Sazuna/UAT_keywords huggingface dataset:
The Galactic Halo Contribution to the Dispersion Measure of Extragalactic Fast Radio Bursts. A new model of the Milky Way (MW) halo component of the dispersion measure (DM) for extragalactic sources, such as fast radio bursts, is presented in light of recent diffuse X-ray observations. In addition to the spherical component of isothermal gas (kT ∼ 0.3 keV) in hydrostatic equilibrium with the Galactic gravitational potential, our model includes a disk-like nonspherical hot gas component to reproduce the directional dependence of the observed X-ray emission measure (EM). The total gas mass (1.2 × 1011 M⊙) is dominated by the spherical component, and is consistent with the total baryon mass of the MW expected from the dark matter mass and the cosmic baryon-to-dark-matter ratio. Our model predicts a mean halo DM of $43\,\mathrm{pc}\ {\mathrm{cm}}^{-3}$ , with a full range of 30- $245\,\mathrm{pc}\ {\mathrm{cm}}^{-3}$ over the whole sky. The large scatter seen in the X-ray EM data implies a ∼0.2 dex (rms) fluctuation of the MW halo DM. We provide an analytic formula to estimate the MW halo DM of our model along any line of sight, which can be easily used to compute the total MW component of DM toward extragalactic sources, in combination with existing DM models of the warm ionized medium associated with the Galactic disk.

Keywords: Radio transient sources, Diffuse x-ray background, Circumgalactic medium
Galaxy Cluster Mass Estimates in the Presence of Substructure. We develop and implement a model to analyze the internal kinematics of galaxy clusters that may contain subpopulations of galaxies that do not independently trace the cluster potential. The model allows for substructures within the cluster environment and disentangles cluster members from contaminating foreground and background galaxies. We estimate the cluster velocity dispersion and/or mass while marginalizing over uncertainties in all of the above complexities. Using mock observations from the MultiDark simulation, we compare the true substructures from the simulation with the substructures identified by our model, showing that 50% of the identified substructures have at least 79% of its members are also members of the same true substructure, which is on par with other substructure identification algorithms. Furthermore, we show a ∼35% decrease in scatter in the inferred velocity dispersion versus true cluster mass relationship when comparing a model that allows three substructures to a model that assumes no substructure. In a first application to our published data for A267, we identify up to four distinct galaxy subpopulations. We use these results to explore the sensitivity of inferred cluster properties to the treatment of substructure. Compared to a model that assumes no substructure, our substructure model reduces the dynamical mass of A267 by ∼22% and shifts the cluster mean velocity by ∼100 km s-1, approximately doubling the offset with respect to the velocity of A267's brightest cluster galaxy. Embedding the spherical Jeans equation within this framework, we infer for A267 a halo mass M200 = (7.0 ± 1.3) × 1014 M☉ h-1 and concentration ${\mathrm{log}}_{10}{c}_{200}=0.71\pm 0.38$ , consistent with the mass-concentration relation found in cosmological simulations.

Keywords: Galaxy clusters, Galaxy distances, Astronomy data modeling, Astronomy data analysis, Jeans mass, Abell clusters, Redshift surveys
Optical Variability Modeling of Newly Identified Blazar Candidates behind Magellanic Clouds. We present an optical variability study of 44 newly identified blazar candidates behind the Magellanic Clouds, including 27 flat spectrum radio quasars (FSRQs) and 17 BL Lacertae objects (BL Lacs). All objects in the sample possess high photometric accuracy and irregularly sampled optical light curves (LCs) in I filter from the long-term monitoring conducted by the Optical Gravitational Lensing Experiment. We investigated the variability properties to look for blazar-like characteristics and to analyze the long-term behavior. We analyzed the LCs with the Lomb-Scargle periodogram to construct power spectral densities (PSDs), found breaks for several objects, and linked them with accretion disk properties. In this way we constrained the black hole (BH) masses of 18 FSRQs to lie within the range $8.18\leqslant \mathrm{log}({M}_{\mathrm{BH}}/{M}_{\odot })\leqslant 10.84$ , assuming a wide range of possible BH spins. By estimating the bolometric luminosities, we applied the fundamental plane of active galactic nuclei variability as an independent estimate, resulting in $8.4\leqslant \mathrm{log}({M}_{\mathrm{BH}}/{M}_{\odot })\leqslant 9.6$ , with a mean error of 0.3. Many of the objects have very steep PSDs, with high-frequency spectral index in the range 3-7. An alternative attempt to classify the LCs was made using the Hurst exponent, H, and the ${ \mathcal A }\mbox{--}{ \mathcal T }$ plane. Two FSRQs and four BL Lacs yielded H &gt; 0.5, indicating presence of long-term memory in the underlying process governing the variability. Additionally, two FSRQs with exceptional PSDs stand out as well in the ${ \mathcal A }\mbox{--}{ \mathcal T }$ plane.

