Sazuna/UAT_keywords huggingface dataset:
Clumpy, Dense Gas in the Outflow of NGC 1266. Outflows are one of the most spectacular mechanisms through which active galactic nuclei (AGN) impact their host galaxy, though the role of AGN-driven outflows in global star formation regulation across the galaxy population is unclear. NGC 1266 is an excellent case study for investigating outflows and star formation quenching because it is a nearby (D ∼ 30 Mpc) AGN host galaxy with an outflow driving shocks through the interstellar medium (ISM) and has recently quenched its star formation outside the nucleus. While previous works have studied the molecular outflow from its CO emission, to fully characterize the impact the outflow has on the ISM observations probing the dense, cold gas are necessary. Our Atacama Large Millimeter/submillimeter Array Cycle 0 observations do not detect a molecular outflow in 13CO(2─1) and yield a lower limit of 12CO/13CO ≥ 250, suggesting a highly optically thin CO outflow with low 13CO abundance. In contrast, we detect substantial HCN(1─0) emission in the outflow, with an HCN(1─0)/12CO(1─0) ratio of 0.09, consistent with global measurements of many star-forming galaxies and luminous infrared galaxies. We conclude that the CO emission traces a diffuse component of the molecular gas with a low optical depth, whereas the HCN(1─0) traces dense clumps of gas entrained in the outflow. We measure an upper limit molecular outflow rate of &lt;85 M⊙ yr─1. Assuming the ongoing nuclear star formation and outflow continue at the same rates, NGC 1266 will deplete its gas reservoir in 450 Myr or longer, indicating that relatively low-level AGN feedback is capable of gradually expelling the molecular gas reservoir after a rapid quenching event.

Keywords: Galaxy quenching, Molecular gas, Active galactic nuclei, Post-starburst galaxies
X-Ray Polarization and Spectral Variations in an Extreme High-synchrotron-peaked Blazar 1ES 1101─232. We present the first X-ray polarimetric observation of the extreme high-synchrotron-peaked blazar 1ES 1101─232, conducted by the Imaging X-ray Polarimetry Explorer (IXPE). The data analysis incorporates simultaneous and quasi-simultaneous observations from the Swift X-Ray Telescope and NuSTAR. Our results reveal a significant detection of X-ray polarization in the 2─6 keV band at a confidence level (CL) of 6.6σ, with a polarization degree of ΠX = 17.9% ± 2.7% and an electric vector position angle (EVPA) of ψX = 10 .° 0 ± 4 .° 4. An even higher polarization degree of ΠX = 38.9% ± 9.1% with an EVPA of ψX = 13 .° 9 ± 6 .° 7 is observed within a narrower time interval, at a CL of 4.3σ. During the IXPE observational campaign, the X-ray spectrum of 1ES 1101─232 exhibits a clear soft-to-hard spectral evolution in the 0.3─10 keV band, although no significant flux variability is detected. Additionally, a clockwise hysteresis loop is identified in the flux─photon index plane. These findings collectively indicate that the X-ray emission from 1ES 1101─232 originates in a region characterized by a well-ordered magnetic field through synchrotron radiation.

Keywords: Spectropolarimetry, Blazars, Non-thermal radiation sources, X-ray active galactic nuclei, Polarimetry
Spiral Structure Properties, Dynamics, and Evolution in Milky Way─mass Galaxy Simulations. The structure of spiral galaxies is essential to understanding the dynamics and evolution of disk galaxies; however, the precise nature of spiral arms remains uncertain. Two challenges in understanding the mechanisms driving spirals are how galactic environment impacts spiral morphology and how they evolve over time. We present a catalog characterizing the properties, dynamics, and evolution of m = 2 spiral structure in 10 Milky Way─mass galaxies from the FIRE-2 cosmological zoom-in simulations. Consistent with previous literature, we find that FIRE-2 spirals are transient, recurring features simultaneously present in the disk at varying pattern speeds (Ωp) that broadly decrease with radius. These spirals persist on gigayear timescales (mean duration of 1.90 Gyr), but fluctuate in amplitude on timescales of hundreds of millions of years. Tidal interactions and bar episodes impact the resulting m = 2 spiral structure: strong satellite interactions generally produce shorter-lived, stronger spirals with larger radial extent, and bars can increase Ωp. Galactic environment influences spiral structure, in which kinematically colder disks can support longer-lived, stronger spirals. The properties of identified spirals in FIRE-2 vary widely in radial extent (0.3─10.8 kpc), duration (1.00─6.00 Gyr), and amplitude (a2,max = 0.018─0.192). We find the presence of spirals in all age populations, suggesting these are density-wave-driven features. This work represents the first time that spiral structure has been cataloged in this manner in cosmological simulations; the catalog can be leveraged with current and forthcoming observational surveys, enabling systematic comparisons to further our understanding of galaxy evolution.

