adsabs/SciX_UAT_keywords huggingface dataset:
The Role of Active Galactic Nuclei in the Quenching of Massive Galaxies in the SQuIGG ěc{L} E Survey

We study the incidence of nuclear activity in a large sample of massive post-starburst (PSB) galaxies at $z\sim 0.7$ selected from the Sloan Digital Sky Survey, and identify active galactic nuclei based on radio continuum and optical emission lines. Over our mass range of ${10}^{10.6}\mbox{--}{10}^{11.5}$ ${M}_{\odot }$ , the incidence of radio activity is weakly dependent on stellar mass and independent of stellar age, while radio luminosity depends strongly on stellar mass. Optical nuclear activity incidence depends most strongly on the Dn4000 line index, a proxy for stellar age, with an active fraction that is ∼10 times higher in the youngest versus oldest PSB galaxies. Since a similar trend is seen between age and molecular gas fractions, we argue that, like in local galaxies, the age trend reflects a peak in available fueling rather than feedback from the central black hole on the surrounding galaxy.

Keywords: agn host galaxies; radio galaxies; quenched galaxies
Deriving Thermonuclear Supernova Properties from Gamma-Ray Line Measurements

We illustrate methods for deriving properties of thermonuclear, or Type Ia, supernovae, including synthesized 56Ni mass, total ejecta mass, ejecta kinetic energy, and 56Ni distribution in velocity, from gamma-ray line observations. We simulate data from a small number of published SNe Ia models for a simple gamma-ray instrument, and measure their underlying properties from straightforward analyses. Assuming spherical symmetry and homologous expansion, we calculate exact line profiles for all 56Co and 56Ni lines at all times, requiring only the variation of mass density and 56Ni mass fraction with expansion velocity as input. By parameterizing these quantities, we iterate the parameters to fit the simulated data. We fit the full profiles of multiple lines, or we integrate over the lines and fit line fluxes only versus time. Line profile fits are more robust, but in either case, we can recover accurately the values of the aforementioned properties of the models simulated, given sufficient signal to noise in the lines. A future gamma-ray mission with line sensitivity approaching 10-6 photons cm-2 s-1 would measure these properties for many SNe Ia, and with unprecedented precision and accuracy for a few per year. Our analyses applied to the reported 56Co lines from SN 2014J favor a low 56Ni mass and low ejecta mass, relative to other estimates.

Keywords: type ia supernovae; gamma-ray lines
The Intermediate-ionization Lines as Virial Broadening Estimators for Population A Quasars

The identification of a virial broadening estimator in the quasar UV rest frame suitable for black hole mass computation at high redshift has become an important issue. We compare the H I Balmer H β line width to the ones of two intermediate-ionization lines: the Al III λ1860 doublet and the C III] λ1909 line, over a wide interval of redshift and luminosity (0 ≲ z ≲ 3.5; $43\lesssim \mathrm{log}L\lesssim 48.5$ [erg s-1]), for 48 sources belonging to the quasar population characterized by intermediate to high values of the Eddington ratio (Population A). The present analysis indicates that the line widths of Al III λ1860 and H β are highly correlated and can be considered equivalent for most Population A quasars over five orders of magnitude in luminosity; for C III] λ1909, multiplication by a constant correction factor ξ ≈ 1.25 is sufficient to bring the FWHM of C III] in agreement with that of H β. The statistical concordance between low-ionization and intermediate-ionization lines suggests that they predominantly arise from the same virialized part of the broad-line region. However, blueshifts of modest amplitude (few hundred kilometers per second) with respect to the quasar rest frame and an excess (≲1.1) Al III broadening with respect to H β are found in a fraction of our sample. Scaling laws to estimate M BH of high-redshift quasars using the Al III and C III] line widths have rms scatter ≈0.3 dex. The Al III scaling law takes the form $\mathrm{log}{M}_{\mathrm{BH}}\approx 0.58\mathrm{log}{L}_{\mathrm{1700,44}}+2\mathrm{logFWHM}+0.49$ [M ⊙]. *Based in part on observations made with ESO Telescopes at the Paranal Observatory under programs 082.B-0572(A) and 083.B-0273(A).