Keywords: BL Lacertae objects, Active galaxies, Small Magellanic Cloud, Large Magellanic Cloud, Active galactic nuclei, Magellanic Clouds
The Strength of the 2175 Å Feature in the Attenuation Curves of Galaxies at 0.1 &lt; z ≲ 3. We update the spectral modeling code MAGPHYS to include a 2175 Å absorption feature in its UV to near-IR dust attenuation prescription. This allows us to determine the strength of this feature and the shape of the dust attenuation curve in ∼5000 star-forming galaxies at $0.1\lt z\lesssim 3$ in the COSMOS field. We find that a 2175 Å absorption feature of ∼1/3 the strength of that in the Milky Way is required for models to minimize residuals. We characterize the total effective dust attenuation curves as a function of several galaxy properties and find that the UV slopes of the attenuation curve for COSMOS galaxies show a strong dependence on star formation rate (SFR) and total dust attenuation (AV), such that galaxies with higher SFR and AV have shallower curves and vice versa. These results are consistent with expectations from radiative transfer that attenuation curves become shallower as the effective dust optical depth increases. We do not find significant trends in the strength of the 2175 Å absorption feature as a function of galaxy properties, but this may result from the high uncertainties associated with this measurement. The updated code is publicly available online (following acceptance).

Keywords: Interstellar dust, Interstellar dust extinction, Infrared galaxies, Galaxy evolution, Interstellar medium
HST Imaging of the Ionizing Radiation from a Star-forming Galaxy at z = 3.794. We report on the Hubble Space Telescope (HST) detection of the Lyman-continuum (LyC) radiation emitted by a galaxy at redshift z = 3.794 dubbed Ion1. The LyC from Ion1 is detected at 820-890 Å with HST WFC3/UVIS in the F410M band (m410 = 27.60 ± 0.36 mAB, peak signal-to-noise ratio (S/N) = 4.17 in an r = 0"12 aperture) and 700-830 Å with the Very Large Telescope (VLT)/VIMOS in the U band (mU = 27.84 ± 0.19 mAB, peak S/N = 6.7 with an r = 0"6 aperture). A 20 hr VLT/VIMOS spectrum shows low- and high-ionization interstellar metal absorption lines and the P Cygni profile of C IV and Lyα in absorption. The latter spectral feature differs from what observed in known LyC emitters, which show strong Lyα emission. An HST far-UV color map reveals that the LyC emission escapes from a region of the galaxy that is bluer than the rest. The F410M image shows that the centroid of the LyC emission is offset from the centroid of the nonionizing UV emission by 0"12 ± 0"03, corresponding to 0.85 ± 0.21 kpc, and that its morphology is likely moderately resolved. These morphological characteristics favor a scenario where the LyC photons produced by massive stars escape from low H I column density "cavities" in the interstellar medium. We also collect the VIMOS U-band images of 107 Lyman-break galaxies at 3.40 &lt; zspec &lt; 3.95, I.e., sampling the LyC, and stack them with inverse-variance weights. No LyC emission is detected in the stacked image, resulting in a 32.5 mAB flux limit (1σ) and an upper limit of absolute LyC escape fraction fescabs ≤ 0.63%.

