Sazuna/UAT_keywords huggingface dataset:
The High-Redshift Gas-Phase Mass–Metallicity Relation in FIRE-2. The unprecedented infrared spectroscopic capabilities of JWST have provided high-quality interstellar medium metallicity measurements and enabled characterization of the gas-phase mass–metallicity relation (MZR) for galaxies at z ≳ 5 for the first time. We analyze the gas-phase MZR and its evolution in a high-redshift suite of FIRE-2 cosmological zoom-in simulations at z = 5–12 and for stellar masses M * ∼ 106–1010 M ⊙. These simulations implement a multichannel stellar feedback model and produce broadly realistic galaxy properties, including when evolved to z = 0. The simulations predict very weak redshift evolution of the MZR over the redshift range studied, with the normalization of the MZR increasing by less than 0.01 dex as redshift decreases from z = 12 to z = 5. The median MZR in the simulations is well approximated as a constant power-law relation across this redshift range given by . We find good agreement between our best-fit model and recent observations made by JWST at high redshift. The weak evolution of the MZR at z &gt; 5 contrasts with the evolution at z ≲ 3, where increasing normalization of the MZR with decreasing redshift is observed and predicted by most models. The FIRE-2 simulations predict increasing scatter in the gas-phase MZR with decreasing stellar mass, in qualitative agreement with some observations.

Keywords: Early universe, Galaxy formation, Galaxy chemical evolution, Astronomical simulations, Chemical abundances, James Webb Space Telescope, Galaxy abundances, Interstellar medium, Metallicity, High-redshift galaxies, Galaxies
A Strong He II λ1640 Emitter with an Extremely Blue UV Spectral Slope at z = 8.16: Presence of Population III Stars?. Cosmic hydrogen reionization and cosmic production of the first metals are major phase transitions of the Universe occurring during the first billion years after the Big Bang; however, these are still underexplored observationally. Using the JWST/NIRSpec prism spectroscopy, we report the discovery of a sub-L * galaxy at z spec = 8.1623 ± 0.0007, dubbed RX J2129–z8He II, via the detection of a series of strong rest-frame UV/optical nebular emission lines and the clear Lyman break. RX J2129–z8He II shows a pronounced UV continuum with an extremely steep (i.e., blue) spectral slope of , the steepest among all spectroscopically confirmed galaxies at z spec ≳ 7, in support of its very hard ionizing spectrum that could lead to a significant leakage of its ionizing flux. Therefore, RX J2129–z8He II is representative of the key galaxy population driving the cosmic reionization. More importantly, we detect a strong He II λ1640 emission line in its spectrum, one of the highest redshifts at which such a line is robustly detected. Its high rest-frame equivalent width (EW = 21 ± 4 Å) and extreme flux ratios with respect to UV metal and Balmer lines raise the possibility that part of RX J2129–z8He II's stellar population could be Pop III (Pop III)-like. Through careful photoionization modeling, we show that the physically calibrated phenomenological models of the ionizing spectra of Pop III stars with strong mass loss can successfully reproduce the emission line flux ratios observed in RX J2129–z8He II. Assuming the Eddington limit, the total mass of the Pop III stars within this system is estimated to be 7.8 ± 1.4 × 105 M ⊙. To date, this galaxy presents the most compelling case in the early Universe where trace Pop III stars might coexist with metal-enriched populations.

Keywords: Metallicity, Reionization, High-redshift galaxies, Population III stars
Deneb Is a Large-amplitude Polarimetric Variable. We write to report the discovery that Deneb is a large-amplitude polarization variable. Over a ∼400 days time span from 2022 August Deneb's polarization was typically around 3900 parts per million (ppm) in the SDSS g' band. Yet, it varied by several hundred parts per million in an irregular way on a timescale of weeks. The largest polarization change, amounting to 2500 ppm, occurred shortly after the last pulsation "resumption" event identified by Abt et al. in TESS photometry. The relationship between the observed polarization—particularly corresponding to the resumption event—and its brightness and H α  spectra suggests a mechanism involving density changes in its wind and/or extended atmosphere. Smaller effects due to pulsations are not ruled out, and further study is recommended.