Keywords: Hydrodynamical simulations, Galaxy dynamics, Galaxy evolution, Disk galaxies
The Discovery of Little Red Dots in the Local Universe: Signatures of Cool Gas Envelopes. JWST observations have revealed a population of high-redshift "little red dots" (LRDs) that challenge conventional active galactic nucleus (AGN) models. We report the discovery of three local LRDs at z = 0.1─0.2, initially selected from the Sloan Digital Sky Survey database, with follow-up optical/near-IR spectroscopy and photometry. They exhibit properties fully consistent with those of high-redshift LRDs, including broad hydrogen and helium emission lines, compact morphologies, V-shaped UV-optical spectral energy distribution, declining near-IR continua, and no significant variability. Two sources were targeted but not detected in X-rays with statistical significance. All three sources show blue-shifted He I absorption, while two exhibit Hα and Na D absorption lines. We detect full Balmer and Paschen line series in all three objects, along with abundant narrow [Fe II] emission in two. The emission-line analyses suggest narrow lines originate from AGN-powered, metal-poor regions with minimal dust; broad lines come from inner regions with exceptionally high density or atypical dust properties; and [Fe II] emission arises from dense gas between broad- and narrow-line regions. One of our objects, J1025+1402 (nicknamed "The Egg"), shows extremely high equivalent width Na D, K I, and Ca II triplet absorption lines, along with other potential low-ionization absorption features, suggesting the presence of a cool (∼5000 K), metal-enriched gas envelope. The optical/near-IR continua of these LRDs are also consistent with theoretical models featuring an atmosphere around black holes (BHs). The Wide-field Infrared Survey Explorer─detected IR emission is consistent with weak dust emission of T ∼ 102─103 K. We propose a conceptual model consisting of a largely thermalized cool-gas envelope surrounding the central BH and an extended emission-line region with high-density outflowing gas to explain the observed properties of these local LRDs.

Keywords: High-redshift galaxies, Active galactic nuclei, Black holes
A Comparison of One-dimensional and Three-dimensional Exoplanet Atmosphere Model Grids: ScCHIMERA and the SPARC/MiTgcm. Inferring the properties of transiting exoplanet atmospheres relies on comparing models to spectroscopic observations. Atmosphere models, however, make a range of assumptions, from one-dimensional (1D, varying with altitude) radiative-convective equilibrium (RCE) to three-dimensional (3D) global circulation models (GCMs). The goal of this investigation is to determine the causes of differences in dayside thermal emission spectra resulting from 3D-GCMs (using SPARC/MITgcm) and 1D-RCE models (using ScCHIMERA). We conduct a one-to-one comparison of 1D-RCE models and 3D-GCMs with the same outgoing bolometric thermal flux over a grid of equilibrium temperatures, gravities, metallicities, and rotation periods. Each 1D-RCE model assumes heat redistribution in the planet's atmosphere consistent with that in the corresponding 3D-GCM's photosphere. Comparing corresponding models, the dayside average pressure─temperature (or PT) structures can be broken into four vertical regions, each influencing wavelength-dependent differences in their spectra. Furthermore, the dayside average 3D-GCM PTs for planets with Teq = 1400 K exhibit a temperature inversion, whereas corresponding 1D-RCE models do not. We find that spectral differences between 1D-RCE models and 3D-GCMs with the same parameters decrease for hotter planets because the spectral shapes more closely resemble blackbodies. To a lesser extent, spectral differences increase for planets with longer rotation periods because of smaller day─night temperature contrasts in the photosphere. Finally, we compare spectral differences to realistic observational uncertainties from JWST with the NIRISS SOSS, NIRSpec G395H, and MIRI long-resolution spectroscopy instrument modes. We find that 1D-RCE models and 3D-GCMs with the same parameters can produce dayside spectral differences larger than JWST's uncertainty, potentially biasing data─model inferences.

