Sazuna/UAT_keywords huggingface dataset:
Holographic Beam Measurements of the Canadian Hydrogen Intensity Mapping Experiment (CHIME). We present the first results of the holographic beam-mapping program for the Canadian Hydrogen Intensity Mapping Experiment (CHIME). We describe the implementation of a holographic technique as adapted for CHIME, and introduce the processing pipeline which prepares the raw holographic timestreams for analysis of beam features. We use data from six bright sources across the full 400–800 MHz observing band of CHIME to provide measurements of the copolar and cross-polar beam response in both amplitude and phase for all 1024 dual-polarized feeds in the array. In addition, we present comparisons with independent probes of the CHIME beam, which indicate the presence of polarized beam leakage. Holographic measurements of the beam have already been applied in science with CHIME, e.g., in estimating the detection significance of far-sidelobe fast radio bursts, and in validating the beam models used for CHIME's first detections of 21 cm emission (in cross-correlation with measurements of large-scale structure from galaxy surveys and the Lyα forest). Measurements presented in this paper, and future holographic results, will provide a unique data set to characterize the CHIME beam and improve the experiment's prospects for a detection of the baryon acoustic oscillation signal.

Keywords: Calibration, Holographic interferometry
Tracing the Propagation of Shocks in the Equatorial Ring of SN 1987A over Decades with the Hubble Space Telescope. The nearby SN 1987A offers a unique opportunity to investigate the complex shock interaction between the ejecta and circumstellar medium. We track the evolution of the optical hot spots within the equatorial ring (ER) by analyzing 33 Hubble Space Telescope imaging observations between 1994 and 2022. By fitting the ER with an elliptical model, we determine its inclination to be 42.°85 ± 0.°50 with its major axis oriented ‑6.°24 ± 0.°31 from the west. We identify 26 distinct hot spots across the ER, with additional ones emerging over time, particularly on the western side. The hot spots initially show high velocities ranging from 390 to 1660 km s‑1, followed by a deceleration phase around day ∼ 8000. Subsequent velocities vary from 40 to 660 km s‑1. The light curves of the hot spots reach maxima between 7000 and 9000 days, suggesting a connection with the deceleration. Many spots are spatially resolved and show elongation perpendicular to the direction of motion, indicative of a short cooling time. To explain these results, we propose that each hot spot comprises dense substructures embedded in less dense gas. The initial velocities are then phase velocities, where the break occurs when the blast wave leaves the ER, while the late velocities reflect the propagation of radiative shocks in the dense substructures. We estimate that the dense substructures have a volumetric filling factor of  ∼0.3ne/106cm‑3‑2%  and a total mass of  ∼0.24ne/106cm‑3‑1×10‑2M⊙ .

Keywords: Supernova remnants, Shocks, Core-collapse supernovae
The Variability of Persistent Radio Sources of Fast Radio Bursts. Over 700 bright millisecond-duration radio transients, known as fast radio bursts (FRBs), have been identified to date. Nevertheless, the origin of FRBs remains unknown. Two repeating FRBs (FRB 20121102A and FRB 20190520B) have been verified to be associated with persistent radio sources (PRSs), making them the best candidates to study the nature of FRBs. Monitoring the variability in PRSs is essential for understanding their physical nature. We conducted 22 observations of the PRSs linked to FRB 20121102A and FRB 20190520B using the Karl G. Jansky Very Large Array, to study their variability. We have observed significant flux variability for the PRSs of FRB 20121102A and FRB 20190520B, with a confidence level exceeding 99.99%, based on the observations covering the longest timescale recorded to date. The observed variability of the two PRSs exhibits no significant difference in amplitude across both short and long timescales. We found that the radio-derived star formation rates of the two FRB hosts are significantly higher than those measured by the optical H α  emissions, indicating that their host galaxies are highly obscured or most radio emissions are not from star formation processes. The observed timescale of PRS flux evolution constrained the magnetic field of FRB 20121102A with B ∥ ≳ 1 mG and FRB 20190520B with B ∥ ≳ 0.1 mG.

