Sazuna/UAT_keywords huggingface dataset:
Igniting Weak Interactions in Neutron Star Postmerger Accretion Disks. The merger of two neutron stars or a neutron star and a black hole typically results in the formation of a postmerger accretion disk. Outflows from disks may dominate the overall ejecta from mergers and be a major source of r-process nuclei in our universe. We explore the parameter space of such disks and their outflows and r-process yields by performing 3D general-relativistic magnetohydrodynamic simulations with weak interactions and approximate neutrino transport. We discuss the mapping between the initial binary parameters and the parameter space of the resulting disks, chiefly characterized by their initial accretion rate. We demonstrate the existence of an ignition threshold for weak interactions at around ~10-3 M⊙ s-1 for typical parameters by means of analytic calculations and numerical simulations. We find a degenerate, self-regulated, neutrino-cooled regime above the threshold and an advection-dominated regime below the threshold. Excess heating in the absence of neutrino cooling below the threshold leads to ≳60% of the initial disk mass being ejected in outflows, with typical velocities of ~(0.1-0.2)c, compared to ≲40% at ~(0.1-0.15)c above the threshold. While disks below the threshold show suppressed production of light r-process elements, disks above the threshold can produce the entire range of r-process elements, in good agreement with the observed solar system abundances. Disks below the ignition threshold may produce an overabundance of actinides seen in actinide-boost stars. As gravitational-wave detectors start to sample the neutron star merger parameter space, different disk realizations may be observable via their associated kilonova emission.

Keywords: Accretion, Neutron stars, Magnetohydrodynamics, Black holes, Nucleosynthesis, Gravitation, Nuclear abundances
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: Exoplanet atmospheres, Brown dwarfs, Stellar atmospheres, T dwarfs
SiO Outflows as Tracers of Massive Star Formation in Infrared Dark Clouds. To study the early phases of massive star formation, we present ALMA observations of SiO(5-4) emission and VLA observations of 6 cm continuum emission toward 32 Infrared Dark Cloud clumps, spatially resolved down to ≲0.05 pc. Out of the 32 clumps, we detect SiO emission in 20 clumps, and in 11 of them the SiO emission is relatively strong and likely tracing protostellar outflows. Some SiO outflows are collimated, while others are less ordered. For the six strongest SiO outflows, we estimate basic outflow properties. In our entire sample, where there is SiO emission, we find 1.3 mm continuum and infrared emission nearby, but not vice versa. We build the spectral energy distributions (SEDs) of cores with 1.3 mm continuum emission and fit them with radiative transfer models. The low luminosities and stellar masses returned by SED fitting suggest these are early-stage protostars. We see a slight trend of increasing SiO line luminosity with bolometric luminosity, which suggests more powerful shocks in the vicinity of more massive YSOs. We do not see a clear relation between the SiO luminosity and the evolutionary stage indicated by L/M. We conclude that, as a protostar approaches a bolometric luminosity of ~102 L⊙, the shocks in the outflow are generally strong enough to form SiO emission. The VLA 6 cm observations toward the 15 clumps with the strongest SiO emission detect emission in four clumps, which is likely from shock-ionized jets associated with the more massive ones of these protostellar cores.

