a higher merger fraction as size increases. This is likely due to the observational bias that the spatial resolution limits the detection of high-z compact galaxies, while low redshift LyC leakers are more selected as compact starbursts.

Keywords: Reionization, High-redshift galaxies
On the Anisotropic Velocity Distribution of Newborn Pickup Ions in the Heliosheath. The evolution of the velocity distribution of pickup ions is crucial for understanding the energetic neutral atom (ENA) fluxes observed by Interstellar Boundary Explorer. Pickup ions in the heliosheath contain two main components: those transmitted across the heliospheric termination shock and those locally created within the heliosheath. In this work, we discuss the velocity distribution of the latter locally created component. We find that pickup ions created by the charge exchange of neutral solar wind (NSW) may be a significant source of the observed ENA fluxes between about 100 eV and 1 keV. Moreover, newborn pickup ions can maintain highly anisotropic velocity distribution in the heliosheath. This is because the kinetic instabilities are weak after the solar wind flow decelerates at the termination shock. Hybrid kinetic simulations show the mirror instability to be the dominant mode for conditions in the heliosheath close to the termination shock. We estimate that effects of NSW and anisotropy may enhance the expected phase space density of newborn pickup ions by more than a factor of 100.

Keywords: Pickup ions, Heliosheath, Heliosphere
Spatially Resolved Polarization Variation of the Crab Nebula. We examined the spatially resolved polarization variations in the Crab Nebula over 2 yr, using observational data from the Imaging X-ray Polarimetry Explorer, and offer key insights into its magnetic field structures and evolution. The results show significant temporal changes in the polarization degree (PD) across three regions of interest in the 2–8 keV energy band. Regions (a) and (b), located in the northern and the southwestern parts of the study area, exhibit PD variations with significance levels greater than 4σ and 3σ, respectively. Region (c), located in the southwest, shows a notable decrease in PD with a significance greater than 5σ. However, no significant variation in the polarization angle was observed. Meanwhile, notable flux variations were detected, likely influenced by dynamic processes such as magnetized turbulence within the nebula.

Keywords: X-ray astronomy, Polarimetry, Pulsar wind nebulae
Citizen Science Identification of Isolated Blue Stellar Systems in the Virgo Cluster. We present a catalog of 34 new candidate (13 high confidence) isolated, young stellar systems within the Virgo galaxy cluster identified through a citizen science search of public optical and ultraviolet imaging. "Blue blobs" are a class of blue, faint, isolated, extremely low stellar mass, and metal-rich star-forming clouds embedded in the hot intracluster medium of the Virgo cluster. Only six blue blobs were known previously and here we confirm an additional six of our candidates through velocity and metallicity measurements from follow-up optical spectroscopy on the Hobby–Eberly Telescope (HET). Our 13 high confidence candidates (including the six confirmed) have properties consistent with prior known blue blobs and are inconsistent with being low-mass galaxies. Most candidates are concentrated in relatively dense regions, roughly following filamentary structures within the cluster, but avoiding its center. Three of our candidates are likely the stellar counterparts of known "optically dark" clouds of neutral hydrogen in the cluster, while a further four are widely separated extensions to previously known blue blobs. The properties of our new candidates are consistent with previous conclusions that blue blobs likely originated from ram pressure stripping events, however, their locations in velocity–projected cluster-centric radius phase space imply that their parent galaxies are not on their first infall into the cluster. Through our ongoing follow-up program with HET we aim to confirm additional candidates, however, detailed understanding of the stellar populations and star formation histories of blue blobs will require JWST observations. *Based on observations obtained with the Hobby–Eberly Telescope (HET), which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximillians-Universität München, and Georg-August Universität Göttingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly.