Keywords: Extragalactic radio sources, Burst astrophysics, Radio continuum emission, Radio interferometry, Radio transient sources
A Young Super Star Cluster Powering a Nebula of Retained Massive Star Ejecta. We suggest that "Godzilla" of the lensed Sunburst galaxy (z = 2.37) is a young super star cluster powering a nebula of gravitationally trapped stellar ejecta. Employing Hubble Space Telescope photometry and spectroscopy from the Very Large Telescope (VLT) MUSE and VLT/X-Shooter, we infer the physical and chemical properties of the cluster and nebula, finding that Godzilla is young, 4─6 Myr; massive, 2 × 106 M ⊙ (1000/μ); of stellar metallicity, Z ≃ 0.25 Z ⊙; and has a compact far-UV component of ≲1 pc (1000/μ), where μ is the flux magnification factor. The gas is significantly enriched with N and He, indicating stellar wind material, and has highly elevated O relative to the stellar metallicity, indicating entrainment of core-collapse supernova (CCSN) ejecta. The high density, n e ≃ 107−8 cm−3, implies a highly pressurized intracluster environment. We propose that the pressure results from CCSN-driven supersonic turbulence in warm, self-shielding gas, which has accumulated in the cluster center after runaway radiative cooling and is dense enough to resist removal by CCSNe. The nebula gas shows subsolar C/O, Ne/O, and Si/O, which may reflect the CCSN element yields for initial stellar masses &gt;40 M ⊙. A comparison to element yield synthesis models for young star clusters shows that the gas abundances are consistent with complete retention and mixture of stellar winds and CCSN ejecta until the inferred cluster age. The inferred O and He enhancement may have implications for the formation of multiple stellar populations in globular clusters, as stars formed from this gas would contradict the observed abundances of second-population stars.

Keywords: Stellar populations, Chemical enrichment, Young star clusters, Galaxies
A JWST MIRI MRS View of the η Tel Debris Disk and Its Brown Dwarf Companion. We report JWST Mid-Infrared Instrument (MIRI) Medium Resolution Spectrograph (MRS) observations of the β Pic moving-group member, η Tel A, along with its brown dwarf binary companion, η Tel B. Following point-spread-function subtraction, we recover the spatially resolved flux from the debris disk around η Tel A, along with the position of the companion exterior to the disk. We present a new 5–26 μm epoch of spectroscopy for the disk, in which we discover a 20 μm silicate feature, and the first ever 11–21 μm spectrum of η Tel B, which indicates a bare photosphere. We derive a new epoch of relative astrometry for the companion, extending the baseline of measurements to 25 yr, and find that it is currently located near the apocenter of an eccentric long-period orbit. The companion's orbit is close enough to the disk that it should significantly perturb the planetesimals within it, resulting in a detectable mid-IR pericenter glow and near alignment with the companion. Contrary to expectations, however, we find that the disk appears to be axisymmetric and potentially misaligned with the companion in the MIRI MRS data. We posit that this may be due to the presence of an additional, as-yet-undetected ∼0.7–30 M  J  planet orbiting interior to the disk, with a semimajor axis of ∼3–19 au.

Keywords: Orbits, Brown dwarfs, Debris disks, Circumstellar disks
Probing the Morphology of Polarized Emission Induced by Fluctuation Dynamo Using Minkowski Functionals. The morphology and the characteristic scale of polarized structures provide crucial insights into the mechanisms that drive turbulence and maintain magnetic fields in magneto-ionic plasma. We aim to establish the efficacy of Minkowski functionals as quantitative statistical probes of filamentary morphology of polarized synchrotron emission resulting from fluctuation dynamo action. Using synthetic observations generated from magnetohydrodynamic simulations of fluctuation dynamos with varying driving scales (ℓ f) of turbulence in isothermal, incompressible, and subsonic media, we study the relation between different morphological measures and their connection to fractional polarization (p f). We find that Faraday depolarization at low frequencies gives rise to small-scale polarized structures that have higher filamentarity as compared to the intrinsic structures that are comparable to ℓ f. Above ∼3 GHz, the number of connected polarized structures per unit area (N CC,peak) is related to the mean p f (&lt;p f&gt;) of the emitting region as  &lt;pf&gt;∝NCC,peak‑1/4 , provided the scale of the detectable emitting region is larger than ℓ f. This implies that N CC,peak represents the number of turbulent cells projected on the plane of the sky and can be directly used to infer ℓ f via the relation  ℓf∝NCC,peak‑1/2 . An estimate of ℓ f thus directly allows for pinning down the turbulence-driving mechanism in astrophysical systems. While the simulated conditions are mostly prevalent in the intracluster medium of galaxy clusters, the qualitative morphological features are also applicable in the context of interstellar medium in galaxies.

