adsabs/SciX_UAT_keywords huggingface dataset:
Cosmological Simulation of Galaxy Groups and Clusters. I. Global Effect of Feedback from Active Galactic Nuclei

In this study we quantify the properties of the gas and dark matter around active galactic nuclei (AGNs) in simulated galaxy groups and clusters and analyze the effect of AGN feedback on the surrounding intracluster (group) medium. Our results suggest downsizing of AGN luminosity with host halo mass, supporting the results obtained from clustering studies of AGNs. By examining the temperature and density distribution of the gas in the vicinity of AGNs we show that due to feedback from the central engine, the gas gets displaced from the center of the group/cluster resulting in a reduction of the density but an enhancement of temperature. We show that these effects are pronounced at both high and low redshifts and propose new observables to study the effect of feedback in higher-redshift galaxies. We also show that the average stellar mass is decreased in halos in the presence of AGN feedback confirming claims from previous studies. Our work for the first time uses a fully cosmological hydrodynamic simulation to evaluate the global effects of AGN feedback on their host dark matter halos as well as galaxies at scales of galaxy groups and clusters.

Keywords: galaxy clusters; active galactic nuclei
A 38 Million Year Old Neptune-sized Planet in the Kepler Field

Kepler 1627A is a G8V star previously known to host a 3.8 R ⊕ planet on a 7.2 day orbit. The star was observed by the Kepler space telescope because it is nearby (d = 329 pc) and it resembles the Sun. Here, we show using Gaia kinematics, TESS stellar rotation periods, and spectroscopic lithium abundances that Kepler 1627 is a member of the ${38}_{-5}^{+6}$ Myr old δ Lyr cluster. To our knowledge, this makes Kepler 1627Ab the youngest planet with a precise age yet found by the prime Kepler mission. The Kepler photometry shows two peculiarities: the average transit profile is asymmetric, and the individual transit times might be correlated with the local light-curve slope. We discuss possible explanations for each anomaly. More importantly, the δ Lyr cluster is one of ~103 coeval groups whose properties have been clarified by Gaia. Many other exoplanet hosts are candidate members of these clusters; their ages can be verified with the trifecta of Gaia, TESS, and ground-based spectroscopy.

Keywords: exoplanet evolution; open star clusters; stellar ages
Updated Proper Motion of the Neutron Star in the Supernova Remnant Cassiopeia A

In this paper, we present updated estimates of the velocity of the neutron star (NS) in the supernova remnant Cassiopeia A using over two decades of Chandra observations. We use two methods: (1) recording the NS positions from dozens of Chandra observations, including the astrometric uncertainty estimates on the data points, but not correcting the astrometry of the observations; and (2) correcting the astrometry of the 13 Chandra observations that have a sufficient number of point sources with identified Gaia counterparts. For method #1, we observe a heliocentric velocity of 275 ± 121 km s‑1, with an angle of 177° ± 22° east of north. For method #2, we observe a heliocentric velocity of 436 ± 89 km s‑1 at an angle of 158° ± 12°. Correcting for galactic rotation and the Sun's peculiar motion decreases these estimates to 256 km s‑1 at 167° and 433 km s‑1 at 151°, respectively. Both of our estimates match with the explosion-center-estimated velocity of ∼350 km s‑1 and the previous 10 yr baseline proper-motion measurement of 570 ± 260 km s‑1, but our use of additional data over a longer baseline has led to a smaller uncertainty by a factor of 2–3. Our estimates rule out velocities ≳600 km s‑1 and better match with simulations of Cassiopeia A that include NS kick mechanisms.

