adsabs/SciX_UAT_keywords huggingface dataset:
High-redshift Extreme Variability Quasars from Sloan Digital Sky Survey Multiepoch Spectroscopy

We perform a systematic search for high-redshift ( $z\,\gt $ 1.5) extreme variability quasars (EVQs) using repeat spectra from the Sixteenth Data Release of the Sloan Digital Sky Survey, which provides a baseline spanning up to ∼18 yr in the observed frame. We compile a sample of 348 EVQs with a maximum continuum variability at rest frame 1450 Å of more than 100% (i.e., δV ≡ (Max - Min)/Mean > 1). The EVQs show a range of emission-line variability, including 23 where at least one line in our redshift range disappears below detectability, which can then be seen as analogous to low-redshift changing-look quasars (CLQs). Importantly, spurious CLQs caused by problematic SDSS spectral flux calibration, e.g., fiber-drop issue, have been rejected. The similar properties (e.g., continuum/line, difference-composite spectra and Eddington ratio) of normal EVQs and CLQs imply that they are basically the same physical population with analogous intrinsic variability mechanisms, as a tail of a continuous distribution of normal quasar properties. In addition, we find no reliable evidence (≲1σ) to support that CLQs are a subset of EVQs with less efficient accretion. Finally, we also confirm the antibreathing of C IV (i.e., the line width increases as luminosity increases) in EVQs and find that in addition to the ∼0.4 dex systematic uncertainty in single-epoch C IV virial black hole mass estimates, an extra scatter of ∼0.3 dex will be introduced by extreme variability.

Keywords: active galactic nuclei; quasars; black hole physics; spectroscopy; time domain astronomy
Heavy Magnetic Neutron Stars

We systematically study the properties of pure nucleonic and hyperonic magnetic stars using a density-dependent relativistic mean-field (DD-RMF) equations of state. We explore several parameter sets and hyperon coupling schemes within the DD-RMF formalism. We focus on sets that are in better agreement with nuclear and other astrophysical data while generating heavy neutron stars. Magnetic field effects are included in the matter equation of state and in general relativity solutions, which in addition fulfill Maxwell's equations. We find that pure nucleonic matter, even without magnetic field effects, generates neutron stars that satisfy the potential GW 190814 mass constraint; however, this is not the case for hyperonic matter, which instead only satisfies the more conservative 2.1 M⊙ constraint. In the presence of strong but still somehow realistic internal magnetic fields ≈1017 G, the stellar charged particle population re-leptonizes and de-hyperonizes. As a consequence, magnetic fields stiffen hyperonic equations of state and generate more massive neutron stars, which can satisfy the possible GW 190814 mass constraint but present a large deformation with respect to spherical symmetry.

Keywords: neutron stars; magnetars
Unscrambling the Lensed Galaxies in JWST Images behind SMACS 0723

The first deep field images from the James Webb Space Telescope (JWST) of the galaxy cluster SMACS J0723.3-7327 reveal a wealth of new lensed images at uncharted infrared wavelengths, with unprecedented depth and resolution. Here we securely identify 14 new sets of multiply imaged galaxies totaling 42 images, adding to the five sets of bright and multiply imaged galaxies already known from Hubble Space Telescope data. We find examples of arcs crossing critical curves, allowing detailed community follow-up, such as JWST spectroscopy for precise redshift determinations, and measurements of the chemical abundances and of the detailed internal gas dynamics of very distant, young galaxies. One such arc contains a pair of compact knots that are magnified by a factor of hundreds, and features a microlensed transient. We also detect an Einstein cross candidate only visible thanks to JWST's superb resolution. Our parametric lens model is available through the following link (https://www.dropbox.com/sh/gwup2lvks0jsqe5/AAC2RRSKce0aX-lIFCc9vhBXa?dl=0) and will be regularly updated using additional spectroscopic redshifts. The model is constrained by 16 of these sets of multiply imaged galaxies, three of which have spectroscopic redshifts, and reproduces the multiple images to better than an rms of 0.″5, allowing for accurate magnification estimates of high-redshift galaxies. The intracluster light extends beyond the cluster members, exhibiting large-scale features that suggest a significant past dynamical disturbance. This work represents a first taste of the enhanced power JWST will have for lensing-related science.

