adsabs/SciX_UAT_keywords huggingface dataset:
Substructures in Compact Disks of the Taurus Star-forming Region

Observations of substructure in protoplanetary disks have largely been limited to the brightest and largest disks, excluding the abundant population of compact disks, which are likely sites of planet formation. Here, we reanalyze ~0.″1, 1.33 mm Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations of 12 compact protoplanetary disks in the Taurus star-forming region. By fitting visibilities directly, we identify substructures in six of the 12 compact disks. We then compare the substructures identified in the full Taurus sample of 24 disks in single-star systems and the ALMA DSHARP survey, differentiating between compact (R eff,90% < 50 au) and extended (R eff,90% ≥50 au) disk sources. We find that substructures are detected at nearly all radii in both small and large disks. Tentatively, we find fewer wide gaps in intermediate-sized disks with R eff,90% between 30 and 90 au. We perform a series of planet-disk interaction simulations to constrain the sensitivity of our visibility-fitting approach. Under the assumption of planet-disk interaction, we use the gap widths and common disk parameters to calculate potential planet masses within the Taurus sample. We find that the young planet occurrence rate peaks near Neptune masses, similar to the DSHARP sample. For 0.01 M J/M ⊙ ≲M p/M * ≲0.1 M J/M ⊙, the rate is 17.4% ± 8.3%; for 0.1 M J/M ⊙ ≲M p/M * ≲1 M J/M ⊙, it is 27.8% ± 8.3%. Both of them are consistent with microlensing surveys. For gas giants more massive than 5 M J, the occurrence rate is 4.2% ± 4.2%, consistent with direct imaging surveys.

Keywords: protoplanetary disks; planetary-disk interactions; exoplanet systems
Distortion of Magnetic Fields in a Starless Core. VI. Application of Flux Freezing Model and Core Formation of FeSt 1-457

Observational data for the hourglass-like magnetic field toward the starless dense core FeSt 1-457 were compared with a flux freezing magnetic field model. Fitting of the observed plane-of-sky magnetic field using the flux freezing model gave a residual angle dispersion comparable to the results based on a simple 3D parabolic model. The best-fit parameters for the flux freezing model were a line-of-sight magnetic inclination angle of γmag = 35° ± 15° and a core center to ambient (background) density contrast of ρc/ρbkg = 75. The initial density for core formation (ρ0) was estimated to be ρc/75 = 4670 cm-3, which is about one order of magnitude higher than the expected density (∼300 cm-3) for the interclump medium of the Pipe Nebula. FeSt 1-457 is likely to have been formed from the accumulation of relatively dense gas, and the relatively dense background column density of AV ≃ 5 mag supports this scenario. The initial radius (core formation radius) R0 and the initial magnetic field strength B0 were obtained to be 0.15 pc (1.64R) and 10.8-14.6 μG, respectively. We found that the initial density ρ0 is consistent with the mean density of the nearly critical magnetized filament with magnetic field strength B0 and radius R0. The relatively dense initial condition for core formation can be naturally understood if the origin of the core is the fragmentation of magnetized filaments.

Keywords: magnetic fields; interstellar dust; infrared astronomy; dense interstellar clouds; starlight polarization
Revisit of Open Clusters UPK 39, UPK 41, and PHOC 39: A New Binary Open Cluster Found

We investigate the three open clusters near the Aquila Rift cloud, named UPK 39 (c1 hereafter), UPK 41 (c2 hereafter) in Sim et al. (2019), and PHOC 39 (c3 hereafter) in Hunt & Reffert (2021). Using photometric passpands, reddening, and extinction from Gaia DR3, we construct the color-absolute-magnitude diagram. Using isochrone fits, their ages are estimated as 6.3 ± 0.9, 8.1 ± 1.4 and 21.8 ± 2.2 Myr. Their proper motions and radial velocities, estimated using data from Gaia and LAMOST, are very similar. From their orbits, relative distances among them at different times, kinematics, ages, and metallicities, we conclude that c1 and c2 are primordial binary open cluster, which are likely to have been formed at the same time, and c3 may capture c1, c2 in the future.