Keywords: active galactic nuclei; quasars; supermassive black holes
Spectroscopic Detection of the Pre-White Dwarf Companion of Regulus

Mass transfer in an interacting binary will often strip the mass donor of its entire envelope and spin up the mass gainer to near critical rotation. The nearby B-type star Regulus represents a binary in the post-mass transfer stage: it is a rapid rotator with a very faint companion in a 40 days orbit. Here we present the results of a search for the spectral features of the stripped-down star in an extensive set of spectra with high signal-to-noise ratio and high resolution obtained with the CFHT/ESPaDOnS and TBL/NARVAL spectrographs. We first determine revised orbital elements in order to set accurate estimates of the orbital Doppler shifts at the times of observation. We then calculate cross-correlation functions of the observed and model spectra, and we search for evidence of the companion signal in the residuals after removal of the strong primary component. We detect a weak peak in the co-added residuals that has the properties expected for a faint pre-white dwarf. We use the dependence of the peak height and width on assumed secondary velocity semiamplitude to derive the semiamplitude, which yields masses of M1/M⊙ = 3.7 ± 1.4 and M2/M⊙ = 0.31 ± 0.10 (assuming orbital inclination equals the spin inclination of Regulus). We estimate the temperature of the pre-white dwarf Teff = (20 ± 4) kK through tests with differing temperature model spectra, and we find the radius R2/R⊙ = 0.061 ± 0.011 from the component temperatures and the flux ratio associated with the amplitude of the signal in the cross-correlation residuals.

Keywords: binary stars; white dwarf stars; b stars
X-Ray and UV Observations of the Contact Binary KIC 9832227

We investigate the X-ray and UV emission from the contact binary star KIC 9832227, which was observed with XMM-Newton for one orbital cycle. The binary is detected with an average X-ray luminosity of 3.4 × 1030 erg s-1. The X-ray emission is restricted to energies below 3 keV and originates from a multitemperature plasma with temperatures up to 1 keV. The X-ray spectrum has at least two distinct components, a cooler, mostly steady component, and a hotter component exhibiting significant variability. The variable X-ray emission appears to originate from a compact flare near the contact region between the two stars that is being eclipsed by the secondary. We analyze the eclipse profile to constrain the location, size, and density of the flaring region. The remaining X-ray emission is not eclipsed and could originate from the polar region on the primary star or an extended corona. The UV emission exhibits the same nearly sinusoidal modulation at half the orbital period that is observed at longer wavelengths. The primary and secondary eclipses have slightly different depths, which is generally attributed to starspot activity. Using simulations of the UV light curve with stellar atmosphere models, we deduce the presence of a starspot near the polar region of the primary, and we determine the time of primary eclipse.

Keywords: contact binary stars; stellar x-ray flares; x-ray binary stars; ultraviolet sources; eclipsing binary stars
Production and Persistence of Extreme Two-temperature Plasmas in Radiative Relativistic Turbulence

Turbulence is a predominant process for energizing electrons and ions in collisionless astrophysical plasmas, and thus is responsible for shaping their radiative signatures (luminosity, spectra, and variability). To better understand the kinetic properties of a collisionless radiative plasma subject to externally driven turbulence, we investigate particle-in-cell simulations of relativistic plasma turbulence with external inverse Compton cooling acting on the electrons. We find that ions continuously heat up while electrons gradually cool down (due to the net effect of radiation), and hence the ion-to-electron temperature ratio Ti/Te grows in time. We show that Ti/Te is limited only by the size and duration of the simulations (reaching ${T}_{i}/{T}_{e}\sim {10}^{3}$ ), indicating that there are no efficient collisionless mechanisms of electron-ion thermal coupling. This result has implications for models of radiatively inefficient accretion flows, such as observed in the Galactic center and in M87, for which so-called two-temperature plasmas with ${T}_{i}/{T}_{e}\gg 1$ have been invoked to explain their low luminosity. Additionally, we find that electrons acquire a quasi-thermal distribution (dictated by the competition of turbulent particle energization and radiative cooling), while ions undergo efficient nonthermal acceleration (acquiring a harder distribution than in equivalent nonradiative simulations). There is a modest nonthermal population of high-energy electrons that are beamed intermittently in space, time, and direction; these beamed electrons may explain rapid flares in certain high-energy astrophysical systems (e.g., in the Galactic center). These numerical results demonstrate that extreme two-temperature plasmas can be produced and maintained by relativistic radiative turbulence.