Keywords: Extragalactic astronomy, Reionization, High-redshift galaxies
Spectral Classification and Ionized Gas Outflows in z ∼ 2 WISE-selected Hot Dust-obscured Galaxies. We present Very Large Telescope/XSHOOTER rest-frame UV-optical spectra of 10 hot dust-obscured galaxies (Hot DOGs) at z ∼ 2 to investigate active galactic nucleus (AGN) diagnostics and assess the presence and effect of ionized gas outflows. Most Hot DOGs in this sample are narrow-line-dominated AGNs (type 1.8 or higher) and have higher Balmer decrements than typical type 2 quasars. Almost all (8/9) sources show evidence for ionized gas outflows in the form of broad and blueshifted [O III] profiles, and some sources have such profiles in Hα (5/7) or [O II] (3/6). Combined with the literature, these results support additional sources of obscuration beyond the simple torus invoked by AGN unification models. Outflow rates derived from the broad [O III] line (≳103 M☉ yr-1) are greater than the black hole accretion and star formation rates, with feedback efficiencies (∼0.1%-1%) consistent with negative feedback to the host galaxy's star formation in merger-driven quasar activity scenarios. We find that the broad emission lines in luminous, obscured quasars are often better explained by outflows within the narrow-line region and caution that black hole mass estimates for such sources in the literature may have substantial uncertainty. Regardless, we find lower bounds on the Eddington ratio for Hot DOGs near unity.

Keywords: Active galaxies
Matter Mixing in Aspherical Core-collapse Supernovae: Three-dimensional Simulations with Single-star and Binary Merger Progenitor Models for SN 1987A. We perform three-dimensional hydrodynamic simulations of aspherical core-collapse supernovae, focusing on the matter mixing in SN 1987A. The impacts of four progenitor (pre-supernova) models and parameterized aspherical explosions are investigated. The four pre-supernova models include a blue supergiant (BSG) model based on a slow-merger scenario developed recently for the progenitor of SN 1987A (Urushibata et al. 2018). The others are a BSG model based on a single-star evolution and two red supergiant (RSG) models. Among the investigated explosion (simulation) models, a model with the binary merger progenitor model and an asymmetric bipolar-like explosion, which invokes a jetlike explosion, best reproduces constraints on the mass of high-velocity 56Ni, as inferred from the observed [Fe II] line profiles. The advantage of the binary merger progenitor model for the matter mixing is the flat and less extended ρ r3 profile of the C+O core and the helium layer, which may be characterized by the small helium core mass. From the best explosion model, the direction of the bipolar explosion axis (the strongest explosion direction) and the neutron star (NS) kick velocity and direction are predicted. Other related implications and future prospects are also given.

Keywords: Neutron stars, Hydrodynamical simulations, Explosive nucleosynthesis, Core-collapse supernovae, Stellar evolutionary models, Supergiant stars, Supernova dynamics
Observing the Redshifted 21 cm Signal around a Bright QSO at z ∼ 10. We use hydrodynamics and radiative transfer simulations to study the 21 cm signal around a bright QSO at z ∼ 10. Due to its powerful UV and X-ray radiation, the QSO quickly increases the extent of the fully ionized bubble produced by the pre-existing stellar type sources, in addition to partially ionizing and heating the surrounding gas. As expected, a longer QSO lifetime, tQSO, results in a 21 cm signal in emission located at increasingly larger angular radii, θ, and covering a wider range of θ. Similar features can be obtained with a higher galactic emissivity efficiency, fUV, such that determining the origin of a large ionized bubble (I.e., QSO versus stars) is not straightforward. Such degeneracy could be reduced by taking advantage of the finite light travel time effect, which is expected to affect an H II region produced by a QSO differently from one created by stellar type sources. From an observational point of view, we find that the 21 cm signal around a QSO at various tQSO could be detected by Square Kilometre Array1-low instrument with a high signal-to-noise ratio (S/N). As a reference, for tQSO = 10 Myr, a S/N ∼ 8 is expected assuming that no pre-heating of the intergalactic medium has taken place due to high-z energetic sources, while it can reach values above 10 in cases of pre-heating. Observations of the 21 cm signal from the environment of a high-z bright QSO could then be used to set constraints on its lifetime, as well as to reduce the degeneracy between fUV and tQSO.