Keywords: neutron stars; core-collapse supernovae; x-ray point sources; supernova remnants; stellar kinematics
Self-ionizing Galactic Winds

We present hydrodynamical simulations of galactic winds from star-forming galaxies including nonequilibrium ionization and frequency-dependent radiative transfer, processes that have remained largely unaccounted for in galactic wind studies. We consider radiation from massive stars, the metagalactic UV/X-ray background, and the self-radiation of the supernovae heated gas. We compare our results to classical galactic wind solutions and show the importance of our newly included physical processes toward observations of ions such as O III, O VI, O VII, and O VIII plus the observable soft X-ray spectra. Nonequilibrium ionization is reflected in overionized gas compared to equilibrium solutions, leading to much enhanced column densities of highly ionized species. The wind produces excess soft X-ray (E ≳ 100 eV) radiation that is several orders of magnitude higher compared to the metagalactic background. This radiation ionizes the higher ions (such as O VII) somewhat, but affects the lower ions (such as O III) significantly. We predict that the observable X-ray spectra should contain the signatures of such nonequilibrium effects, especially in X-ray lines such as O VII and O VIII. Simple estimates suggest that both the temperature and density of the winds may be overestimated by factors of a few to almost 2 orders of magnitude using simple equilibrium models. We conclude that both the nonequilibrium ionization and the radiation from the wind itself need to be considered for proper modeling of the optical/UV/X-ray emitting plasma in galactic winds.

Keywords: galactic winds; starburst galaxies; x-ray sources; hydrodynamical simulations; radiative transfer simulations
Induced Metal-free Star Formation around a Massive Black Hole Seed

The direct formation of a massive black hole is a potential seeding mechanism of the earliest observed supermassive black holes. We investigate how the existence of a massive black hole seed impacts the ionization and thermal state of its pre-galactic host halo and subsequent star formation. We show that its X-ray radiation ionizes and heats the medium, enhancing H2 formation in shielded regions, within the nuclear region in the span of a million years. The enhanced molecular cooling triggers the formation of a ∼104 M⊙ metal-free stellar cluster at a star formation efficiency of ∼0.1% in a single event. Star formation occurs near the edges of the H II region that is partially ionized by X-rays; thus, the initial size depends on the black hole properties and surrounding environment. The simulated metal-free galaxy has an initial half-light radius of ∼10 pc but expands to ∼50 pc after 10 million years because of the outward velocities of their birth clouds. Supernova feedback then quenches any further star formation for tens of millions of years, allowing the massive black hole to dominate the spectrum once the massive metal-free stars die.

Keywords: supermassive black holes; star formation; radiative transfer simulations; galaxy evolution
Identification of an X-Ray Pulsar in the BeXRB System IGR J18219-1347

We report on observations of the candidate Be/X-ray binary (BeXRB) IGR J18219-1347 with the Swift/X-ray Telescope, the Nuclear Spectroscopic Telescope ARray, and the Neutron Star Interior Composition Explorer during Type-I outbursts in 2020 March and June. Our timing analysis revealed the spin period of a neutron star with P spin = 52.46 s. This periodicity, combined with the known orbital period of 72.4 days, indicates that the system is a BeXRB. Furthermore, by comparing the spectral energy distribution of the infrared counterpart to that of known BeXRBs, we confirm this classification and set a distance of approximately 10-15 kpc for the source. The broadband X-ray spectrum (1.5-50 keV) of the source is described by an absorbed power law with a photon index Γ ~ 0.5 and a cutoff energy at ~13 keV.

Keywords: x-ray astronomy; high mass x-ray binary stars; pulsars; neutron stars
Probing the Early History of Cosmic Reionization by Future Cosmic Microwave Background Experiments

Cosmic reionization imprints its signature on the temperature and polarization anisotropies of the cosmic microwave background (CMB). Advances in CMB telescopes have already placed a significant constraint on the history of reionization. As near-future CMB telescopes target the maximum sensitivity, or observations limited only by the cosmic variance (CV), we hereby forecast the potential of future CMB observations in constraining the history of reionization. In this study, we perform Markov Chain Monte Carlo analysis for CV-limited E-mode polarization observations such as the Lite (Light) satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection (LiteBIRD), based on a few different methods that vary in the way of sampling reionization histories. We focus especially on estimating the very early history of reionization that occurs at redshifts z > 15, which is quantified by the partial CMB optical depth due to free electrons at z > 15, τ z>15. We find that reionization with τ z>15 ~ 0.008, which is well below the current upper limit τ z>15 ~ 0.02, is achievable by reionization models with minihalo domination in the early phase and can be distinguished from those with τ z>15 ≲ 5 × 10-4 through CV-limited CMB polarization observations. An accurate estimation of τ z>15, however, remains somewhat elusive. We investigate whether resampling the E-mode polarization data with limited spherical-harmonic modes may resolve this shortcoming.

