adsabs/SciX_UAT_keywords huggingface dataset:
Second Data Release of the COSMOS Lyα Mapping and Tomography Observations: The First 3D Maps of the Detailed Cosmic Web at 2.05 < z < 2.55

We present the second data release of the COSMOS Lyα Mapping And Tomography Observations Survey conducted with the Low Resolution Imaging Spectrometer on the Keck I telescope. This project used Lyα forest absorption in the spectra of faint star-forming galaxies and quasars at z ~ 2-3 to trace neutral hydrogen in the intergalactic medium. In particular, we use 320 objects over a footprint of ~0.2 deg2 to reconstruct the absorption field at 2.05 < z < 2.55 at ~2 h -1 Mpc resolution. We apply a Wiener filtering technique to the observed data to reconstruct three-dimensional (3D) maps of the field over a volume of 4.1 × 105 h -3 Mpc3. In addition to the filtered flux maps, for the first time we infer the underlying dark matter field through a forward-modeling framework from a joint likelihood of galaxy and Lyα forest data, finding clear examples of the detailed cosmic web consisting of cosmic voids, sheets, filaments, and nodes. In addition to traditional figures, we present a number of interactive 3D models to allow exploration of the data and qualitative comparisons to known galaxy surveys. We find that our inferred overdensities are consistent with those found from galaxy fields. We will make all our reduced spectra, extracted Lyα forest pixel data, and reconstructed tomographic maps publicly available upon publication.

Keywords: intergalactic medium; extragalactic astronomy; intergalactic filaments; intergalactic gas; voids; high-redshift galaxy clusters; galaxy clusters; lyman alpha forest; spectroscopy; redshift surveys; surveys; hubble space telescope
Widespread Detection of Two Components in the Hot Circumgalactic Medium of the Milky Way

Surrounding the Milky Way (MW) is the circumgalactic medium (CGM), an extended reservoir of hot gas that has significant implications for the evolution of the MW. We used the HaloSat all-sky survey to study the CGM's soft X-ray emission in order to better define its distribution and structure. We extend a previous HaloSat study of the southern CGM (Galactic latitude b < -30°) to include the northern CGM (b > 30°) and find evidence that at least two hot gas model components at different temperatures are required to produce the observed emission. The cooler component has a typical temperature of kT ~0.18 keV, while the hotter component has a typical temperature of kT ~0.7 keV. The emission measure in both the warm and hot components has a wide range (~0.005-0.03, and ~0.0005-0.004 cm-6 pc, respectively), indicating that the CGM is clumpy. A patch of relatively consistent CGM was found in the north, allowing for the CGM spectrum to be studied in finer detail using a stacked spectrum. The stacked spectrum is well described with a model including two hot gas components at temperatures of kT = 0.166 ± 0.005 keV and kT = ${0.69}_{-0.05}^{+0.04}$ keV. As an alternative to adding a hot component, a neon-enhanced single-temperature model of the CGM was also tested and found to have worse fit statistics and poor residuals.

Keywords: circumgalactic medium; milky way galaxy; stellar feedback
Bremsstrahlung in GRMHD Models of Accreting Black Holes

The role of bremsstrahlung in the emission from hot accretion flows around slowly accreting supermassive black holes is not thoroughly understood. In order to appraise the importance of bremsstrahlung relative to other radiative processes, we compute spectral energy distributions (SEDs) of accretion disks around slowly accreting supermassive black holes including synchrotron radiation, inverse Compton scattering, and bremsstrahlung. We compute SEDs for (i) four axisymmetric radiative general relativistic magnetohydrodynamics (RadGRMHD) simulations of 108M⊙ black holes with accretion rates between ${10}^{-8}{\dot{M}}_{\mathrm{Edd}}$ and ${10}^{-5}{\dot{M}}_{\mathrm{Edd}}$ , (ii) four axisymmetric RadGRMHD simulations of M87* with varying dimensionless spin a* and black hole mass, and (iii) a 3D GRMHD simulation scaled for Sgr A*. At ${10}^{-8}{\dot{M}}_{\mathrm{Edd}}$ , most of the luminosity is synchrotron radiation, while at ${10}^{-5}{\dot{M}}_{\mathrm{Edd}}$ the three radiative processes have similar luminosities. In most models, bremsstrahlung dominates the SED near 512 keV. In the M87* models, bremsstrahlung dominates this part of the SED if a* = 0.5, but inverse Compton scattering dominates if a* = 0.9375. Since scattering is more variable than bremsstrahlung, this result suggests that 512 keV variability could be a diagnostic of black hole spin. In the Appendix, we compare some bremsstrahlung formulae found in the literature.

