adsabs/SciX_UAT_keywords huggingface dataset:
Huffing and Puffing and Blowing Your House In: Strong Stellar Wind Interaction with a Supermassive Black Hole

We present analytical and numerical models of a cluster wind flow resulting from the interaction of stellar winds of massive stars with a supermassive black hole (SMBH). We consider the motion of the stars as well as the gravitational force of the SMBH. In the numerical simulations we consider two cases: the first one with the stars in circular orbits around the SMBH, and the second one with the stars in eccentric orbits. We found that after the system reaches an equilibrium, the circular and elliptical cases are very similar. We found a very good agreement between the analytical and numerical results, not only from our numerical simulations but also from other high-resolution numerical calculations. The analytical models are very interesting, since the properties of such complex systems involving strong winds and a massive compact object can be rapidly inferred without the need of a numerical calculation.

Keywords: stellar winds; black holes; hydrodynamical simulations; wolf-rayet stars
The Nature of Luminous Quasars with Very Large C IV Equivalent Widths

We report results for a complete sample of 10 luminous radio-quiet quasars with large C IV equivalent widths (EW ≥ 150 Å). For 8/10 we performed Chandra snapshot observations. We find that, in addition to the enhanced C IV line EW, their He II and Mg II lines are enhanced, but the C III] line is not. Their X-ray emission is substantially stronger than expected from their ultraviolet luminosity. Additionally, these large C IV EW quasars show small C IV blueshifts and possibly low Eddington ratios, suggesting that they are "extreme low Eigenvector 1 (EV1)" quasars. The mean excess He II EW is well matched by radiation pressure compression (RPC) photoionization models, with the harder α ox ionizing spectrum. However, these results do not reproduce well the enhancement pattern of the C IV, Mg II, and C III] EWs, or the observed high C IV/Mg II ratio. RPC calculations indicate that the C IV/Mg II line ratio is an effective metallicity indicator, and models with subsolar-metallicity gas and a hard ionizing continuum reproduce well the enhancement pattern of all four ultraviolet lines. We find that the C IV/Mg II line ratio in quasars is generally correlated with the excess X-ray emission. Extremely high EV1 quasars are characterized by high metallicity and suppressed X-ray emission. The underlying mechanism relating gas metallicity and X-ray emission is not clear but may be related to radiation-pressure-driven disk winds, which are enhanced at high metallicity, and consequent mass loading reducing coronal X-ray emission.

Keywords: quasars; x-ray quasars; photoionization; metallicity
Planes of Satellites around Simulated Disk Galaxies. II. Time-persistent Planes of Kinematically Coherent Satellites in ΛCDM

We use two zoom-in ΛCDM hydrodynamical simulations of massive disk galaxies to study the possible existence of fixed satellite groups showing a kinematically coherent behavior across evolution (angular momentum conservation and clustering). We identify three such groups in the two simulations, defining kinematically coherent persistent planes (KPPs) that last at least from virialization to z = 0 (more than 7 Gyr). This proves that orbital pole clustering is not necessarily set in at low redshift, representing a long-lived property of galaxy systems. KPPs are thin and oblate, represent ~25%-40% of the total number of satellites in the system, and are roughly perpendicular to their corresponding central disk galaxies during certain periods, consistently with Milky Way z = 0 data. KPP satellite members are statistically distinguishable from satellites outside KPPs: they show higher specific orbital angular momenta, orbit more perpendicularly to the central disk galaxy, and have larger pericentric distances than the latter. We numerically prove, for the first time, that KPPs and the best-quality positional planes share the same space configuration across time, such that KPPs act as "skeletons" preventing the latter from being washed out in short timescales. In one of the satellite-host systems, we witness the late capture of a massive dwarf galaxy endowed with its own satellite system, also organized into a KPP configuration prior to its capture. We briefly explore the consequences this event has on the host's KPP and on the possible enhancement of the asymmetry in the number of satellites rotating in one sense or the opposite within the KPP.