Keywords: Galaxy clusters, Magnetohydrodynamics, Radio astronomy, Spectropolarimetry, Intracluster medium, Magnetic fields, Magnetohydrodynamical simulations
The SPT-Chandra BCG Spectroscopic Survey. I. Evolution of the Entropy Threshold for ICM Cooling and AGN Feedback in Galaxy Clusters over the Last 10 Gyr. We present a multiwavelength study of the brightest cluster galaxies (BCGs) in a sample of the 95 most massive galaxy clusters selected from the South Pole Telescope Sunyaev─Zeldovich (SZ) survey. Our sample spans a redshift range of 0.3 &lt; z &lt; 1.7, and is complete with optical spectroscopy from various ground-based observatories, as well as ground and space-based imaging from optical, X-ray, and radio wave bands. At z ∼ 0, previous studies have shown a strong correlation between the presence of a low-entropy cool core and the presence of both star formation and radio-loud active galactic nuclei in the central BCG. We show for the first time that the central entropy threshold for triggering star formation, which is universally seen in nearby systems, persists out to z ∼ 1, with only marginal (∼1σ) evidence for evolution in the threshold entropy value itself. In contrast, we do not find a similar high-z analog for an entropy threshold for feedback, but instead measure a strong evolution in the fraction of radio-loud BCGs in high-entropy cores, decreasing with increasing redshift. This could imply that the cooling-feedback loop was not as tight in the past, or that some other fuel source like mergers are fueling the radio sources more often with increasing redshift, making the radio luminosity an increasingly unreliable proxy for radio jet power. We also find that our SZ-based sample is missing a small (∼4%) population of the most luminous radio sources (ν L  ν  &gt; 1042 erg s−1), likely due to radio contamination suppressing the SZ signal with which these clusters are detected.

Keywords: Cooling flows, High-redshift galaxy clusters, Star formation, Active galactic nuclei, Intracluster medium
Luminosity Function of Collapsar Gamma-Ray Bursts: The Progenitor of Long Gamma-Ray Bursts Is Not Singular. Gamma-ray bursts (GRBs) are powerful probes of the high-redshift Universe. However, the proportion of collapsar GRBs among long GRBs and their event rate relative to the star formation rate (SFR) remain contentious issues. We assume that long GRBs with z ≥ 2 are all collapsar GRBs and construct the luminosity function using a high-redshift sample from the Swift satellite spanning 2004 to 2019. We model the luminosity function with a broken power-law form and consider three scenarios: no evolution, luminosity evolution, and density evolution. Our results are as follows: (1) The no-evolution model can be ruled out. (2) The fitting results indicate that to adequately explain the observations, a significant redshift evolution in either luminosity (evolution index  δ=1.54‑0.22+0.21 ) or density ( δ=2.09‑0.26+0.29 ) is required. This excludes the possibility that the evolution of long GRBs with redshift is due to contamination from noncollapsar GRBs. (3) The luminosity evolution model predicts that the number of collapsar GRBs with z &lt; 2 and P ≥ 1 ph cm‑2 s‑1 is 138.6, accounting for 82.5% of the observed long GRBs with z &lt; 2 and P ≥ 1 ph cm‑2 s‑1. The density evolution model predicts that the number of collapsar GRBs with z &lt; 2 and P ≥ 1 ph cm‑2 s‑1 is 80.2, accounting for 47.7% of the observation. Regardless of the model, a substantial portion of the long GRBs are not collapsar GRBs.