Keywords: plasma astrophysics; high energy astrophysics; accretion; non-thermal radiation sources; cosmic rays; relativistic jets
No Compact Radio Emission from the Proposed Blazar Candidate Counterpart for the Fermi Source 4FGL J1848.7-0129

By assessing available radio data, we argue that the recently proposed new counterpart for the Fermi γ-ray source 4FGL J1848.7-0129 is unlikely to be a blazar. The radio source coincident with a Chandra X-ray point source is extended on ~10″ angular scale, has no detected compact component (3 GHz flux density ≲1 mJy), and its radio spectrum is steep. These properties contradict to what is expected for blazars with relativistically beamed radio jet emission.

Keywords: gamma-ray sources; blazars; radio jets
How to Obtain the Redshift Distribution from Probabilistic Redshift Estimates

A reliable estimate of the redshift distribution n(z) is crucial for using weak gravitational lensing and large-scale structures of galaxy catalogs to study cosmology. Spectroscopic redshifts for the dim and numerous galaxies of next-generation weak-lensing surveys are expected to be unavailable, making photometric redshift (photo-z) probability density functions (PDFs) the next best alternative for comprehensively encapsulating the nontrivial systematics affecting photo-z point estimation. The established stacked estimator of n(z) avoids reducing photo-z PDFs to point estimates but yields a systematically biased estimate of n(z) that worsens with a decreasing signal-to-noise ratio, the very regime where photo-z PDFs are most necessary. We introduce Cosmological Hierarchical Inference with Probabilistic Photometric Redshifts (CHIPPR), a statistically rigorous probabilistic graphical model of redshift-dependent photometry that correctly propagates the redshift uncertainty information beyond the best-fit estimator of n(z) produced by traditional procedures and is provably the only self-consistent way to recover n(z) from photo-z PDFs. We present the chippr prototype code, noting that the mathematically justifiable approach incurs computational cost. The CHIPPR approach is applicable to any one-point statistic of any random variable, provided the prior probability density used to produce the posteriors is explicitly known; if the prior is implicit, as may be the case for popular photo-z techniques, then the resulting posterior PDFs cannot be used for scientific inference. We therefore recommend that the photo-z community focus on developing methodologies that enable the recovery of photo-z likelihoods with support over all redshifts, either directly or via a known prior probability density.

Keywords: observational cosmology; galaxy photometry; astronomical methods; astrostatistics; hierarchical models; posterior distribution; prior distribution; bayesian statistics; redshift surveys; two-point correlation function; broad band photometry; markov chain monte carlo
A Tale of Two Disks: Mapping the Milky Way with the Final Data Release of APOGEE

We present new maps of the Milky Way disk showing the distribution of metallicity ([Fe/H]), α-element abundances ([Mg/Fe]), and stellar age, using a sample of 66,496 red giant stars from the final data release (DR17) of the Apache Point Observatory Galactic Evolution Experiment survey. We measure radial and vertical gradients, quantify the distribution functions for age and metallicity, and explore chemical clock relations across the Milky Way for the low-α disk, high-α disk, and total population independently. The low-α disk exhibits a negative radial metallicity gradient of -0.06 ± 0.001 dex kpc-1, which flattens with distance from the midplane. The high-α disk shows a flat radial gradient in metallicity and age across nearly all locations of the disk. The age and metallicity distribution functions shift from negatively skewed in the inner Galaxy to positively skewed at large radius. Significant bimodality in the [Mg/Fe]-[Fe/H] plane and in the [Mg/Fe]-age relation persist across the entire disk. The age estimates have typical uncertainties of ~0.15 in log(age) and may be subject to additional systematic errors, which impose limitations on conclusions drawn from this sample. Nevertheless, these results act as critical constraints on galactic evolution models, constraining which physical processes played a dominant role in the formation of the Milky Way disk. We discuss how radial migration predicts many of the observed trends near the solar neighborhood and in the outer disk, but an additional more dramatic evolution history, such as the multi-infall model or a merger event, is needed to explain the chemical and age bimodality elsewhere in the Galaxy.