Keywords: dwarf galaxies; galaxy planes; galaxy kinematics; milky way galaxy
Observational Constraints on Sunyaev–Zeldovich Effect Halos around High-z Quasars

We present continuum observations from the Atacama Large Millimeter/submillimeter Array of 10 high-redshift (2.2 ≤ z ≤ 2.7) ultraluminous quasars (QSOs) and constrain the presence of hot, ionized, circumgalactic gas in a stacking analysis. We measure a Compton-y parameter profile with a peak value of (1.7 ± 1.1) × 10‑6 at a radius of ∼50 kpc. We compare our stacked observations to active galactic nucleus feedback wind models and generalized Navarro–Frenk–White pressure profile models to constrain the wind luminosity and halo mass of the stacked QSOs. Our observations constrain the observed average halo mass to M 500 < 1 × 1013 M ⊙ and the average feedback wind power <1 × 1012 L ⊙, which is <1% of the bolometric luminosity of the quasar.

Keywords: sunyaev-zeldovich effect; quasars; active galactic nuclei; galaxy evolution
Dwarf–Dwarf Interactions Can Both Trigger and Quench Star Formation

It is exceedingly rare to find quiescent low-mass galaxies in the field at low redshift. UGC 5205 is an example of such a quenched field dwarf (M ⋆ ∼ 3 × 108 M ⊙). Despite a wealth of cold gas (M HI ∼ 3.5 × 108 M ⊙) and UV emission that indicates significant star formation in the past few hundred megayears, there is no detection of Hα emission—star formation in the last ∼10 Myr—across the face of the galaxy. Meanwhile, the near equal-mass companion of UGC 5205, PGC 027864, is starbursting (which has an Hα equivalent width > 1000 Å). In this work, we present new Karl G. Jansky Very Large Array 21 cm line observations of UGC 5205, showing that the lack of star formation is caused by an absence of H I in the main body of the galaxy. The H I of UGC 5205 is highly disturbed; the bulk of the H I resides in several-kiloparsec–long tails, while the H I of PGC 027864 is dominated by ordered rotation. We model the stellar populations of UGC 5205 to show that, as indicated by the UV and Hα emission, the galaxy underwent a coordinated quenching event ∼100–300 Myr ago. The asymmetry of outcomes for UGC 5205 and PGC 027864 demonstrate that major mergers can both quench and trigger star formation in dwarfs. However, because the gas remains bound to the system, we suggest that such mergers only temporarily quench star formation. We estimate a total quenched time of ∼560 Myr for UGC 5205, consistent with established upper limits on the quenched fraction of a few percent for dwarfs in the field.

Keywords: galaxy interactions; star formation; tidal tails; galaxy quenching; interstellar atomic gas
Physical Environments of the Luminosity Outburst Source NGC 6334I Traced by Thermal and Maser Lines of Multiple Molecules

We have conducted a systematic line survey, primarily focused on transitions of the methanol and ammonia molecules, and monitoring observations of masers toward the high-mass star-forming region NGC 6334I. These observations were undertaken between 2019 and 2022 in the C, K, Ka, and Q bands with the Tianma Radio Telescope. In total, 63 CH3OH (including 11 class I and nine class II maser or maser candidate), 18 13CH3OH, and 34 NH3 (including seven maser or maser candidate) transitions were detected. The emission is likely associated with the luminosity outburst source MM1. Rotation diagram analysis of multiple ammonia transitions shows that the gas temperature in the molecular core was a factor of 2 higher than that measured in previous observations in the pre-burst stage. This suggests that the molecular core has likely been heated by radiation originating from the luminosity outburst. Maser variability in the methanol and excited-state OH masers shows a general trend that the maser components associated with the luminosity outburst have decreased in their intensity since 2020. The decay in the maser luminosity indicates that the outburst is possibly declining, and as a result, the duration of the MM1 luminosity outburst may be shorter than the predicted 40 yr duration. Compared to the masers detected toward another luminosity outburst source, G358.93-0.03, abundant class I methanol masers and strong water maser flares were also detected toward NGC 633I, but masers from rare class II methanol transitions and new molecules were absent toward NGC 6334I. The large number of detections of maser transitions toward the two burst sources provided a database for further maser modeling to explore the physical environments associated with accretion burst events.