Keywords: Submillimeter astronomy, Interstellar line emission, Jets, Infrared dark clouds, Massive stars, Protostars, Star formation, Radio continuum emission, Shocks
Molecular Line Observations in Two Dusty Star-forming Galaxies at z = 6.9. SPT0311-58 is the most massive infrared luminous system discovered so far during the Epoch of Reionization (EoR). In this paper, we present a detailed analysis of the molecular interstellar medium at z = 6.9, through high resolution observations of the CO(6-5), CO(7-6), CO(10-9), [C I](2-1), and p-H2O(21,1 -20,2) lines and dust continuum emissions with the Atacama Large Millimeter/submillimeter Array. The system consists of a pair of intensely star-forming, gravitationally lensed galaxies (labeled West and East). The intrinsic far-infrared luminosity is (16 ± 4) × 1012 L☉ in West and (27 ± 4) × 1011 L☉ in East. We model the dust, CO, and [C I] using non-local thermodynamic equilibrium radiative transfer models and estimate the intrinsic gas mass to be (5.4 ± 3.4) × 1011 M☉ in West and (3.1 ± 2.7) × 1010 M☉ in East. We find that the CO spectral line energy distribution in West and East are typical of high-redshift submillimeter galaxies (SMGs). The CO-to-H2 conversion factor (αCO) and the gas depletion timescales estimated from the model are consistent with the high-redshift SMGs in the literature within the uncertainties. We find no evidence of evolution of depletion time with redshift in SMGs at z &gt; 3. This is the most detailed study of molecular gas content of a galaxy in the EoR to date, with the most distant detection of H2O in a galaxy without any evidence for active galactic nuclei in the literature.

Keywords: Starburst galaxies, Ultraluminous infrared galaxies, High-redshift galaxies
Hα Reverberation Mapping of the Intermediate-mass Active Galactic Nucleus in NGC 4395. We present the results of a high-cadence spectroscopic and imaging monitoring campaign of the active galactic nucleus (AGN) of NGC 4395. High signal-to-noise-ratio spectra were obtained at the Gemini-N 8 m telescope using the GMOS integral field spectrograph (IFS) on 2019 March 7 and at the Keck I 10 m telescope using the Low-Resolution Imaging Spectrometer with slit masks on 2019 March 3 and April 2. Photometric data were obtained with a number of 1 m-class telescopes during the same nights. The narrow-line region (NLR) is spatially resolved; therefore, its variable contributions to the slit spectra make the standard procedure of relative flux calibration impractical. We demonstrate that spatially resolved data from the IFS can be effectively used to correct the slit-mask spectral light curves. While we obtained no reliable lag owing to the lack of a strong variability pattern in the light curves, we constrain the broad-line time lag to be less than 3 hr, consistent with the photometric lag of ~80 minutes reported by Woo et al. By exploiting the high-quality spectra, we measure the second moment of the broad component of the Hα emission line to be 586 ± 19 km s-1, superseding the lower value reported by Woo et al. Combining the revised line dispersion and the photometric time lag, we update the black hole mass to (1.7 ± 0.3) × 104 M☉.

Keywords: Active galactic nuclei
Investigation of the Physical Origin of Overionized Recombining Plasma in the Supernova Remnant IC 443 with XMM-Newton. The physical origin of the overionized recombining plasmas (RPs) in supernova remnants (SNRs) has been attracting attention because its understanding provides new insight into SNR evolution. However, the process of the overionization, although it has been discussed in some RP-SNRs, is not yet fully understood. Here, we report on spatially resolved spectroscopy of X-ray emission from IC 443 with XMM-Newton. We find that RPs in regions interacting with dense molecular clouds tend to have lower electron temperature and lower recombination timescale. These tendencies indicate that RPs in these regions are cooler and more strongly overionized, which is naturally interpreted as a result of rapid cooling by the molecular clouds via thermal conduction. Our result on IC 443 is similar to that on W44 showing evidence for thermal conduction as the origin of RPs at least in older remnants. We suggest that evaporation of clumpy gas embedded in a hot plasma rapidly cools the plasma as was also found in the W44 case. We also discuss if ionization by protons accelerated in IC 443 is responsible for RPs. Based on the energetics of particle acceleration, we conclude that the proton bombardment is unlikely to explain the observed properties of RPs.