Keywords: accretion; low-luminosity active galactic nuclei; radiative processes; supermassive black holes; radiative transfer
Tracing Dark Matter Halos with Satellite Kinematics and the Central Stellar Velocity Dispersion of Galaxies

It has been suggested that the central stellar velocity dispersion of galaxies can trace dark matter halo mass directly. We test this hypothesis using a complete spectroscopic sample of isolated galaxies surrounded by faint satellite galaxies from the Sloan Digital Sky Survey Data Release 12. We apply a friends-of-friends algorithm with projected linking length ${\rm{\Delta }}D\lt 100\,\,\mathrm{kpc}$ and radial velocity linking length ${\rm{\Delta }}V\lt 1000$ km s-1 to construct our sample. Our sample includes 2807 isolated galaxies with 3417 satellite galaxies at $0.01\lt z\lt 0.14$ . We divide the sample into two groups based on the primary galaxy color: red and blue primary galaxies separated at ${\left(g-r\right)}_{0}=0.85$ . The central stellar velocity dispersions of the primary galaxies are proportional to the luminosities and stellar masses of the same galaxies. Stacking the sample based on the central velocity dispersion of the primary galaxies, we derive the velocity dispersions of their satellite galaxies, which trace the dark matter halo mass of the primary galaxies. The system velocity dispersion of the satellite galaxies shows a remarkably tight correlation with the central velocity dispersion of the primary galaxies for both red and blue samples. In particular, the slope of the relation is identical to 1 for red primary systems. This tight relation suggests that the central stellar velocity dispersion of galaxies is indeed an efficient and robust tracer for dark matter halo mass. We provide empirical relations between the central stellar velocity dispersion and the dark matter halo mass.

Keywords: galaxy dark matter halos; galaxy dynamics; galaxy kinematics; early-type galaxies; late-type galaxies
Evidence for r-process Delay in Very Metal-poor Stars

The abundances of r-process elements of very metal-poor stars capture the history of the r-process enrichment in the early stage of star formation in a galaxy. Currently, various types of astrophysical sites including neutron star mergers (NSMs), magneto-rotational supernovae, and collapsars, are suggested as the origin of r-process elements. The time delay between the star formation and the production of r-process elements is the key to distinguish these scenarios, with the caveat that the diffusion of r-process elements in the interstellar medium may induce the delay in r-process enrichment because r-process events are rare. Here we study the observed Ba abundance data of very metal-poor stars as the tracer of the early enrichment history of r-process elements. We find that the gradual increase of [Ba/Mg] with [Fe/H], which is remarkably similar among the Milky Way and classical dwarfs, Requires a significant time delay (100 Myr-1 Gyr) of r-process events from star formation rather than the diffusion-induced delay. We stress that this conclusion is robust to the assumption regarding s-process contamination in the Ba abundances because the sources with no delay would overproduce Ba at very low metallicities, even without the contribution from the s-process. Therefore, we conclude that sources with a delay, possibly NSMs, are the origins of r-process elements.

Keywords: galaxy abundances; chemical abundances; stellar abundances; r-process; nuclear astrophysics
The Spectrum Variabilities of FSRQ 3C 273

3C 273 is a well-studied FSRQ. In order to analyze its spectrum variabilities, we make spectroscopic observations of 3C 273 using the 2.16 m telescope at Xinglong Observatory of the National Astronomical Observatories. Based on these observations and some other spectra from the literature, we study the spectrum variabilities and the physical origin of the optical spectrum. The main results are as follows: (1) The continuum spectrum (S c ) shows obvious variabilities and displays quasi-periodic properties, P = 3.39 ± 1.13 yr, consistent with the result calculated from photometric observations. (2) The spectral energy distribution (SED) was modeled by a combination of blackbody emission that originated from the accretion disk and the dusty torus, synchrotron emission from the jet, the synchrotron self-Compton (SSC) emission, and the external Compton (EC) emission from the broad-line region, accretion disk, and dusty torus. The SED suggests that the optical continuum is dominated by the thermal emission from the accretion disk. (3) A time delay of ${\tau }_{c{{\rm{H}}}_{\beta }}=209.42\pm 9.38$ days lies between the slope of the continuum spectrum (S c ) and H β emission line. (4) The relationships between the spectrum and polarization can be explained by the jet model.