Keywords: James Webb Space Telescope, Astronomical models, Exoplanet atmospheres
Accretion History of AGNs: A Multiwavelength Comparison of X-Ray- and Infrared-selected AGNs. Identifying active galactic nuclei (AGNs) using only one wavelength region may miss AGNs with characteristics unfavorable for the identification method, which introduces bias in the sample. To better understand these selection effects, we compare the multiwavelength properties of 2584 X-ray- and IR-selected AGNs at z &lt; 3 in the COSMOS field. The X-ray-selected sample consists of the 2219 AGNs with intrinsic 0.5─10 keV X-ray luminosity greater than 1043 erg s−1; the 993 IR-selected AGNs are identified by their high-contrast, power-law IR colors using Spitzer/IRAC observations. We find that both selection methods miss a significant fraction of AGNs, as only 24.3% of AGNs (628 out of the total of 2584 AGNs) are recovered by both selection criteria. X-ray selection can capture the most diverse range of multiwavelength spectral emission features, while IRAC selection is biased against AGNs with a steeply decreasing power flux (λFλ) between 1 and 6 μm. For AGNs with X-ray detections, IRAC-selected sources are 2.5× more X-ray luminous than AGNs not identified by their IR colors. IRAC-selected AGNs without detectable X-rays are obscured, as they have a mean X-ray correction factor  log(LX,obs/LX,int)=  −1.4; 28.5%─42.2% of these AGNs are Compton-thick (according to estimated column densities). Only 1.4% of X-ray-selected AGNs are Compton-thick. The AGN selection technique used significantly impacts the overall characteristics of the resulting AGN sample.

Keywords: AGN host galaxies, X-ray astronomy, Quasars, Two-color diagrams, Infrared astronomy, Active galactic nuclei, Spectral energy distribution, X-ray active galactic nuclei
The GeV γ-Ray Emission from the Pulsar Wind Nebula DA 495. We present an analysis of GeV γ-ray emission from the region of the pulsar wind nebula (PWN) DA 495, using 17 yr of PASS 8 data from the Fermi Large Area Telescope. In this region, we identify two point sources with markedly different spectra in the GeV band: one exhibits a soft γ-ray spectrum with an index of 3.26 ± 0.21, while the other shows a hard spectrum with an index of 1.54 ± 0.45 that aligns smoothly with the TeV spectrum of VER J2016+371, supporting its identification as the GeV counterpart of this TeV source. Given the difficulties in interpreting the entire system with a standard PWN model, we adopt a composite scenario in which a supernova remnant (SNR) shock is incorporated alongside the PWN to account for the multicomponent γ-ray emission. The soft GeV component is attributed to hadronic interactions between the SNR shock and the ambient gas. In contrast, VER J2016+371 with the hard GeV spectrum is well explained by a leptonic PWN model, where the multiwavelength data can be reproduced by a broken power-law electron distribution with parameters consistent with those of typical γ-ray PWNs. The compact X-ray emission is interpreted as arising from a separate population of electrons, described by a power-law energy distribution in a region of relatively high magnetic field strength. Deeper multiwavelength observations aimed at detecting the putative SNR shock, as well as future TeV observations with LHAASO and the Cherenkov Telescope Array, will be essential for clarifying the nature of the γ-ray emission and the overall structure of DA 495.

Keywords: Supernova remnants, Gamma-ray astronomy, Gamma-ray sources, Pulsar wind nebulae
First Results from the PanRadio Gamma-Ray Burst Collaboration: The 400-day Afterglow of GRB 230815A. We introduce the PanRadio Gamma-ray Burst (GRB) program carried out on the Australia Telescope Compact Array: a systematic, multiyear, radio survey of all southern Swift GRB events, comprehensively following the multifrequency evolution of their afterglows from within an hour to years postburst. We present the results of the 400-day observing campaign following the afterglow of the long-duration (collapsar) GRB 230815A—the first one detected through this program. Typically, GRB 230815A would not otherwise receive traditional radio follow-up, given it has no known redshift and lacks comprehensive multiwavelength follow-up, due to its high line-of-sight extinction with AV = 2.3. We found its early X-ray jet break at ∼0.1 days postburst to be at odds with the evolution of the multifrequency radio light curves that were traced over an unusually long duration of 400 days. The radio light curves approximately evolved (with minor deviations) according to the standard self-similar expansion for a relativistic blast wave in a homogeneous environment prior to the jet break, showing no evidence for evolutions of the microphysical parameters describing the electron acceleration processes. We reconcile these features by proposing a two-component jet: the early X-ray break originates from a narrow component with a half-opening angle of ∼2 .° 1, while the evolution of the radio afterglow stems from a wider component with a half-opening angle of ⪆35°. The PanRadio GRB program will establish a sample of comprehensively followed GRBs, where a rigorous inspection of their microphysical and dynamical parameters can be performed, thereby revealing the diversity of features in their outflows and environments.