Keywords: Supernova remnants, Plasma astrophysics, X-ray astronomy, Molecular clouds
Can Warm Absorbers Be Driven by Ultra-fast Outflows?. Warm absorbers (WAs) located approximately in the region of 1-1000 pc are common phenomena in many active galactic nuclei (AGNs). The driving mechanism of WAs is still under debate. Ultra-fast outflows (UFOs) that are launched very close to the central black hole are also frequently observed in AGNs. When UFOs move outward, they collide with the interstellar medium (ISM) gas. In this paper, we study the possibility that WAs can be generated by the interaction between ISM gas and the UFOs. We find that under some ISM gas conditions, WAs can be generated. However, the covering factor of WAs is much smaller than that given by observations. This indicates that other mechanisms should also be at work. We also find that the properties of the WAs mainly depend on the density of the ISM injected into the computational domain from the outer radial boundary (1000 pc). The higher the density of the ISM is, the higher the mass flux and kinetic power of the WAs will be. The kinetic power of the UFO-driven WAs is much less than 1% of the bolometric luminosity of the host AGNs. Therefore, the UFO-driven WAs might not contribute sufficient feedback to the host galaxy.

Keywords: Accretion, Black hole physics, Active galaxies, Galaxy nuclei, Active galactic nuclei
4-8 GHz Spectrotemporal Emission from the Galactic Center Magnetar PSR J1745-2900. Radio magnetars are exotic sources noted for their diverse spectrotemporal phenomenology and pulse profile variations over weeks to months. Unusual for radio magnetars, the Galactic Center (GC) magnetar PSR J1745-2900 has been continually active since its discovery in 2013. We monitored the GC magnetar at 4-8 GHz for 6 hr in 2019 August-September using the Robert C. Byrd Green Bank Telescope. During our observations, the GC magnetar emitted a flat fluence spectrum over 5-8 GHz to within 2σ uncertainty. From our data, we estimate a 6.4 GHz period-averaged flux density, ${\overline{S}}_{6.4}\approx (240\pm 5)$ μJy. Tracking the temporal evolution of ${\overline{S}}_{6.4}$ , we infer a gradual weakening of GC magnetar activity during 2016-2019 relative to that between 2013 and 2015.5. Typical single pulses detected in our study reveal marginally resolved subpulses with opposing spectral indices, a feature characteristic of radio magnetars but unseen in rotation-powered pulsars. However, unlike in fast radio bursts, these subpulses exhibit no perceptible radio frequency drifts. Throughout our observing span, ≃5 ms scattered pulses significantly jitter within two stable emission components of widths 220 ms and 140 ms, respectively, in the average pulse profile.

Keywords: Neutron stars, Magnetars, Galactic center, Radio transient sources
Energetic Particles Associated with a Coronal Mass Ejection Shock Interacting with a Convected Magnetic Structure. On 2020 November 30, Parker Solar Probe (PSP) was crossed by a coronal mass ejection (CME)-driven shock, which we suggest was also crossing a convected, isolated magnetic structure (MS) at about the same time. By analyzing PSP/FIELDS magnetic field measurements, we find that the leading edge of the MS coincided with the crossing of the shock, while its trailing edge, identified as a crossing of a current sheet, overtook PSP about 7 minutes later. Prior to the arrival of the shock, the flux of 30 keV-3 MeV ions and electrons, as measured by PSP/Integrated Science Investigation of the Sun (ISOIS)/Energetic Particle Instrument (EPI-Lo), increased gradually, peaking at the time of the shock passage. However, during the crossing of the MS downstream of the shock, the energetic-ion flux dropped dramatically, before recovering at about the time of the crossing of the trailing edge of the MS. Afterwards, the ion fluxes remained approximately constant within the sheath region of the CME shock. We interpret this depletion of energetic ions within the MS as the result of insufficient time to accelerate particles at the shock within the MS, given that the structure moves along the shock surface owing to its advection with the solar wind. We present results from a quantitative numerical model of the interaction of an idealized MS with a shock, which supports this interpretation.