Keywords: open star clusters; stellar kinematics
An Asymmetric Eclipse Seen toward the Pre-main-sequence Binary System V928 Tau

K2 observations of the weak-lined T Tauri binary V928 Tau A and B show the detection of a single, asymmetric eclipse, which may be due to a previously unknown substellar companion eclipsing one component of the binary with an orbital period >66 days. Over an interval of about 9 hr, one component of the binary dims by around 60%, returning to its normal brightness about 5 hr later. From modeling of the eclipse shape, we find evidence that the eclipsing companion may be surrounded by a disk or a vast ring system. The modeled disk has a radius of 0.9923 ± 0.0005 R*, with an inclination of 56°78 ± 0°03, a tilt of 41°22 ± 0°05, an impact parameter of -0.2506 ± 0.0002 R*, and an opacity of 1.00. The occulting disk must also move at a transverse velocity of 6.637 ± 0.002 R* day-1, which, depending on whether it orbits V928 Tau A or B, corresponds to approximately 73.53 or 69.26 km s-1. A search in ground-based archival data reveals additional dimming events, some of which suggest periodicity, but no unambiguous period associated with the eclipse observed by K2. We present a new epoch of astrometry that is used to further refine the orbit of the binary, presenting a new lower bound of 67 yr, and constraints on the possible orbital periods of the eclipsing companion. The binary is also separated by 18″ (∼2250 au) from the lower-mass CFHT-BD-Tau 7, which is likely associated with V928 Tau A and B. We also present new high-dispersion optical spectroscopy that we use to characterize the unresolved stellar binary.

Keywords: planetary rings; pre-main sequence stars; astrometric binary stars; eclipses; substellar companion stars
Spitzer/IRS Full Spectral Modeling to Characterize Mineralogical Properties of Silicate Dust in Heavily Obscured AGNs

Mid-infrared silicate dust bands observed in heavily obscured active galactic nuclei (AGNs) include information on the mineralogical properties of silicate dust. We aim to investigate the mineralogical picture of the circumnuclear region of heavily obscured AGNs to reveal obscured AGN activities through the picture. In our previous study, we investigated the properties of silicate dust in heavily obscured AGNs, focusing on the mineralogical composition and the crystallinity with Spitzer/IRS 5.3-12 μm spectra. In this study, we model the full-range Spitzer/IRS 5-30 μm spectra of 98 heavily obscured AGNs using a one-dimensional radiative transfer calculation with four dust species in order to evaluate wider ranges of the properties of silicate dust more reliably. Comparing fitting results between four dust models with different sizes and porosities, 95 out of the 98 galaxies prefer a porous silicate dust model without micron-sized large grains. The pyroxene mass fraction and the crystallinity are overall consistent with-but significantly different from-the previous results for the individual galaxies. The pyroxene-poor composition, small dust size, and high porosity are similar to newly formed dust around mass-loss stars as seen in our Galaxy, which presumably originates from the recent circumnuclear starburst activity. The high crystallinity on average suggests dust processing induced by AGN activities.

Keywords: astrophysical dust processes; infrared galaxies; active galactic nuclei
Electron-impact Excitation of Fe I

The Fe I spectra emitted by astrophysical sources contain information on plasma parameters such as chemical abundances and magnetic fields. However, to determine these parameters requires detailed plasma modeling, which in turn needs accurate atomic data for processes such as radiative decay and electron-impact excitation in Fe I. A lack of fine-structure resolved collision strengths for transitions in Fe I is addressed in this paper with the presentation of data obtained from a Dirac R-matrix calculation. The suitability of our choice of target description is shown, with our energies generally within 7% of literature values. Various A-values are compared with other theoretical and experimental results, and the quality of the collision strengths produced in this work demonstrated. A comparison of 300- and 1000-level close-coupling expansions is made, the latter shown to eliminate pseudoresonances in the collision strengths at electron energies between 0.5 and 1.0 Ry. Maxwell-averaged effective collision strengths are presented, and the convergence of our data is shown in the temperature range 1000-100,000 K.

Keywords: atomic physics; excitation rates; de-excitation rates
A Unified Framework for X-shaped Radio Galaxies

We propose a radically different picture for X-shaped radio galaxies compared with existing models as transition objects between cold-mode accreting, low-spinning retrograde black holes and low-spinning prograde black holes. This model explains their smaller average black hole masses; their general aversion for cluster compared with isolated environments; the negligible difference in spectral index between primary and secondary jets, despite a time difference in their formation; their absence among the most powerful radio quasars and radio galaxies; and their connection to the elusive Fanaroff-Riley I quasar class, among others. The key to their formation is cold gas accretion onto Schwarzschild black holes.