Keywords: Ram pressure stripped tails, Virgo Cluster, Star forming regions, Dwarf galaxies, Low surface brightness galaxies
Infant Type Ia Supernovae from the KMTNet. I. Multicolor Evolution and Populations. We conduct a systematic analysis of the early multiband light curves and colors of 19 Type Ia supernovae (SNe) from the Korea Microlensing Telescope Network SN Program, including 16 previously unpublished events. Seven are detected ≲1 day (as early as ≲1 hr) since the estimated epoch of first light and the rest ≲3 days. Some show excess emission within &lt;0.5 day to ∼2 days, but most show pure power-law rises. Colors are initially diverse before ∼5 days, but converge to similar values at ∼10 days. We identify at least three populations based on 2─5 day color evolution: (1) "early-blues" exhibit slowly evolving colors consistent with a ∼17,000 K blackbody; (2) "early-reds" have initially blue B − V and red V − i colors that cannot simultaneously be fit with a blackbody—likely due to suppression of B- and i-band flux by Fe II/III and Ca II—and evolve more rapidly; and (3) "early-yellows" evolve blueward, consistent with thermal heating from ∼8000─13,000 K. Distributions of early-blue and early-red colors are compatible with them being either distinct populations—with early-reds comprising (60 ± 15)% of them—or extreme ends of one continuous population, whereas the early-yellow population identified here is clearly distinct. Compared to the other populations, early-blues in our sample differ by exhibiting excess emission within 1─2 days, nearly constant peak brightness regardless of ∆m15(B) after standardization, and shallower Si II features. Early-blues also prefer star-forming host environments, while early-yellows and, to a lesser extent, early-reds prefer quiescent ones. These preferences appear to indicate at least two Type Ia SN production channels based on stellar population age, while early-reds and early-blues may still share a common origin.

Keywords: Binary stars, White dwarf stars, Transient sources, Galaxy ages, Type Ia supernovae, Time domain astronomy, Supernovae
Proton Intensity Dropout in Isotropic Turbulence Regime during Gradual Solar Energetic Particle Events in Solar Cycle 23. When the Wind spacecraft started its only journey to Lagrange point L2 in 2003 October, it entered an isotropic turbulent environment with radially mean magnetic field (Bm) and slow solar wind speed (VSW). On October 26, it detected a particle intensity dropout interval following a gradual solar energetic particle event. In addition, it recorded three magnetic field rotations corresponding to one-sided increases in VSW, indicating the occurrence of magnetic switchback in the Alfvénic solar wind. Since the last switchback interval is just before the dropout interval, we studied the difference of the pitch angle distribution (PAD) of protons between them. In the switchback interval (Bm perpendicular to Vsw), the PAD maximum is located at μ ∼ +1, where μ is the pitch angle cosine, while, in the dropout interval (Bm antiparallel to Vsw), the maximum is at μ ∼ 0. The difference indicates that protons with greater gyroradii cannot be confined in the curved magnetic field lines and can be injected into the dropout region with μ ∼ 0. Therefore, the analysis of proton pitch angle scattering in the dropout interval can be greatly simplified due to the short duration of the interval and the sharp initial conditions. Compared with the analytical solution of the Fokker–Planck equation, we deduce that the parallel mean free path of 2.1 MeV protons is 3.7 ± 0.5 au, which means that the dropout of proton intensity in the isotropic turbulent regime is also caused by insufficient spatial diffusion of protons.

Keywords: Interplanetary turbulence, Solar energetic particles, Solar wind, Solar magnetic fields, Solar particle emission
The Structure of the Local Interstellar Medium. VII. Additional New Mg II, Fe II, and Mn II Observations toward Stars within 100 pc. We present new high-resolution (R ∼ 114,000), near-ultraviolet spectra in the direction of 36 nearby (&lt;100 pc) stars to uncover the structure and composition of the local interstellar medium (LISM). The spectra were obtained using the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. We model the LISM absorption due to Mg II, Fe II, and Mn II in order to measure new velocities, Doppler broadening parameters, and column densities for interstellar clouds; refine the extent of known clouds; and identify new clouds. Based on our analyses of these 36 new sight lines, we find one to four discrete LISM features for each individual sight line, with the number of components remaining relatively flat until increasing at ≈60 pc. By comparing our final measurements with a dynamical model of the LISM by S. Redfield &amp; J. L. Linsky, we determine that 77% of the predictions made by the kinematic model are confirmed by observed components in the new lines of sight and identify 10 LISM features among eight sight lines that do not match the model. In addition to testing and refining three-dimensional kinematic models of the LISM, the substantially increased number of integrated Mg II emission fluxes presented here will be valuable for predicting the far-ultraviolet and extreme-ultraviolet emission for these stars. We also find that six stars in our sample show possible circumstellar disk absorption, including 47 UMa, for which a disk has not yet been confirmed.