Keywords: cosmic microwave background radiation; population iii stars; reionization
Texas Spectroscopic Search for Lyα Emission at the End of Reionization. III. The Lyα Equivalent-width Distribution and Ionized Structures at z > 7

Lyα emission from galaxies can be utilized to characterize the ionization state in the intergalactic medium (IGM). We report our search for Lyα emission at z > 7 using a comprehensive Keck/MOSFIRE near-infrared spectroscopic data set, as part of the Texas Spectroscopic Search for Lyα Emission at the End of Reionization Survey. We analyze data from 10 nights of MOSFIRE observations which together target 72 high-z candidate galaxies in the GOODS-N field, all with deep exposure times of 4.5-19 hr. Utilizing an improved automated emission-line search, we report 10 Lyα emission lines detected (>4σ) at z > 7, significantly increasing the spectroscopically confirmed sample. Our sample includes large equivalent-width (EW) Lyα emitters (>50 Å), and additional tentative Lyα emission lines detected at 3σ-4σ from five additional galaxies. We constrain the Lyα EW distribution at z ∼ 7.6, finding a significant drop from z ≲ 6, suggesting an increasing fraction of neutral hydrogen (H I) in the IGM in this epoch. We estimate the Lyα transmission through the IGM (=EWz ∼ 7.6/EW ${}_{z\sim 2\mbox{--}6}$ ) and infer an IGM H I fraction (XHI) of ${49}_{-19}^{+19}{\rm{ \% }}$ at z ∼ 7.6, which is lower in modest tension (>1σ) with recent measurements at z ∼ 7.6. The spatial distribution of the detected Lyα emitters implies the presence of a potential highly ionized region at z ∼ 7.55, which hosts four Lyα emitters within a ∼40 cMpc spatial separation. The prominence of this ionized region in our data set could explain our lower inferred value of XHI, though our analysis is also sensitive to the chosen reference Lyα EW distribution values and reionization models.

Keywords: high-redshift galaxies; galaxies; intergalactic medium; extragalactic astronomy; reionization; early universe; galaxy distances; galaxy evolution; galaxy formation
Inferring Vortex and Dust Devil Statistics from InSight

The InSight mission has operated on the surface of Mars for nearly two Earth years, returning detections of the first marsquakes. The lander also deployed a meteorological instrument package and cameras to monitor local surface activity. These instruments have detected boundary layer phenomena, including small-scale vortices. These vortices register as short-lived, negative pressure excursions and closely resemble those that could generate dust devils. Although our analysis shows that InSight encountered more than 900 vortices and collected more than 1000 images of the Martian surface, no active dust devils were imaged. In spite of the lack of dust devil detections, we can leverage the vortex detections and InSight's daily wind speed measurements to learn about the boundary layer processes that create dust devils. We discuss our analysis of InSight's meteorological data to assess the statistics of vortex and dust devil activity. We also infer encounter distances for the vortices and, therefrom, the maximum vortex wind speeds. Surveying the available imagery, we place upper limits on what fraction of vortices carry dust (i.e., how many are bona fide dust devils) and estimate threshold wind speeds for dust lifting. Comparing our results to detections of dust devil tracks seen in space-based observations of the InSight landing site, we can also infer thresholds and frequency of track formation by vortices. Comparing vortex encounters and parameters with advective wind speeds, we find evidence that high wind speeds at InSight may have suppressed the formation of dust devils, explaining the lack of imaged dust devils.

Keywords: mars; planetary atmospheres
COOL-LAMPS. II. Characterizing the Size and Star Formation History of a Bright Strongly Lensed Early-type Galaxy at Redshift 1.02