Keywords: milky way galaxy; milky way disk; galactic abundances; stellar ages; galaxy stellar content; galactic archaeology; galaxy structure; milky way formation; milky way evolution
Density Profile of the Ambient Circumnuclear Medium in Seyfert 1 Galaxies

The shape of the ambient circumnuclear medium (ACM) density profile can probe the history of accretion onto the central supermassive black holes in galaxies and the circumnuclear environment. However, due to the limitations of instrument resolution, the density profiles of the ACM for most galaxies remain largely unknown. In this work, we propose a novel method to measure the ACM density profile of active galactic nuclei (AGNs) by the equilibrium between the radiation pressure on the warm absorbers (WAs, a type of AGN outflow) and the drag pressure from the ACM. We study the correlation between the outflow velocity and ionization parameter of WAs in each of the five Seyfert 1 galaxies (NGC 3227, NGC 3783, NGC 4051, NGC 4593, and NGC 5548), inferring that the density profile of the ACM is between n ∝ r -1.7 and n ∝ r -2.15 (n is number density and r is distance) from 0.01 pc to parsec scales in these five AGNs. Our results indicate that the ACM density profile in Seyfert 1 galaxies is steeper than the prediction by the spherically symmetric Bondi accretion model and the simulated results of the hot accretion flow, but more in line with the prediction by the standard thin-disk model.

Keywords: active galactic nuclei; accretion; seyfert galaxies; galaxy nuclei; interstellar medium
GB6 J2113+1121: A Multiwavelength Flaring γ-Ray Blazar Temporally and Spatially Coincident with the Neutrino Event IceCube-191001A

A radio-emitting tidal disruption event (AT2019dsg) is proposed as a likely counterpart to the IceCube neutrino event IC 191001A. In this work, we have revisited the Fermi-LAT data in the direction of the neutrino and confirmed no signal at the site of AT2019dsg. Instead, at the edge of the 90% confidence level error region of this neutrino, there is a γ-ray transient source associated with the blazar GB6 J2113+1121. In 2019 May, GB6 J2113+1121 was undergoing a γ-ray flare that is unprecedented since the start of the Fermi-LAT operation, with a variability amplitude of about 20 fold. Similar violent flares of GB6 J2113+1121, unobserved before, have also been detected in the optical bands. Moreover, the blazar remained in a high-flux state in the infrared bands when IC 191001A arrived, though the blazar 's γ-ray and optical activities have temporarily ceased. Motivated by this spatial and temporal coincidence, we suggest that GB6 J2113+1121 is a candidate to be the counterpart to IC 191001A. The jet properties of GB6 J2113+1121 are investigated, which are found to be comparable with that of neutrino-emitting blazars (candidates). A specific analysis of archival IceCube data in this direction and future observations would put further constraints on the origin of the neutrino.

Keywords: galaxy jets; radio loud quasars; gamma-ray sources
Heating Rates for Protons and Electrons in Polar Coronal Holes: Empirical Constraints from the Ultraviolet Coronagraph Spectrometer

Ultraviolet spectroscopy of the extended solar corona is a powerful tool for measuring the properties of protons, electrons, and heavy ions in the accelerating solar wind. The large coronal holes that expand up from the north and south poles at solar minimum are low-density collisionless regions in which it is possible to detect departures from one-fluid thermal equilibrium. An accurate characterization of these departures is helpful in identifying the kinetic processes ultimately responsible for coronal heating. In this paper, Ultraviolet Coronagraph Spectrometer (UVCS) measurements of the H I Lyα line are analyzed to constrain values for the solar wind speed, electron density, electron temperature, proton temperature (parallel and perpendicular to the magnetic field), and Alfvén-wave amplitude. The analysis procedure involves creating a large, randomized ensemble of empirical models, simulating their Lyα profiles, and building posterior probability distributions for only the models that agree with the UVCS data. The resulting temperatures do not exhibit a great deal of radial variation between heliocentric distances of 1.4 and 4 solar radii. Typical values for the electron, parallel proton, and perpendicular proton temperatures are 1.2, 1.8, and 1.9 MK, respectively. Resulting values for the "nonthermal" Alfvén wave amplitude show evidence for weak dissipation, with a total energy-loss rate that agrees well with an independently derived total heating rate for the protons and electrons. The moderate Alfvén-wave amplitudes appear to resolve some tension in the literature between competing claims of both higher (undamped) and lower (heavily damped) values.

Keywords: alfven waves; solar coronal holes; solar ultraviolet emission; solar wind; space plasmas; spectroscopy
Sustaining Star Formation in the Galactic Star Cluster M 36?

