adsabs/SciX_UAT_keywords huggingface dataset:
EMPRESS. IX. Extremely Metal-poor Galaxies are Very Gas-rich Dispersion-dominated Systems: Will the James Webb Space Telescope Witness Gaseous Turbulent High-z Primordial Galaxies?

We present kinematics of six local extremely metal-poor galaxies (EMPGs) with low metallicities (0.016-0.098 Z ⊙) and low stellar masses (104.7-107.6 M ⊙). Taking deep medium/high-resolution (R ~ 7500) integral-field spectra with 8.2 m Subaru, we resolve the small inner velocity gradients and dispersions of the EMPGs with Hα emission. Carefully masking out substructures originating by inflow and/or outflow, we fit three-dimensional disk models to the observed Hα flux, velocity, and velocity dispersion maps. All the EMPGs show rotational velocities (v rot) of 5-23 km s-1 smaller than the velocity dispersions (σ 0) of 17-31 km s-1, indicating dispersion-dominated (v rot/σ 0 = 0.29-0.80 < 1) systems affected by inflow and/or outflow. Except for two EMPGs with large uncertainties, we find that the EMPGs have very large gas-mass fractions of f gas ≃ 0.9-1.0. Comparing our results with other Hα kinematics studies, we find that v rot/σ 0 decreases and f gas increases with decreasing metallicity, decreasing stellar mass, and increasing specific star formation rate. We also find that simulated high-z (z ~ 7) forming galaxies have gas fractions and dynamics similar to the observed EMPGs. Our EMPG observations and the simulations suggest that primordial galaxies are gas-rich dispersion-dominated systems, which would be identified by the forthcoming James Webb Space Telescope observations at z ~ 7.

Keywords: galaxy formation; galaxy structure; star formation; galaxy kinematics; dwarf galaxies
Afterglow Constraints on the Viewing Angle of Binary Neutron Star Mergers and Determination of the Hubble Constant

One of the key properties of any binary is its viewing angle (i.e., inclination), θobs. In binary neutron star (BNS) mergers it is of special importance due to the role that it plays in the measurement of the Hubble constant, H0. The opening angle of the jet that these mergers launch, θj, is also of special interest. Following the detection of the first BNS merger, GW170817, there were numerous attempts to estimate these angles using the afterglow light curve, finding a wide range of values. Here we provide a simple formula for the ratio θobs/θj based on the afterglow light curve and show that this is the only quantity that can be determined from the light curve alone. Our result explains the inconsistency of the values found by the various studies of GW170817 that were largely driven by the different priors taken in each study. Among the additional information that can be used to estimate θobs and θj, the most useful is a VLBI measurement of the afterglow image superluminal motion. An alternative is an identification of the afterglow transition to the subrelativistic phase. These observations are possible only for mergers observed at small viewing angles, whose afterglow is significantly brighter than the detector's threshold. We discuss the implications of these results to measurements of H0 using GW observations. We show that while the viewing angle will be measured only in a small fraction of future BNS mergers, it can significantly reduce the uncertainty in H0 in each one of these events, possibly to a level of 4%-5%.

Keywords: hubble constant; gamma-ray bursts; gravitational waves; gravitational wave astronomy
Imbalanced Turbulence Modified by Large-scale Velocity Shears in the Solar Wind

We have investigated how the degree of imbalance in solar wind turbulence is modified by large-scale velocity shears in the solar wind plasma. The balance between counterpropagating Alfvénic fluctuations, which interact nonlinearly to generate the turbulence, has been quantified by the cross helicity and Elsasser ratio. Velocity shears at a 30 minute timescale were identified, with the shear amplitude defined in terms of the linear Kelvin-Helmholtz (KH) instability threshold. The shears were associated with 74 interplanetary coronal mass ejection (ICME) sheaths observed by the Wind spacecraft at 1 au between 1997 and 2018. Typically weaker shears upstream of the sheaths and downstream in the ICME ejecta were also analyzed. In shears below the KH threshold, imbalance was approximately invariant or weakly rising with shear amplitude. Above the KH threshold, fluctuations tended toward a balanced state with increasing shear amplitude. Magnetic compressibility was also found to increase above the KH threshold. These findings are consistent with velocity shears being local sources of sunward fluctuations that act to reduce net imbalances in the antisunward direction, and suggest that the KH instability plays a role in this process.

