adsabs/SciX_UAT_keywords huggingface dataset:
The Connection Between Galactic Outflows and the Escape of Ionizing Photons

We analyze spectra of a gravitationally lensed galaxy, known as the Sunburst Arc, that is leaking ionizing photons, also known as the Lyman continuum (LyC). Magnification from gravitational lensing permits the galaxy to be spatially resolved into one region that leaks ionizing photons and several that do not. Rest-frame UV and optical spectra from Magellan target 10 different regions along the lensed Arc, including six multiple images of the LyC leaking region and four regions that do not show LyC emission. The rest-frame optical spectra of the ionizing photon emitting regions reveal a blueshifted (ΔV = 27 km s-1) broad emission component (FWHM = 327 km s-1), comprising 55% of the total [O III] line flux, in addition to a narrow component (FWHM = 112 km s-1), suggesting the presence of strong highly ionized gas outflows. This is consistent with the high-velocity ionized outflow inferred from the rest-frame UV spectra. In contrast, the broad emission component is less prominent in the nonleaking regions, comprising ~26% of total [O III] line flux. The high-ionization absorption lines are prominent in both the leaker and the nonleaker, but the low-ionization absorption lines are very weak in the leaker, suggesting that the line-of-sight gas is highly ionized in the leaker. Analyses of stellar wind features reveal that the stellar population of the LyC leaking regions is considerably younger (~3 Myr) than that of the nonleaking regions (~12 Myr), emphasizing that stellar feedback from young stars may play an important role in ionizing photon escape.

Keywords: high-redshift galaxies; reionization
The JCMT BISTRO Survey: Studying the Complex Magnetic Field of L43

We present observations of polarized dust emission at 850 μm from the L43 molecular cloud, which sits in the Ophiuchus cloud complex. The data were taken using SCUBA-2/POL-2 on the James Clerk Maxwell Telescope as a part of the BISTRO large program. L43 is a dense ( ${N}_{{{\rm{H}}}_{2}}\sim {10}^{22}$ -1023 cm-2) complex molecular cloud with a submillimeter-bright starless core and two protostellar sources. There appears to be an evolutionary gradient along the isolated filament that L43 is embedded within, with the most evolved source closest to the Sco OB2 association. One of the protostars drives a CO outflow that has created a cavity to the southeast. We see a magnetic field that appears to be aligned with the cavity walls of the outflow, suggesting interaction with the outflow. We also find a magnetic field strength of up to ~160 ± 30 μG in the main starless core and up to ~90 ± 40 μG in the more diffuse, extended region. These field strengths give magnetically super- and subcritical values, respectively, and both are found to be roughly trans-Alfvénic. We also present a new method of data reduction for these denser but fainter objects like starless cores.

Keywords: stellar-interstellar interactions; interstellar magnetic fields; young stellar objects; dust continuum emission; starlight polarization; molecular clouds
On the Optical Transients from Double White-dwarf Mergers

Double white dwarf (DWD) mergers are relevant astrophysical sources expected to produce massive, highly magnetized white dwarfs (WDs), supernovae (SNe) Ia, and neutron stars (NSs). Although they are expected to be numerous sources in the sky, their detection has evaded the most advanced transient surveys. This article characterizes the optical transient expected from DWD mergers in which the central remnant is a stable (sub-Chandrasekhar) WD. We show that the expansion and cooling of the merger's dynamical ejecta lead to an optical emission peaking at 1-10 days postmerger, with luminosities of 1040-1041 erg s-1. We present simulations of the light curves, spectra, and the color evolution of the transient. We show that these properties, together with the estimated rate of mergers, are consistent with the absence of detection, e.g., by the Zwicky Transient Facility. More importantly, we show that the Legacy Survey of Space and Time of the Vera C. Rubin Observatory will likely detect a few/several hundred per year, opening a new window to the physics of WDs, NSs, and SNe Ia.