We present COOL J1323+0343, an early-type galaxy at z = 1.0153 ± 0.0006, strongly lensed by a cluster of galaxies at z = 0.353 ± 0.001. This object was originally imaged by DECaLS and noted as a gravitational lens by COOL-LAMPS, a collaboration initiated to find strong-lensing systems in recent public optical imaging data, and confirmed with follow-up data. With ground-based grzH imaging and optical spectroscopy from the Las Campanas Observatory and the Nordic Optical Telescope, we derive a stellar mass, metallicity, and star formation history from stellar-population synthesis modeling. The lens modeling implies a total magnification, summed over the three images in the arc, of μ ~ 113. The stellar mass in the source plane is M * ~ 10.64 M ⊙ and the 1σ upper limit on the star formation rate (SFR) in the source plane is SFR ~ 3.75 × 10-2 M ⊙ yr-1 (log sSFR = -12.1 yr-1) in the youngest two age bins (0-100 Myr), closest to the epoch of observation. Our measurements place COOL J1323+0343 below the characteristic mass of the stellar mass function, making it an especially compelling target that could help clarify how intermediate-mass quiescent galaxies evolve. We reconstruct COOL J1323+0343 in the source plane and fit its light profile. This object is below the expected size evolution of an early-type galaxy at this mass with an effective radius r e ~ 0.5 kpc. This extraordinarily magnified and bright lensed early-type galaxy offers an exciting opportunity to study the morphology and star formation history of an intermediate-mass early-type galaxy in detail at z ~ 1.

Keywords: early-type galaxies; elliptical galaxies; galaxy evolution; high-redshift galaxies; quenched galaxies; galaxy quenching; spectral energy distribution; strong gravitational lensing; galaxy spectroscopy
The Near-infrared Spectrum of the Nuclear Star Cluster: Looking below the Tip of the Iceberg, and Comparisons with Extragalactic Nuclei

Long-slit near-infrared (NIR) spectra of the Galactic nuclear star cluster (NSC) are discussed. The spectra sample the major axis of the NSC out to its half-light radius. The absorption spectrum of the central regions of the NSC is averaged over angular scales of tens of arc seconds in order to sample globular cluster-like total luminosities, and the results are compared with model spectra. The equivalent widths of Na I2.21 μm and Ca 2.26 μm outside of the center of the NSC, where light from nuclear bulge stars contributes a large fraction to the total flux, are consistent with solar chemical mixtures. In contrast, the equivalent widths of Na I2.21 μm and Ca I2.26 μm near the center of the NSC are larger than expected from models with solar chemical mixtures, even after light from the brightest evolved stars is removed. The depths of spectroscopic features changing along the major axis of the NSC are consistent with imaging studies that have found evidence of population gradients in the NSC. That Na I2.21 μm and Ca I2.26 μm are deeper than predicted for solar chemical mixtures over a range of evolutionary states is consistent with previous studies that find that the majority of stars near the center of the NSC formed from material that had nonsolar chemical mixtures. The depths of the Na I2.21 μm and Ca I2.26 μm features in the central regions of the NSC are comparable to those in the nuclear spectrum of the early-type Virgo disk galaxy NGC 4491, and are deeper than in the central spectra of NGC 253 and 7793. A spectrum of nebular emission and the youngest stars near the galactic center is also extracted. The equivalent widths of emission features in the extracted NIR spectrum are similar to those in the nuclear spectrum of NGC 253, and it is argued that this agreement is best achieved if the current episode of star formation near the center of the NSC has been in progress for at least a few megayears. * Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministério da Ciência, Tecnologia e Inovação (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

Keywords: galactic center
The Carbon Isotopic Ratio and Planet Formation

We present the first detection of 13CCH in a protoplanetary disk (TW Hya). Using observations of C2H, we measure CCH/13CCH = 65 ± 20 gas with a CO isotopic ratio of 12CO/13CO = 21 ± 5. The TW Hya disk exhibits a gas phase C/O that exceeds unity, and C2H is the tracer of this excess carbon. We confirm that the TW Hya gaseous disk exhibits two separate carbon isotopic reservoirs, as noted previously. We explore two theoretical solutions for the development of this dichotomy. One model represents TW Hya today with a protoplanetary disk exposed to a cosmic-ray ionization rate that is below interstellar as consistent with current estimates. We find that this model does not have sufficient ionization in cold (T < 40 K) layers to activate carbon isotopic fractionation. The second model investigates a younger TW Hya protostellar disk exposed to an interstellar cosmic-ray ionization rate. We find that the younger model has sources of ionization deeper in a colder disk that generates two independent isotopic reservoirs. One reservoir is 12C-enriched carried by methane/hydrocarbon ices, and the other is 13C-enriched carried by gaseous CO. The former potentially provides a source of methane/hydrocarbon ices to power the chemistry that generates the anomalously strong C2H emission in this (and other) disk systems in later stages. The latter provides a source of gaseous 13C-rich material to generate isotopic enrichments in forming giant planets, as recently detected in the super-Jupiter TYC 8998-760-1 b by Zhang et al.