Keywords: solar wind; interplanetary turbulence; interplanetary magnetic fields; solar coronal mass ejections
Joint Constraints on the Hubble Constant, Spatial Curvature, and Sound Horizon from the Late-time Universe with Cosmography

In this paper, using the latest Pantheon+ sample of Type Ia supernovae, baryon acoustic oscillation measurements, and observational Hubble data, we carry out a joint constraint on the Hubble constant H 0, the spatial curvature ΩK, and the sound horizon at the end of the drag epoch r d. To be model-independent, four cosmography models-i.e., the Taylor series in terms of redshift y 1 = z/(1 + z), ${y}_{2}=\arctan (z)$ , ${y}_{3}=\mathrm{ln}(1+z)$ , and the Padé approximants-are used without the assumption of a flat Universe. The results show that H 0 is anticorrelated with ΩK and r d, indicating that smaller ΩK or r d would be helpful in alleviating the Hubble tension. The values of H 0 and r d are consistent with the estimate derived from the Planck cosmic microwave background data based on the flat ΛCDM model, but H 0 is in 2.3 ~ 3.0σ tension with that obtained by Riess et al. in all these cosmographic approaches. Meanwhile, a flat Universe is preferred by the present observations under all approximations except the third order of y 1 and y 2 of the Taylor series. Furthermore, according to the values of the Bayesian evidence, we found that the flat ΛCDM remains to be the most favored model by the joint data sets, and the Padé approximant of order (2,2), the third order of y 3 and y 1 are the top three cosmographic expansions that fit the data sets best, while the Taylor series in terms of y 2 are essentially ruled out.

Keywords: observational cosmology; hubble constant; cosmological parameters
GOALS-JWST: Gas Dynamics and Excitation in NGC 7469 Revealed by NIRSpec

We present new JWST NIRSpec integral field spectroscopy (IFS) data for the luminous infrared galaxy NGC 7469, a nearby (70.6 Mpc) active galaxy with a Seyfert 1.5 nucleus that drives a highly ionized gas outflow and a prominent nuclear star-forming ring. Using the superb sensitivity and high spatial resolution of the JWST instrument NIRSpec IFS, we investigate the role of the Seyfert nucleus in the excitation and dynamics of the circumnuclear gas. Our analysis focuses on the [Fe II], H2, and hydrogen recombination lines that trace the radiation/shocked-excited molecular and ionized interstellar medium around the active galactic nucleus (AGN). We investigate gas excitation through H2/Brγ and [Fe II]/Paβ emission line ratios and find that photoionization by the AGN dominates within the central 300 pc of the galaxy except in a small region that shows signatures of shock-heated gas; these shock-heated regions are likely associated with a compact radio jet. In addition, the velocity field and velocity dispersion maps reveal complex gas kinematics. Rotation is the dominant feature, but we also identify noncircular motions consistent with gas inflows as traced by the velocity residuals and the spiral pattern in the Paα velocity dispersion map. The inflow is 2 orders of magnitude higher than the AGN accretion rate. The compact nuclear radio jet has enough power to drive the highly ionized outflow. This scenario suggests that the inflow and outflow are in a self-regulating feeding–feedback process, with a contribution from the radio jet helping to drive the outflow.

Keywords: luminous infrared galaxies; galaxy nuclei; active galactic nuclei; seyfert galaxies; galaxy winds; galaxy kinematics; galaxy dynamics
Revising Natal Kick Prescriptions in Population Synthesis Simulations

Natal kicks are a matter of debate and they significantly affect the merger rate density of compact objects. Here, we present a new simple formalism for natal kicks of neutron stars (NSs) and black holes (BHs). We describe the magnitude of the kick as {V}kick∝ {f}H05 mej mrem-1, where fH05 is a normalization factor, drawn from a Maxwellian distribution with one-dimensional rms velocity σ = 265 km s-1, mej is the mass of the supernova (SN) ejecta, and mrem is the mass of the compact object. This formalism matches the proper motions of young Galactic pulsars and can naturally account for the differences between core-collapse SNe of single stars, electron-capture SNe and ultra-stripped SNe occurring in interacting binaries. Finally, we use our new kick formalism to estimate the local merger rate density of binary NSs (RBNS), BH-NS binaries (RBHNS), and binary BHs (RBBH), based on the cosmic star formation rate density and metallicity evolution. In our fiducial model, we find RBNS ∼ 600 Gpc-3 yr-1, RBHNS ∼ 10 Gpc-3 yr-1, and RBBH ∼ 50 Gpc-3 yr-1, fairly consistent with the numbers inferred from the LIGO-Virgo collaboration.