Keywords: Alpha Cygni variable stars, Polarimetry, Starlight polarization
The Physical Origin of the Periodic Activity for FRB 20180916B. Fast radio bursts (FRBs) are transient radio signals with millisecond-duration, large dispersion measure and extremely high brightness temperature. Among them, FRB 20180916B has been found to have a 16 days periodically modulated activity. However, the physical origin of the periodicity is still a mystery. Here, we utilize the comprehensive observational data to diagnose the periodic models. We find that the ultralong rotation model is the most probable one for the periodic activity. However, this model cannot reproduce the observed rotation measure (RM) variations. We propose a self-consistent model, i.e., a massive star binary containing a slowly rotational neutron star and a massive star with large mass loss, which can naturally accommodate the wealth of observational features for FRB 20180916B. In this model, the RM variation is periodic, which can be tested by future observations.

Keywords: Magnetars, High mass x-ray binary stars, Radio transient sources
Light Curves of the Explosion of ONe White Dwarf + CO White Dwarf Merger Remnant and Type Icn Supernovae. Type Icn supernovae (SNe Icn) are a newly detected, rare subtype of interacting stripped-envelope supernovae that show narrow P Cygni lines of highly ionized carbon, oxygen, and neon in their early spectra due to the interactions of the SNe ejecta with dense hydrogen- and helium-deficient circumstellar material (CSM). It has been suggested that SNe Icn may have multiple progenitor channels, such as the explosion of carbon-rich Wolf–Rayet stars or the explosion of stripped-envelope SNe, which undergo binary interactions. Among the SNe Icn, SN 2019jc shows unique properties, and previous work inferred that it may stem from the ultrastripped supernova, but other possibilities still exist. In this work, we aim to simulate the light curves from the explosions of oxygen-neon and carbon-oxygen double white dwarf (WD) merger remnants and to further investigate whether the corresponding explosions can appear as some particular SNe Icn. We generate the light curves from the explosive remnants and analyze the influence of different parameters on the light curves, such as the ejecta mass, explosion energy, mass of 56Ni, and CSM properties. Comparing our results with some SNe Icn, we found that the light curves from the explosions of double WD merger remnants can explain the observable properties of SN 2019jc, from which we infer that this special SN Icn may have a different progenitor. Our results indicate that double WD merger may be an alternative model in producing at least one of the SNe Icn.

Keywords: White dwarf stars, Supernovae, Core-collapse supernovae, Stellar mergers
Boron Abundances in Early B Dwarfs of the Galactic Open Cluster NGC 3293. New boron abundances or upper limits have been determined for eight early B stars in the young Galactic open cluster NGC 3293, using UV spectra obtained by the Hubble Space Telescope Cosmic Origins Spectrograph. With previous observations, there are now 18 early B stars in this cluster with boron measurements. Six of the newly observed stars have projected rotational velocities greater than 200 km s−1, allowing new constraints on rotationally driven mixing in main-sequence stars. When comparing to synthetic model populations, we find that the majority of our sample stars agree well with the predicted trends of stronger boron depletion for larger rotation and for larger mass or luminosity. Based on those, a smaller than the canonical rotational mixing efficiency (f  c  ≍ 0.0165 versus the more standard value of 0.033) appears to be favored. In addition, the five mostly slowly rotating stars, when considered as a group, tend to show more boron depletion than expected from rotational mixing, and we speculate that most or all of these originate from binary mergers. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with proposal GO-14673.

Keywords: Stellar populations, Stellar abundances, Stellar physics, Stellar rotation, Stellar evolution
New Parameters for Star Cluster Dynamics: The Role of Clusters' Initial Conditions. We recently introduced three new parameters that describe the shape of the normalized cumulative radial distribution (nCRD) of the innermost stars in globular clusters (GCs) and trace the clusters' dynamical evolution. Here, we extend our previous investigations to the case of a large set of Monte Carlo simulations of GCs, started from a broad range of initial conditions. All the models are analyzed at the same age of 13 Gyr when they have reached different evolutionary phases. The sample of models is well representative of the structural properties of the observed population of Galactic GCs. We confirm that the three nCRD parameters are powerful tools to distinguish systems in the early stages of dynamical evolution from those that have already experienced core collapse. They might also help disentangle clusters hosting a low-mass intermediate-mass black hole of a few hundred solar masses from cases with large concentrations of dark remnants in their centers. With respect to other dynamical indicators, the nCRD parameters offer the advantage of being fully empirical and easier to measure from observational data.