Keywords: Interstellar absorption, Interstellar clouds, Interstellar medium
A Spectroastrometric Study of the Low-velocity Wind from DG Tau A. We obtained high-spectral resolution spectra (Δv ∼ 2.5 km s‑1) for DG Tau A from 4800 Å to 7500 Å using Subaru High Dispersion Spectrograph for the first time. The low-velocity components (LVCs, ∣v∣ &lt; 100 km s‑1) were observed in the [O I] 5577, 6300, 6364 Å, [S II] 6716, 6731 Å lines. The offset position spectra observed in a component within the LVC velocity range between –16 km s‑1 and –41 km s‑1, namely, LVC-M, show a "negative velocity gradient," supporting the presence of a wide-angled wind. With 12–70 au wind lengths measured using spectroastrometry, we estimate a lower limit to the wind mass-loss rate of ∼10‑8 M⊙ yr‑1. In addition to the LVCs, we identify two high-velocity components (HVCs, ∣v∣ &gt; 100 km s‑1) associated with the collimated jet in 26 lines ([N I], [N II], [O I], [O II], [O III], [S II], [Ca II], [Fe II], Hα, Hβ, He I). The one with a clear spatial offset from the star (ne ∼ 104 cm‑3, HVC1) is associated with an internal shock surface of the jet, while the other at the base (ne ∼ 106 cm‑3, HVC2) may be a stationary shock component. We find that the observed line profiles and the spatial scales of the LVC emission do not agree with the existing predictions for photoevaporative or magnetohydrodynamical disk winds. These could be explained by the X-wind model, but synthetic observations are required for detailed comparisons. *This research is based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. We are honored and grateful for the opportunity to observe the Universe from Maunakea, which has cultural, historical, and natural significance in Hawaii.

Keywords: High resolution spectroscopy, Stellar winds, Stellar jets, Classical T Tauri stars
Limited Hysteresis in the Atmospheric Dynamics of Hot Jupiters. Over the past two decades, a coherent picture has emerged of the atmospheric dynamics of hot Jupiters from a combination of three-dimensional general circulation models and astronomical observations. This paradigm consists of hot Jupiters being spin-synchronized due to their close-in orbit, with a resulting large day-to-night irradiation gradient driving a day-to-night temperature contrast. This day-to-night temperature contrast in turn raises day-to-night pressure gradients that are balanced by a circulation with wind speeds on the order of km s‑1. The dominant feature of this circulation is a super-rotating equatorial jet, maintained by eddy-mean flow interactions that pump momentum into the jet. In this work, I explore the dependence of this circulation paradigm on the initial thermal and dynamical conditions in atmospheric circulation models of hot Jupiters. To do so, I conduct MITgcm simulations of the atmospheric circulation of hot Jupiters with both varying initial wind directions and initial temperature profiles. I find that the results are insensitive to the initial conditions, implying that the current paradigm of hot-Jupiter circulation exhibits at most limited hysteresis. I demonstrate that there is a single characteristic wind speed of hot Jupiters for given planetary and atmospheric parameters using an idealized scaling theory, and discuss implications for the interpretation of hot Jupiter observations.