Keywords: binary stars; supernovae; black holes; gravitational waves
Large Myr-old Disks Are Not Severely Depleted of Gas-phase CO or Carbon

We present an ACA search for [C I] 1-0 emission at 492 GHz toward large T Tauri disks (gas radii ≳ 200 au) in the ~1-3 Myr-old Lupus star-forming region. Combined with Atacama Large Millimeter/submillimeter Array 12 m archival data for IM Lup, we report [C I] 1-0 detections in six out of 10 sources, thus doubling the known detections toward T Tauri disks. We also identify four Keplerian double-peaked profiles and demonstrate that the [C I] 1-0 fluxes correlate with 13CO, C18O, and 12CO(2-1) fluxes, as well as with the gas disk outer radius measured from the latter transition. These findings are in line with the expectation that atomic carbon traces the disk surface. In addition, we compare the carbon and carbon monoxide (CO) line luminosities of a Lupus and literature sample with [C I] 1-0 detections with predictions from the self-consistent disk thermo-chemical models of Ruaud et al. These models adopt interstellar medium carbon and oxygen elemental abundances as input parameters. With the exception of the disk around Sz 98, we find that these models reproduce all the available line luminosities and upper limits, with gas masses comparable to or higher than the minimum-mass solar nebula and gas-to-dust mass ratios ≥10. Thus, we conclude that the majority of large Myr-old disks conform to the simple expectation that they are not significantly depleted in gas, CO, or carbon.

Keywords: protoplanetary disks; exoplanet formation; co line emission; millimeter astronomy
The Effect of Gravitational Decoupling on Constraining the Mass and Radius for the Secondary Component of GW190814 and Other Self-bound Strange Stars in f(Q) Gravity Theory

Inspired by the conundrum of the gravitational event GW190814, which brings to light the coalescence of a 23 M ⊙ black hole with a yet-to-be-determined secondary component, we look to modeling compact objects within the framework of $f({ \mathcal Q })$ gravity by employing the method of gravitational decoupling. We impose a quadratic equation of state (EOS) for the interior matter distribution, which in the appropriate limit reduces to the MIT bag model. The governing field equations arising from gravitational decoupling bifurcate into the $\rho ={\theta }_{0}^{0}$ and ${p}_{r}={\theta }_{1}^{1}$ sectors, leading to two distinct classes of solutions. Both families of solutions are subjected to rigorous tests, qualifying them to describe a plethora of compact objects, including neutron stars, strange stars, and the possible progenitor of the secondary component of GW190814. Using observational data of mass-radius relations for compact objects LMC X-4, Cen X-3, PSR J1614-2230, and PSR J0740+6620, we show that it is possible to generate stellar masses and radii beyond 2.0 M ⊙ for neutron stars. Our findings reveal that the most suitable and versatile model in this framework is the quadratic EOS, which accounts for a range of low-mass stars and typical stellar candidates describing the secondary component of GW190814.

Keywords: compact objects; neutron stars; theoretical models
Dynamical Properties of Molecular-forming Gas Clumps in Galaxies at the Epoch of Reionization

We study the properties of molecular-forming gas clumps (MGCs) at the epoch of reionization using cosmological zoom-in simulations. We identify MGCs in a $z\simeq 6$ prototypical galaxy ("Althæa") using an H2 density-based clump finder. We compare their mass, size, velocity dispersion, gas surface density, and virial parameter ( ${\alpha }_{\mathrm{vir}}$ ) to observations. In Althæa, the typical MGC mass and size are ${M}_{\mathrm{gas}}\simeq {10}^{6.5}$ M⊙ and $R\simeq 45\mbox{--}100$ pc, which are comparable to those found in nearby spirals and starburst galaxies. MGCs are highly supersonic and supported by turbulence, with rms velocity dispersions of ${\sigma }_{\mathrm{gas}}\,\simeq $ 20-100 km s-1 and pressure of $P/{{\rm{K}}}_{B}\simeq {10}^{7.6}\,{\rm{K}}\,$ ${\mathrm{cm}}^{-3}$ (I.e., $\gt 1000\times $ with respect to the Milky Way), similar to those found in nearby and z ∼ 2 gas-rich starburst galaxies. In addition, we perform stability analysis to understand the origin and dynamical properties of MGCs. We find that MGCs are globally stable in the main disk of Althæa. Densest regions where star formation is expected to take place in clouds and cores on even smaller scales instead have lower ${\alpha }_{\mathrm{vir}}$ and Toomre Q values. Detailed studies of the star-forming gas dynamics at the epoch of reionization thus require a spatial resolution of ≲40 pc (≃ $0\buildrel{\prime\prime}\over{.} 01$ ), which is within reach with the Atacama Large (sub-)Millimeter Array and the Next Generation Very Large Array.