Keywords: Solar energetic particles, Interplanetary discontinuities, Interplanetary shocks
Lyα Line Properties at z = 3.78 and Their Environmental Dependence: A Case Study around a Massive Protocluster. Lyα-emitting galaxies (LAEs) are easily detectable in the high-redshift universe and are potentially efficient tracers of large-scale structure at early epochs, as long as their observed properties do not depend strongly on environment. We investigate the luminosity and equivalent width functions of LAEs in the overdense field of a protocluster at redshift z ≃ 3.78. Using a large sample of LAEs (many spectroscopically confirmed), we find that the Lyα luminosity distribution is well represented by a Schechter function with $\mathrm{log}({L}^{* }/\mathrm{erg}\ {{\rm{s}}}^{-1})={43.26}_{-0.22}^{+0.20}$ and $\mathrm{log}({\phi }^{* }/{\mathrm{Mpc}}^{-3})=-{3.40}_{-0.04}^{+0.03}$ with α = -1.5. Fitting the equivalent width distribution as an exponential, we find a scale factor of $\omega ={79}_{-15}^{+15}$ Å. We also measured the Lyα luminosity and equivalent width functions using the subset of LAEs lying within the densest cores of the protocluster, finding similar values for L* and ω. Hence, despite having a mean overdensity more than 2× that of the general field, the shapes of the Lyα luminosity function and equivalent width distributions in the protocluster region are comparable to those measured in the field LAE population by other studies at similar redshift. While the observed Lyα luminosities and equivalent widths show correlations with the UV continuum luminosity in this LAE sample, we find that these are likely due to selection biases and are consistent with no intrinsic correlations within the sample. This protocluster sample supports the strong evolutionary trend observed in the Lyα escape fraction and suggests that LAEs at lower redshift can be on average significantly more dusty that their counterparts at higher redshift.

Keywords: Luminosity function, High-redshift galaxy clusters, Protoclusters, Narrow band photometry, High-redshift galaxies
Testing the Strong Equivalence Principle. II. Relating the External Field Effect in Galaxy Rotation Curves to the Large-scale Structure of the Universe. Theories of modified gravity generically violate the strong equivalence principle, so that the internal dynamics of a self-gravitating system in freefall depends on the strength of the external gravitational field (the external field effect). We fit rotation curves (RCs) from the SPARC database with a model inspired by Milgromian dynamics (MOND), which relates the outer shape of an RC to the external Newtonian field from the large-scale baryonic matter distribution through a dimensionless parameter eN. We obtain a &gt; 4σ statistical detection of the external field effect (i.e. eN &gt; 0 on average), confirming previous results. We then locate the SPARC galaxies in the cosmic web of the nearby universe and find a striking contrast in the fitted eN values for galaxies in underdense versus overdense regions. Galaxies in an underdense region between 22 and 45 Mpc from the celestial axis in the northern sky have RC fits consistent with eN ≃ 0, while those in overdense regions adjacent to the CfA2 Great Wall and the Perseus-Pisces Supercluster return eN that are a factor of two larger than the median for SPARC galaxies. We also calculate independent estimates of eN from galaxy survey data and find that they agree with the eN inferred from the RCs within the uncertainties, the chief uncertainty being the spatial distribution of baryons not contained in galaxies or clusters.

Keywords: Gravitation, Non-standard theories of gravity, Modified Newtonian dynamics, Disk galaxies
Tidal Response and Shape of Hot Jupiters. We study the response of hot Jupiters to a static tidal perturbation using the concentric MacLaurin spheroid method. For strongly irradiated planets, we first performed radiative transfer calculations to relate the planet's equilibrium temperature, Teq, to its interior entropy. We then determined the gravity harmonics, shape, moment of inertia, and static Love numbers for a range of two-layer interior models that assume a rocky core plus a homogeneous and isentropic envelope composed of hydrogen, helium, and heavier elements. We identify general trends and then study HAT-P-13b, the WASP planets 4b, 12b, 18b, 103b, and 121b, and Kepler-75b and CoRot-3b. We compute the Love numbers, knm, and transit radius correction, ΔR, which we compare with predictions in the literature. We find that the Love number, k22, of tidally locked giant planets cannot exceed a value of 0.6, and that the high Teq consistent with strongly irradiated hot Jupiters tends to further lower k22. While most tidally locked planets are well described by a linear regime response of k22 = 3J2/q0 (where q0 is the rotation parameter of the gravitational potential), for extreme cases such as WASP-12b, WASP-103b, and WASP-121b, nonlinear effects can account for over 10% of the predicted k22. The k22 values larger than 0.6, as they have been reported for planets WASP-4b and HAT-P13B, cannot result from a static tidal response without extremely rapid rotation and thus are inconsistent with their expected tidally locked state.