Keywords: Reionization, High-redshift galaxies, Radiative transfer, Quasars
Exploring the "L-σ" Relation of H II Galaxies and Giant Extragalactic H II Regions Acting as Standard Candles. Cosmological applications of H II galaxies and giant extragalactic H II regions (GEHRs) to construct the Hubble diagram at high redshifts require knowledge of the "L-σ" relation of the standard candles used. In this paper, we study the properties of a large sample of 156 sources (25 high-z H II galaxies, 107 local H II galaxies, and 24 GEHRs) compiled by Terlevich et al. Using the cosmological distances reconstructed through two new cosmology-independent methods, we investigate the correlation between the Hβ emission-line luminosity L and the ionized gas velocity dispersion σ. The method is based on non-parametric reconstruction using the measurements of Hubble parameters from cosmic clocks, as well as the simulated data of gravitational waves from the third-generation gravitational wave detector (the Einstein Telescope, ET), which can be considered as standard sirens. Assuming the relation between emission-line luminosity and ionized gas velocity dispersion, $\mathrm{log}L({\rm{H}}\beta )=\alpha \mathrm{log}\sigma ({\rm{H}}\beta )+\kappa $ , we find that the full sample provides a tight constraint on the correlation parameters. However, similar analysis done on three different subsamples seems to support the scheme of treating H II galaxies and GEHRs with distinct strategies. Using the corrected "L-σ" relation for the H II observational sample beyond the current reach of Type Ia supernovae, we obtain values of the matter density parameter, Ωm = 0.314 ± 0.054 (calibrated with standard clocks) and Ωm = 0.311 ± 0.049 (calibrated with standard sirens), in the spatially flat ΛCDM cosmology.

Keywords: Standard candles, H II regions, Cosmological parameters
A Lower Limit on the Mass of Our Galaxy from the H3 Survey. The timing argument provides a lower limit on the mass of the Milky Way. Using a sample of 32 stars at R &gt; 60 kpc drawn from the H3 Spectroscopic Survey and mock catalogs created from published numerical simulations, we find that M200 &gt; 0.91 × 1012 M⊙ with 90% confidence. We recommend using this limit to refine the allowed prior mass range in more complex and sophisticated statistical treatments of Milky Way dynamics. The use of such a prior would have significantly reduced many previously published uncertainty ranges. Our analysis suggests that the most likely value of M200 is ≈1.5 × 1012 M⊙, but establishing this as the Milky Way mass requires a larger sample of outer halo stars and a more complete analysis of the inner halo stars in H3. The imminent growth in the sample of outer halo stars due to ongoing and planned surveys will make this possible.

Keywords: Milky Way dark matter halo, Milky Way stellar halo, Milky Way Galaxy
Probing the Properties of the Pulsar Wind in the Gamma-Ray Binary HESS J0632+057 with NuSTAR and VERITAS Observations. HESS J0632+057 is a gamma-ray binary composed of a compact object orbiting a Be star with a period of about 315 days. Extensive X-ray and TeV gamma-ray observations have revealed a peculiar light curve containing two peaks, separated by a dip. We present the results of simultaneous observations in hard X-rays with NuSTAR and in TeV gamma-rays with VERITAS, performed in 2017 November and December. These observations correspond to the orbital phases φ ≈ 0.22 and 0.3, where the fluxes are rising toward the first light-curve peak. A significant variation of the spectral index from 1.77 ± 0.05 to 1.56 ± 0.05 is observed in the X-ray data. The multiwavelength spectral energy distributions (SED) derived from the observations are interpreted in terms of a leptonic model, in which the compact object is assumed to be a pulsar and nonthermal radiation is emitted by high-energy electrons accelerated at the shock formed by the collision between the stellar and pulsar wind. The results of the SED fitting show that our data can be consistently described within this scenario, and allow us to estimate the magnetization of the pulsar wind at the location of the shock formation. The constraints on the pulsar wind magnetization provided by our results are shown to be consistent with those obtained from other systems.

