adsabs/SciX_UAT_keywords huggingface dataset:
BASS. XXVI. DR2 Host Galaxy Stellar Velocity Dispersions

We present new central stellar velocity dispersions for 484 Sy 1.9 and Sy 2 from the second data release of the Swift/BAT AGN Spectroscopic Survey (BASS DR2). This constitutes the largest study of velocity dispersion measurements in X-ray-selected obscured active galactic nuclei (AGN) with 956 independent measurements of the Ca II H and K λ3969, 3934 and Mg I λ5175 region (3880–5550 Å) and the calcium triplet region (8350–8730 Å) from 642 spectra mainly from VLT/X-Shooter or Palomar/DoubleSpec. Our sample spans velocity dispersions of 40–360 km s1, corresponding to 4–5 orders of magnitude in black hole mass (M BH = 105.5‑9.6 M ⊙), bolometric luminosity (L bol ∼ 1042–46 erg s‑1), and Eddington ratio (L/L Edd ∼ 10‑5 to 2). For 281 AGN, our data and analysis provide the first published central velocity dispersions, including six AGN with low-mass black holes (M BH = 105.5‑6.5 M ⊙), discovered thanks to high spectral resolution observations (σ inst ∼ 25 km s‑1). The survey represents a significant advance with a nearly complete census of velocity dispersions of hard X-ray–selected obscured AGN with measurements for 99% of nearby AGN (z < 0.1) outside the Galactic plane (∣b∣ > 10°). The BASS AGN have much higher velocity dispersions than the more numerous optically selected narrow-line AGN (i.e., ∼150 versus ∼100 km s‑1) but are not biased toward the highest velocity dispersions of massive ellipticals (i.e., >250 km s‑1). Despite sufficient spectral resolution to resolve the velocity dispersions associated with the bulges of small black holes (∼104–5 M ⊙), we do not find a significant population of super-Eddington AGN. Using estimates of the black hole sphere of influence from velocity dispersion, direct stellar and gas black hole mass measurements could be obtained with existing facilities for more than ∼100 BASS AGN.

Keywords: supermassive black holes; x-ray surveys; sky surveys; x-ray active galactic nuclei; agn host galaxies
Influence of the Gaia-Sausage-Enceladus on the Density Shape of the Galactic Stellar Halo Revealed by Halo K Giants from the LAMOST Survey

We present a study of the influence of the Gaia-Sausage-Enceladus (GSE) on the density shape of the Galactic stellar halo using 11,624 K giants from the LAMOST survey. Every star is assigned a probability of being a member of the GSE based on its spherical velocities and metallicity by a Gaussian mixture model. We divide the stellar halo into two parts by the obtained probabilities, of which one is composed of the GSE members and defined as the GSE-related halo, and the other one is referred to as the GSE-removed halo. Using a nonparametric method, the radial number density profiles of the two stellar halos can be well described by a single power law with a variable flattening q ( $r=\sqrt{{R}^{2}+{\left[(Z/q(r))\right]}^{2}},\nu ={\nu }_{0}{r}^{-\alpha }$ r=R2+(Z/q(r))2,ν=ν0r-α ). The index α is 4.92 ± 0.12 for the GSE-related halo and 4.25 ± 0.14 for the GSE-removed halo. Both of the stellar halos are vertically flattened at smaller radii but become more spherical at larger radii. We find that the GSE-related halo is less vertically flattened than the GSE-removed halo, and the difference of q between the two stellar halos ranges from 0.07 to 0.15. However, after the consideration of the bias, it is thought to be within 0.08 at most of the radii. Finally, we compare our results with two Milky Way analogs that experience a significant major merger in the TNG50 simulation. The study of the two analogs also shows that the major merger-related stellar halo has a smaller ellipticity than the major merger-removed stellar halo.