Keywords: galaxy clusters; strong gravitational lensing; dark matter; high-redshift galaxies; galaxies
Broad and Bidirectional Narrow Quasiperiodic Fast-propagating Wave Trains Associated with a Filament-driven Halo Coronal Mass Ejection on 2023 April 21

This paper presents three distinct wave trains that occurred on 2023 April 21: a broad quasiperiodic fast-propagating (QFP) wave train and bidirectional narrow QFP wave trains. The broad QFP wave train expands outward in a circular wave front, while bidirectional narrow QFP wave trains propagate in the northward and southward directions, respectively. The concurrent presence of the wave trains offers a remarkable opportunity to investigate their respective triggering mechanisms. Measurement shows that the speed of the broad QFP wave train is in the range of 300–1100 km s‑1 in different propagating directions. There is a significant difference in the speed of the bidirectional narrow QFP wave trains: the southward propagation achieves 1400 km s‑1, while the northward propagation only reaches about 550 km s‑1 accompanied by a deceleration of about 1–2 km s‑2. Using the wavelet analysis, we find that the periodicity of the propagating wave trains in the southward and northward directions closely matches the quasiperiodic pulsations exhibited by the flares. Based on these results, the narrow QFP wave trains were most likely excited by the intermittent energy release in the accompanying flare. In contrast, the broad QFP wave train had a tight relationship with the erupting filament, probably attributed to the unwinding motion of the erupting filament, or the leakage of the fast sausage wave train inside the filament body.

Keywords: solar coronal waves; solar corona
The Structure and Composition of Multiphase Galactic Winds in a Large Magellanic Cloud Mass Simulated Galaxy

We present the first results from a high-resolution simulation with a focus on galactic wind driving for an isolated galaxy with a halo mass of ~1011 M ⊙ (similar to the Large Magellanic Cloud) and a total gas mass of ~6 × 108 M ⊙, resulting in ~108 gas cells at ~4 M ⊙ mass resolution. We adopt a resolved stellar feedback model with nonequilibrium cooling and heating, including photoelectric heating and photoionizing radiation, as well as supernovae, coupled to the second-order meshless finite-mass method for hydrodynamics. These features make this the largest resolved interstellar medium (ISM) galaxy model run to date. We find mean star formation rates around 0.05 M ⊙ yr-1 and evaluate typical time-averaged loading factors for mass (η M ~ 1.0, in good agreement with recent observations) and energy (η E ~ 0.01). The bulk of the mass of the wind is transported by the warm (T < 5 × 105 K) phase, while there is a similar amount of energy transported in the warm and the hot phases (T > 5 × 105 K). We find an average opening angle of 30° for the wind, decreasing with higher altitude above the midplane. The wind mass loading is decreasing (flat) for the warm (hot) phase as a function of the star formation surface rate density ΣSFR, while the energy loading shows inverted trends with ΣSFR, decreasing for the warm wind and increasing for the hot wind, although with very shallow slopes. These scalings are in good agreement with previous simulations of resolved wind driving in the multiphase ISM.

Keywords: galactic winds; galaxy evolution; hydrodynamical simulations; stellar feedback; interstellar medium
Pushing the Limits of the Cosmic Origin Spectrograph (COS) with an Optimized Background Correction

Observations utilizing the ultraviolet capabilities of the Cosmic Origin Spectrograph (COS) onboard the Hubble Space Telescope are of unique value to the astronomy community. Spectroscopy down to 900 Å with COS has enabled new science areas. However, contrary to the situation at longer wavelengths, these observations are limited by detector background noise. The background correction currently applied by the standard calibration pipeline (CalCOS) is not optimized for faint targets, limiting the scientific value of low signal-to-noise ratio (S/N) observations. In this work we investigate a possible dependence of the variations of the dark rate in both segments of the COS far-ultraviolet detector on time, detector high voltage (HV), and solar activity. Through our analysis we identified a number of detector states (on a configuration basis, e.g., HV and segment) characterizing the spatial distribution of dark counts, and created superdarks to be used in an optimized two-dimensional (2D) background correction. We have developed and tested Another COS Dark Correction (ACDC), a dedicated pipeline to perform a 2D background correction based on statistical methods, producing background-corrected and flux-calibrated spectra. While our testing of ACDC showed an average improvement in S/N values of ∼10%, in a few cases the improvements in S/N reached 60% across the whole wavelength range of individual segments.