Keywords: blazars; spectrometers; flat-spectrum radio quasars
Threads, Ribbons, and Rings in the Radio Galaxy IC 4296

The nearby elliptical galaxy IC 4296 has produced a large (510 kpc) low-luminosity radio source with typical FR I core/jet/lobe morphology. The unprecedented combination of brightness sensitivity, dynamic range, and angular resolution of a new 1.28 GHz MeerKAT continuum image reveals striking new morphological features, which we call threads, ribbons, and rings. The threads are faint narrow emission features originating where helical Kelvin-Helmholtz instabilities disrupt the main radio jets. The ribbons are smooth regions between the jets and the lobes, and they appear to be relics of jets powered by earlier activity that have since come into pressure equilibrium. Vortex rings in the outer portions of the lobes and their backflows indicate that the straight outer jets and ribbons are inclined by $i=60^\circ \pm 5^\circ $ from the line of sight, in agreement with photometric, geometric, and gas-dynamical estimates of inclination angles near the nucleus.

Keywords: elliptical galaxies; interstellar magnetic fields; radio galaxies; radio jets
CO Emission and CO Hot Spots in Diffuse Molecular Gas

We observed λ3 mm ${}^{12}\mathrm{CO}$ , ${}^{13}\mathrm{CO}$ , ${{\rm{C}}}^{18}{\rm{O}}$ , ${\mathrm{HCO}}^{+}$ , HCN, and CS emission from diffuse molecular gas along sight lines with ${E}_{B-V}$ ≈ 0.1-1 mag. Directions were mostly chosen for their proximity to sight lines toward background millimeter-wave continuum sources studied in ${\mathrm{HCO}}^{+}$ absorption at positions where maps of ${}^{12}\mathrm{CO}$ at 1' resolution showed surprisingly bright integrated CO J = 1-0 emission, ${W}_{\mathrm{CO}}$ = 5-12 K km s-1, but we also observed in L121 near ζ Oph. Coherence emerges when the data are considered over a broad range of ${}^{12}\mathrm{CO}$ and ${}^{13}\mathrm{CO}$ brightness. In this work ${W}_{\mathrm{CO}}$ / ${W}_{13}$ and N( ${}^{12}\mathrm{CO}$ )/N( ${}^{13}\mathrm{CO}$ ) are 20-40 for ${W}_{\mathrm{CO}}$ ≲ 5 K km s-1 and N(CO) $\lesssim \ 5\times {10}^{15}\,{\mathrm{cm}}^{-2}$ , increasing with much scatter for larger ${W}_{\mathrm{CO}}$ or N(CO). Here N( ${}^{13}\mathrm{CO}$ )/N( ${{\rm{C}}}^{18}{\rm{O}}$ ) > 20-40 (3σ) versus an intrinsic ratio 13C/18O = 8.4 from a combination of selective photodissociation and enhancement of ${}^{13}\mathrm{CO}$ . The observations are understandable if ${}^{12}\mathrm{CO}$ forms from the thermal recombination of ${\mathrm{HCO}}^{+}$ with electrons, after which the observed ${}^{13}\mathrm{CO}$ forms via endothermic carbon isotope exchange with 13C+. ${W}_{\mathrm{CS}}$ / ${W}_{\mathrm{CO}}$ increases abruptly for ${W}_{\mathrm{CO}}$ ≳ 10 K km s-1, and ${W}_{\mathrm{CS}}$ / ${W}_{{\mathrm{HCO}}^{+}}$ is bimodal, showing two branches having N(CS)/N( ${\mathrm{HCO}}^{+}$ ) ≈5 and 1.25. Because CO formation and ${\mathrm{HCO}}^{+}$ excitation both involve collisions between ${\mathrm{HCO}}^{+}$ and ambient electrons, comparison of the CO and ${\mathrm{HCO}}^{+}$ emission shows that the CO hot spots are small regions of enhanced N(CO) occupying only a small fraction of the column density of the medium in which they are embedded. The ${\mathrm{HCO}}^{+}$ /CO and HCN/CO brightness ratios are 1%-2%, with obvious implications for determinations of the true dense gas fraction.

Keywords: interstellar molecules; interstellar medium
Super-Eddington Mass Growth of Intermediate-mass Black Holes Embedded in Dusty Circumnuclear Disks