Keywords: white dwarf stars; stellar mergers; compact binary stars; compact objects; visible sources
A Program for Multimessenger Standard Siren Cosmology in the Era of LIGO A+, Rubin Observatory, and Beyond

The most promising variation of the standard siren technique combines gravitational-wave (GW) data for binary neutron star (BNS) mergers with redshift measurements enabled by their electromagnetic (EM) counterparts, to constrain cosmological parameters such as H0, Ωm, and w0. Here we evaluate the near- and long-term prospects of multimessenger cosmology in the era of future GW observatories: Advanced LIGO Plus (A+, 2025), Voyager-like detectors (2030s), and Cosmic Explorer-like detectors (2035 and beyond). We show that the BNS horizon distance of ≈ 700 Mpc for A+ is well matched to the sensitivity of the Vera C. Rubin Observatory (VRO) for kilonova detections. We find that one year of joint A+ and VRO observations will constrain the value of H0 to percent-level precision, given a small investment of VRO time dedicated to target-of-opportunity GW follow-up. In the Voyager era, the BNS-kilonova observations begin to constrain Ωm with an investment of a few percent of VRO time. With the larger BNS horizon distance in the Cosmic Explorer era, on-axis short gamma-ray bursts (SGRBs) and their afterglows (though accompanying only some of the GW-detected mergers) supplant kilonovae as the most promising counterparts for redshift identification. We show that five years of joint observations with Cosmic Explorer-like facilities and a next-generation gamma-ray satellite with localization capabilities similar to that presently possible with Swift could constrain both Ωm and w0 to 15%-20%. We therefore advocate for a robust target-of-opportunity (ToO) program with VRO, and a wide-field gamma-ray satellite with improved sensitivity in the 2030s, to enable standard siren cosmology with next-generation gravitational-wave facilities.

Keywords: gravitational waves; cosmological parameters; neutron stars
Jet Mechanism and γ-Ray-emitting Region for Fermi Flat-spectrum Radio Quasars with Broad-line Emissions

Blazars are a subject of intense debate, specifically regarding their jet launch and emission mechanisms, and the origins of their γ-ray radiation. To explore these issues, we have built a comprehensive sample of flat-spectrum radio quasars (FSRQs), with well-characterized spectral energy distribution. This study aims to elucidate the dominant jet launch mechanism and the main processes behind the inverse Compton (IC) component. Additionally, we seek to pinpoint the location of the γ-ray dissipation region relative to the central black hole, denoted as R γ . Our approach involves a detailed analysis of broad-line region (BLR) emission, from which we derive robust estimates of the black hole masses using two distinct virial techniques. This enables us to constrain the jet power across a wide array of FSRQs. Our findings lead to several significant conclusions: (i) The correlation of jet power with black hole mass allows us to test the Blandford–Znajek, Blandford–Payne, and hybrid mechanisms. We find that the hybrid mechanism is most effective in explaining the jet power observed in the majority of FSRQs; (ii) The IC component of the γ-rays in FSRQs is predominantly due to the external Compton process. (iii) Through simulations, we determine the minimum and maximum values of R γ (the γ-ray dissipation region) and conclude it is located outside the BLR. This conclusion is derived from the variability timescale analysis.

Keywords: active galactic nuclei; blazars; flat-spectrum radio quasars; jets; black holes
Discovery of Optically Emitting Circumgalactic Nebulae around the Majority of UV-luminous Quasars at Intermediate Redshift

We report the discovery of large, ionized, [O II]-emitting circumgalactic nebulae around the majority of 30 UV-luminous quasars at z = 0.4–1.4 observed with deep, wide-field integral field spectroscopy with the Multi-Unit Spectroscopy Explorer (MUSE) by the Cosmic Ultraviolet Baryon Survey and MUSE Quasar Blind Emitters Survey. Among the 30 quasars, seven (23%) exhibit [O II]-emitting nebulae with major axis sizes greater than 100 kpc, 20 greater than 50 kpc (67%), and 27 (90%) greater than 20 kpc. Such large, optically emitting nebulae indicate that cool, dense, and metal-enriched circumgalactic gas is common in the halos of luminous quasars at intermediate redshift. Several of the largest nebulae exhibit morphologies that suggest interaction-related origins. We detect no correlation between the sizes and cosmological-dimming-corrected surface brightnesses of the nebulae and quasar redshift, luminosity, black hole mass, or radio-loudness, but find a tentative correlation between the nebulae and rest-frame [O II] equivalent width in the quasar spectra. This potential trend suggests a relationship between interstellar medium content and gas reservoirs on CGM scales. The [O II]-emitting nebulae around the z ≈ 1 quasars are smaller and less common than Lyα nebulae around z ≈ 3 quasars. These smaller sizes can be explained if the outer regions of the Lyα halos arise from scattering in more neutral gas, by evolution in the cool circumgalactic medium content of quasar-host halos, by lower-than-expected metallicities on ≳50 kpc scales around z ≈ 1 quasars, or by changes in quasar episodic lifetimes between z = 3 and 1.