Keywords: Gamma-ray sources, High mass x-ray binary stars, Pulsars, Gamma-ray astronomy, Particle astrophysics
The Mean Magnetic Field Strength of CI Tau. We present a blind comparison of two methods to measure the mean surface magnetic field strength of the classical T Tauri star CI Tau based on Zeeman broadening of sensitive spectral lines. Our approach takes advantage of the greater Zeeman broadening at near-infrared compared to optical wavelengths. We analyze a high signal-to-noise, high spectral resolution spectrum from 1.5 to 2.5 μm observed with IGRINS (Immersion GRating INfrared Spectrometer) on the Discovery Channel Telescope. Both stellar parameterization with MoogStokes (which assumes a uniform magnetic field) and modeling with SYNTHMAG (which includes a distribution of magnetic field strengths) yield consistent measurements for the mean magnetic field strength of CI Tau is B of ∼2.2 kG. This value is typical compared with measurements for other young T Tauri stars and provides an important contribution to the existing sample given that it is the only known developed planetary system hosted by a young classical T Tauri star. Moreover, we potentially identify an interesting and suggestive trend when plotting the effective temperature and the mean magnetic field strength of T Tauri stars. While a larger sample is needed for confirmation, this trend only appears for a subset of the sample, which may have implications regarding the magnetic field generation.

Keywords: Fundamental parameters of stars, Pre-main sequence stars, Stellar magnetic fields, Infrared sources
Testing the Spectroscopic Extraction of Suppression of Convective Blueshift. Efforts to detect low-mass exoplanets using stellar radial velocities (RVs) are currently limited by magnetic photospheric activity. Suppression of convective blueshift is the dominant magnetic contribution to RV variability in low-activity Sun-like stars. Due to convective plasma motion, the magnitude of RV contributions from the suppression of convective blueshift is related to the depth of formation of photospheric spectral lines for a given species used to compute the RV time series. Meunier et al. used this relation to demonstrate a method for spectroscopic extraction of the suppression of convective blueshift in order to isolate RV contributions, including planetary RVs, that contribute equally to the time series for each spectral line. Here, we extract disk-integrated solar RVs from observations over a 2.5 yr time span made with the solar telescope integrated with the HARPS-N spectrograph at the Telescopio Nazionale Galileo (La Palma, Canary Islands, Spain). We apply the methods outlined by Meunier et al. We are not, however, able to isolate physically meaningful contributions due to the suppression of convective blueshift from this solar data set, potentially because our data set is taken during solar minimum when the suppression of convective blueshift may not sufficiently dominate activity contributions to RVs. This result indicates that, for low-activity Sun-like stars, one must include additional RV contributions from activity sources not considered in the Meunier et al. model at different timescales, as well as instrumental variation, in order to reach the submeter per second RV sensitivity necessary to detect low-mass planets in orbit around Sun-like stars.

Keywords: Exoplanet detection methods, Plages, Sunspots, Solar faculae, Solar granulation, Solar activity, Radial velocity
A Chandra X-Ray and Infrared Study of the Stellar Population in the High-mass Star-forming Region IRAS 16562-3959. We present the results from Chandra X-ray observations, and near- and mid-infrared analysis, using VISTA/VVV and Spitzer/GLIMPSE catalogs, of the high-mass star-forming region IRAS 16562-3959, which contains a candidate for a high-mass protostar. We detected 249 X-ray sources within the ACIS-I field of view. The majority of the X-ray sources have low count rates (&lt;0.638 cts/ks) and hard X-ray spectra. The search for YSOs in the region using VISTA/VVV and Spitzer/GLIMPSE catalogs resulted in a total of 636 YSOs, with 74 Class I and 562 Class II YSOs. The search for near- and mid-infrared counterparts of the X-ray sources led to a total of 165 VISTA/VVV counterparts, and a total of 151 Spitzer/GLIMPSE counterparts. The infrared analysis of the X-ray counterparts allowed us to identify an extra 91 Class III YSOs associated with the region. We conclude that a total of 727 YSOs are associated with the region, with 74 Class I, 562 Class II, and 91 Class III YSOs. We also found that the region is composed of 16 subclusters. In the vicinity of the high-mass protostar, the stellar distribution has a core-halo structure. The subcluster containing the high-mass protostar is the densest and the youngest in the region, and the high-mass protostar is located at its center. The YSOs in this cluster appear to be substantially older than the high-mass protostar.

Keywords: Massive stars, Young star clusters, Pre-main sequence stars, Star formation, Protostars, X-ray stars