Keywords: radio galaxies
A Long-period Pre-ELM System Discovered from the LAMOST Medium-resolution Survey

We present LAMOST J041920.07+072545.4 (hereafter J0419), a close binary consisting of a bloated, extremely low mass pre-white dwarf (pre-ELM WD) and a compact object with an orbital period of 0.607189 days. The large-amplitude ellipsoidal variations and the evident Balmer and He I emission lines suggest a filled Roche lobe and ongoing mass transfer. No outburst events were detected in the 15 years of monitoring of J0419, indicating a very low mass transfer rate. The temperature of the pre-ELM, ${T}_{\mathrm{eff}}={5793}_{-133}^{+124}\,{\rm{K}}$ , makes it cooler than the known ELMs, but hotter than most cataclysmic variable donors. Combining the mean density within the Roche lobe and the radius constrained from our spectral energy distribution fitting, we obtain the mass of the pre-ELM, M 1 = 0.176 ± 0.014 M ⊙. The joint fitting of light and radial velocity curves yields an inclination angle of $i={66.5}_{-1.7}^{+1.4}$ degrees, corresponding to a mass of the compact object of M 2 = 1.09 ± 0.05 M ⊙. The very bloated pre-ELM has a smaller surface gravity ( $\mathrm{log}g=3.9\pm 0.01$ , R 1 = 0.78 ± 0.02 R ⊙) than the known ELMs or pre-ELMs. The temperature and the luminosity ( ${L}_{\mathrm{bol}}={0.62}_{-0.10}^{+0.11}\,{L}_{\odot }$ ) of J0419 are close to those of the main sequence, which makes the selection of such systems through the H-R diagram inefficient. Based on the evolutionary model, the relatively long period and small $\mathrm{log}g$ indicate that J0419 could be close to the "bifurcation period" in the orbital evolution, which makes J0419 a unique source to connect ELM/pre-ELM WD systems, wide binaries, and cataclysmic variables.

Keywords: close binary stars; cataclysmic variable stars; white dwarf stars; low mass stars
Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). XI. Proximity Zone Analysis for Faint Quasar Spectra at z ∼ 6

We present measurements of the size of the quasar proximity zone (Rp) for 11 low-luminosity ( $-26.16\leqslant {M}_{1450}\leqslant -22.83$ ) quasars at z ∼ 6, discovered by the Subaru High-z Exploration of Low-Luminosity Quasars project. Our faint quasar sample expands the Rp measurement down to ${M}_{1450}=-22.83$ mag, where more common quasar populations dominate at the epoch. We restrict the sample to quasars whose systemic redshifts have been precisely measured by [C II] 158 μm or Mg II λ2798 emission lines. We also update the Rp measurements for 26 luminous quasars presented in Eilers et al. by using the latest systemic redshift results. The luminosity dependence on Rp is found to be consistent with the theoretical prediction assuming a highly ionized intergalactic medium. We find a shallow redshift evolution of the luminosity-corrected Rp, ${R}_{p,\mathrm{corr}}^{-25}$ ( ${R}_{p,\mathrm{corr}}^{-25}\propto {(1+z)}^{-3.79\pm 1.72}$ ) over $5.8\lesssim z\lesssim 6.6$ . This trend is steeper than that of Eilers et al., but significantly shallower than those of the earlier studies. Our results suggest that Rp,corr is insensitive to the neutral fraction of the universe at z ∼ 6. Four quasars show exceptionally small ${R}_{p,\mathrm{corr}}^{-25}$ ( $\lesssim 0.90$ proper Mpc), which could be the result of their young age (<104 yr) in the reionization epoch, though statistics on this are still scarce.