We present comprehensive characterization of the Galactic open cluster M 36. Some 200 member candidates, with an estimated contamination rate of ∼8%, have been identified on the basis of proper motion and parallax measured by the Gaia DR2. The cluster has a proper motion grouping around ( ${\mu }_{\alpha }\cos \delta =-0.15\pm 0.01$ <!-- --> mas yr-1, and μδ = - 3.35 ± 0.02 mas yr-1), distinctly separated from the field population. Most member candidates have parallax values 0.7-0.9 mas, with a median value of 0.82 ± 0.07 mas (distance ∼1.20 ± 0.13 kpc). The angular diameter of $27^{\prime} \pm 0\buildrel{\,\prime}\over{.} 4$ <!-- --> determined from the radial density profile then corresponds to a linear extent of 9.42 ± 0.14 pc. With an estimated age of ∼15 Myr, M 36 is free of nebulosity. To the southwest of the cluster, we discover a highly obscured (AV up to ∼23 mag), compact (∼ $1\buildrel{\,\prime}\over{.} 9\times 1\buildrel{\,\prime}\over{.} 2$ <!-- --> ) dense cloud, within which three young stellar objects in their infancy (ages ≲0.2 Myr) are identified. The molecular gas, 3.6 pc in extent, contains a total mass of (2-3) × 102 M⊙, and has a uniform velocity continuity across the cloud, with a velocity range of -20 to -22 km s-1, consistent with the radial velocities of known star members. In addition, the cloud has a derived kinematic distance marginally in agreement with that of the star cluster. If physical association between M 36 and the young stellar population can be unambiguously established, this manifests a convincing example of prolonged star formation activity spanning up to tens of Myr in molecular clouds.

Keywords: open star clusters; stellar kinematics; stellar dynamics; pre-main sequence stars; extinction; molecular clouds
Vis-NIR Reflectance Microspectroscopy of IDPs

Visible near-infrared (Vis-NIR) reflectance spectroscopy is a powerful nondestructive technique allowing the parent bodies identification of cosmomaterials such as meteorites, micrometeorites, and interplanetary dust particles (IDPs) studied in the laboratory. Previous studies showed that meteorites do not represent the full diversity of the solar system small bodies. We present here an experimental setup we developed for measuring Vis-NIR microspectroscopy of individual IDPs. We acquired diffuse Vis-NIR reflectance spectra of 15 particles ranging 7-31 μm in size. We discuss the requirements, the abilities, as well as the limitations of the technique. For sizes smaller than 17 μm, the slopes increase with decreasing particles sizes, while for sizes larger than 17 μm, the slopes are randomly distributed. The visible reflectance levels do not appear to be affected by the size of the IDPs, and show a bimodal distribution. Among the studied particles, we identified an IDP (L2079C18) exhibiting a feature at 0.66 μm, which is similar to the one observed by remote sensing on the surface of hydrated asteroids. This is the first detection of a hydration band in the reflectance spectrum of an IDP that could indicate a possible link between hydrated IDPs with hydrated asteroid surfaces.

Keywords: spectroscopy; experimental techniques; interplanetary dust; meteorites; asteroids; comets
Formation of Giant Planet Satellites

Recent analyses have shown that the concluding stages of giant planet formation are accompanied by the development of a large-scale meridional flow of gas inside the planetary Hill sphere. This circulation feeds a circumplanetary disk that viscously expels gaseous material back into the parent nebula, maintaining the system in a quasi-steady state. Here, we investigate the formation of natural satellites of Jupiter and Saturn within the framework of this newly outlined picture. We begin by considering the long-term evolution of solid material, and demonstrate that the circumplanetary disk can act as a global dust trap, where s• ∼ 0.1-10 mm grains achieve a hydrodynamical equilibrium, facilitated by a balance between radial updraft and aerodynamic drag. This process leads to a gradual increase in the system's metallicity, and eventually culminates in the gravitational fragmentation of the outer regions of the solid subdisk into ${ \mathcal R }\sim 100$ km satellitesimals. Subsequently, satellite conglomeration ensues via pair-wise collisions but is terminated when disk-driven orbital migration removes the growing objects from the satellitesimal feeding zone. The resulting satellite formation cycle can repeat multiple times, until it is brought to an end by photoevaporation of the parent nebula. Numerical simulations of the envisioned formation scenario yield satisfactory agreement between our model and the known properties of the Jovian and Saturnian moons.

Keywords: natural satellite formation; galilean satellites; saturnian satellites