We perform the first three-dimensional radiation hydrodynamical simulations that investigate the growth of intermediate-mass BHs (IMBHs) embedded in massive self-gravitating, dusty nuclear accretion disks. We explore the dependence of mass accretion efficiency on the gas metallicity Z and mass injection at super-Eddington accretion rates from the outer galactic disk ${\dot{M}}_{\mathrm{in}}$ , and we find that the central BH can be fed at rates exceeding the Eddington rate only when the dusty disk becomes sufficiently optically thick to ionizing radiation. In this case, mass outflows from the disk owing to photoevaporation are suppressed, and thus a large fraction (≳40%) of the mass injection rate can feed the central BH. The conditions are expressed as ${\dot{M}}_{\mathrm{in}}\gt 2.2\times {10}^{-1}\,{\text{}}{M}_{\odot }$ ${\mathrm{yr}}^{-1}{(1+Z/{10}^{-2}{\text{}}{Z}_{\odot })}^{-1}({c}_{{\rm{s}}}/10$ $\mathrm{km}\,{{\rm{s}}}^{-1})$ , where cs is the sound speed in the gaseous disk. With increasing numerical resolution, vigorous disk fragmentation reduces the disk surface density, and dynamical heating by formed clumps makes the disk geometrically thicker. As a result, the photoevaporative mass-loss rate rises and thus the critical injection rate increases for fixed metallicity. This process enables super-Eddington growth of BHs until the BH mass reaches ${M}_{\mathrm{BH}}\sim {10}^{7\mbox{--}8}\,{\text{}}{M}_{\odot }$ , depending on the properties of the host dark-matter halo and metal-enrichment history. In the assembly of protogalaxies, seed BHs that form in overdense regions with a mass variance of 3-4σ at z ∼ 15-20 are able to undergo short periods of rapid growth and transit into the Eddington-limited growth phase afterward to be supermassive BHs observed at z > 6-7.

Keywords: hydrodynamical simulations; supermassive black holes
Searching for Planets Orbiting Fomalhaut with JWST/NIRCam

We report observations with the JWST/NIRCam coronagraph of the Fomalhaut (α PsA) system. This nearby A star hosts a complex debris disk system discovered by the IRAS satellite. Observations in F444W and F356W filters using the round 430R mask achieve a contrast ratio of ~4 × 10-7 at 1″ and ~4 × 10-8 outside of 3″. These observations reach a sensitivity limit of <1 M Jup across most of the disk region. Consistent with the hypothesis that Fomalhaut b is not a massive planet but is a dust cloud from a planetesimal collision, we do not detect it in either F356W or F444W (the latter band where a Jovian-sized planet should be bright). We have reliably detected 10 sources in and around Fomalhaut and its debris disk, all but one of which are coincident with Keck or Hubble Space Telescope sources seen in earlier coronagraphic imaging; we show them to be background objects, including the "Great Dust Cloud" identified in Mid-Infrared Instrument (MIRI) data. However, one of the objects, located at the edge of the inner dust disk seen in the MIRI images, has no obvious counterpart in imaging at earlier epochs and has a relatively red [F356W]-[F444W] > 0.7 mag (Vega) color. Whether this object is a background galaxy, brown dwarf, or a Jovian-mass planet in the Fomalhaut system will be determined by an approved Cycle 2 follow-up program. Finally, we set upper limits to any scattered light from the outer ring, placing a weak limit on the dust albedo at F356W and F444W.

Keywords: exoplanets; high contrast techniques; direct imaging; coronagraphic imaging; circumstellar disks; infrared photometry; james webb space telescope; infrared observatories; space observatories; exoplanet detection methods; exoplanet astronomy; debris disks
Searching for Binary Asteroids in Pan-STARRS1 Archival Images

We developed two different point-spread function (PSF) analysis techniques for discovering wide separation binary asteroids in wide-field surveys. We then applied these techniques to images of main belt asteroids in the 4-60 km size range captured by Pan-STARRS1. Johnston lists fewer than 10 known binaries in this size range with separations greater than 10% of the primary's Hill radius, so discovering more wide binary asteroids is crucial for understanding the limits of binary stability and improving our knowledge of asteroid masses. We analyzed each image by (i) comparing the major axis orientation of the asteroid's elliptical PSF to its nonsidereal rate on the sky and (ii) comparing the one-dimensional median profile created by collapsing the image along the asteroid's direction of motion to that of nearby field stars. For both methods, we flagged any results that deviated significantly from the expected measurements of single asteroids, and those targets with the most flags were identified as binary candidates for confirmation with high-acuity imaging.

