adsabs/SciX_UAT_keywords huggingface dataset:
A Catalog of 406 AGNs in MaNGA: A Connection between Radio-mode AGNs and Star Formation Quenching

Accurate active galactic nucleus (AGN) identifications and spatially resolved host galaxy properties are a powerful combination for studies of the role of AGNs and AGN feedback in the coevolution of galaxies and their central supermassive black holes. Here, we present robust identifications of 406 AGNs in the first 6261 galaxies observed by the integral field spectroscopy survey Mapping Nearby Galaxies at Apache Point Observatory. Instead of using optical line flux ratios, which can be difficult to interpret in light of the effects of shocks and metallicity, we identify the AGNs via mid-infrared Wide-field Infrared Survey Explorer colors, Swift/BAT ultrahard X-ray detections, NVSS and FIRST radio observations, and broad emission lines in SDSS spectra. We subdivide the AGNs into radio-quiet and radio-mode AGNs, and examine the correlations of the AGN classes with host galaxy star formation rates and stellar populations. When compared to the radio-quiet AGN host galaxies, we find that the radio-mode AGN host galaxies are preferentially elliptical, lie further beneath the star-forming main sequence (with lower star formation rates at fixed galaxy mass), have older stellar populations, and have more negative stellar age gradients with galactocentric distance (indicating inside-out quenching of star formation). These results establish a connection between radio-mode AGNs and the suppression of star formation.

Keywords: active galaxies; radio galaxies; star formation
Resolved SPLASH Chemodynamics in Andromeda's PHAT Stellar Halo and Disk: On the Nature of the Inner Halo along the Major Axis

Stellar kinematics and metallicity are key to exploring formation scenarios for galactic disks and halos. In this work, we characterized the relationship between kinematics and photometric metallicity along the line of sight to M31's disk. We combined optical Hubble Space Telescope/Advanced Camera for Surveys photometry, from the Panchromatic Hubble Andromeda Treasury survey, with Keck/DEIMOS spectra, from the Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo survey. The resulting sample of 3512 individual red giant branch stars spans 4-19 projected kpc, making it a useful probe of both the disk and inner halo. We separated these stars into disk and halo populations, by modeling the line-of-sight velocity distributions as a function of position across the disk region, where ~73% stars have a high likelihood of belonging to the disk and ~14% to the halo. Although stellar halos are typically thought to be metal-poor, the kinematically identified halo contains a significant population of stars (~29%) with disk-like metallicity ([Fe/H]phot ~ -0.10). This metal-rich halo population lags the gaseous disk to a similar extent as the rest of the halo, indicating that it does not correspond to a canonical thick disk. Its properties are inconsistent with those of tidal debris originating from the Giant Stellar Stream merger event. Moreover, the halo is chemically distinct from the phase-mixed component previously identified along the minor axis (i.e., away from the disk), implying contributions from different formation channels. These metal-rich halo stars provide direct chemodynamical evidence in favor of the previously suggested "kicked-up" disk population in M31's inner stellar halo.

Keywords: galaxy stellar disks; andromeda galaxy; galaxy formation; galaxy stellar content; stellar kinematics; stellar abundances; galaxy stellar halos
PeV-EeV Neutrinos from Gamma-Ray Blazars due to Ultrahigh-energy Cosmic-Ray Propagation

Blazars are potential sources of cosmic-ray acceleration up to ultrahigh energies (E ≳ 1018 eV). For an efficient cosmic-ray injection from blazars, pγ collisions with extragalactic background light (EBL) and cosmic microwave background (CMB) can produce neutrino spectra with peaks near to PeV and EeV energies, respectively. In this work, we analyze the contribution of these neutrinos to the diffuse background measured by the IceCube neutrino observatory. The fraction of neutrino luminosity originating from individual redshift ranges is calculated using the distribution of BL Lacs and FSRQs provided in the Fermi-LAT 4LAC catalog. Furthermore, we use a luminosity-dependent density evolution to find the neutrino flux of unresolved blazars. The results obtained in our model indicate that as much as ≈10% of the flux upper bound at a few PeV energies can arise from cosmic-ray interactions with EBL. The same interactions will also produce secondary electrons and photons, initiating electromagnetic cascades. The resultant photon spectrum is limited by the isotropic diffuse γ-ray flux measured between 100 MeV and 820 GeV. The latter, together with the observed cosmic-ray flux at E > 1016.5 eV, can constrain the baryonic loading factor, depending on the maximum cosmic-ray acceleration energy.