Keywords: Luminosity function, Gamma-ray bursts, Star formation
Temporal Evolution of the Radial Distribution of Milky Way Satellite Galaxies. The Milky Way (MW) is surrounded by dozens of satellite galaxies, with six-dimensional (6D) phase-space information measured for over 80% of this population. The spatial distribution of these satellites is an essential probe of galaxy formation and for mapping the MW's underlying dark matter distribution. Using measured 6D phase-space information of known MW satellites, we calculate orbital histories in a joint MW+LMC potential, including the gravitational influence of the LMC on all satellites and on the MW's center of mass, and dynamical friction owing to both galaxies, to investigate the evolution of the MW's cumulative radial profile. We conclude that radial profiles become more concentrated over time when we consider the LMC's gravitational influence and the group infall of LMC-associated satellites. The MW's radial distribution is consistently more concentrated at the present day and 1 and 2 Gyr ago compared to recent surveys of nearby MW-like systems. Compared to MW-mass hosts in cosmological, zoom-in simulations, we find the MW's radial profile is also more concentrated than those of simulated counterparts; however, some overlap exists between simulation results and our analysis of the MW's satellite distribution 2 Gyr ago, pre-LMC infall. Finally, we posit that radial profiles of simulated MW-mass analogs also hosting an LMC companion are likely to evolve similarly to our results, such that the accretion of a massive satellite along with its satellites will lead to a more concentrated radial profile as the massive satellite advances toward its host galaxy.

Keywords: Large Magellanic Cloud, Dwarf galaxies, Galaxy evolution, Milky Way Galaxy
Modeling the X-Ray Emission of the Boomerang Nebula and Implication for Its Potential Ultrahigh-energy Gamma-Ray Emission. The Boomerang Nebula is a bright radio and X-ray pulsar wind nebula (PWN) powered by an energetic pulsar, PSR J2229+6114. It is spatially coincident with one of the brightest ultrahigh-energy (UHE; ≥100 TeV) gamma-ray sources, LHAASO J2226+6057. While X-ray observations have provided radial profiles for both the intensity and photon index of the nebula, previous theoretical studies have not reached an agreement on their physical interpretation, which also leads to different anticipation of the UHE emission from the nebula. In this work, we model its X-ray emission with a dynamical evolution model of PWN, considering both convective and diffusive transport of electrons. On the premise of fitting the X-ray intensity and photon index profiles, we find that the magnetic field within the Boomerang Nebula is weak (∼10 μG in the core region and diminishing to 1 μG at the periphery), which therefore implies a significant contribution to the UHE gamma-ray emission by the inverse Compton (IC) radiation of injected electron/positron pairs. Depending on the particle transport mechanism, the UHE gamma-ray flux contributed by the Boomerang Nebula via the IC radiation may constitute about 10%─50% of the flux of LHAASO J2226+6057 at 100 TeV and up to 30% at 500 TeV. Finally, we compare our results with previous studies and discuss potential hadronic UHE emission from the PWN. In our modeling, most of the spindown luminosity of the pulsar may be transformed into thermal particles or relativistic protons.

Keywords: Gamma-ray sources, X-ray sources, Pulsar wind nebulae
Quasi-linear Analysis of Proton-cyclotron Instability. The proton-cyclotron (PC) instability operates in various space plasma environments. In the literature, the so-called velocity moment-based quasi-linear theory is employed to investigate the physical process of PC instability that takes place after the onset of early linear exponential growth. In this method, the proton velocity distribution function (VDF) is assumed to maintain a bi-Maxwellian form for all time, which substantially simplifies the analysis, but its validity has not been rigorously examined by comparing against the actual solution of the kinetic equation. The present paper relaxes the assumption of the velocity moment-based quasi-linear theory by actually solving for the velocity space diffusion equation under the assumption of separable perpendicular and parallel VDFs, and upon comparison with the simplified velocity moment theory, it demonstrates that the simplified method is largely valid, despite the fact that the method slightly overemphasizes the relaxation of temperature anisotropy when the system is close to the marginally stable state. The overall validation is further confirmed with the results of particle-in-cell and hybrid-code simulations. The present paper thus provides a justification for making use of the velocity moment-based quasi-linear theory as an efficient first-cut theoretical tool for the PC instability.