Keywords: milky way stellar halo; galaxy mergers; milky way formation; milky way galaxy physics
The Dynamical State of the Frontier Fields Galaxy Cluster Abell 370

We study the dynamics of Abell 370 (A370), a highly massive Hubble Frontier Fields galaxy cluster, using self-consistent three-dimensional N-body/hydrodynamical simulations. Our simulations are constrained by X-ray, optical spectroscopic and gravitational lensing, and Sunyaev-Zel'dovich (SZ) effect observations. Analyzing archival Chandra observations of A370 and comparing the X-ray morphology to the latest gravitational lensing mass reconstruction, we find offsets of ∼30 and ∼100 kpc between the two X-ray surface brightness peaks and their nearest mass surface density peaks, suggesting that it is a merging system, in agreement with previous studies. Based on our dedicated binary cluster merger simulations, we find that initial conditions of the two progenitors with virial masses of $1.7\times {10}^{15}$ and $1.6\times {10}^{15}\,{M}_{\odot }$ , an infall velocity of 3500 km s-1, and an impact parameter of 100 kpc can explain the positions and the offsets between the peaks of the X-ray emission and mass surface density, the amplitude of the integrated SZ signal, and the observed relative line-of-sight velocity. Moreover, our best model reproduces the observed velocity dispersion of cluster member galaxies, which supports the large total mass of A370 derived from weak lensing. Our simulations strongly suggest that A370 is a post major merger after the second core passage in the infalling phase, just before the third core passage. In this phase, the gas has not settled down in the gravitational potential well of the cluster, which explains why A370 does not follow closely the galaxy cluster scaling relations.

Keywords: relativistic mechanics; sunyaev-zeldovich effect; n-body simulations
LIGO-Virgo-KAGRA's Oldest Black Holes: Probing Star Formation at Cosmic Noon With GWTC-3

In their third observing run, the LIGO-Virgo-KAGRA gravitational-wave (GW) observatory was sensitive to binary black hole (BBH) mergers out to redshifts z merge ≈ 1. Because GWs are inefficient at shrinking the binary orbit, some of these BBH systems likely experienced long delay times τ between the formation of their progenitor stars at z form and their GW merger at z merge. In fact, the distribution of delay times predicted by isolated binary evolution resembles a power law $p(\tau )\propto {\tau }^{{\alpha }_{\tau }}$ with slope -1 ≲ α τ ≲ -0.35 and a minimum delay time of ${\tau }_{\min }=10\,\mathrm{Myr}$ . We use these predicted delay time distributions to infer the formation redshifts of the ~70 BBH events reported in the third GW transient catalog GWTC-3 and the formation rate of BBH progenitors. For our default α τ = -1 delay time distribution, we find that GWTC-3 contains at least one system (with 90% credibility) that formed earlier than z form > 4.4. Comparing our inferred BBH progenitor formation rate to the star formation rate, we find that at z form = 4, the number of BBH progenitor systems formed per stellar mass was ${6.4}_{-5.5}^{+9.4}\times {10}^{-6}\,{M}_{\odot }^{-1}$ and this yield dropped to ${0.134}_{-0.127}^{+1.6}\times {10}^{-6}\,{M}_{\odot }^{-1}$ by z form = 0. We discuss implications of this measurement for the cosmic metallicity evolution, finding that for typical assumptions about the metallicity dependence of the BBH yield, the average metallicity at z form = 4 was $\langle {\mathrm{log}}_{10}(Z/{Z}_{\odot })\rangle =-{0.3}_{-0.4}^{+0.3}$ , although the inferred metallicity can vary by a factor of ≈3 for different assumptions about the BBH yield. Our results highlight the promise of current GW observatories to probe high-redshift star formation.

Keywords: massive stars; astrophysical black holes; stellar mass black holes; star formation; metallicity; gravitational wave astronomy
Modeling Dust Production, Growth, and Destruction in Reionization-era Galaxies with the CROC Simulations: Methods and Parameter Exploration

We introduce a model for the explicit evolution of interstellar dust in a cosmological galaxy formation simulation. We post-process a simulation from the Cosmic Reionization on Computers project, integrating an ordinary differential equation for the evolution of the dust-to-gas ratio along pathlines in the simulation sampled with a tracer particle technique. This model incorporates the effects of dust grain production in asymptotic giant branch star winds and supernovae, grain growth due to the accretion of heavy elements from the gas phase of the interstellar medium, and grain destruction due to thermal sputtering in the high-temperature gas of supernova remnants. A main conclusion of our analysis is the importance of a carefully chosen dust destruction model, for which different reasonable parameterizations can predict very different values at the ~100 pc resolution of the interstellar medium (ISM) in our simulations. We run this dust model on the single most massive galaxy in a 10 h-1 comoving megaparsec box, which attains a stellar mass of ~2 × 109 M ⊙ by z = 5. We find that the model is capable of reproducing dust masses and dust-sensitive observable quantities broadly consistent with existing data from high-redshift galaxies. The total dust mass in the simulated galaxy is somewhat sensitive to parameter choices for the dust model, especially the timescale for grain growth due to accretion in the ISM. Consequently, observations that can constrain galaxy dust masses at these epochs are potentially useful for placing constraints on dust physics.