Keywords: reionization; intergalactic medium; quasar absorption line spectroscopy
Constraints on the Muon Fraction and Density Profile in Neutron Stars

Muons in neutron stars (NSs) play especially important roles in addressing several interesting new physics questions associated with detecting as well as understanding interactions and astrophysical effects of muonphilic dark matter particles. The key model inputs for studying the latter are the total muon mass Mμ, the muon mass fraction Mμ/MNS over the NS mass MNS, and the muon radial density profile ρμ(r) in NSs of varying masses. We investigate these quantities within a minimum model for the core of NSs consisting of neutrons, protons, electrons, and muons using an explicitly isospin-dependent parametric equation of state (EOS) constrained by available nuclear laboratory experiments and the latest astrophysical observations of NS masses, radii, and tidal deformabilities. We found that the absolutely maximum muon mass Mμ and its mass fraction Mμ/MNS in the most massive NSs allowed by causality are about 0.025 M⊙ and 1.1%, respectively. For the most massive NS of mass 2.14 M⊙ observed so far, they reduce to about 0.020 M⊙ and 0.9%, respectively. We also study respective effects of individual parameters describing the EOS of high-density neutron-rich nucleonic matter on the muon contents in NSs with varying masses. We found that the most important but uncertain nuclear physics ingredient for determining the muon contents in NSs is the high-density nuclear symmetry energy.

Keywords: neutron stars; dark matter; high energy astrophysics; nuclear astrophysics; nuclear physics
Simulations of High-redshift [O III] Emitters: Chemical Evolution and Multiline Diagnostics

Recent observations by the James Webb Space Telescope discovered a number of high-redshift galaxies with strong emission lines from doubly ionized oxygen. Combined with Atacama Large Millimeter/submillimeter Array observations of far-infrared lines, multiline diagnostics can be applied to the high-redshift galaxies in order to probe the physical conditions of the interstellar medium. We study the formation and evolution of galaxies using the FirstLight simulation suite, which provides outputs of 62 high-resolution, zoom-in galaxy simulations. We devise a physical model of H II regions and calculate spatially resolved [O III] line emission. We show that massive galaxies with stellar masses of M * > 109 M ⊙ chemically evolve rapidly to z = 9. Young stellar populations in the star-forming galaxies boost the [O III] line emission, rendering the ratio of line luminosity to star formation rate larger than that for low-redshift galaxies, which is consistent with recent observations. Measuring the flux ratios of rest-frame optical and far-infrared lines allows us to estimate the physical conditions such as density and metallicity of the star-forming gas in high-redshift [O III] emitters.

Keywords: galaxy evolution
Linear Polarization of the 21 cm Line from the Epoch of Reionization

The 21 cm linear polarization due to Thomson scattering off free electrons can probe the distribution of neutral hydrogen in the intergalactic medium during the epoch of reionization, complementary to the 21 cm temperature fluctuations. A previous study estimated the strength of polarization with a toy model and claimed that it can be detected with 1 month observation of the Square Kilometre Array (SKA). Here we revisit this investigation with account of nonlinear terms due to inhomogeneous reionization, using semi-numerical reionization simulations to provide the realistic estimation of the 21 cm TE and EE angular power spectra ( ${C}_{{\ell }}^{\mathrm{TE}}$ and ${C}_{{\ell }}^{\mathrm{EE}}$ ). We find that (1) both power spectra are enhanced on sub-bubble scales but suppressed on super-bubble scales, compared with previous results; (2) ${C}_{{\ell }}^{\mathrm{TE}}$ displays a zero crossing at ℓ < 100, and its angular scale is sensitive to the scale dependence of H I bias on large scales; (3) the ratios of the power spectrum to its maximum value during reionization at a given ℓ, i.e., ${C}_{{\ell }}^{\mathrm{TE}}/{C}_{{\ell },\max }^{\mathrm{TE}}$ and ${C}_{{\ell }}^{\mathrm{EE}}/{C}_{{\ell },\max }^{\mathrm{EE}}$ , show robust correlations with the global ionized fraction. However, measurement of this signal will be very challenging not only because the overall strength is weaker than the sensitivity of SKA, but also because of the polarized foregrounds from diffuse synchrotron emission, and Faraday rotation, which modifies the observed polarization. Nevertheless, the 21 cm linear polarization signal may still likely be detectable through other approaches, e.g., its cross-correlation with other probes.