Keywords: high energy astrophysics; blazars; relativistic jets; gamma-rays; neutrino astronomy; high-energy cosmic radiation
Resonance of Low-frequency Electromagnetic and Ion-sound Modes in the Solar Wind

Parker Solar Probe measurements have recently shown that coherent fast magnetosonic and Alfvén ion-cyclotron waves are abundant in the solar wind and can be accompanied by higher-frequency electrostatic fluctuations. In this Letter we reveal the nonlinear process capable of channelling the energy of low-frequency electromagnetic to higher-frequency electrostatic fluctuations observed on board Parker Solar Probe. We present Hall-MHD simulations demonstrating that low-frequency electromagnetic fluctuations can resonate with the ion-sound mode, which results in steepening of plasma density fluctuations, electrostatic spikes, and harmonics in the electric field spectrum. The resonance can occur around the wavenumber determined by the ratio between local sound and Alfvén speeds, but only in the case of oblique propagation to the background magnetic field. The resonance wavenumber, its width, and steepening timescale are estimated, and all indicate that the revealed two-wave resonance can frequently occur in the solar wind. This process can be a potential channel of energy transfer from cyclotron resonant ions producing the electromagnetic fluctuations to Landau resonant ions and electrons absorbing the energy of the higher-frequency electrostatic fluctuations.

Keywords: solar wind; alfven waves; space plasmas
KELT-9 b's Asymmetric TESS Transit Caused by Rapid Stellar Rotation and Spin-Orbit Misalignment

KELT-9 b is an ultra-hot Jupiter transiting a rapidly rotating, oblate early-A-type star in a polar orbit. We model the effect of rapid stellar rotation on KELT-9 b's transit light curve using photometry from the Transiting Exoplanet Survey Satellite to constrain the planet's true spin-orbit angle and to explore how KELT-9 b may be influenced by stellar gravity darkening. We constrain the host star's equatorial radius to be 1.089 ± 0.017 times as large as its polar radius and its local surface brightness to vary by ∼38% between its hot poles and cooler equator. We model the stellar oblateness and surface brightness gradient and find that it causes the transit light curve to lack the usual symmetry around the time of minimum light. We take advantage of the light-curve asymmetry to constrain KELT-9 b's true spin-orbit angle ( ${87^\circ }_{{-11}^{^\circ }}^{{+10}^{^\circ }}$ ), agreeing with Gaudi et al. that KELT-9 b is in a nearly polar orbit. We also apply a gravity-darkening correction to the spectral energy distribution model from Gaudi et al. and find that accounting for rapid rotation gives a better fit to available spectroscopy and yields a more reliable estimate for the star's polar effective temperature.

Keywords: transit photometry; exoplanets; exoplanet evolution; von zeipel theorem; gravity darkening; stellar rotation; exoplanet astronomy; hot jupiters
Anomalous Proton Velocity Diffusion by Quasi-monochromatic Kinetic Alfvén Waves

The anomalous diffusion of resonant protons in parallel and perpendicular velocity space by kinetic Alfvén waves is discussed. The velocity diffusion coefficient is calculated by employing an autocorrelation function for proton trajectories. It is found that for protons resonant with the waves, the perpendicular diffusion coefficient decays away for a sufficiently long time, but parallel diffusion monotonically increases in time until it saturates at a certain level. This result indicates that a portion of resonant protons can undergo anomalous diffusion along the background magnetic field even if the intensity of the kinetic Alfvén wave is sufficiently low. The present findings imply that under suitable conditions, astrophysical charged-particle acceleration can take place in the parallel direction.