Keywords: interstellar dust processes; hydrodynamical simulations; galaxy formation; computational methods
SN 2020jfo: A Short-plateau Type II Supernova from a Low-mass Progenitor

We present spectroscopic and photometric observations of the Type IIP supernova, SN 2020jfo, in ultraviolet and optical wavelengths. SN 2020jfo occurred in the spiral galaxy M61 (NGC 4303), with eight observed supernovae in the past 100 yr. SN 2020jfo exhibited a short plateau lasting < 65 days, and achieved a maximum brightness in Vband of M V = -17.4 ± 0.4 mag at about 8.0 ± 0.5 days since explosion. From the bolometric light curve, we have estimated the mass of 56Ni synthesized in the explosion to be 0.033 ± 0.006 M ⊙. The observed spectral features are typical for a Type IIP supernova except for shallow Hα absorption throughout the evolution and the presence of stable 58Ni feature at 7378 Å, in the nebular phase. Using hydrodynamical modeling in the MESA + STELLA framework, an ejecta mass of ~5 M ⊙ is estimated. Models also indicate SN 2020jfo could be the result of a red supergiant progenitor with M ZAMS ~ 12 M ⊙. Bolometric light-curve modeling revealed the presence of a secondary radiation source for initial ~20 days, which has been attributed to interaction with a circumstellar material of mass ~ 0.2 M ⊙, which most likely was ejected due to enhanced mass loss about 20 yr prior to the supernova explosion.

Keywords: core-collapse supernovae; type ii supernovae; supernova dynamics; observational astronomy; red supergiant stars; supernovae; ejecta
Unraveling the Complexity of Dwarf Galaxy Dynamics: A Study of Binary Orbital Motions

We investigate the impact of binary orbital motions on the dynamical modeling of dwarf galaxies with intrinsic line-of-sight velocity dispersions ( ${\sigma }_{{v}_{r}}$ ) of 1-9 km s-1. Using dwarf galaxies from the AURIGA level-2 and level-3 simulations, we apply the Jeans Anisotropic Multi-Gaussian Expansion modeling to tracer stars before and after including binaries to recover the dynamical masses. The recovered total masses within the half-mass radius of tracers, M(< r half), are always inflated due to binary motions, with greater inflations occurring for smaller ${\sigma }_{{v}_{r}}$ . However, many dwarf galaxies experience central density deflated due to binary motions, with little dependence on ${\sigma }_{{v}_{r}}$ . This is due to the negative radial gradients in the velocity dispersion profiles, with the fractional inflation in ${\sigma }_{{v}_{r}}$ due to binaries more significant in outskirts. An extreme binary fraction of 70% can lead to central density deflation of up to 10%-20% at 3 km s-1 < ${\sigma }_{{v}_{r}}$ < 8 km s-1, with M( < r half) inflated by 4% at 9 km s-1 and up to 15% at 3 km s-1. A lower binary fraction of 36% leads to similar deflations, with the inflations decreasing to approximately 10% at 3 km s-1 and becoming statistically insignificant. The choice of binary orbit distribution models does not result in significant differences, and observational errors tend to slightly weaken the deflations in the recovered central density. Two observations separated by 1 yr to exclude binaries lead to almost zero inflations/deflations for a binary fraction of 36% over 3 km s-1 < ${\sigma }_{{v}_{r}}\lt 9$ km s-1. For ${\sigma }_{{v}_{r}}\sim 1$ km s-1 to 3 km s-1, a binary fraction of 70% (36%) still results in 60% (30%) to 10% (1%) of inflations in M( < r half), even with two-epoch observation.