Keywords: Globular star clusters, Dynamical evolution, Milky Way Galaxy, Star clusters
Are High-Σ<SUB>1</SUB> Massive Blue Spiral Galaxies Rejuvenated Systems?. Quiescent galaxies generally possess denser cores than star-forming galaxies with similar mass. As a measurement of the core density, the central stellar mass surface density within a radius of 1 kpc (Σ1) was thus suggested to be closely related to galaxy quenching. Massive star-forming galaxies with high Σ1 do not fit into this picture. To understand the origin of such galaxies, we compare the spatially resolved stellar population and star formation properties of massive (&gt;1010.5 M ⊙) blue spiral galaxies with high and low Σ1, divided by Σ1 = 109.4 M ⊙ kpc‑2, based on the final release of MaNGA integral field unit data. We find that both high-Σ1 and low-Σ1 blue spirals show large diversities in stellar population and star formation properties. Despite the diversities, high-Σ1 blue spirals are statistically different from the low-Σ1 ones. Specifically, the radial profiles of the luminosity-weighted age and Mgb/〈Fe〉 show that high-Σ1 blue spirals consist of a larger fraction of galaxies with younger and less α-element-enhanced centers than their low-Σ1 counterparts, ∼55% versus ∼30%. The galaxies with younger centers mostly have higher central specific star formation rates, which still follow the spaxel-based star formation main-sequence relation. Examinations of the Hα velocity field and the optical structures suggest that galactic bars or galaxy interactions should be responsible for the rejuvenation of these galaxies. The remaining ∼45% of high-Σ1 blue spirals are consistent with the inside-out growth scenario.

Keywords: Galaxy formation, Spiral galaxies, Galaxy ages, Galaxy evolution, Galaxy spectroscopy
What Is the Nature of Little Red Dots and what Is Not, MIRI SMILES Edition. We study 31 little red dots (LRD) detected by JADES/NIRCam and covered by the SMILES/MIRI survey, of which ∼70% are detected in the two bluest MIRI bands and 40% in redder MIRI filters. The median/quartiles redshifts are  z=6.95.97.7  (55% spectroscopic). The spectral slopes flatten in the rest-frame near-infrared, consistent with a 1.6 μm stellar bump but bluer than direct pure emission from active galactic nuclei (AGN) tori. The apparent dominance of stellar emission at these wavelengths for many LRDs expedites stellar mass estimation: the median/quartiles are  logM⋆/M⊙=9.49.19.7 . The number density of LRDs is 10‑4.0±0.1 Mpc‑3, accounting for 14% ± 3% of the global population of galaxies with similar redshifts and masses. The rest-frame near-/mid-infrared (2–4 μm) spectral slope reveals significant amounts of warm dust (bolometric attenuation ∼3–4 mag). Our spectral energy distribution modeling implies the presence of &lt;0.4 kpc diameter knots, heated by either dust-enshrouded OB stars or an AGN producing a similar radiation field, obscured by A(V) &gt; 10 mag. We find a wide variety in the nature of LRDs. However, the best-fitting models for many of them correspond to extremely intense and compact starburst galaxies with mass-weighted ages 5–10 Myr, very efficient in producing dust, with their global energy output dominated by the direct (in the flat rest-frame ultraviolet and optical spectral range) and dust-recycled emission from OB stars with some contribution from an obscured AGN (in the infrared).

