adsabs/SciX_UAT_keywords huggingface dataset:
A Hard Look at Local, Optically Selected, Obscured Seyfert Galaxies

We study the X-ray spectra of a sample of 19 obscured, optically selected Seyfert galaxies (Sy 1.8, 1.9, and 2) in the local universe (d ≤ 175 Mpc), drawn from the CfA Seyfert sample. Our analysis is driven by the high sensitivity of NuSTAR in the hard X-rays, coupled with soft X-ray spectra using XMM-Newton, Chandra, Suzaku, and Swift/XRT. We also analyze the optical spectra of these sources in order to obtain accurate mass estimates and Eddington fractions. We employ four different models to analyze the X-ray spectra of these sources, which all provide consistent results. We find that 79%-90% of the sources are heavily obscured with line-of-sight column density NH > 1023 cm-2. We also find a Compton-thick (NH > 1024 cm-2) fraction of 37%-53%. These results are consistent with previous estimates based on multiwavelength analyses. We find that the fraction of reprocessed to intrinsic emission is positively correlated with NH and negatively correlated with the intrinsic, unabsorbed X-ray luminosity (in agreement with the Iwasawa-Taniguchi effect). Our results support the hypothesis that radiation pressure regulates the distribution of the circumnuclear material. * Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under program ID 099.A-0403.

Keywords: active galactic nuclei; x-ray active galactic nuclei; active galaxies; high energy astrophysics; x-ray astronomy; seyfert galaxies; x-ray surveys
Dwarf Satellites of High-z Lyman Break Galaxies: A Free Lunch for JWST

We show that the James Webb Space Telescope (JWST) will be able to detect dwarf satellites of high-z Lyman break galaxies (LBGs). To this end, we use cosmological simulations following the evolution of a typical M⋆ ≃ 1010 M⊙ LBG up to z ≃ 6, and analyze the observational properties of its five satellite dwarf galaxies (107 M⊙ < M⋆ < 109 M⊙). Modeling their stellar emission and dust attenuation, we reconstruct their rest-frame ultraviolet-optical spectra for 6 < z < 6.5. JWST/NIRCam synthetic images show that the satellites can be spatially resolved from their host, and their emission is detectable by planned deep surveys. Moreover, we build synthetic spectral energy distributions and color-magnitude diagrams for the satellites. We conclude that the color F200W-F356W is a powerful diagnostic tool for understanding their physical properties once they have been identified. For example, F200W-F356W ≲ -0.25 can be used to identify star-bursting (SFR ∼ 5 M⊙ yr-1), low-mass (M⋆ ≲ 5 × 108 M⊙) systems, with ∼80% of their stars being young and metal poor $[\mathrm{log}({Z}_{\star }/{Z}_{\odot })\lt -0.5$ ].

Keywords: high-redshift galaxies; dwarf galaxies; cosmology
When Spectral Modeling Meets Convolutional Networks: A Method for Discovering Reionization-era Lensed Quasars in Multiband Imaging Data

Over the last two decades, around 300 quasars have been discovered at z ≳ 6, yet only one has been identified as being strongly gravitationally lensed. We explore a new approach-enlarging the permitted spectral parameter space, while introducing a new spatial geometry veto criterion-which is implemented via image-based deep learning. We first apply this approach to a systematic search for reionization-era lensed quasars, using data from the Dark Energy Survey, the Visible and Infrared Survey Telescope for Astronomy Hemisphere Survey, and the Wide-field Infrared Survey Explorer. Our search method consists of two main parts: (i) the preselection of the candidates, based on their spectral energy distributions (SEDs), using catalog-level photometry; and (ii) relative probability calculations of the candidates being a lens or some contaminant, utilizing a convolutional neural network (CNN) classification. The training data sets are constructed by painting deflected point-source lights over actual galaxy images, to generate realistic galaxy-quasar lens models, optimized to find systems with small image separations, i.e., Einstein radii of θ E ≤ 1″. Visual inspection is then performed for sources with CNN scores of P lens > 0.1, which leads us to obtain 36 newly selected lens candidates, which are awaiting spectroscopic confirmation. These findings show that automated SED modeling and deep learning pipelines, supported by modest human input, are a promising route for detecting strong lenses from large catalogs, which can overcome the veto limitations of primarily dropout-based SED selection approaches.