Keywords: dwarf galaxies; hydrodynamical simulations; dark matter; binary stars
Science Opportunities for IMAP-Lo Observations of Interstellar Neutral Helium, Neon, and Oxygen during a Maximum of Solar Activity

Direct-sampling observations of interstellar neutral (ISN) species and their secondary populations give information about the physical state of the local interstellar medium and processes occurring in the outer heliosheath. Such observations are performed from Earth's orbit by the IBEX-Lo experiment on board the Interstellar Boundary Explorer (IBEX) mission. IBEX ISN viewing is restricted to directions close to perpendicular to the Earth-Sun line, which limits the observations of interstellar species to several months during the year. A greatly improved data set will be possible for the upcoming Interstellar Mapping and Acceleration Probe (IMAP) mission due to a novel concept of putting the IMAP ISN detector, IMAP-Lo, on a pivot platform that varies the angle of observation relative to the Sun-Earth line and the detector boresight. Here, we suggest a 2 yr scenario for varying the viewing angle in such a way that all the necessary atom components can be observed sufficiently well to achieve the science goals of the nominal IMAP mission. This scenario facilitates, among others, removal of the correlation of the inflow parameters of interstellar gas, unambiguous analysis of the primary and secondary populations of interstellar helium (He), neon (Ne), and oxygen (O), and determination of the ionization rates of He and Ne free of possible calibration bias. The scheme is operationally simple, provides good counting statistics, and synergizes observations of interstellar species and heliospheric energetic neutral atoms.

Keywords: interstellar clouds; interstellar medium; interstellar magnetic fields; heliosphere
Redshift Survey of 12 Moderate-redshift Clusters

We conducted a redshift survey of 12 X-ray selected clusters in the redshift range z = 0.35-0.50 with MMT/Hectospec. The redshift surveys confirm that these clusters are massive systems. There are no massive groups or clusters projected along the line of sight that might contaminate the observed cluster X-ray properties significantly. We identify 25-79 members per cluster and refine the estimates of each cluster's mean redshift. We include the 8004 new redshifts in Data Behind the Figure.

Keywords: redshift surveys; galaxy clusters
Key Signatures of Prominence Materials and Category of Cold Materials Identified by Random Forest Classifier

The origin of cold materials identified by different criteria is unclear. They are highly suspected to be erupted prominences. However, some cold materials defined by charge depletion exist in both quiet solar wind and interplanetary coronal mass ejections (ICMEs). Recently, solar observations show failed prominence eruption in coronal mass ejections (CMEs) that the prominence sometimes did not propagate into interplanetary space. This work uses Random Forest Classifier (RFC), which is an interpretable supervised machine-learning algorithm to study the distinct signatures of prominence cold materials (PCs) compared to quiet solar wind (QSW) and ICMEs excluding cold materials (ICMEEs). Twelve physical features measured by ACE at 1 au and the monthly averaged sunspot number are used in this study. The measurements from ACE are proton moments, magnetic field component B z , He/H, He/O, Fe/O, mean charge of oxygen and carbon, C6+/C5, C6+/C4+, and O7+/O6+. According to the returned weights from RFC that are checked by support vector machine classifier, the most important in situ signatures of PCs are obtained. Next, the trained RFC is used to check the category of the cold materials not related to CME observations. The results show that most segments of the cold materials are from prominences, but four of them are possibly from ICMEEs; another one segment is possibly from QSW. The most distinct signatures of PCs are lower (C6+/C5+)/(O7+/O6+), proton temperature, and He/O. Considering the obvious overlaps on key physical features between QSW, ICMEEs, and PCs, the multifeature classifier shows an advantage in identifying them than solid criteria.

Keywords: solar prominences; solar coronal mass ejections
Comets in Context: Comparing Comet Compositions with Protosolar Nebula Models

Comets provide a valuable window into the chemical and physical conditions at the time of their formation in the young solar system. We seek insights into where and when these objects formed by comparing the range of abundances observed for nine molecules and their average values across a sample of 29 comets to the predicted midplane ice abundances from models of the protosolar nebula. Our fiducial model, where ices are inherited from the interstellar medium, can account for the observed mixing ratio ranges of each molecule considered, but no single location or time reproduces the abundances of all molecules simultaneously. This suggests that each comet consists of material processed under a range of conditions. In contrast, a model where the initial composition of disk material is "reset," wiping out any previous chemical history, cannot account for the complete range of abundances observed in comets. Using toy models that combine material processed under different thermal conditions, we find that a combination of warm (CO-poor) and cold (CO-rich) material is required to account for both the average properties of the Jupiter-family and Oort cloud comets, and the individual comets we consider. This could occur by the transport (either radial or vertical) of ice-coated dust grains in the early solar system. Comparison of the models to the average Jupiter-family and Oort cloud comet compositions suggests the two families formed in overlapping regions of the disk, in agreement with the findings of A'Hearn et al. and with the predictions of the Nice model.