Keywords: circumgalactic medium; cool intergalactic medium; quasars
Cool, Luminous, and Highly Variable Stars in the Magellanic Clouds. II. Spectroscopic and Environmental Analysis of Thorne-Żytkow Object and Super-AGB Star Candidates

In previous work, we identified a population of 38 cool and luminous variable stars in the Magellanic Clouds and examined 11 in detail in order to classify them as either Thorne-Żytkow objects (TŻOs; red supergiants with a neutron star cores) or super-asymptotic giant branch (sAGB) stars (the most massive stars that will not undergo core collapse). This population includes HV 2112, a peculiar star previously considered in other works to be either a TŻO or high-mass asymptotic giant branch (AGB) star. Here we continue this investigation, using the kinematic and radio environments and local star formation history of these stars to place constraints on the age of the progenitor systems and the presence of past supernovae. These stars are not associated with regions of recent star formation, and we find no evidence of past supernovae at their locations. Finally, we also assess the presence of heavy elements and lithium in their spectra compared to red supergiants. We find strong absorption in Li and s-process elements compared to RSGs in most of the sample, consistent with sAGB nucleosynthesis, while HV 2112 shows additional strong lines associated with TŻO nucleosynthesis. Coupled with our previous mass estimates, the results are consistent with the stars being massive (~4-6.5 M ⊙) or sAGB (~6.5-12 M ⊙) stars in the thermally pulsing phase, providing crucial observations of the transition between low- and high-mass stellar populations. HV 2112 is more ambiguous; it could either be a maximally massive sAGB star, or a TŻO if the minimum mass for stability extends down to ≲13 M ⊙.

Keywords: massive stars; asymptotic giant branch stars; chemically peculiar stars; lithium stars; spectroscopy; stellar kinematics; magellanic clouds
Angular Distribution and Polarization of the 3C and 3D Lines Following Electron-impact Excitation of Fe16+ Ions

The electron-impact excitations from the ground state to the excited levels $1{s}^{2}2{s}^{2}2{p}_{1/2}^{5}3{d}_{3/2}\,J=1$ <!-- --> and $1{s}^{2}2{s}^{2}2{p}_{3/2}^{5}3{d}_{5/2}\,J=1$ <!-- --> as well as the subsequent radiative decays of neonlike Fe16+ ions have been investigated within the framework of the multiconfigurational Dirac-Fock method and the relativistic distorted-wave theory. Special attention has been paid to emission behaviors of the astrophysically relevant resonance 3C and intercombination 3D lines emitted in the radiative decays of Fe16+ ions. To this end, we calculate the angular distribution and linear polarization of both of the lines for a series of impact electron energies. It is found that the angular and polarization behaviors of the resonance 3C line are nearly the same as those of the intercombination 3D line. Nevertheless, the angular and polarization behaviors of both of the lines are found to be very sensitive to the impact electron energy, especially at low impact energies. Based on such a sensitivity, it is expected that high-precision angular and polarization measurements of the 3C and 3D lines could be served as a tool for revealing detailed information such as electron energy of relevant laboratory and astrophysical plasmas.

Keywords: atomic physics; atomic spectroscopy; radiative processes; theoretical models
Magnetically Aligned Striations in the L914 Filamentary Cloud

We present CO(J = 1–0) multiline observations toward the L914 dark cloud in the vicinity of the Cygnus X region, using the 13.7 m millimeter telescope of the Purple Mountain Observatory. The CO observations reveal in the L914 cloud a long filament with an angular length of ∼3.°6, corresponding to approximately 50 pc at the measured distance of ∼ 760 pc. Furthermore, a group of hair-like striations are discovered in two subregions of the L914 cloud, which are connected with the dense ridge of the filament. These striations display quasiperiodic characteristics in both the CO intensity images and position–velocity diagrams. Two of the striations also show increasing velocity gradients and dispersions toward the dense ridge, which could be fitted by accretion flows under gravity. Based on the Planck 353 GHz dust polarization data, we find that the striations are well aligned with the magnetic fields. Moreover, both the striations and magnetic fields are perpendicular to the dense ridge, constructing a bimodal configuration. Using the classic method, we estimate the strength of the magnetic field and further evaluate the relative importance of gravity, turbulence, and the magnetic field, finding that the L914 cloud is strongly magnetized. Our results suggest that magnetic fields play an important role in the formation of filamentary structures by channeling the material along the striations toward the dense ridge. The comparison between the observations and simulations suggests that striations could be a product of the magnetohydrodynamic process.