Keywords: solar magnetic fields
Multifrequency Observations of the Candidate Neutrino-emitting Blazar BZB J0955+3551

The recent spatial and temporal coincidence of the blazar TXS 0506+056 with the IceCube-detected neutrino event IC-170922A has opened up a realm of multimessenger astronomy with blazar jets as a plausible site of cosmic-ray acceleration. After TXS 0506+056, a second blazar, BZB J0955+3551, was recently found to be spatially coincident with the IceCube-detected neutrino event IC-200107A and undergoing its brightest X-ray flare measured so far. Here we present the results of our multifrequency campaign to study this peculiar event that includes observations with the NuSTAR, Swift, Neutron star Interior Composition Explorer (NICER), and 10.4 m Gran Telescopio Canarias (GTC). The optical spectroscopic observation from GTC secured its redshift as $z={0.55703}_{-0.00021}^{+0.00033}$ and the central black hole mass as ${10}^{8.90\pm 0.16}$ ${M}_{\odot }$ . Both NuSTAR and NICER data reveal a rapid flux variability, albeit at low significance ( $\lesssim 3.5\sigma $ ). We explore the origin of the target photon field needed for the photopion production using analytical calculations and considering the observed optical-to-X-ray flux level. We conclude that seed photons may originate from outside the jet, similar to that reported for TXS 0506+056, although a scenario invoking a comoving target photon field (e.g., electron synchrotron) cannot be ruled out. The electromagnetic output from the neutrino-producing photohadronic processes are likely to make only a subdominant contribution to the observed spectral energy distribution, suggesting that the X-ray flaring event may not be directly connected with IC-200107A.

Keywords: relativistic jets; bl lacertae objects; neutrino astronomy; x-ray active galactic nuclei
Nonlinear Evolution of the Magnetorotational Instability in Eccentric Disks

The magnetorotational instability (MRI) has been extensively studied in circular magnetized disks, and its ability to drive accretion has been demonstrated in a multitude of scenarios. There are reasons to expect eccentric magnetized disks to also exist, but the behavior of the MRI in these disks remains largely uncharted territory. Here we present the first simulations that follow the nonlinear development of the MRI in eccentric disks. We find that the MRI in eccentric disks resembles circular disks in two ways, in the overall level of saturation and in the dependence of the detailed saturated state on magnetic topology. However, in contrast with circular disks, the Maxwell stress in eccentric disks can be negative in some disk sectors, even though the integrated stress is always positive. The angular momentum flux raises the eccentricity of the inner parts of the disk and diminishes the same of the outer parts. Because material accreting onto a black hole from an eccentric orbit possesses more energy than material tracing the innermost stable circular orbit, the radiative efficiency of eccentric disks may be significantly lower than circular disks. This may resolve the "inverse energy problem" seen in many tidal disruption events.

Keywords: magnetohydrodynamical simulations; accretion; black hole physics; gravitation
Peculiarities in the Horizontal Branch Stars of Globular Cluster NGC 1851: Discovery of a Blue Straggler Companion to an EHB Star

We present a study of far-UV (FUV) bright horizontal branch (HB) stars to understand the peculiarities seen in the HB sequence of the globular cluster NGC 1851, using ground- and space-based multiwavelength data. Optical and UV color-magnitude diagrams are used to classify HB stars and their membership from Hubble Space Telescope and Gaia DR2 data. The spectral energy distributions (SEDs) of the hot HB stars located from the core to tidal radii are constructed. The SEDs reveal that the HB stars near the "Grundahl jump" show a decrease in the FUV flux when atmospheric models of cluster metallicity are used for fitting, but a better fit is found with higher-metallicity models, as expected due to atmospheric diffusion. We report on four particularly interesting extreme HB (EHB) stars, two each in the inner and outer regions. We detect a subluminous EHB and "blue-hook" candidates with temperatures Teff ∼ 25,000 K and 31,000 K, respectively. We found an EHB star (Teff ∼ 17,000 K) with a radius that lies between the BHB and normal EHB stars. The most peculiar of our EHB stars (Teff ∼ 28,000 K) is found to be a photometric binary to a blue straggler star (BSS; Teff ∼ 7000 K), which is an important target for spectroscopic study. This discovery of the candidate EHB+BSS binary system could help to explain the mass loss in the red giant branch phase, leading to the formation of EHB stars.