Keywords: Gamma-ray bursts, Time domain astronomy
Circumplanetary Disk Candidate in the Disk of HD 163296 Traced by Localized Emission from Simple Organics. Atacama Large Millimeter/submillimeter Array observations suggest that the disk of HD 163296 is being actively shaped by embedded yet unseen protoplanets, as indicated by numerous gas and dust substructures consistent with planet─disk interaction models. We report the first detection of simple organic molecules, HCN and C2H, tracing a candidate circumplanetary disk (CPD) in the HD 163296 system, located at an orbital radius of R = 88 ± 7 au and azimuth ϕ = 46∘ ± 3∘ (or  R=0.″75 , PA = 350∘ in projected sky coordinates), and originating near the midplane of the circumstellar disk. The signature is localized but spectrally resolved, and it overlaps with a previously reported planet candidate, P94, identified through kinematic perturbations traced by CO lines. We propose a scenario in which the observed chemical anomalies arise from increased heating driven by the forming planet and ongoing accretion through its CPD, facilitating the thermal desorption of species that would otherwise remain frozen out in the disk midplane, and potentially triggering the activation barriers of chemical reactions that lead to enhanced molecular production. Based on a first-order dynamical analysis of the HCN spectrum from the CPD—isolated with a 7σ significance—we infer an upper limit on the planet mass of 1.8MJup, consistent with predictions from CO kinematics and constraints from direct imaging studies. By comparing the CPD sizes derived from our models with theoretical expectations where the CPD radius corresponds to roughly one-third of the planet's Hill radius, we favor CPD gas temperatures T &gt; 150 K, planet masses Mp &lt; 1.0MJup, and CPD radii RCPD &lt; 2 au.

Keywords: Exoplanet detection methods, Planetary-disk interactions, Protoplanetary disks, Astrochemistry
Cosmogenic Origin of KM3-230213A: Delayed Gamma-Ray Emission from a Cosmic-Ray Transient. The highest-energy cosmic neutrino detected by the ARCA detector of KM3NeT has reignited the quest to pinpoint the sources of ultrahigh-energy cosmic rays (UHECRs; E ≳ 0.1 EeV). By uncovering the associated multimessenger signals, we investigate the origin of the 220 PeV νμ event KM3-230213A from an unknown transient that accelerated cosmic rays to ∼10 EeV. Unlike an astrophysical origin, where the νμ is produced inside the source, here we consider UHECR protons that escape the source interact with the cosmic background radiation, producing a PeV─EeV cosmogenic neutrino spectrum. The secondary e± and γ-rays initiate an electromagnetic cascade, resulting in a cosmogenic γ-ray spectrum. The latter peaks at a delayed time of ≳104 yr compared to the light travel time from the transient to observer, due to deflection of charged particles in the extragalactic magnetic field (EGMF). Our results shed light on the nature of the UHECR source for the νμ event and provide crucial insights into the detection of multi-TeV γ-rays of cosmogenic origin from similar past cosmological transients. Using the γ-ray sensitivity of currently operating and next-generation imaging atmospheric Cherenkov telescopes, the flux and time-delay distribution can constrain the source distance. We further show that the detection of such a γ-ray signal above the background depends on the EGMF strength. Together with the nondetection of coincident spatial or temporal photon counterparts at the current epoch, this detection is the first compelling candidate for a sub-EeV cosmogenic neutrino.