Keywords: active galactic nuclei; active galaxies; early universe; high-redshift galaxies; quasars; reionization; supermassive black holes; strong gravitational lensing; gravitational lensing
Statistical Detection of IGM Structures during Cosmic Reionization Using Absorption of the Redshifted 21 cm line by H I against Compact Background Radio Sources

Detecting neutral hydrogen structures in the intergalactic medium (IGM) during cosmic reionization via absorption (21 cm forest) against a background radiation is considered independent and complementary to the three-dimensional tomography and power spectrum techniques. The direct detection of this absorption requires very bright (≳10-100 mJy) background sources at high redshifts (z ≳ 8), which are evidently rare; very long times of integration; or instruments of very high sensitivity. This motivates a statistical one-dimensional (1D) power spectrum approach along narrow sightlines but with fainter background objects (∼1-10 mJy), which are likely to be more abundant and significant contributors at high redshifts. The 1D power spectrum reduces cosmic variance and improves sensitivity especially on small spatial scales. Using standard radiative transfer and fiducial models for the instrument, the background sources, and the evolution of IGM structures during cosmic reionization, the potential of the 1D power spectrum along selected narrow directions is investigated against uncertainties from thermal noise and the chromatic synthesized point spread function (PSF) response. Minimum requirements on the number of high-redshift background sources, the telescope sensitivity, and the PSF quality are estimated for a range of instrumental, background source, and reionization model parameters. The 1D power spectrum is intrinsically stronger at higher redshifts. A ∼1000 hr observing campaign targeting ∼100 narrow sightlines to radio-faint, high-redshift background objects with modern radio telescopes, especially the Square Kilometre Array, can detect the 1D power spectrum on a range of spatial scales and redshifts, and potentially discriminate between models of cosmic reionization.

Keywords: reionization; radio spectroscopy; radio interferometers; radiative transfer equation; observational cosmology; large-scale structure of the universe; intergalactic medium; high-redshift galaxies; h i line emission; early universe; discrete radio sources; aperture synthesis
The Galactic Chemical Evolution of Chlorine

We measured 35Cl abundances in 52 M giants with metallicities in the range -0.5 < [Fe/H] < 0.12. Abundances and atmospheric parameters were derived using infrared spectra from CSHELL on the NASA Infrared Telescope Facility and from optical echelle spectra. We measured Cl abundances by fitting a H35Cl molecular feature at 3.6985 μm with synthetic spectra. We also measured the abundances of O, Ca, Ti, and Fe using atomic absorption lines. We find that the [Cl/Fe] ratio for our stars agrees with chemical evolution models of Cl, and the [Cl/Ca] ratio is broadly consistent with the solar ratio over our metallicity range. Both indicate that Cl is primarily made in core-collapse supernovae with some contributions from Type Ia supernovae. We suggest that other potential nucleosynthesis processes, such as the ν-process, are not significant producers of Cl. Finally, we also find our Cl abundances are consistent with H II and planetary nebular abundances at a given oxygen abundance, although there is scatter in the data.

Keywords: stellar abundances; galaxy chemical evolution
Are Brightest Cluster Galaxies Special?

A longstanding question when studying Brightest Cluster Galaxies (BCGs) and their evolution is whether their luminosities are statistical extremes of the luminosity distribution of other cluster member galaxies, or whether their luminosities follow a different,"special" distribution. To explore this question, we use the two Tremaine-Richstone (TR) statistics that sometimes lead to different conclusions about BCG specialness. We run Monte Carlo simulations of galaxy clusters with varying galaxy luminosity functions and BCG properties, and explore the sensitivity of the TR statistics to the adjusted BCG properties. We identify cases where the two statistics lead to different conclusions. The first of the TR statistics, which relies on the spread of BCG luminosities, is more reliable for determining specialness than the second, which utilizes the spread in the luminosity gap between the BCG and second ranked galaxy.