Keywords: reionization; h i line emission; radio interferometry; intergalactic medium; large-scale structure of the universe; two-point correlation function
A Rapid and Large-amplitude X-Ray Dimming Event in a z ≈ 2.6 Radio-quiet Quasar

We report a dramatic, fast X-ray dimming event in a z = 2.627 radio-quiet type 1 quasar, which has an estimated supermassive black hole (SMBH) mass of 6.3 × 109 M ⊙. In the high X-ray state, it showed a typical level of X-ray emission relative to its UV/optical emission. Then its 0.5-2 keV (rest-frame 1.8-7.3 keV) flux dropped by a factor of ≈7.6 within two rest-frame days. The dimming is associated with spectral hardening, as the 2-7 keV (rest-frame 7.3-25.4 keV) flux dropped by only 17%, and the effective power-law photon index of the X-ray spectrum changed from ≈2.3 to ≈0.9. The quasar has an infrared (IR)-to-UV spectral energy distribution and a rest-frame UV spectrum similar to those of typical quasars, and it does not show any significant long-term variability in the IR and UV/optical bands. Such an extremely fast and large-amplitude X-ray variability event has not been reported before in luminous quasars with such massive SMBHs. The X-ray dimming is best explained by a fast-moving absorber crossing the line of sight and fully covering the X-ray emitting corona. Adopting a conservatively small size of 5 GM BH/c 2 for the X-ray corona, the transverse velocity of the absorber is estimated to be ≈0.9c. The quasar is likely accreting with a high or even super-Eddington accretion rate, and the high-velocity X-ray absorber is probably related to a powerful accretion-disk wind. Such an energetic wind may eventually evolve into a massive galactic-scale outflow, providing efficient feedback to the host galaxy.

Keywords: x-ray active galactic nuclei; active galactic nuclei; x-ray quasars; quasars
Uniform Forward-modeling Analysis of Ultracool Dwarfs. II. Atmospheric Properties of 55 Late-T Dwarfs

We present a large uniform forward-modeling analysis for 55 late-T (T7-T9) dwarfs, using low-resolution (R ≈ 50-250) near-infrared (1.0-2.5 μm) spectra and cloudless Sonora-Bobcat model atmospheres. We derive the objects' effective temperatures, surface gravities, metallicities, radii, masses, and bolometric luminosities using our newly developed Bayesian framework, and use the resulting population properties to test the model atmospheres. We find (1) our objects' fitted metallicities are 0.3-0.4 dex lower than those of nearby stars; (2) their ages derived from spectroscopic parameters are implausibly young (10 Myr-0.4 Gyr); (3) their fitted effective temperatures show a similar spread to empirical temperature scales at a given spectral type but are ~50-200 K hotter for ≥T8 dwarfs; and (4) their spectroscopically inferred masses are unphysically small (mostly 1-8 MJup). These suggest the Sonora-Bobcat assumptions of cloudless and chemical-equilibrium atmospheres do not adequately reproduce late-T dwarf spectra. We also find a gravity and metallicity dependence of effective temperature as a function of spectral type. Combining the resulting parameter posteriors of our sample, we quantify the degeneracy between the fitted surface gravity and metallicity such that an increase in Z combined with a 3.4× increase in logg results in a spectrum that has similar fitted parameters. We note the systematic difference between the late-T dwarf spectra and Sonora-Bobcat models is on average ≈2%-4% of the objects' peak J-band fluxes over the 1.0-2.5 μm range, implying modeling systematics will exceed measurement uncertainties when analyzing data with J-band S/N ≳ 50. Using our large, high-quality sample, we examine the spectral-fitting residuals as a function of wavelength and atmospheric properties to discern how to improve the model assumptions. Our work constitutes the largest analysis of brown dwarf spectra using multimetallicity models and the most systematic examination of ultracool model atmospheres to date.

Keywords: brown dwarfs; t dwarfs; stellar atmospheres; exoplanet atmospheres
A CO Survey of the Entire Northern Sky

We present a very large extension of the Galactic plane CO survey of Dame et al. to the entire northern sky (δ > -17°). The extension was carried out with the same telescope as was used for the plane survey, the CfA 1.2 m, and perfectly meshes with its irregular boundaries in latitude. A total of 382,202 CO(1-0) spectra uniformly sample the high-latitude sky with a true-angle spacing of 0.°25 or better. The final reduced and folded spectra have a uniform sensitivity of 0.18 K in 0.65 km s-1 channels and provide a velocity coverage of ±47.1 km s-1. We describe the observational techniques and the data reduction and provide various summary maps of the spatial and velocity distributions of CO emission over the northern sky, and a catalog of the molecular clouds we found there. We also describe the CO spectral line data cubes that we have made available online.

Keywords: molecular clouds; diffuse molecular clouds; interstellar molecules; interstellar line emission; solar neighborhood