Keywords: Tidal distortion, Hot Jupiters, Exoplanets, Gravitational fields, Oblateness, Tidal radius, Exoplanet tides, Tides, Tidal interaction, Planetary interior
New Families in our Solar Neighborhood: Applying Gaussian Mixture Models for Objective Classification of Structures in the Milky Way and in Simulations. The standard picture of galaxy formation motivates the decomposition of the Milky Way into 3-4 stellar populations with distinct kinematic and elemental abundance distributions: the thin disk, thick disk, bulge, and stellar halo. To test this idea, we construct a Gaussian mixture model (GMM) for both simulated and observed stars in the solar neighborhood, using measured velocities and iron abundances (i.e., an augmented Toomre diagram) as the distributions to be decomposed. We compare results for the Gaia-APOGEE DR16 crossmatch catalog of the solar neighborhood with those from a suite of synthetic Gaia-APOGEE crossmatches constructed from FIRE-2 cosmological simulations of Milky Way mass galaxies. We find that in both the synthetic and real data, the best-fit GMM uses five independent components, some of whose properties resemble the standard populations predicted by galaxy formation theory. Two components can be identified unambiguously as the thin disk and another as the halo. However, instead of a single counterpart to the thick disk, there are three intermediate components with different age and alpha abundance distributions (although these data are not used to construct the model). We use decompositions of the synthetic data to show that the classified components indeed correspond to stars with different origins. By analogy with the simulated data, we show that our mixture model of the real Gaia-APOGEE crossmatch distinguishes the following components: (1) a classic thin disk of young stars on circular orbits (46%), (2) thin disk stars heated by interactions with satellites (22%), (3, 4) two components representing the velocity asymmetry of the alpha-enhanced thick disk (27%), and (5) a stellar halo consistent with early, massive accretion (4%).

Keywords: Galaxy dynamics, Milky Way dynamics, Solar neighborhood, Milky Way Galaxy physics, Galactic abundances
Dynamical Analysis of the Dark Matter and Central Black Hole Mass in the Dwarf Spheroidal Leo I. We measure the central kinematics for the dwarf spheroidal galaxy Leo I using integrated-light measurements and previously published data. We find a steady rise in the velocity dispersion from 300″ into the center. The integrated-light kinematics provide a velocity dispersion of 11.76 ± 0.66 km s-1 inside 75″. After applying appropriate corrections to crowding in the central regions, we achieve consistent velocity dispersion values using velocities from individual stars. Crowding corrections need to be applied when targeting individual stars in high-density stellar environments. From integrated light, we measure the surface brightness profile and find a shallow cusp toward the center. Axisymmetric, orbit-based models measure the stellar mass-to-light ratio, black hole mass, and parameters for a dark matter halo. At large radii it is important to consider possible tidal effects from the Milky Way, so we include a variety of assumptions regarding the tidal radius. For every set of assumptions, models require a central black hole consistent with a mass (3.3 ± 2) × 106 M⊙. The no-black-hole case for any of our assumptions is excluded at over 95% significance, with 6.4 &lt; Δχ2 &lt; 14. A black hole of this mass would have significant effects on dwarf galaxy formation and evolution. The dark halo parameters are heavily affected by the assumptions for the tidal radii, with the circular velocity only constrained to be above 30 km s-1. Reasonable assumptions for the tidal radius result in stellar orbits consistent with an isotropic distribution in the velocities. These more realistic models have little need for a dark matter halo.

Keywords: Supermassive black holes, Dwarf galaxies, Galaxy kinematics