Keywords: brightest cluster galaxies
Analysis of Turbulence Properties in the Mercury Plasma Environment Using MESSENGER Observations

Turbulence is ubiquitous in space and astrophysical plasmas, such as the solar wind, planetary magnetospheres, and the interstellar medium. It plays a key role in converting electric and magnetic energies into kinetic energy of the plasma particles. Here, the properties of MHD and kinetic-scale magnetic fluctuations in the Mercury environment are investigated using data collected by the MESSENGER spacecraft from 2011 March 23 to 2015 April 28. It is found that spectral indices at MHD scales vary from ∼-5/3 in the near-Planet solar wind (possibly the foreshock) to ∼-1.3 within the magnetosheath close to bow shock. The spectra steepen further in the magnetosheath close to magnetopause, and reach ∼-2.2 within the magnetosphere. Only 15% of events were found to have the Kolmogorov scaling ∼-5/3 in the magnetosheath. The high variability of the spectral indices implies that the scaling of turbulent fluctuations in the magnetosheath is not universal, and it emphasizes the role of the bow shock on the turbulence dynamics, at least at the largest scales. Analysis of the magnetic compressibility shows that only ∼30% of events with Kolmogorov inertial range in the magnetosheath are dominated by (shear) Alfvénic fluctuations, which contrasts with well-known features of solar wind turbulence. At kinetic scales, the steepest spectra (slopes ∼-2.8) occur in the solar wind, before flattening to ∼-2 near the bow shock, then steepening again to ∼-2.8 in the magnetosheath. The spectral indices at kinetic scales are close to the ones at large scales in the magnetosphere, which may be caused by the presence of heavy ions in the latter. The statistical results are compared with previous observations reported in other planetary plasma environments.

Keywords: interplanetary shocks; plasma astrophysics; space plasmas; megamasers; magnetohydrodynamics; interplanetary particle acceleration
The JWST Advanced Deep Extragalactic Survey: Discovery of an Extreme Galaxy Overdensity at z = 5.4 with JWST/NIRCam in GOODS-S

We report the discovery of an extreme galaxy overdensity at z = 5.4 in the GOODS-S field using James Webb Space Telescope (JWST)/NIRCam imaging from JADES and JEMS alongside JWST/NIRCam wide-field slitless spectroscopy from FRESCO. We identified potential members of the overdensity using Hubble Space Telescope+JWST photometry spanning λ = 0.4–5.0 μm. These data provide accurate and well-constrained photometric redshifts down to m ≈ 29–30 mag. We subsequently confirmed N = 81 galaxies at 5.2 < z < 5.5 using JWST slitless spectroscopy over λ = 3.9–5.0 μm through a targeted line search for Hα around the best-fit photometric redshift. We verified that N = 42 of these galaxies reside in the field, while N = 39 galaxies reside in a density around ∼10 times that of a random volume. Stellar populations for these galaxies were inferred from the photometry and used to construct the star-forming main sequence, where protocluster members appeared more massive and exhibited earlier star formation (and thus older stellar populations) when compared to their field galaxy counterparts. We estimate the total halo mass of this large-scale structure to be $12.6\lesssim {\mathrm{log}}_{10}\left({M}_{\mathrm{halo}}/{M}_{\odot }\right)\lesssim 12.8$ using an empirical stellar mass to halo mass relation, which is likely an underestimate as a result of incompleteness. Our discovery demonstrates the power of JWST at constraining dark matter halo assembly and galaxy formation at very early cosmic times.

Keywords: early universe; galaxy evolution; galaxy formation; high-redshift galaxies; high-redshift galaxy clusters
A Lattice Boltzmann Scheme for Polarized Radiative Transfer in Planetary Atmospheres

Quantitative calculation of reflected polarized light from planets is of great significance to interpret the polarimetric observations of planetary atmospheres. In this work, we propose a lattice Boltzmann (LB) scheme for polarized radiative transfer in planetary atmospheres. The LB scheme obtains the Stokes vector through the vector LB equation performing simple collision and streaming processes. The vector radiative transfer equation is rigorously derived from the vector LB equation via the Maxwell iteration technique. Polarized radiative transfer of a single point on the planetary surface with Rayleigh and Mie scattering atmospheres are first accurately solved by our LB scheme. Afterward, we systematically investigate the disk-integrated polarization of finite and semi-infinite, conservative and nonconservative Rayleigh scattering planetary atmospheres. The disk-integrated phase curves of the Stokes parameters and degree of polarization and spherical and geometric albedos are produced, which are in good agreement with the benchmark results for different cases. The numerical results indicate that our LB scheme is efficient and accurate for polarized radiative transfer in planetary atmospheres. Our LB scheme is expected to provide a competitive numerical tool to interpret the polarimetric observations of planetary atmospheres.