Keywords: calibration; hubble space telescope; ultraviolet astronomy; publicly available software
A Complete 16 μm Selected Galaxy Sample at z ∼ 1: Mid-infrared Spectral Energy Distributions

We describe a complete, flux-density-limited sample of galaxies at redshift 0.8 < z < 1.3 selected at 16 μm. At the selection wavelength near 8 μm rest, the observed emission comes from both dust heated by intense star formation and active galactic nuclei (AGNs). Fitting the spectral energy distributions (SEDs) of the sample galaxies to local-galaxy templates reveals that more than half the galaxies have SEDs dominated by star formation. About one-sixth of the galaxy SEDs are dominated by an AGN, and nearly all of the rest of the SEDs are composite. Comparison with X-ray and far-infrared observations shows that combinations of luminosities at rest-frame 4.5 and 8 μm give good measures of both AGN luminosity and star formation rate. The sample galaxies mostly follow the established star-forming main sequence for z = 1 galaxies, but of the galaxies more than 0.5 dex above that main sequence, more than half have AGN-type SEDs. Similarly, the most luminous AGNs tend to have higher star formation rates than the main-sequence value. Galaxies with stellar masses >1011 M⊙ are unlikely to host an AGN. About 1% of the sample galaxies show an SED with dust emission typical of neither star formation nor an AGN.

Keywords: infrared galaxies; luminous infrared galaxies; sky surveys; spectral energy distribution
The Role of Binarity and Stellar Rotation in the Split Main Sequence of NGC 2422

In addition to the extended main-sequence turnoffs widely found in young and intermediate-age (~600 Myr to 2 Gyr old) star clusters, some younger clusters even exhibit split main sequences (MSs). Different stellar rotation rates are proposed to account for the bifurcated MS pattern, with red and blue MSs (rMS and bMS) populated by fast and slowly rotating stars, respectively. Using photometry from Gaia Early Data Release 3, we report a Galactic open cluster with a bifurcated MS, NGC 2422 (~90 Myr). We exclude the possibilities that the bifurcated MS pattern is caused by photometric noise or differential reddening. We aim to examine if stellar rotation can account for the split MS. We use spectra observed with the Canada-France-Hawaii Telescope and the Southern African Large Telescope and directly measured $v\sin i$ , the projected rotational velocities, for stars populating the bMS and rMS. We find that their $v\sin i$ values are weakly correlated with their loci in the color-magnitude diagram because of contamination caused by a large fraction of rMS stars with low projected rotational velocities. Based on the spectral energy distribution fitting method, we suggest that these slowly rotating stars at the rMS may hide a binary companion, which breaks the expected $v\sin i$ -color correlation. Future time-domain studies focusing on whether these slowly rotating stars are radial velocity variables are crucial to test the roles of stellar rotation and binarity in generating the split MSs.

Keywords: open star clusters; star clusters; stellar rotation
Probing the Bright End of the Rest-frame Ultraviolet Luminosity Function at z = 8-10 with Hubble Pure-parallel Imaging

Looking for bright galaxies born in the early universe is fundamental to investigating the Epoch of Reionization, the era when the first stars and galaxies ionized the intergalactic medium. We utilize Hubble Space Telescope pure-parallel imaging to select galaxy candidates at a time 500-650 million years after the Big Bang, which corresponds to redshifts z ∼ 8-10. These data come from the Brightest of Reionizing Galaxies Survey (BoRG) Cycle 22 data set, which consists of pure-parallel imaging in ∼90 different lines of sight that sum up to an area of ∼420 arcmin2. This survey uses five filters and has the advantage (compared to the Cycle 21 BoRG program) of including imaging in the JH140 band, covering continuous wavelengths from the visible to near-infrared (λ = 0.35-1.7 μm). This allows us to perform a reliable selection of galaxies at z ≥ 8 using the photometric-redshift technique. We use these galaxy candidates to constrain the bright end of the rest-frame ultraviolet luminosity function in this epoch. These candidates are excellent targets for follow-up observations, particularly with the James Webb Space Telescope.