Keywords: Galaxy formation, Stellar populations, Galaxy stellar content, Galaxy ages, James Webb Space Telescope, Active galactic nuclei, Galaxy evolution, Broad band photometry, High-redshift galaxies
A Multipeak Solar Flare with a High Turnover Frequency of the Gyrosynchrotron Spectra from the Loop-top Source. The origin of multiple peaks in light curves of various wavelengths remains illusive during flares. Here we discuss the flare of SOL2023-05-09T03:54M6.5 with six flux peaks as recorded by a tandem of new microwave and hard X-ray (HXR) instruments. According to its microwave spectra, the flare represents a high-turnover-frequency (&gt;15 GHz) event. The rather-complete microwave and HXR spectral coverage provides a rare opportunity to uncover the origin of such an event together with simultaneous EUV images. We concluded that (1) the microwave sources originates around the top section of the flaring loops with a trend of source spatial dispersion with frequency; (2) the visible movement of the microwave source from peak to peak originates from the process of new flaring loops appearing sequentially along the magnetic neutral line; (3) the optically thin microwave spectra are hard with the indices (α tn) varying from ∼‑1.2 to ‑0.4, and the turnover frequency always exceeds 15 GHz; (4) higher turnover/peak frequency corresponds to stronger peak intensity and harder optically thin spectra. Using the Fokker–Planck and GX Simulator codes we obtained a good fit to the observed microwave spectra and spatial distribution of the sources at all peaks, if assuming the radiating energetic electrons have the same spatial distribution and single-power-law spectra but with the number density varying in a range of ∼30%. We conclude that the particle acceleration in this flare happens in a compact region nearing the loop-top. These results provide new constraints on the acceleration of energetic electrons and the underlying flare intermittent reconnection process.

Keywords: Solar flares, Solar magnetic reconnection, Solar energetic particles, Solar radio emission, Solar corona
Stochastic Averaging of Radiative Transfer Coefficients for Relativistic Electrons. Synchrotron emissivities, absorptivities, and Faraday rotation and conversion coefficients are needed in modeling a variety of astrophysical sources, including Event Horizon Telescope (EHT) sources. We develop a method for estimating transfer coefficients that exploits their linear dependence on the electron distribution function, decomposing the distribution function into a sum of parts each of whose emissivity can be calculated easily. We refer to this procedure as stochastic averaging and apply it in two contexts. First, we use it to estimate the emissivity of an isotropic κ distribution function with a high-energy cutoff. The resulting coefficients can be evaluated efficiently enough to be used directly in ray-tracing calculations, and we provide an example calculation. Second, we use stochastic averaging to assess the effect of subgrid turbulence on the volume-averaged emissivity and along the way provide a prescription for a turbulent emissivity. We find that for parameters appropriate to EHT sources turbulence reduces the emissivity slightly. In the infrared, turbulence can dramatically increase the emissivity.

Keywords: Magnetohydrodynamics, Black holes, Radiative transfer, Radiative processes
Observations of Nonthermal Velocities and Comparisons with an Alfvén Wave Turbulence Model in Solar Active Regions. We present a study of spectral line width measurements from the Extreme-ultraviolet Imaging Spectrometer on Hinode. We used spectral line profiles of Fe XVI 262.984 Å, Fe XIV 264.787 Å, Fe XIV 270.519 Å, Fe XIV 274.203 Å, and Fe XV 284.160 Å, and studied 11 active regions. Previous studies of spectral line widths have shown that in hot loops in the cores of active regions, the observed nonthermal velocities are smaller than predicted from models of reconnection jets in the corona or shock heating associated with Alfvén waves. The observed line widths are also inconsistent with models of chromospheric evaporation due to coronal nanoflares. We show that recent advances in higher resolution Alfvén wave turbulence modeling enables us to obtain nonthermal velocities similar to those measured in active regions. The observed nonthermal velocities for the 11 active regions in our study are in the range of 17─30 km s−1, consistent with the spectral line nonthermal widths predicted from our model of 16 interacting flux tubes, which are in the range of 15─37 km s−1.