Keywords: globular star clusters; blue straggler stars; horizontal branch stars; hertzsprung russell diagram
Dependence of Lunar Pickup Ion Flux on Source Location: ARTEMIS Observations

The Moon is enveloped in an exosphere, which is comprised of a variety of neutral atoms and molecules. Once exospheric neutrals are ionized by photons, protons, or electrons from the Sun, the resulting ions are accelerated by the electromagnetic fields of their surroundings and can thereby travel away from their source locations. These ions are the so-called pickup ions and are frequently observed by the two Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) spacecraft. In this study, we identify 115 events from an 11 yr period of ARTEMIS observations, which contain a total of 11,987 samples for our statistics. By using analytical ion trajectory calculations, we trace the source location of each pickup ion observation. Most pickup ion trajectories originate near the subsolar point, consistent with the efficiency of sputtering. We find that the flux of pickup ions strongly anticorrelates with the source altitude, providing indirect evidence of decreasing exospheric ion flux with increasing altitude. We also find that the flux of pickup ions does not show a significant relationship with the crustal magnetic field intensity. This implies that a depression of sputtering efficiency or the trapping of near-surface freshly born ions by a crustal magnetic anomaly may not reduce the subsequent pickup ion flux as effectively as expected. In summary, the present paper provides a statistical view of lunar pickup ion fluxes in association with the altitude, local time, and local crustal magnetic field of their source locations.

Keywords: the moon; lunar science; solar wind; space plasmas
Estimating Distances from Parallaxes. VI. A Method for Inferring Distances and Transverse Velocities from Parallaxes and Proper Motions Demonstrated on Gaia Data Release 3

The accuracy of stellar distances inferred purely from parallaxes degrades rapidly with distance. Proper motion measurements, when combined with some idea of typical velocities, provide independent information on stellar distances. Here, I build a direction- and distance-dependent model of the distribution of stellar velocities in the Galaxy, then use this together with parallaxes and proper motions to infer kinegeometric distances and transverse velocities for stars in Gaia DR3. Using noisy simulations, I assess the performance of the method and compare its accuracy to purely parallax-based (geometric) distances. Over the whole Gaia catalog, kinegeometric distances are on average 1.25 times more accurate than geometric ones. This average masks a large variation in the relative performance, however. Kinegeometric distances are considerably better than geometric ones beyond several kpc, for example. On average, kinegeometric distances can be measured to an accuracy of 19% and velocities ( $\sqrt{{v}_{\alpha * }^{2}+{v}_{\delta }^{2}}$ ) to 16 km s-1 (median absolute deviations). In Gaia DR3, kinegeometric distances are smaller than geometric ones on average for distant stars, but the pattern is more complex in the bulge and disk. With the much more accurate proper motions expected in Gaia DR5, a further improvement in the distance accuracy by a factor of (only) 1.35 on average is predicted (with kinegeometric distances still 1.25 times more accurate than geometric ones). The improvement attained from proper motions is limited by the width of the velocity prior, in a way that the improvement from better parallaxes is not limited by the width of the distance prior.

Keywords: catalogs; bayesian statistics; distance indicators; stellar distance; stellar motion; astrometry; parallax; proper motions
On the Sound Speed in Neutron Stars

Determining the sound speed c s in compact stars is an important open question with numerous implications on the behavior of matter at large densities and hence on gravitational-wave emission from neutron stars. To this scope, we construct more than 107 equations of state (EOSs) with continuous sound speed and build more than 108 nonrotating stellar models consistent not only with nuclear theory and perturbative QCD, but also with astronomical observations. In this way, we find that EOSs with subconformal sound speeds, i.e., with ${c}_{s}^{2}\lt 1/3$ within the stars, are possible in principle but very unlikely in practice, being only 0.03% of our sample. Hence, it is natural to expect that ${c}_{s}^{2}\gt 1/3$ somewhere in the stellar interior. Using our large sample, we obtain estimates at 95% credibility of neutron-star radii for representative stars with 1.4 and 2.0 solar masses, ${R}_{1.4}={12.42}_{-0.99}^{+0.52}\,\mathrm{km}$ , ${R}_{2.0}={12.12}_{-1.23}^{+1.11}\,\mathrm{km}$ , and for the binary tidal deformability of the GW170817 event, ${\tilde{{\rm{\Lambda }}}}_{1.186}={485}_{-211}^{+225}$ . Interestingly, our lower bounds on the radii are in very good agreement with the prediction derived from very different arguments, namely, the threshold mass. Finally, we provide simple analytic expressions to determine the minimum and maximum values of $\tilde{{\rm{\Lambda }}}$ as a function of the chirp mass.