Keywords: observational cosmology; high-redshift galaxies; galaxy evolution; reionization; random forests
Study of the Mass-loss Rate from the Sun

We investigate the temporal evolution of the yearly total mass-loss rate (YTMLR) from the Sun through coronal mass ejections (CMEs) over solar cycles 23 and 24. The mass determination of CMEs can be subject to significant uncertainty. To minimize this problem, we have used extensive statistical analysis. For this purpose, we employed data included in the Coordinated Data Analysis Workshop (CDAW) catalog. We estimated the contributions to mass loss from the Sun from different subsamples of CMEs (selected on the basis of their masses, angular widths, and position angles). The temporal variations of the YTMLR were compared to those of the sunspot number (SSN), X-ray flare flux, and the Disturbance Storm Time (Dst) index. We show that the CME mass included in the CDAW catalog reflects with high accuracy the actual mass-loss rate from the Sun through CMEs. Additionally, it is shown that the CME mass distribution in the log-lin representation reflects the Gaussian distribution very well. This means that the CMEs included in the CDAW catalog form one coherent population of ejections that have been correctly identified. Unlike the CME occurrence rate, it turns out that the YTMLR is a very good indicator of solar activity (e.g., SSN) and space weather (e.g., Dst index) consequences. These results are very important, since the YTMLR, unlike the mass loss through solar wind, significantly depends on solar cycles.

Keywords: the sun; solar activity; solar storm
Two of a Kind: Comparing Big and Small Black Holes in Binaries with Gravitational Waves

When modeling the population of merging binary black holes, analyses have generally focused on characterizing the distribution of primary (i.e., more massive) black holes in the binary, while using simplistic prescriptions for the distribution of secondary masses. However, the secondary mass distribution and its relationship to the primary mass distribution provide a fundamental observational constraint on the formation history of coalescing binary black holes. If both black holes experience similar stellar evolutionary processes prior to collapse, as might be expected in dynamical formation channels, the primary and secondary mass distributions would show similar features. If they follow distinct evolutionary pathways (for example, due to binary interactions that break symmetry between the initially more massive and less massive stars), their mass distributions may differ. We present the first analysis of the binary black hole population that explicitly fits for the secondary mass distribution. We find that the data is consistent with a ∼30 M ⊙ peak existing only in the distribution of secondary rather than primary masses. This would have major implications for our understanding of the formation of these binaries. Alternatively, the data is consistent with the peak existing in both component mass distributions, a possibility not included in most previous studies. In either case, the peak is observed at ${31.4}_{-2.6}^{+2.3}\,{M}_{\odot }$ , which is shifted lower than the value obtained in previous analyses of the marginal primary mass distribution, placing this feature in further tension with expectations from a pulsational pair-instability supernova pileup.

Keywords: gravitational wave sources; gravitational waves; gravitational wave astronomy; binary stars; globular star clusters; common envelope evolution; hierarchical models; bayesian statistics; a supergiant stars; supernova remnants
Constraints on the Origins of the Galactic Neutrino Flux Detected by IceCube

Galactic and extragalactic objects in the Universe are sources of high-energy neutrinos that may contribute to the astrophysical neutrino signal seen by IceCube. Recently, a study done using cascade-like events seen by IceCube reported neutrino emission from the Galactic plane with >4σ significance. In this work, we put a lower limit on the number of Galactic sources required to explain this emission. To achieve this, we use a simulation package created to simulate point sources in the Galaxy along with the neutrino and gamma-ray flux emissions originating from them. Along with using past IceCube discovery potential curves, we also account for Eddington bias effects due to Poisson fluctuations in the number of detected neutrino events. We present a toy Monte Carlo simulation to show that there must be at least eight sources, each with luminosity less than 1.6 × 1035 erg s‑1, responsible for the Galactic neutrino emission. Our results constrain the number of individual point-like emission regions, which apply both to discrete astrophysical sources and to individual points of diffuse emission.