Keywords: High energy astrophysics, Neutrino astronomy, Transient sources, Cosmic ray sources, Gamma-rays, Ultra-high-energy cosmic radiation
JWST Spectroscopy of GRB 250702B: An Extremely Rare and Exceptionally Energetic Burst in a Dusty, Massive Galaxy at z = 1.036. We present follow-up observations of the day-long, repeating gamma-ray burst (GRB) GRB 250702B with the Near Infrared Spectrograph on board the James Webb Space Telescope. Through the identification of narrow hydrogen emission lines at a consistent redshift of z = 1.036 ± 0.004, we calibrate the distance scale, and therefore the energetics, of this unique extragalactic transient. At this distance, the resulting γ-ray energy release is at least Eγ,iso = 2.2 × 1054 erg. We find no evidence for ongoing transient emission at the GRB position and exclude any accompanying supernova (SN) with a luminosity comparable to the Type Ic broad-line SN 2023lcr, though we are unable to rule out a fainter SN counterpart owing to high extinction. The inferred rate of such events, assuming at most one in the lifetime of Fermi, suggests that such bursts are very rare, with volumetric rates over 1000 times lower than normal high-luminosity long GRBs and &gt;105 times lower than core-collapse SNe, when corrected for beaming. Furthermore, we find that the host galaxy is unique among GRB host galaxies and extremely rare in the general galaxy population, being extremely large and dusty and with high stellar mass. The identification of such an exotic GRB in such an unusual galaxy raises the possibility that the environment was important in the progenitor channel creating GRB 250702B.

Keywords: Galaxies, Gamma-ray bursts, High energy astrophysics
A Spatial Gap in the Sky Distribution of Fast Radio Burst Detections Coinciding with Galactic Plasma Overdensities. We analyze the positional and morphological properties of about 3600 unique fast radio burst (FRB) sources reported in the second FRB catalog generated by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. We find a two-dimensional dependence of FRB detections on sky position and identify a significant absence of detections in a roughly circular region centered at Galactic coordinates (77 .° 7, 0 .° 9), spanning an area of 213.6 deg2. This detection gap spatially coincides with the Cygnus X region—a plasma-rich star-forming region in the Milky Way. This feature is most likely the result of increased sky temperature and strong multipath scattering by turbulent ionized plasma, which broadens the FRB signals beyond detectability in the CHIME band. Our simulations yield a mean of six expected FRB detections within the gap when accounting for the elevated sky temperature in the direction of the detection gap. We infer that a lower limit of the maximum scattering timescale τsc, 1 GHz ≥ 5.59 ms, obtained without assuming a model of the Galactic electron distribution, is sufficient to suppress the brightness of all coincident FRBs. A similar suppression is seen in Catalog 2 along other high emission measure (EM) sight lines (i.e., EM ≥ 2900 pc cm−6), further supporting a broader trend of suppression due to Galactic scattering. Future very long baseline interferometry measurements of scattering disks with CHIME Outriggers can help confirm our interpretation. Our work highlights the notion that FRBs can serve as new, model-independent tracers of the warm ionized medium within our Galaxy.

Keywords: High energy astrophysics, Interstellar plasma, Radio bursts, Interstellar scattering, Radio transient sources
No Metallicity Preference in Fast Radio Burst Host Galaxies. Fast radio bursts (FRBs) are millisecond-duration extragalactic radio transients of unknown origin, and studying their host galaxies could offer clues to constrain progenitor models. Among host properties, gas-phase metallicity is a key factor influencing stellar evolution and transient productions. We analyze the largest uniformly selected sample of FRB host galaxies, measuring oxygen abundances ( 12+log(O/H)=8.04 ─8.85) for 31 hosts at redshifts z = 0.04─0.98, using consistent emission-line diagnostics. Using a volume-limited subsample, we compare the distributions of stellar mass, star formation rate (SFR), and metallicity to a control sample of star-forming galaxies selected by the same criteria. We find that FRB host galaxies span a wide metallicity range and are broadly consistent with the SFR-weighted mass─metallicity relation of star-forming galaxies. We find no clear lower metallicity bound, suggesting that FRB progenitors can form in any metallicity environment through channels largely insensitive to metal abundance. Encouragingly, this implies that FRBs can arise even in low-metallicity, high-redshift galaxies, supporting their potential as probes of matter distribution across cosmic time. Additionally, we find marginal (∼2σ) evidence for a −0.09 ± 0.04 dex metallicity offset from the fundamental metallicity relation. Despite model uncertainties, if real, this offset likely reflects suppressed SFRs at fixed mass and metallicity rather than metal deficiency. Similar offsets are observed in local post-merger galaxies and may reflect a post-starburst phase following galaxy interactions. Such systems may host FRB progenitors formed during the starburst that produce FRBs after a 100─500 Myr delay, broadly consistent with observed delay-time distributions, although further data are needed to confirm this interpretation.

Keywords: Metallicity, Galaxy evolution, Radio transient sources