Keywords: Exoplanet atmospheric dynamics, Hot Jupiters, Planetary atmospheres, Exoplanet atmospheres
Cosmology and Astrophysics with the Diffuse eRASS1 X-Ray Angular Power Spectrum. The recent tension in the value of the cosmological parameter  , which represents the amplitude of the matter density fluctuations of the Universe, has not been resolved. In this work, we present constraints on S8 with the X-ray angular power spectra of clusters and groups measured with the half-sky map from eROSITA All Sky Survey Data Release 1 (eRASS1). Thanks to the extensive sky coverage of eRASS1, it achieves unprecedented precision compared to previous power spectrum measurements. Using a well-calibrated, physical halo gas model that includes astrophysics of feedback and nonthermal pressure support, we obtain   with 1σ uncertainty that is competitive against other cosmological probes. Our derived S8 value is smaller than the primary cosmic microwave background measurements from Planck, but still consistent to within 1σ. We also obtain constraints on the astrophysics of feedback, nonthermal pressure, equation of state in cluster cores, and gas boundaries in clusters and groups. We discuss how additional X-ray observations, and cosmological surveys in microwave and optical, will further improve the cosmological constraints with the angular power spectrum. Our work demonstrates that the angular power spectrum of clusters and groups is a promising probe of both cosmology and astrophysics.

Keywords: Galaxy clusters, Large-scale structure of the universe, Observational cosmology, Cosmological parameters from large-scale structure, Intracluster medium
Lorentz Invariance Violation from Gamma-Ray Bursts. Lorentz invariance violation (LV) is examined through the time delay between high-energy and low-energy photons in gamma-ray bursts (GRBs). Previous studies determined the LV energy scale as ELV ≃ 3.60 × 1017 GeV using Fermi Gamma-ray Space Telescope (FGST) data. This study updates the time-delay model and reaffirms these findings with new observations. High-energy photons from GRBs at GeV and TeV bands are analyzed, including the 99.3 GeV photon from GRB 221009A (FGST), the 1.07 TeV photon from GRB 190114C (MAGIC), and the 12.2 TeV photon from GRB 221009A (LHAASO). Our analysis, in conjunction with previous data, consistently shows that high-energy photons are emitted earlier than low-energy photons at the source. By evaluating 17 high-energy photons from 10 GRBs observed by FGST, MAGIC, and LHAASO, we estimate the LV energy scale to be ELV ≃ 3.00 × 1017 GeV. The null hypothesis of dispersion-free vacuum E = pc (or, equivalently, the constant light speed vγ = c) is rejected at a significance level of 3.1σ or higher.

Keywords: High energy astrophysics, Gamma-rays, Particle astrophysics, Particle physics
The Qz5 Survey. I. How the H I Mass Density of the Universe Evolves with Cosmic Time. We report that the neutral hydrogen (H I) mass density of the Universe (ρH I) increases with cosmic time since z ∼ 5, peaks at z ∼ 3, and then decreases toward z ∼ 0. This is the first result of Qz5, our spectroscopic survey of 63 quasars at z ≳ 5 with VLT/X-SHOOTER and Keck/ESI aimed at characterizing intervening H I gas absorbers at z ∼ 5. The main feature of Qz5 is the high resolution (R ∼ 7000─9000) of the spectra, which allows us to (1) accurately detect high column density H I gas absorbers in an increasingly neutral intergalactic medium at z ∼ 5 and (2) determine the reliability of previous ρH I measurements derived with lower resolution spectroscopy. We find five intervening damped Lyα absorbers (DLAs) at z &gt; 4.5, which corresponds to the lowest DLA incidence rate ( ) at z ≳ 2. We also measure the lowest ρH I at z ≳ 2 from our sample of DLAs and subDLAs, corresponding to ρH I   Mpc−3 at z ∼ 5. Taking into account our measurements at z ∼ 5 and systematic biases in the DLA detection rate at lower spectral resolutions, we conclude that ρH I doubles from z ∼ 5 to z ∼ 3. From these results emerges a qualitative agreement between how the cosmic densities of H I gas mass, molecular gas mass, and star formation rate build up with cosmic time.