Keywords: Solar atmosphere, The Sun, Solar coronal heating, Solar physics, Solar corona
The Cosmic Ultraviolet Baryon Survey (CUBS). VII. On the Warm-hot Circumgalactic Medium Probed by O VI and Ne VIII at 0.4 ≲ z ≲ 0.7. This paper presents a newly established sample of 103 unique galaxies or galaxy groups at 0.4 ≲ z ≲ 0.7 from the Cosmic Ultraviolet Baryon Survey (CUBS) for studying the warm-hot circumgalactic medium (CGM) probed by both O VI and Ne VIII absorption. The galaxies and associated neighbors are identified at &lt;1 physical Mpc from the sightlines toward 15 CUBS QSOs at z QSO ≳ 0.8. A total of 30 galaxies or galaxy groups exhibit associated O VI λ λ 1031, 1037 doublet absorption within a line-of-sight velocity interval of ±250 km s−1, while the rest show no trace of O VI to a detection limit of  logNOVI/cm−2≍13.7 . Meanwhile, only five galaxies or galaxy groups exhibit the Ne VIII λ λ 770, 780 doublet absorption, down to a limiting column density of  logNNeVIII/cm−2≍14.0 . These O VI- and Ne VIII-bearing halos reside in different galaxy environments with stellar masses ranging from  logMstar/M⊙≍8  to ≍11.5. The warm-hot CGM around galaxies of different stellar masses and star formation rates exhibits different spatial profiles and kinematics. In particular, star-forming galaxies with  logMstar/M⊙≍9─11  show a significant concentration of metal-enriched warm-hot CGM within the virial radius, while massive quiescent galaxies exhibit flatter radial profiles of both column densities and covering fractions. In addition, the velocity dispersion of O VI absorption is broad with σ  υ  &gt; 40 km s−1 for galaxies of  logMstar/M⊙&gt;9  within the virial radius, suggesting a more dynamic warm-hot halo around these galaxies. Finally, the warm-hot CGM probed by O VI and Ne VIII is suggested to be the dominant phase in sub-L* galaxies with  logMstar/M⊙≍9─10  based on their high ionization fractions in the CGM.

Keywords: Surveys, Galaxy evolution, Quasar absorption line spectroscopy, Circumgalactic medium
A Spatially Resolved [C II] Survey of 31 z ∼ 7 Massive Galaxies Hosting Luminous Quasars. The [C II] 158 μm emission line and the underlying far-infrared (FIR) dust continuum are important tracers for studying star formation and kinematic properties of early galaxies. We present a survey of the [C II] emission lines and FIR continua of 31 luminous quasars at z &gt; 6.5 using the Atacama Large Millimeter Array (ALMA) and the NOrthern Extended Millimeter Array at sub-arcsec resolution. This survey more than doubles the number of quasars with [C II] and FIR observations at these redshifts and enables statistical studies of quasar host galaxies deep into the epoch of reionization. We detect [C II] emission in 27 quasar hosts with a luminosity range of L [C II] = (0.3–5.5) × 109 L ⊙ and detect the FIR continuum of 28 quasar hosts with a luminosity range of L FIR = (0.5–13.0) × 1012 L ⊙. Both L [C II] and L FIR are correlated (ρ ≃ 0.4) with the quasar bolometric luminosity, albeit with substantial scatter. The quasar hosts detected by ALMA are clearly resolved with a median diameter of ∼5 kpc. About 40% of the quasar host galaxies show a velocity gradient in [C II] emission, while the rest show either dispersion-dominated or disturbed kinematics. Basic estimates of the dynamical masses of the rotation-dominated host galaxies yield M dyn = (0.1–7.5) × 1011 M ⊙. Considering our findings alongside those of literature studies, we found that the ratio between M BH and M dyn is about 10 times higher than that of local M BH–M dyn relation on average but with substantial scatter (the ratio difference ranging from ∼0.6 to 60) and large uncertainties.

Keywords: Early universe, Supermassive black holes, Galaxies, Quasars
An ALMA Search for Substructure and Fragmentation in Starless Cores in Orion B North. We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 3 observations of 73 starless and protostellar cores in the Orion B North molecular cloud. We detect a total of 34 continuum sources at 106 GHz, and after comparisons with other data, four of these sources appear to be starless. Three of the four sources are located near groupings of protostellar sources, while one source is an isolated detection. We use synthetic observations of a simulation modeling a collapsing turbulent, magnetized core to compute the expected number of starless cores that should be detectable with our ALMA observations and find at least two (1.52) starless cores should be detectable (at 5σ), consistent with our data. We run a simple virial analysis of the cores to put the Orion B North observations into context with similar previous ALMA surveys of cores in Chamaeleon I and Ophiuchus. We conclude that the Chamaeleon I starless core population is characteristically less bounded than the other two populations, along with external pressure contributions dominating the binding energy of the cores. These differences may explain why the Chamaeleon I cores do not follow turbulent model predictions, while the Ophiuchus and Orion B North cores are consistent with the model.

Keywords: Millimeter astronomy, Star forming regions, Molecular clouds, Star formation, Dust continuum emission, Submillimeter astronomy, Radio interferometry, Collapsing clouds