Keywords: neutrino astronomy; high energy astrophysics; astronomical simulations
Bimodal Black Hole Mass Distribution and Chirp Masses of Binary Black Hole Mergers

In binary black hole mergers from isolated binary-star evolution, both black holes are from progenitor stars that have lost their hydrogen-rich envelopes by binary mass transfer. Envelope stripping is known to affect the pre-supernova core structures of such binary-stripped stars and thereby their final fates and compact remnant masses. In this paper, we show that binary-stripped stars give rise to a bimodal black hole mass spectrum with characteristic black hole masses of about 9 M ⊙ and 16 M ⊙ across a large range of metallicities. The bimodality is linked to carbon and neon burning becoming neutrino dominated, which results in interior structures that are difficult to explode and likely lead to black hole formation. The characteristic black hole masses from binary-stripped stars have corresponding features in the chirp-mass distribution of binary black hole mergers: peaks at about 8 and 14 M ⊙ and a dearth in between these masses. Current gravitational-wave observations of binary black hole mergers show evidence for a gap at 10-12 M ⊙ and peaks at 8 and 14 M ⊙ in the chirp-mass distribution. These features are in agreement with our models of binary-stripped stars. In the future, they may be used to constrain the physics of late stellar evolution and supernova explosions and may even help measure the cosmological expansion of the universe.

Keywords: stellar evolution; multiple star evolution; stellar remnants; black holes; neutron stars; gravitational wave sources
Figuring Out Gas & Galaxies in Enzo (FOGGIE). III. The Mocky Way: Investigating Biases in Observing the Milky Way's Circumgalactic Medium

The circumgalactic medium (CGM) of the Milky Way is mostly obscured by nearby gas in position-velocity space because we reside inside the Galaxy. Substantial biases exist in most studies of the Milky Way's CGM that focus on easier-to-detect high-velocity gas. With mock observations on a Milky Way analog from the Figuring Out Gas & Galaxies in Enzo (FOGGIE) simulation, we investigate four observational biases related to the Milky Way's CGM. First, QSO absorption-line studies probe a limited amount of the CGM mass: only 35% of the mass is at high Galactic latitudes $| b| \gt 20^\circ $ , of which only half is moving at $| {V}_{\mathrm{LSR}}| \gtrsim 100\,\mathrm{km}\,{{\rm{s}}}^{-1}$ . Second, the inflow rate ( $\dot{M}$ ) of the cold gas observable in H I 21 cm is reduced by a factor of ∼10 as we switch from the local standard of rest to the galaxy's rest frame; meanwhile, the $\dot{M}$ of the cool and warm gas does not change significantly. Third, O VI and N V are promising ions to probe the Milky Way's outer CGM ( $r\gtrsim 15$ kpc), but C IV may be less sensitive. Lastly, the scatter in ion column density is a factor of 2 higher if the CGM is observed from the inside out than from external views because of the gas radial density profile. Our work highlights that observations of the Milky Way's CGM, especially those using H I 21 cm and QSO absorption lines, are highly biased. We demonstrate that these biases can be quantified and calibrated through synthetic observations with simulated Milky Way analogs.

Keywords: circumgalactic medium; milky way galaxy; hydrodynamical simulations; high-velocity clouds; spectroscopy; quasar absorption line spectroscopy
Morphometry and Temperature of Simple Craters in Mercury's Northern Hemisphere: Implications for Stability of Water Ice

Multiple lines of evidence support the hypothesis that Mercury's polar regions host deposits of water ice in permanently shadowed regions, often within the interiors of craters. Pre-MErcury, Surface, Space, ENvironment, GEochemisty, and Ranging (MESSENGER) thermal modeling of the temperature of idealized simple craters found that the interiors of these craters were too hot to host near-surface ice on geologic timescales unless within 2° of the poles. However, results from the Arecibo Observatory and the MESSENGER mission identified many small, <10 km diameter, simple craters that host radar-bright deposits located considerably farther than 2° from the pole. Here we investigate the location and morphometry of north polar craters with diameters of 5-10 km and find that the craters were, on average, 30% shallower than the idealized simple crater morphometry assumed in previous thermal studies. The craters that host radar-bright deposits have an asymmetric longitudinal distribution that cannot be fully explained by the thermal environment and may be related to the original water ice deposition. We also investigate the maximum and average temperatures of the shadowed regions in these craters and find that many of them possess temperatures that allow water ice to be stable under a thermally insulating layer on geologic timescales outside of 2° from the pole. Thus, while the presence of radar-bright deposits in 5-10 km craters is not necessarily a constraint on the stability of the deposits, it provides additional information on the distribution and deposition of the water ice.

Keywords: mercury (planet); planetary polar regions; impact phenomena