Keywords: interstellar masers; star formation; accretion; massive stars; young stellar objects
Discovery of Hydrogen Radio Recombination Lines at z = 0.89 toward PKS 1830-211

We report the detection of stimulated hydrogen radio recombination line (RRL) emission from ionized gas in a z = 0.89 galaxy using 580-1670 MHz observations from the MeerKAT Absorption Line Survey. The RRL emission originates in a galaxy that intercepts and strongly lenses the radio blazar PKS 1830-211 (z = 2.5). This is the second detection of RRLs outside of the local Universe and the first clearly associated with hydrogen. We detect effective H144α (and H163α) transitions at observed frequencies of 1156 (798) MHz by stacking 17 (27) RRLs with 21σ (14σ) significance. The RRL emission contains two main velocity components and is coincident in velocity with H I 21 cm and OH 18 cm absorption. We use the RRL spectral line energy distribution and a Bayesian analysis to constrain the density (n e ) and the volume-averaged path length (ℓ) of the ionized gas. We determine $\mathrm{log}({n}_{e})={2.0}_{-0.7}^{+1.0}$ cm-3 and $\mathrm{log}({\ell })=-{0.7}_{-1.1}^{+1.1}$ pc toward the northeast (NE) lensed image, likely tracing the diffuse thermal phase of the ionized ISM in a thin disk. Toward the southwest (SW) lensed image, we determine $\mathrm{log}({n}_{e})={3.2}_{-1.0}^{+0.4}$ cm-3 and $\mathrm{log}({\ell })=-{2.7}_{-0.2}^{+1.8}$ pc, tracing gas that is more reminiscent of H scii regions. We estimate a star formation (surface density) rate of ΣSFR ~ 0.6 M ⊙ yr-1 kpc-2 or SFR ~ 50 M ⊙ yr-1, consistent with a star-forming main-sequence galaxy of M ⋆ ~ 1011 M ⊙. The discovery presented here opens up the possibility of studying ionized gas at high redshifts using RRL observations from current and future (e.g., SKA and ngVLA) radio facilities.

Keywords: quasar absorption line spectroscopy; radio galaxies; galaxies; radio spectroscopy; interstellar medium
GRB 221009A: Revealing a Hidden Afterglow during the Prompt Emission Phase with Fermi-GBM Observations

Recently, LHAASO reported the detection of the brightest-of-all-time GRB 221009A, revealing the early onset of a TeV afterglow. We analyze the spectral evolution of the X-ray/gamma-ray emission of GRB 221009A measured by the Fermi Gamma-ray Burst Monitor (GBM) during the dips of two prompt emission pulses (i.e., intervals T 0 + [300-328] s and T 0 + [338-378] s, where T 0 is the GBM trigger time). We find that the spectra at the dips transit from the Band function to a power-law function, indicating a transition from the prompt emission to the afterglow. After ~T 0 + 660 s, the spectrum is well described by a power-law function, and the afterglow becomes dominant. Remarkably, the underlying afterglow emission at the dips smoothly connect with the afterglow after ~T 0 + 660 s. The entire afterglow emission measured by GBM can be fitted by a power-law function F ~ t -0.95±0.05, where t is the time since the first main pulse at T* = T 0 + 226 s, consistent with the TeV afterglow decay measured by LHAASO. The start time of this power-law decay indicates that the afterglow peak of GRB 221009A should be earlier than T 0 + 300 s. We also test the possible presence of a jet break in the early afterglow light curve, finding that both the jet break model and single power-law decay model are consistent with the GBM data. The two models cannot be distinguished with the GBM data alone because the inferred jet break time is quite close to the end of the GBM observations.

Keywords: gamma-ray bursts; high energy astrophysics
Implication of Spin Constraints by the Event Horizon Telescope on Stellar Orbits in the Galactic Center

The center of the Milky Way hosts the closest supermassive black hole, Sgr A*. Decades of near-infrared observations of our Galactic Center have shown the presence of a small population of stars (the so-called S-star cluster) orbiting Sgr A*, which were recently reported to be arranged into two orthogonal disks. In this case, the timescale for the Lense-Thirring precession of S stars should be longer than their age, implying a low spin for Sgr A*. In contrast, the recent results by the Event Horizon Telescope favor a highly spinning Sgr A*, which seems to suggest that the S stars could not be arranged in disks. Alternatively, the spin of Sgr A* must be small, suggesting that the models for its observed image are incomplete.

Keywords: black holes; kerr black holes; galactic center
Do All Low-Mass Stars Undergo Extra Mixing Processes?