Keywords: molecular clouds; interstellar medium; interstellar filaments; interstellar magnetic fields; polarimetry
Evidence for Low-level Dynamical Excitation in Near-resonant Exoplanet Systems

The geometries of near-resonant planetary systems offer a relatively pristine window into the initial conditions of exoplanet systems. Given that near-resonant systems have likely experienced minimal dynamical disruptions, the spin-orbit orientations of these systems inform the typical outcomes of quiescent planet formation, as well as the primordial stellar obliquity distribution. However, few measurements have been made to constrain the spin-orbit orientations of near-resonant systems. We present a Rossiter-McLaughlin measurement of the near-resonant warm Jupiter TOI-2202 b, obtained using the Carnegie Planet Finder Spectrograph on the 6.5 m Magellan Clay Telescope. This is the eighth result from the Stellar Obliquities in Long-period Exoplanet Systems survey. We derive a sky-projected 2D spin-orbit angle $\lambda ={26}_{-15}^{+12}{^\circ} $ and a 3D spin-orbit angle $\psi ={31}_{-11}^{+13}{^\circ} $ , finding that TOI-2202 b-the most massive near-resonant exoplanet with a 3D spin-orbit constraint to date-likely deviates from exact alignment with the host star's equator. Incorporating the full census of spin-orbit measurements for near-resonant systems, we demonstrate that the current set of near-resonant systems with period ratios P 2/P 1 ≲ 4 is generally consistent with a quiescent formation pathway, with some room for low-level (≲20°) protoplanetary disk misalignments or post-disk-dispersal spin-orbit excitation. Our result constitutes the first population-wide analysis of spin-orbit geometries for near-resonant planetary systems. * This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: exoplanet astronomy; exoplanet dynamics; exoplanet migration; exoplanet formation; exoplanet evolution; orbital resonances; exoplanet systems; exoplanets; planetary alignment; orbital evolution
Physical Characterization of Serendipitously Uncovered Millimeter-wave Line-emitting Galaxies at z 2.5 behind the Local Luminous Infrared Galaxy VV 114

We present a detailed investigation of millimeter-wave line emitters ALMA J010748.3-173028 (ALMA-J0107a) and ALMA J010747.0-173010 (ALMA-J0107b), which were serendipitously uncovered in the background of the nearby galaxy VV 114 with spectral scan observations at λ = 2-3 mm. Via Atacama Large Millimeter/submillimeter Array (ALMA) detection of CO(4-3), CO(3-2), and [C I](1-0) lines for both sources, their spectroscopic redshifts are unambiguously determined to be z = 2.4666 ± 0.0002 and z = 2.3100 ± 0.0002, respectively. We obtain the apparent molecular gas masses Mgas of these two line emitters from [C I] line fluxes as (11.2 ± 3.1) × 1010 M⊙ and (4.2 ± 1.2) × 1010 M⊙, respectively. The observed CO(4-3) velocity field of ALMA-J0107a exhibits a clear velocity gradient across the CO disk, and we find that ALMA-J0107a is characterized by an inclined rotating disk with a significant turbulence, that is, a deprojected maximum rotation velocity to velocity dispersion ratio ${v}_{\max }/{\sigma }_{v}$ of 1.3 ± 0.3. We find that the dynamical mass of ALMA-J0107a within the CO-emitting disk computed from the derived kinetic parameters, (1.1 ± 0.2) × 1010 M⊙, is an order of magnitude smaller than the molecular gas mass derived from dust continuum emission, (3.2 ± 1.6) × 1011 M⊙. We suggest this source is magnified by a gravitational lens with a magnification of μ ≳ 10, which is consistent with the measured offset from the empirical correlation between CO-line luminosity and width.

Keywords: high-redshift galaxies
Confirming the Existence of Twin Stars in a NICER Way

We demonstrate that future radius measurements of the NICER mission have the potential to reveal the existence of a strong phase transition in dense neutron star matter by confirming the existence of so-called twin stars, compact star configurations with the same mass but different radii. The latest radius constraints from NICER for the pulsars J0740+6620 as well as J0030+0451 are discussed using relativistic mean field equations of state with varying stiffness, connected with a first-order phase transition to quark matter. We show that twin star solutions are compatible with the new radius constraint but are located at radii below the present constraints from NICER, serving as a smoking gun for a strong phase transition in neutron star matter. This scenario is realized if a strong phase transition takes place in neutron stars of the first branch with masses above 2 M ⊙.