Keywords: radiative transfer; planetary atmospheres
First Results from the JWST Early Release Science Program Q3D: The Warm Ionized Gas Outflow in z 1.6 Quasar XID 2028 and Its Impact on the Host Galaxy

Quasar feedback may regulate the growth of supermassive black holes, quench coeval star formation, and impact galaxy morphology and the circumgalactic medium. However, direct evidence for quasar feedback in action at the epoch of peak black hole accretion at z ≈ 2 remains elusive. A good case in point is the z = 1.6 quasar WISEA J100211.29+013706.7 (XID 2028), where past analyses of the same ground-based data have come to different conclusions. Here, we revisit this object with the integral-field unit of the Near Infrared Spectrograph on board the JWST as part of Early Release Science program Q3D. The excellent angular resolution and sensitivity of the JWST data reveal new morphological and kinematic substructures in the outflowing gas plume. An analysis of the emission-line ratios indicates that photoionization by the central quasar dominates the ionization state of the gas with no obvious sign for a major contribution from hot young stars anywhere in the host galaxy. The rest-frame near-UV emission aligned along the wide-angle cone of outflowing gas is interpreted as a scattering cone. The outflow has cleared a channel in the dusty host galaxy, through which some of the quasar ionizing radiation is able to escape and heat the surrounding interstellar and circumgalactic media. Although the warm ionized outflow is not powerful enough to impact the host galaxy via mechanical feedback, radiative feedback by the active galactic nucleus, aided by the outflow, may help to explain the unusually small molecular gas mass fraction in the galaxy host.

Keywords: galaxy winds; quasars; active galaxies; agn host galaxies
Yonsei Evolutionary Population Synthesis (YEPS) Model. III. Surface Brightness Fluctuation of Normal and Helium-enhanced Simple Stellar Populations

We present an evolutionary population synthesis model of the surface brightness fluctuation (SBF) for normal and He-enriched simple stellar populations (SSPs). While our SBF model for the normal He population agrees with other existing models, the He-rich population, containing hotter horizontal branch stars and brighter red clump stars than the normal He population, entails a substantial change in the SBF of SSPs. We show that the SBF magnitudes are affected by He-rich populations at least ∼0.3 mag even in I- and near-infrared bands at given colors, from which the SBF-based distances are often derived. Due to uncertainties both in observations and models, however, the SBFs of Galactic globular clusters and early-type galaxies do not allow verifying the He-enriched model. We propose that when combined with independent metallicity and age indicators such as Mg2 and Hβ, the UV and optical SBFs can readily detect underlying He-rich populations in unresolved stellar systems at a distance out to ≳20 Mpc. A full set of the spectro-photometric and SBF data for SSPs from the Yonsei Evolutionary Population Synthesis (YEPS) model is available for download at http://cosmic.yonsei.ac.kr/YEPS.htm.

Keywords: galaxy distances; stellar distance; galaxy stellar content; globular star clusters; horizontal branch stars; stellar evolution; stellar abundances
Rotation in Event Horizon Telescope Movies

The Event Horizon Telescope (EHT) has produced images of M87* and Sagittarius A*, and will soon produce time sequences of images, or movies. In anticipation of this, we describe a technique to measure the rotation rate, or pattern speed Ω p , from movies using an autocorrelation technique. We validate the technique on Gaussian random field models with a known rotation rate and apply it to a library of synthetic images of Sgr A* based on general relativistic magnetohydrodynamics simulations. We predict that EHT movies will have Ω p ≈ 1° per GMc -3, which is of order 15% of the Keplerian orbital frequency in the emitting region. We can plausibly attribute the slow rotation seen in our models to the pattern speed of inward-propagating spiral shocks. We also find that Ω p depends strongly on inclination. Application of this technique will enable us to compare future EHT movies with the clockwise rotation of Sgr A* seen in near-infrared flares by GRAVITY. Pattern speed analysis of future EHT observations of M87* and Sgr A* may also provide novel constraints on black hole inclination and spin, as well as an independent measurement of black hole mass.