Keywords: gravitation; nuclear astrophysics; fundamental parameters of stars; stellar interiors; neutron stars; neutron star cores; nuclear physics
Chandra Observations of Excess Fe Kα Line Emission in Galaxies with High Star Formation Rates: X-Ray Reflection on Galaxy Scales?

In active galactic nuclei (AGNs), fluorescent Fe Kα (iron) line emission is generally interpreted as originating from obscuring material around a supermassive black hole on the scale of a few parsecs. However, recent Chandra studies indicate the existence of iron line emission extending to kiloparsec scales in the host galaxy. The connection between iron line emission and large-scale material can be spatially resolved directly only in nearby galaxies, but could be inferred in more distant AGNs by a connection between line emission and star-forming gas and dust that is more extended than the parsec-scale torus. Here we present the results from a stacking analysis and X-ray spectral fitting performed on sources in the Chandra Deep Field South (CDFS) 7 Ms observations. From the deep stacked spectra, we select sources with stellar mass $\mathrm{log}({M}_{* }/{M}_{\odot })\gt 10$ at 0.5 < z < 2, obtaining 25 sources with high-infrared (IR) luminosity (star formation rate, SFRFIR ≥ 17 M⊙ yr-1) and 32 sources below this threshold. We find that the equivalent width (EW) of the iron line EW(Fe) is a factor of three higher with 3σ significance for high-IR luminosity measured from Herschel observations, indicating a connection between iron line emission and star-forming material on galaxy scales. We show that there is no significant dependence of the EW(Fe) on M* or X-ray luminosity, suggesting that the reflection of AGN X-ray emission over large scales in their host galaxies may be widespread.

Keywords: active galactic nuclei; agn host galaxies; x-ray active galactic nuclei; x-ray astronomy; far infrared astronomy; extragalactic astronomy
Upgraded GMRT Observations of the Coma Cluster of Galaxies: The Observations

We have used the upgraded Giant Metrewave Radio Telescope to map the Coma cluster of galaxies at 250-500 MHz and 1050-1450 MHz bands. These 6"26 and 2"18 resolutions observations allow detailed radio structures to be determined of all detected radio sources that show both discrete pointlike and extended morphologies. We present images of a subset of 32 brightest (Sν ≳ 30 mJy) and dominant sources, and several sources show discrete pointlike radio morphologies. We find the steepening of the spectra consistent with synchrotron cooling in the majority of sources and the median for spectral indices is -0.78, suggesting that ∼59% sources have steep spectra. The nature and the statistical properties of the radio sources in the Coma cluster will be discussed in subsequent papers.

Keywords: active galaxies; radio jets; radio active galactic nuclei; coma cluster; radio continuum emission; galaxy clusters
Simulation of Freezing Cryomagma Reservoirs in Viscoelastic Ice Shells

Brine reservoirs in Europa's icy crust, if they exist, could represent the most accessible liquid water bodies in the outer solar system. Any potential subsurface reservoirs are key for the exploration of ocean worlds and the search for habitability and life beyond Earth. Previous studies have demonstrated that freezing cryoreservoirs might trigger eruptions due to the pressurization associated with volume change as liquid water expands to become water ice, but those studies did not take into account the deformation of the reservoir wall. Viscoelastic deformation of the wall can act to accommodate the growing overpressure and prevent eruptions. Here we utilize a semianalytical numerical approach to calculate the pressure-induced deformation of a freezing cryoreservoir on Europa as a function of the far-field ice temperature. We find that shallow reservoirs located in relatively cold ice deform slightly and can be pressurized by freezing, but that deeper reservoirs located in warmer ice deform more easily and in some cases cannot reach the threshold overpressure required for spontaneous eruption. We identify a transition depth around 4-8 km depending on the reservoir radius, assuming a conductive ice shell structure consistent with current best estimates. Further, we find that shallow lens-shaped reservoirs may store a large volume of cryomagma and can be easily pressurized by freezing; they represent the best candidates for the mobilization of cryovolcanic material at Europa's surface.

Keywords: europa; volcanism; natural satellite surfaces