Keywords: high-redshift galaxies; lyman-break galaxies; galaxy formation; galaxy properties; interstellar medium; molecular clouds
Discovery of Extensive [O III] Emission Near M31

We report the discovery of a broad, 1.°5 long filamentary [O III] emission nebulosity some 1.°2 southeast of the M31 nucleus. This nebulosity is not detected in Hα and has no obvious emission counterparts in X-ray, UV, optical, infrared, and radio surveys. To our knowledge, this emission feature has not been previously reported in the literature. We briefly discuss its possible origin.

Keywords: galaxy stellar halos; interstellar filaments
A Multiepoch X-Ray Study of the Nearby Seyfert 2 Galaxy NGC 7479: Linking Column Density Variability to the Torus Geometry

Active galactic nuclei are powered by accreting supermassive black holes, surrounded by a torus of obscuring material. Recent studies have shown how the torus structure, formerly thought to be homogeneous, appears to be "patchy": the detection of variability in the line-of-sight hydrogen column density, in fact, matches the description of an obscurer with a complex structure made of clouds with different column density. In this work, we perform a multiepoch analysis of the X-ray spectra of the Seyfert 2 galaxy NGC 7479 in order to estimate its torus properties, such as the average column density and the covering factor. The measurement of the line-of-sight hydrogen column density variability of the torus allows us to obtain an upper limit on the cloud distance from the central engine. In addition, using the X-ray luminosity of the source, we estimate the Eddington ratio to be in a range of λ Edd = 0.04-0.05 over all epochs.

Keywords: x-ray active galactic nuclei; supermassive black holes; seyfert galaxies
A Global Simulation of the Dynamo, Zonal Jets, and Vortices on Saturn

The fluid dynamics planet Saturn gives rise to alternating east-west jet streams, large cyclonic and anticyclonic vortices, and a dipole-dominant magnetic field that is highly axisymmetric about the planetary rotation axis. Modeling these features in a self-consistent manner is crucial for understanding the dynamics of Saturn's interior and atmosphere. Here we report a turbulent high-resolution dynamo simulation in a spherical shell that produces these features simultaneously for the first time. A crucial model ingredient is a long-hypothesized stably stratified layer (SSL), sandwiched between a deep metallic hydrogen layer and an outer low-conductivity molecular layer, born out of the limited solubility of helium inside metallic hydrogen at certain depths. The model spontaneously produces polar cyclones and significant low-latitude and midlatitude jet stream activity in the molecular layer. The off-equatorial low-latitude jet streams partially penetrate into the SSL and interact with the magnetic field. This helps to axisymmetrize the magnetic field about the rotation axis and convert some of the poloidal magnetic field to a toroidal field, which appears as two global magnetic energy rings surrounding the deeper dynamo region. The simulation also mimics a distinctive dip in the fifth spherical harmonic in Saturn's magnetic energy spectrum as inferred from the Cassini Grand Finale measurements. Our model highlights the role of an SSL in shaping the fluid dynamical and magnetic features of giant planets, as exemplified at Saturn.

Keywords: saturn; planetary atmospheres; planetary interior; planetary science; magnetohydrodynamical simulations; magnetohydrodynamics
Type IIP Supernova Progenitors. II. Stellar Mass and Obscuration by the Dust in the Circumstellar Medium

It has been well established from a variety of observations that red supergiants (RSGs) lose a lot of mass in stellar wind. Dust that has formed in this emitted gas over a few decades before core-collapse can lead to substantial extinction and obscure the intrinsic luminosity of the progenitor RSG. This may lead to a difficulty in determining the range of progenitor masses that lead to the different classes of supernovae. Even nearby, well-studied supernovae with pre-explosion observations, such as SN 2013ej, may suffer from this uncertainty in the progenitor mass. We explore here two different masses proposed for its progenitor. We compute their pre-supernova characteristics using Modules for Experiments in Stellar Astrophysics. We show that a non-rotating star with an initial mass of 26 M⊙ would require a considerable amount of circumstellar medium (AV ∼ 3) to obscure its high luminosity given the observed pre-explosion magnitudes detected by the Hubble Space Telescope (HST). Such a high value of visual extinction appears to be inconsistent with that derived for SN 2013ej as well as SN 2003gd in the same host galaxy, M74. In contrast, the evolutionary models of a lower mass (13 M⊙) star are easily accommodated within the observed HST magnitudes. Some of the 26 M⊙ simulations show luminosity variation in the last few years, which could be discriminated by high-cadence and multiband monitoring of supernova candidates in nearby galaxies. We demonstrate that our calculations are well resolved with adequate zoning and evolutionary time steps.