Keywords: black holes; magnetohydrodynamical simulations
The Far-UV Interstellar Radiation Field in Galactic Disks: Numerical and Analytic Models

The intensity of the far-ultraviolet (FUV; 6-13.6 eV) interstellar radiation field (ISRF) in galaxies determines the thermal and chemical evolution of the neutral interstellar gas and is key for interpreting extragalactic observations and for theories of star formation. We run a series of galactic disk models and derive the FUV ISRF intensity as a function of the dust-to-gas ratio, star formation rate density, gas density, scale radius, and observer position. We develop an analytic formula for the median FUV ISRF flux. We identify two-dimensionless parameters in the problem: (1) the dimensionless galactic radius, X, which measures the radial extent of FUV sources (OB stellar associations) in the disk; and (2) the opacity over the intersource distance, τ⋆, which measures the importance of dust absorption. These parameters encapsulate the dependence on all of the physical parameters. We find that there exists a critical τ⋆, or equivalently a critical dust-to-gas ratio, ${Z}_{d,\mathrm{crit}}^{{\prime} }\approx 0.01-0.1$ , the Milky Way value, at which the ISRF changes behavior. For ${Z}_{d}^{{\prime} }\gt {Z}_{d,\mathrm{crit}}^{{\prime} }$ the ISRF is limited by dust absorption. With decreasing ${Z}_{d}^{{\prime} }$ , the ISRF intensity increases as more sources contribute to the flux. For ${Z}_{d}^{{\prime} }\lt {Z}_{d,\mathrm{crit}}^{{\prime} }$ the ISRF saturates as the disk becomes optically thin. We find that the ISRF per star formation rate density in low-metallicity systems, such as dwarf and high-redshift galaxies, is higher by up to a factor of 3-6 compared to their Milky Way counterparts. We discuss the implications these findings have for the potential mechanisms that regulate star formation in low-metallicity galaxies.

Keywords: interstellar medium; interstellar radiation field; ob stars; ob associations; ultraviolet extinction; interstellar dust extinction; star formation; stellar feedback; photodissociation regions; interstellar phases
Photons' Scattering in Relativistic Plasma with Velocity Shear: Generation of High Energy Power-law Spectra

A high energy power law is a common feature in the spectra of many astrophysical objects. We show that the photons in an unmagnetized relativistic plasma composed of electrons and protons with a variable Lorentz factor (or a velocity shear) go through repeated scattering with electrons to gain energy. The escaped population of photons naturally produces a power-law-shaped spectrum making it a photon's analog to the conventional Fermi acceleration mechanism for charged particles. Thus, this mechanism provides a natural alternative to current explanations of high energy power-law spectra via synchrotron or thermal Comptonization. The model is applicable to any relativistic plasma beam with an arbitrary Lorentz factor profile. We implement the theory to the gamma-ray burst prompt phase and show that the obtained range of the photon indices is compatible with the observed values and the results of Monte Carlo simulations that we carry out independently. Therefore, the observed high energy spectral indices provide a unique indicator of the jet structure.

Keywords: high energy astrophysics; gamma-ray bursts; relativistic jets; theoretical models
Exomoons and Exorings with the Habitable Worlds Observatory. I. On the Detection of Earth–Moon Analog Shadows and Eclipses

The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy was the construction of an observatory capable of characterizing habitable worlds. In this paper series we explore the detectability of and interference from exomoons and exorings serendipitously observed with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting in this manuscript with Earth–Moon analog mutual events. Unlike transits, which only occur in systems viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every star–planet–moon system. The cadence of these events can vary widely from ∼yearly to multiple events per day, as was the case in our younger Earth–Moon system. Leveraging previous space-based (EPOXI) light curves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive the detectability of Moon analogs with HWO. We determine that Earth–Moon analogs are detectable with observation of ∼2–20 mutual events for systems within 10 pc, and larger moons should remain detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet features and weather. We find that HWO wavelength coverage in the near-infrared, specifically in the 1.4 μm water band where large moons can outshine their host planet, will aid in differentiating exomoon signals from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin to our Moon are more likely to be detected in younger systems, where shorter orbital periods and favorable geometry enhance the probability and frequency of mutual events.

Keywords: transits; eclipses; direct imaging; natural satellites (extrasolar)