Keywords: astrochemistry; comet origins; interstellar molecules; protoplanetary disks; solar nebulae
The OTELO Survey: The Star Formation Rate Evolution of Low-mass Galaxies

We present the analysis of a sample of Hα, Hβ, and [O II] emission line galaxies from the OTELO survey, with masses typically below $\mathrm{log}({M}_{* }/{M}_{\odot })\sim 9.4$ and redshifts between z ~ 0.4 and 1.43. We study the star formation rate, star formation rate density, and their number density and evolution with redshift. We obtain a robust estimate of the specific star formation rate-stellar mass relation based on the lowest-mass sample published so far. We also determine a flat trend of the star formation rate density (SFRD) and number density with redshift. Our results suggest a scenario of no evolution of the number density of galaxies, regardless of their masses, up to redshift z ~ 1.4. This implies a gradual change of the relative importance of the star-forming processes, from high-mass galaxies to low-mass galaxies, with decreasing redshift. We also find little or no variation of the SFRD in the redshift range of 0.4 < z < 1.43.

Keywords: luminosity function; observational cosmology; star formation; starburst galaxies; surveys
The Polarized Cosmic Hand: IXPE Observations of PSR B1509-58/MSH 15-52

We describe IXPE polarization observations of the pulsar wind nebula (PWN) MSH 15-52, the "Cosmic Hand." We find X-ray polarization across the PWN, with B-field vectors generally aligned with filamentary X-ray structures. High-significance polarization is seen in arcs surrounding the pulsar and toward the end of the "jet," with polarization degree PD > 70%, thus approaching the maximum allowed synchrotron value. In contrast, the base of the jet has lower polarization, indicating a complex magnetic field at significant angle to the jet axis. We also detect significant polarization from PSR B1509-58 itself. Although only the central pulse phase bin of the pulse has high individual significance, flanking bins provide lower-significance detections and, in conjunction with the X-ray image and radio polarization, can be used to constrain rotating vector model solutions for the pulsar geometry.

Keywords: pulsar wind nebulae; rotation powered pulsars; polarimetry
Characterization of the Ejecta from the NASA/DART Impact on Dimorphos: Observations and Monte Carlo Models

The NASA Double Asteroid Redirection Test (DART) spacecraft successfully crashed on Dimorphos, the secondary component of the binary (65803) Didymos system. Following the impact, a large dust cloud was released, and a long-lasting dust tail developed. We have extensively monitored the dust tail from the ground and the Hubble Space Telescope. We provide a characterization of the ejecta dust properties, i.e., particle size distribution and ejection speeds, ejection geometric parameters, and mass, by combining both observational data sets and using Monte Carlo models of the observed dust tail. The size distribution function that best fits the imaging data is a broken power law having a power index of -2.5 for particles of r ≤ 3 mm and -3.7 for larger particles. The particles range in size from 1 μm up to 5 cm. The ejecta is characterized by two components, depending on velocity and ejection direction. The northern component of the double tail, observed since 2022 October 8, might be associated with a secondary ejection event from impacting debris on Didymos, although is also possible that this feature results from the binary system dynamics alone. The lower limit to the total dust mass ejected is estimated at ~6 × 106 kg, half of this mass being ejected to interplanetary space.

Keywords: asteroid dynamics
The Behavior of Bp He-weak Stars in the Far UV-Paper IX: HD 142990

The analysis of eighteen spectra of the B6 He-weak star HD 142990 recorded by the SWP camera on board the International Ultraviolet Explorer reveals variations of the far-ultraviolet spectral energy distribution shortwards of 1700 Å over about 6 hr, ie. about 25% of the rotational period. Several Si II, Si III and Si IV vary consistently. Silicon must be distributed in a non uniform manner over the surface of HD 142990 so as to modulate the FUV flux over the rotational period. The low resolution spectra also confirm this variability.

Keywords: chemically peculiar stars; helium-weak stars
On the Angle of Sunset

We calculate the angle ψ between the Sun path at sunset and the horizon to be $\psi =\arctan \left[\sqrt{1-\tfrac{{\sin }^{2}\delta }{{\cos }^{2}\phi }}\ \tan (90^\circ -\phi )\right]$ , where δ is the decl. of the Sun, and ϕ is the latitude of the place. We dub this angle the ghorub angle, after غروب, the Arabic word for sunset.

Keywords: the sun; astrometry