Keywords: neutron star cores; pulsars; compact objects; nuclear astrophysics
Toward Unveiling Cosmic Reionization: The Ionizing Photon Production Efficiency (ξ ion) of Low-mass Hα Emitters at z ∼ 2.3

We investigate the galaxy properties of ∼400 low-mass (<109 M ⊙) Hα emitters (HAEs) at z ∼ 2.3 in the ZFOURGE survey. The selection of these HAEs is based on the excess in the observed K s broadband flux compared to the stellar continuum estimated from the best-fit spectral energy distribution. These low-mass HAEs have elevated SFR(Hα) above the star formation main sequence, making them potential analogs of the galaxies that reionized the Universe during the Epoch of Reionization. The ionizing photon production efficiencies (ξ ion) of the low-mass HAEs have a median value of , assuming the Calzetti (SMC) curve for the stellar continuum dust correction. This value is higher than that of main-sequence galaxies by ∼0.2 dex at similar redshift, indicating that the low-mass HAEs are more efficient in producing ionizing photons. Our results also consolidate the trend of increasing ξ ion with redshift, but reveal a "downsizing" relationship between ξ ion and stellar mass (M ⊙) with increasing redshift. We further explore the dependence of ξ ion on other galaxy properties, such as the UV spectral slope (β UV), the UV magnitude (M UV), and the equivalent widths of Hα and [O III] emission lines. Galaxies with bluer UV slopes, fainter UV luminosities, and higher equivalent widths exhibit elevated ξ ion by a factor of ∼2 compared to the median ξ ion of our sample. JWST data will provide an opportunity to extend our method and further investigate the properties of low-mass galaxies at high redshifts.

Keywords: high-redshift galaxies; emission line galaxies; reionization; galaxy evolution
Re-estimating the Spin Parameter of the Black Hole in Cygnus X-1

Cygnus X-1 is a well-studied persistent black hole X-ray binary. Recently, the three parameters needed to estimate the black hole spin of this system, namely the black hole mass M, the orbital inclination i, and the source distance D, have been updated. In this work we redetermine the spin parameter using the continuum-fitting technique for those updated parameter values. Based on the assumption that the spin axis of the black hole is aligned with the orbital plane, we fit the thermal disk component to a fully relativistic thin accretion disk model. The error in the spin estimate arising from the combined observational uncertainties is obtained via Monte Carlo simulations. We demonstrate that, without considering the counteracting torque effect, the new spin parameter is constrained to be a* > 0.9985 (3σ), which confirms that the spin of the black hole in Cygnus X-1 is extreme.

Keywords: x-ray binary stars; black hole physics; high energy astrophysics
On the Kinematics of Cold, Metal-enriched Galactic Fountain Flows in Nearby Star-forming Galaxies

We use medium-resolution Keck/Echellette Spectrograph and Imager spectroscopy of bright quasars to study cool gas traced by Ca II λλ3934, 3969 and Na I λλ5891, 5897 absorption in the interstellar/circumgalactic media of 21 foreground star-forming galaxies at redshifts 0.03 < z < 0.20 with stellar masses 7.4 ≤ log M */M ⊙ ≤ 10.6. The quasar-galaxy pairs were drawn from a unique sample of Sloan Digital Sky Survey quasar spectra with intervening nebular emission, and thus have exceptionally close impact parameters (R ⊥ < 13 kpc). The strength of this line emission implies that the galaxies' star formation rates (SFRs) span a broad range, with several lying well above the star-forming sequence. We use Voigt profile modeling to derive column densities and component velocities for each absorber, finding that column densities N(Ca II) > 1012.5 cm-2 (N(Na I) > 1012.0 cm-2) occur with an incidence f C(Ca II) = 0.63+0.10 -0.11 (f C(Na I) = 0.57+0.10 -0.11). We find no evidence for a dependence of f C or the rest-frame equivalent widths W r (Ca II K) or W r (Na I 5891) on R ⊥ or M *. Instead, W r (Ca II K) is correlated with local SFR at >3σ significance, suggesting that Ca II traces star formation-driven outflows. While most of the absorbers have velocities within ±50 km s-1 of the host redshift, their velocity widths (characterized by Δv 90) are universally 30-177 km s-1 larger than that implied by tilted-ring modeling of the velocities of interstellar material. These kinematics must trace galactic fountain flows and demonstrate that they persist at R ⊥ > 5 kpc. Finally, we assess the relationship between dust reddening and W r (Ca II K) (W r (Na I 5891)), finding that 33% (24%) of the absorbers are inconsistent with the best-fit Milky Way E(B-V)-W r relations at >3σ significance.

Keywords: galaxies; quasar-galaxy pairs; interstellar medium; circumgalactic medium; quasar absorption line spectroscopy