Keywords: The Sun, Solar wind, Heliosphere, Plasma physics
Neutrino Constraints and Detection Prospects from Gamma-Ray Bursts with Different Jet Compositions. The prompt emission mechanism of gamma-ray bursts (GRBs) is a long-standing open question, and GRBs have been considered as potential sources of high-energy neutrinos. Despite many years of search for the neutrino events associated with GRBs from IceCube, there were no results. However, the absence of search results for neutrinos provides a unique opportunity to constrain the parameter space of GRB jet models. In this paper, we chose four peculiar GRBs with two different types of jet composition to investigate neutrino emission. It is found that only GRB 211211A could be well constrained within the dissipative photosphere model. By adopting the specific parameters of the photosphere, one can obtain ɛ  p /ɛ  e  &lt; 8 for f  p  &gt; 0.2 from GRB 211211A. For the Internal-collision-induced Magnetic Reconnection and Turbulence (ICMART) model, we can effectively constrain neither GRB 230307A nor GRB 080916C. Moreover, we also investigate the detection prospects of high-energy neutrinos from GRBs and find that it is difficult to detect at least one high-energy neutrino associated with GRBs from the ICMART model even during the IceCube-Gen2 operation. For the GRB 211211A-like events, it is possible to detect at least one neutrino coincident with the gravitational wave during the IceCube-Gen2 operation, if such an event originated from mergers of compact stars within the photosphere dissipation.

Keywords: Neutrino astronomy, Gamma-ray bursts
Near-infrared Spectroscopy of the Sun and Solar Analog Star HD 76151: Compiling an Extensive Line List in the Y, J, H, and K Bands. Determining the physical nature of a star requires precise knowledge of its stellar atmospheric parameters, including effective temperature, surface gravity, and metallicity. This study presents a new atomic line list covering a broad spectral range (1─2.5 μm; YJHK bands) for iron (Fe) and α-elements (Ca, Mg, Ti, Si) to improve stellar parameter determination using near-infrared (NIR) spectroscopy. We highlight the limitations of existing line lists, stemming primarily from inconsistencies in oscillator strengths for ionized iron lines within the Apache Point Observatory Galactic Evolution Experiment DR17. The line list was validated using the high-resolution and high-quality disk-center NIR spectra of the Sun and its solar analog HD 76151. As a result of the spectroscopic analyses, the effective temperature of HD 76151 was calculated as 5790 ± 170 K, surface gravity as 4.35 ± 0.18 cgs, metal abundance as 0.24 ± 0.09 dex, and microturbulence velocity of  0.30−0.3+0.5  km s−1 by combining the optical and NIR line lists. A comparison of the model atmospheric parameters calculated for HD 76151 with the PARSEC isochrones resulted in a stellar mass of  1.053−0.068+0.056M⊙ , radius  1.125−0.011+0.035R⊙ , and an age of  5.5−2.1+2.5  Gyr. For the first time, kinematic and dynamical orbital analyses of HD 76151 using a combination of Gaia astrometric and spectroscopic data showed that the star was born in a metal-rich region within the solar circle and is a member of the thin disk population. Thus, the slightly metal-rich nature of the star, as reflected in its spectroscopic analysis, was confirmed by dynamical orbital analysis.

Keywords: Spectral line lists, Infrared spectroscopy, Stellar kinematics, Stellar abundances, The Sun, Spectral line identification, Atomic data, Solar abundances
Velocity-resolved Reverberation Mapping of Changing-look Active Galactic Nucleus NGC 4151 during Outburst Stage. II. Results of Four Seasons of Observation. We present the results of a four-year velocity-resolved reverberation mapping (RM) campaign of the changing-look active galactic nucleus (CL-AGN) NGC 4151 during its outburst phase. By measuring the time lags of the Hα, Hβ, Hγ, He I, and He II emission lines, we confirm a stratified broad-line region (BLR) structure that aligns with predictions from photoionization models. Intriguingly, we observed an "anti-breathing" phenomenon, where the lags of broad emission lines decreased with increasing luminosity, contrary to the typical expectation. This anomaly may be attributed to the influence of the ultraviolet-optical lag or nonvirialized motions in the BLR gas. Velocity-resolved RM and ionization mapping analyses revealed rapid and significant changes in the BLR geometry and kinematics on timescales of less than a year, which cannot be interpreted by any single mechanism, such as an inhomogeneous BLR, variations in radiation pressure, or changes in the illuminated ionizing field. Additionally, the Hβ lags of NGC 4151 and other CL-AGNs agree with the radius–luminosity relationship established for AGNs with low accretion rates, implying that the CL phenomenon is more likely driven by intrinsic changes in the accretion rate rather than obscuration. These findings provide new insights into the complex internal processes of CL-AGNs and highlight the importance of long-term, multiline RM for understanding BLR structures, geometry, and kinematics.

Keywords: Supermassive black holes, Reverberation mapping, Seyfert galaxies, Active galactic nuclei, Time domain astronomy