Keywords: Cosmology, Intergalactic clouds, Quasar absorption line spectroscopy, Intergalactic gas, Damped Lyman-alpha systems, Neutral hydrogen clouds, Circumgalactic medium, Observational cosmology, Intergalactic medium, Extragalactic astronomy, Galaxies
RUBIES Reveals a Massive Quiescent Galaxy at z = 7.3. We report the spectroscopic discovery of a massive quiescent galaxy at zspec = 7.29 ± 0.01, just ∼700 Myr after the big bang. RUBIES-UDS-QG-z7 was selected from public JWST/NIRCam and MIRI imaging from the PRIMER survey and observed with JWST/NIRSpec as part of RUBIES. The NIRSpec/PRISM spectrum reveals one of the strongest Balmer breaks observed thus far at z &gt; 6, with no emission lines but tentative Balmer and Ca absorption features, as well as a Lyman break. Simultaneous modeling of the NIRSpec/PRISM spectrum and NIRCam and MIRI photometry (spanning 0.9–18 μm) shows that the galaxy formed a stellar mass of log  before z ∼ 8 and ceased forming stars 50–100 Myr prior to the time of observation, resulting in  . We measure a small physical size of  , which implies a high stellar-mass surface density within the effective radius of  , comparable to the highest densities measured in quiescent galaxies at z ∼ 2–5. The 3D stellar-mass density profile of RUBIES-UDS-QG-z7 is remarkably similar to the central densities of local massive ellipticals, suggesting that at least some of their cores may have already been in place at z &gt; 7. The discovery of RUBIES-UDS-QG-z7 has strong implications for galaxy formation models: the estimated number density of quiescent galaxies at z ∼ 7 is &gt;100 × larger than predicted from any model to date, indicating that quiescent galaxies have formed earlier than previously expected.

Keywords: Quenched galaxies, Galaxy properties, James Webb Space Telescope, Galaxy photometry, Galaxy evolution, Spectral energy distribution, Galaxy quenching, Galaxy spectroscopy, Post-starburst galaxies
Photon-likeness of Hadron Showers and Impact of Lorentz Boosting. We examine the probability of proton-induced air showers at E &gt; 10 EeV being misidentified as photon induced due to neutral pions receiving a major part of the primary energy in the first interaction, thereby enhancing the electromagnetic shower component by their π0 → γγ decay. Using CORSIKA simulations, we demonstrate the relevance of this effect at EeV energies. However, the probability for such photon-like events drops down strongly at the highest energies due to the increasing probability of Lorentz-boosted π0's suffering hadronic interactions before decay. Different hadronic interaction models suggest that photon-like hadronic events may be observed at current ultra-high-energy cosmic-ray observatories. A quantitative comparison of the observed number of background events found in recent photon searches published by the Pierre Auger Collaboration suggests that the hypothesis of upward fluctuations in π0 production alone is insufficient to explain the data. Detailed detector simulations will be needed to quantify the significance of these differences.

Keywords: Special relativity, Cosmic ray showers, Astrophysical processes, Gamma-rays, Cosmic rays
Strong Amplitude Modulation of Hard-band X-Ray Quasiperiodic Oscillation with Soft-band Flux in RE J1034+396. The X-ray quasiperiodic oscillation (QPO) is a remarkable form of variability in systems of compact object accretion. RE J1034+396, harboring the most significant X-ray QPO in active galactic nuclei (AGNs), is the most noteworthy source for in-depth analysis of AGN X-ray QPO properties. A long-term evolution of its QPO has been observed over the course of the observations. However, the short-term variability of its QPO properties remains unexplored within each observation that has long good time intervals (GTIs). We collect 12 XMM-Newton observations of RE J1034+396 with GTIs longer than 60 ks from publicly available data and conduct a detailed wavelet analysis focusing on the short-time modulation of the QPO. The QPO signals are found to undergo amplitude modulation in both the soft and hard bands, with a typical timescale of 17 ks. The soft flux is significantly higher when the hard QPO is present. They are highly correlated, with an average cross-correlation function (CCF) peak coefficient of 0.61 and a lag of approximately 3 ks. This novel finding provides fresh insights into the potential connection between the components of the corona emitting soft and hard X-ray photons. The CCF lag between the soft flux and the hard QPO evolves across the observations, potentially sharing the same origin as the previously observed interconnected evolution between QPO frequency and time lag.

Keywords: Active galactic nuclei, Galaxy accretion disks, X-ray active galactic nuclei