Standard stellar evolution models that only consider convection as a physical process to mix material inside of stars predict the production of significant amounts of 3He in low-mass stars (M < 2 M ⊙), with peak abundances of 3He/H ~ few × 10-3 by number. Over the lifetime of the Galaxy, this ought to produce 3He/H abundances that diminish with increasing Galactocentric radius. Observations of 3He+ in H II regions throughout the Galactic disk, however, reveal very little variation in the 3He abundance with values of 3He/H similar to the primordial abundance, ${\left({}^{3}{\rm{H}}{\rm{e}}/{\rm{H}}\right)}_{p}\sim {10}^{-5}$ . This discrepancy, known as the "3He problem," can be resolved by invoking in stellar evolution models an extra mixing mechanism due to the thermohaline instability. Here we observe 3He+ in the planetary nebula (PN) J320 (G190.3-17.7) with the Jansky Very Large Array to confirm a previous 3He+ detection made with the Very Large Array that supports standard stellar yields. This measurement alone indicates that not all stars undergo extra mixing. Our more sensitive observations do not detect 3He+ emission from J320 with an rms noise of 58.8 μJy beam-1 after smoothing the data to a velocity resolution of 11.4 km s-1. We estimate an abundance limit of 3He/H ≤ 2.75 × 10-3 by number using the numerical radiative transfer code NEBULA. This result nullifies the last significant detection of 3He+ in a PN and allows for the possibility that all stars undergo extra mixing processes.

Keywords: late stellar evolution; planetary nebulae; radio spectroscopy
SDSS-IV MaNGA: Refining Strong Line Diagnostic Classifications Using Spatially Resolved Gas Dynamics

We use the statistical power of the MaNGA integral-field spectroscopic galaxy survey to improve the definition of strong line diagnostic boundaries used to classify gas ionization properties in galaxies. We detect line emission from 3.6 million spaxels distributed across 7400 individual galaxies spanning a wide range of stellar masses, star formation rates, and morphological types, and find that the gas-phase velocity dispersion σHα correlates strongly with traditional optical emission-line ratios such as [S II]/Hα, [N II]/Hα, [O I]/Hα, and [O III]/Hβ. Spaxels whose line ratios are most consistent with ionization by galactic H II regions exhibit a narrow range of dynamically cold line-of-sight velocity distributions (LOSVDs) peaked around 25 km s-1 corresponding to a galactic thin disk, while those consistent with ionization by active galactic nuclei (AGNs) and low-ionization emission-line regions (LI(N)ERs) have significantly broader LOSVDs extending to 200 km s-1. Star-forming, AGN, and LI(N)ER regions are additionally well separated from each other in terms of their stellar velocity dispersion, stellar population age, Hα equivalent width, and typical radius within a given galaxy. We use our observations to revise the traditional emission-line diagnostic classifications so that they reliably identify distinct dynamical samples both in two-dimensional representations of the diagnostic line ratio space and in a multidimensional space that accounts for the complex folding of the star-forming model surface. By comparing the MaNGA observations to the SDSS single-fiber galaxy sample, we note that the latter is systematically biased against young, low-metallicity star-forming regions that lie outside of the 3″ fiber footprint.

Keywords: galaxy kinematics
Exploring the Sgr-Milky Way-disk Interaction Using High-resolution N-body Simulations

The ongoing merger of the Sagittarius (Sgr) dwarf galaxy with the Milky Way is believed to strongly affect the dynamics of the Milky Way's disk. We present a suite of 13 N-body simulations, with 500 million-1 billion particles, modeling the interaction between the Sgr dwarf galaxy and the Galactic disk. To quantify the perturbation to the disk's structure and dynamics in the simulation, we compute the number count asymmetry and the mean vertical velocity in a solar-neighborhood-like volume. We find that, overall, the trends in the simulations match those seen in a simple one-dimensional model of the interaction. We explore the effects of changing the mass model of Sgr, the orbital kinematics of Sgr, and the mass of the Milky Way halo. We find that none of the simulations match the observations of the vertical perturbation using Gaia Data Release 2. In the simulation that is the most similar, we find that the final mass of Sgr far exceeds the observed mass of the Sgr remnant, the asymmetry wavelength is too large, and the shape of the asymmetry does not match past z ≈ 0.7 kpc. We therefore conclude that our simulations support the conclusion that Sgr alone could not have caused the observed perturbation to the solar neighborhood.