Keywords: asteroid satellites; main belt asteroids; sky surveys; astronomical techniques
METAL-Z: Measuring Dust Depletion in Low-metallicity Dwarf Galaxies

The cycling of metals between interstellar gas and dust is a critical aspect of the baryon cycle of galaxies, yet our understanding of this process is limited. This study focuses on understanding dust depletion effects in the low-metallicity regime (<20% Z ⊙) typical of cosmic noon. Using medium-resolution UV spectroscopy from the Cosmic Origins Spectrograph on board the Hubble Space Telescope, gas-phase abundances and depletions of iron and sulfur were derived toward 18 sight lines in local dwarf galaxies IC 1613 and Sextans A. The results show that the depletion of Fe and S is consistent with that found in the Milky Way (MW), LMC, and SMC. The depletion level of Fe increases with gas column density, indicating dust growth in the interstellar medium. The level of Fe depletion decreases with decreasing metallicity, resulting in the fraction of iron in gas ranging from 3% in the MW to 9% in IC 1613 and ∼19% in Sextans A. The dust-to-gas and dust-to-metal ratios (D/G, D/M) for these dwarf galaxies were estimated based on the MW relations between the depletion of Fe and other elements. The study finds that D/G decreases only slightly sublinearly with metallicity, with D/M decreasing from 0.41 ± 0.05 in the MW to 0.11 ± 0.11 at 0.10 Z ⊙ (at log N(H) = 21 cm‑2). The trend of D/G versus metallicity using depletion in local systems is similar to that inferred in Damped Lyα systems from abundance ratios but lies higher than the trend inferred from far-IR measurements in nearby galaxies.

Keywords: interstellar medium; interstellar dust processes; galaxy chemical evolution; gas-to-dust ratio; interstellar abundances; interstellar absorption; interstellar line absorption
Spectroscopy from Photometry: A Population of Extreme Emission Line Galaxies at 1.7 ≲ z ≲ 6.7 Selected with JWST Medium Band Filters

We use JWST/NIRCam medium band photometry in a single pointing of the Canadian NIRISS Unbiased Cluster Survey to identify 118 extreme emission-line galaxies (EELGs) over 1.7 ≲ z ≲ 6.7, selected using a set of color cuts that target galaxies with extreme [O III] + Hβ and Hα emission. We show that our medium band color selections are able to select galaxies based on emission-line EW, which is advantageous to more commonly used selections since it does not require strong continuum emission, and can select galaxies with faint or red continuum fluxes. The median EWs of our sample is EW(Hα) = 893 Å and EW ([O III] + Hβ) = 1255 Å and includes some objects with EW ([O III] + Hβ) ~ 3000 Å. These systems are mostly compact with low stellar mass (median $\mathrm{log}({M}_{\star }/{M}_{\odot })=8.03$ ), low metallicity (median Z = 0.14 Z ⊙), little dust (median A V = 0.18 mag), and high SSFR (median SSFR = 1.18 × 10-8 yr-1). Additionally, galaxies in our sample show increasing EW(Hα) and EW([O III] + Hβ) with redshift, an anticorrelation of EW(Hα) with stellar mass, and no correlation between EW([O III] + Hβ) and stellar mass. Finally, we present NIRSpec spectroscopy of 15 of the EELGs in our sample. These spectra confirm the redshifts and EWs of the EELGs calculated from the medium bands, which demonstrates the accuracy and efficiency of our color selections. Overall, we show that there are significant advantages to using medium band photometry to identify and study EELGs at a wide range of redshifts.

Keywords: emission line galaxies; starburst galaxies; high-redshift galaxies; james webb space telescope
Five Stellar Populations in M22 (NGC 6656)

We present the Ca-CN-CH photometry of the metal-complex globular cluster (GC) M22 (NGC 6656). Our photometry clearly shows the discrete double CN-CH anticorrelations in M22 red giant branch (RGB) stars, due to the difference in the mean metallicity. The populational number ratio between the two main groups is n(G1):n(G2) = 63:37(±3), with the G1 being more metal-poor. Furthermore, the G1 can be divided into two subpopulations with the number ratio of n(CN-w):n(CN-s) = 51:49 (±4), while the G2 can be divided into three subpopulations with n(CN-w):n(CN-I):n(CN-s) = 24:32:44 (±5). The proper motion of individual stars in the cluster shows evidence of internal rotation, showing the G2 with a faster rotation, confirming our previous results from radial velocities. The cumulative radial distributions (CRDs) of individual subpopulations are intriguing in the following aspects: (1) In both main groups, the CRDs of the CN-s subpopulations are more centrally concentrated than other subpopulations. (2) The CRDs of the the G1 CN-s and the G2 CN-s are very similar. (3) Likewise, the G1 CN-w and the G2 CN-w and CN-I have almost identical CRDs. We also estimate the relative helium abundance of individual subpopulations by comparing their RGB bump magnitudes, finding that no helium abundance variation can be seen in the G1, while significant helium enhancements by {{Δ }}Y ≈ 0.03-0.07 are required in the G2. Our results support the idea that M22 formed via a merger of two GCs.

Keywords: hertzsprung russell diagram; globular star clusters; stellar abundances; stellar evolution