Keywords: core-collapse supernovae; stellar evolutionary models; computational methods; massive stars; type ii supernovae; supergiant stars; circumstellar dust; stellar interiors; stellar mass loss; hertzsprung russell diagram
The Gas Content and Stripping of Local Group Dwarf Galaxies

The gas content of the complete compilation of Local Group dwarf galaxies (119 within 2 Mpc) is presented using H I survey data. Within the virial radius of the Milky Way (224 kpc here), 53 of 55 dwarf galaxies are devoid of gas to limits of MH I < 104 M⊙. Within the virial radius of M31 (266 kpc), 27 of 30 dwarf galaxies are devoid of gas (with limits typically <105 M⊙). Beyond the virial radii of the Milky Way and M31, the majority of the dwarf galaxies have detected H I gas and H I masses higher than the limits. When the relationship between gas content and distance is investigated using a Local Group virial radius, more of the nondetected dwarf galaxies are within this radius (85 ± 1 of the 93 nondetected dwarf galaxies) than within the virial radii of the Milky Way and M31. Using the Gaia proper-motion measurements available for 38 dwarf galaxies, the minimum gas density required to completely strip them of gas is calculated. Halo densities between 10-5 and 5 × 10-4 cm-3 are typically required for instantaneous stripping at perigalacticon. When compared to halo density with radius expectations from simulations and observations, 80% of the dwarf galaxies with proper motions are consistent with being stripped by ram pressure at Milky Way pericenter. The results suggest that a diffuse gaseous galactic halo medium is important in quenching dwarf galaxies, and that a Local Group medium also potentially plays a role.

Keywords: local group; dwarf galaxies; galaxy quenching; circumgalactic medium; interstellar medium; intergalactic medium; andromeda galaxy; milky way galaxy
Multiple Stellar Populations at Less Evolved Stages. III. A Possible Helium Spread in NGC 2210

Helium variations are common features of globular clusters (GCs) with multiple stellar populations. All the formation scenarios predict that secondary population stars are enhanced in helium, but the exact helium content depends on the polluters. Therefore, searching for helium variations in a star cluster is a straightforward method to understand whether it hosts multiple populations or not and to constrain the formation scenario. Although this topic has been well explored for Galactic GCs, GCs beyond the Milky Way are challenging to study because of their large distances. This work studies the helium distribution of GK-type main-sequence (MS) dwarfs in an old (~12.5 Gyr) GC in the Large Magellanic Cloud, NGC 2210, using the deep photometry observed by the Hubble Space Telescope. We compare the observed morphology of the MS with that of synthetic populations with different helium distributions. We confirm that NGC 2210 dwarfs have a helium spread, with an internal dispersion of δ Y ~ 0.06-0.07. The fraction of helium-enriched stars depends on the δ Y distribution. A continuous δ Y distribution would indicate that more than half of MS stars are helium enriched (~55%). If the δ Y distribution is discrete (bimodal), a fraction of ~30% enriched stars is able to explain the observed morphology of the MS. We also find that the He-enriched population stars are more centrally concentrated than He-normal stars.

Keywords: globular star clusters; stellar populations; stellar abundances
Fermi Large Area Telescope Fourth Source Catalog

We present the fourth Fermi Large Area Telescope catalog (4FGL) of γ-ray sources. Based on the first eight years of science data from the Fermi Gamma-ray Space Telescope mission in the energy range from 50 MeV to 1 TeV, it is the deepest yet in this energy range. Relative to the 3FGL catalog, the 4FGL catalog has twice as much exposure as well as a number of analysis improvements, including an updated model for the Galactic diffuse γ-ray emission, and two sets of light curves (one-year and two-month intervals). The 4FGL catalog includes 5064 sources above 4σ significance, for which we provide localization and spectral properties. Seventy-five sources are modeled explicitly as spatially extended, and overall, 358 sources are considered as identified based on angular extent, periodicity, or correlated variability observed at other wavelengths. For 1336 sources, we have not found plausible counterparts at other wavelengths. More than 3130 of the identified or associated sources are active galaxies of the blazar class, and 239 are pulsars.

Keywords: catalogs; gamma-ray astronomy; sky surveys