Keywords: milky way disk; milky way formation; milky way dynamics; milky way evolution; solar neighborhood
Dissecting the Energy Budget of a Gamma-Ray Burst Fireball

The jet composition and radiative efficiency of gamma-ray bursts (GRBs) are poorly constrained from the data. If the jet composition is matter-dominated (i.e., a fireball), the GRB prompt emission spectra would include a dominant thermal component originating from the fireball photosphere and a nonthermal component presumably originating from internal shocks whose radii are greater than the photosphere radius. We propose a method to directly dissect the GRB fireball energy budget into three components and measure their values by combining the prompt emission and early afterglow data. The measured parameters include the initial dimensionless specific enthalpy density (η), bulk Lorentz factors at the photosphere radius (Γph) and before fireball deceleration (Γ0), the amount of mass loading (M), and the GRB radiative efficiency (ηγ). All the parameters can be derived from the data for a GRB with a dominant thermal spectral component, a deceleration bump feature in the early afterglow lightcurve, and a measured redshift. The results only weakly depend on the density n of the interstellar medium when the composition ${ \mathcal Y }$ parameter (typically unity) is specified.

Keywords: gamma-ray bursts; relativistic fluid dynamics
Vanadium Abundance Derivations in 255 Metal-poor Stars

We present vanadium (V) abundances for 255 metal-poor stars derived from high-resolution optical spectra from the Magellan Inamori Kyocera Echelle spectrograph on the Magellan Telescopes at Las Campanas Observatory, the Robert G. Tull Coudé Spectrograph on the Harlan J. Smith Telescope at McDonald Observatory, and the High Resolution Spectrograph on the Hobby-Eberly Telescope at McDonald Observatory. We use updated V I and V II atomic transition data from recent laboratory studies, and we increase the number of lines examined (from one to four lines of V I, and from two to seven lines of V II). As a result, we reduce the V abundance uncertainties for most stars by more than 20% and expand the number of stars with V detections from 204 to 255. In the metallicity range -4.0 < [Fe/H] < -1.0, we calculate the mean ratios [V I/Fe I] = -0.10 ± 0.01 (σ = 0.16) from 128 stars with ≥2 V I lines detected, [V II/Fe II] = +0.13 ± 0.01 (σ = 0.16) from 220 stars with ≥2 V II lines detected, and [V II/V I] = +0.25 ± 0.01 (σ = 0.15) from 119 stars. We suspect that this offset is due to departures from local thermodynamic equilibrium, and we recommend using [V II/Fe II], which is enhanced relative to the solar ratio, as a better representation of [V/Fe]. We provide more extensive evidence for abundance correlations detected previously among scandium, titanium, and vanadium, and we identify no systematic effects in the analysis that can explain these correlations. * This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile, and The McDonald Observatory of The University of Texas at Austin. The Hobby-Eberly Telescope is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.

Keywords: nucleosynthesis; population ii stars; stellar abundances
Jupiter as a Rotating Bipolytrope

Polytropes have long been used to model a wide variety of astrophysical objects. A bipolytrope (composite polytrope) may be used for bodies with a distinct core-envelope structure. In this short paper, I demonstrate that a rotating bipolytrope is a reasonable approximation for Jovian interior. Similar models may be used to probe rotating exoplanets to gain an intuitive understanding of their internal structure.

Keywords: planetary interior; jupiter; computational methods
A White Dwarf Search Model Based on a Deep Transfer-learning Method

White dwarfs represent the ultimate stage of evolution for over 97% of stars and play a crucial role in studies of the Milky Way's structure and evolution. Recent years have witnessed significant progress in using deep-learning methods for identifying unique objects in large-scale data. In this paper, we present a model based on transfer learning for identifying white dwarfs. We constructed a data set using the spectra released by LAMOST DR9 and trained a convolutional neural network model. The model was then further trained using a transfer-learning approach for a binary classification model. Our final model is comprised of a seven-class classification model and a binary classification model. The testing set yielded an accuracy rate of 96.08%. Our proposed model successfully identifies 4314 of the 4479 white dwarfs published in previous papers. We applied this model to filter the 1,121,128 spectral data from the LAMOST DR9 V1 catalog. Subsequently, we obtained 6317 white dwarf candidates, of which 5014 were cross-validated and found to be known white dwarfs. We finally identified 489 new white dwarfs out of the remaining 1303 candidates, containing 377 DAs, 1 DB, 4 DZs, 1 magnetic WD, 101 DA+M binaries, and 1 DB+M binary. Our study also compared transfer-learning methods with non-transfer-learning methods, and the results show that transfer learning provides faster training speed and a higher accuracy rate. We provide the trained model and a corresponding usage program for subsequent studies.

Keywords: convolutional neural networks; white dwarf stars; stellar classification; stellar types