Keywords: protoplanetary disks
A Multistate Low-dissipation Advection Upstream Splitting Method for Ideal Magnetohydrodynamics

We develop a new numerical scheme for ideal magnetohydrodynamic (MHD) simulations, which is robust against one- and multidimensional shocks, and is accurate for low Mach number flows and discontinuities. The scheme belongs to a family of the advection upstream splitting method employed in computational aerodynamics, and it splits the inviscid flux in MHD equations into advection, pressure, and magnetic tension parts, and then individually evaluates mass, pressure, and magnetic tension fluxes at the interface of a computational cell. The mass flux is designed to avoid numerical shock instability in multidimensions, while preserving contact discontinuity. The pressure flux possesses a proper scaling for low Mach number flows, allowing reliable simulations of nearly incompressible flows. The magnetic tension flux is built to be consistent with the HLLD approximate Riemann solver to preserve rotational discontinuity. We demonstrate various benchmark tests to verify the novel performance of the scheme. Our results indicate that the scheme must be a promising tool to tackle astrophysical systems that include both low and high Mach number flows, as well as magnetic field inhomogeneities.

Keywords: magnetohydrodynamical simulations; magnetic fields; shocks
Testing the Jeans, Toomre, and Bonnor-Ebert Concepts for Planetesimal Formation: 3D Streaming-instability Simulations of Diffusion-regulated Formation of Planetesimals

We perform streaming-instability simulations at Hill density and beyond to demonstrate that planetesimal formation is not completed when pebble accumulations exceed the local Hill density. We find that Hill density is not a sufficient criterion for further gravitational collapse of a pebble cloud into a planetesimal, but that additionally the accumulated mass has to be large enough to overcome turbulent diffusion. A Toomre analysis of the system indicates that linear self-gravity modes play no role on the scale of our numerical simulation. We nevertheless find that self-gravity, by vertically contracting the pebble layer, increases the strength of turbulence, which is either an indication of Kelvin-Helmholtz instability or a boost of the streaming instability. We furthermore determine the Bonnor-Ebert central density to which a pebble cloud of a given mass has to be compressed before it would be able to continue contraction against internal diffusion. As the equivalent "solid body" size of the pebble cloud scales with the central density to the power of -1/6, it is much easier to have a pebble cloud of 100 km equivalent size to collapse than one of 10 km for the same level of turbulent diffusion. This can explain the lack of small bodies in the solar system and predicts small objects will form at large pebble-to-gas ratios, so either in the outskirts of the solar nebula or at late times of generally reduced gas mass.

Keywords: solar system formation; circumstellar disks; protoplanetary disks; planetesimals; small solar system bodies; hydrodynamical simulations; trans-neptunian objects; classical kuiper belt objects; asteroids
Quasars: Standard Candles up to z = 7.5 with the Precision of Supernovae Ia

Currently, the Λ cold dark matter model, which relies on the existence of cold dark matter and a cosmological constant Λ, best describes the universe. However, we lack information in the high-redshift (z) region between Type Ia supernovae (SNe Ia; up to z = 2.26) and the cosmic microwave background (z = 1100), an interval crucial to test cosmological models and their possible evolution. We have defined a sample of 983 quasars up to z = 7.54 with a reduced intrinsic dispersion δ = 0.007, which determines the matter density parameter Ω M with the same precision of SNe Ia. Although previous analysis have used quasars as cosmological tools, this is the first time that high-redshift sources, in this case quasars, as standalone cosmological probes yield such tight constraints on Ω M . Our results show the importance of correcting cosmological relationships for selection biases and redshift evolution and how the choice of a golden sample reduces considerably the intrinsic scatter. This proves the reliability of quasars as standard cosmological candles.

Keywords: quasars