adsabs/SciX_UAT_keywords huggingface dataset:
Rapid Variability of the Accretion Disk Wind in the Narrow-line Seyfert 1, PG 1448+273

PG 1448+273 is a luminous, nearby (z = 0.0645), narrow-line Seyfert 1 galaxy, which likely accretes close to the Eddington limit. XMM-Newton observations of PG 1448+273 in 2017 revealed the presence of an ultrafast outflow, as seen through its blueshifted iron K absorption profile, with an outflow velocity of about 0.1 c. Here, the first NuSTAR observation of PG 1448+273, performed in 2022 and coordinated with XMM-Newton, is presented, which shows remarkable variability of its ultrafast outflow. The average count rate is a factor of 2 lower during the last 60 ks of the NuSTAR observation, where a much faster component of the ultrafast outflow was detected with a terminal velocity of 0.26 ± 0.04 c. This is significantly faster than the outflow component that was initially detected in 2017, when overall PG 1448+273 was observed at a lower X-ray flux, and which implies an order of magnitude increase in the wind kinetic power between the 2017 and 2022 epochs. Furthermore, the rapid variability of the ultrafast outflow in 2022, on timescales down to 10 ks, suggests we are viewing through a highly inhomogeneous disk wind in PG 1448+273, where the passage of a denser wind clump could account for the increase in obscuration in the last 60 ks of the NuSTAR observation.

Keywords: active galaxies; quasars; x-ray active galactic nuclei
Giant Radio Quasars: Sample and Basic Properties

We present the largest sample of giant radio quasars (GRQs), which are defined as having a projected linear size greater than 0.7 Mpc. The sample consists of 272 GRQs, of which 174 are new objects discovered through cross-matching the NRAO Very Large Array Sky Survey and the Sloan Digital Sky Survey 14th Data Release Quasar Catalog (DR14Q) and confirmed using Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) radio maps. In our analysis we compare the GRQs with 367 smaller, lobe-dominated radio quasars found using our search method, as well as with quasars from the SDSS DR14Q, investigating the parameters characterizing their radio emission (i.e., total and core radio luminosity, radio core prominence), optical properties (black hole masses, accretion rates, distribution in Eigenvector 1 plane) and infrared colors. For the GRQs and smaller radio quasars we find a strong correlation between [O III] luminosity and radio luminosity at 1.4 GHz, indicating a strong connection between radio emission and conditions in the narrow-line region. We spot no significant differences between GRQs and smaller radio quasars, however we show that most extended radio quasars belong to a quasar population of evolved active galactic nuclei with large black hole masses and low accretion rates. We also show that GRQs have bluer W2-W3 colors compared to SDSS quasars with FIRST detections, indicating differences in the structure of the dusty torus.

Keywords: active galaxies; active galactic nuclei; giant radio galaxies
Spinning up a Daze: TESS Uncovers a Hot Jupiter Orbiting the Rapid Rotator TOI-778

NASA's Transiting Exoplanet Survey Satellite (TESS) mission has been uncovering a growing number of exoplanets orbiting nearby, bright stars. Most exoplanets that have been discovered by TESS orbit narrow-line, slow-rotating stars, facilitating the confirmation and mass determination of these worlds. We present the discovery of a hot Jupiter orbiting a rapidly rotating ( $v\sin \,(i)=35.1\pm 1.0$ km s-1) early F3V-dwarf, HD 115447 (TOI-778). The transit signal taken from Sectors 10 and 37 of TESS's initial detection of the exoplanet is combined with follow-up ground-based photometry and velocity measurements taken from MINERVA-Australis, TRES, CORALIE, and CHIRON to confirm and characterize TOI-778 b. A joint analysis of the light curves and the radial velocity measurements yields a mass, a radius, and an orbital period for TOI-778 b of ${2.76}_{-0.23}^{+0.24}$ M J, 1.370 ± 0.043 R J, and ~4.63 days, respectively. The planet orbits a bright (V = 9.1 mag) F3-dwarf with M = 1.40 ± 0.05 M ⊙, R = 1.70 ± 0.05 R ⊙, and $\mathrm{log}g=4.05\pm 0.17$ . We observed a spectroscopic transit of TOI-778 b, which allowed us to derive a sky-projected spin-orbit angle of 18° ± 11°, consistent with an aligned planetary system. This discovery demonstrates the capability of smaller-aperture telescopes such as MINERVA-Australis to detect the radial velocity signals produced by planets orbiting broad-line, rapidly rotating stars.

Keywords: exoplanets; radial velocity; transit photometry; dynamical evolution
In Search of an Interface between Warm and Hot Gas within the Local Bubble

We have examined UV spectra recorded by the Space Telescope Imaging Spectrograph on the Hubble Space Telescope for three stars, HD32309, 41 Ari, and η Tel, that are located well inside the boundary of the Local Hot Bubble in our search for absorption features of Si IV, C IV, and N V that could reveal the presence of an interface between the local warm (T ∼ 7000 K), neutral medium, and a more distant hot (T ∼ 106 K) interstellar medium. In all cases, we failed to detect such ions. Our most meaningful upper limit is that for log N(C IV) $\lt $ 11.86 toward HD32309, which is below the expectation for a sight line that penetrates either a conductive/evaporative interface or a turbulent mixing layer. We offer conjectures on the reasons for these negative results in terms of either a suppression of a conductive layer caused by the shielding of the local cloud by other clouds, which may make it more difficult for us to sense discrete absorption features from gases at intermediate temperatures, or by the presence of a tangential magnetic field at most locations on the surface of the local cloud.

Keywords: interstellar line absorption; hot ionized medium; warm neutral medium
A Stellar Mass Dependence of Structured Disks: A Possible Link with Exoplanet Demographics

Gaps in protoplanetary disks have long been hailed as signposts of planet formation. However, a direct link between exoplanets and disks remains hard to identify. We present a large sample study of ALMA disk surveys of nearby star-forming regions to disentangle this connection. All disks are classified as either structured (transition, ring, extended) or nonstructured (compact) disks. Although low-resolution observations may not identify large-scale substructure, we assume that an extended disk must contain substructure from a dust evolution argument. A comparison across ages reveals that structured disks retain high dustmasses up to at least 10 Myr, whereas the dustmass of compact, nonstructured disks decreases over time. This can be understood if the dustmass evolves primarily by radial drift, unless drift is prevented by pressure bumps. We identify a stellarmass dependence of the fraction of structured disks. We propose a scenario linking this dependence with that of giant exoplanet occurrence rates. We show that there are enough exoplanets to account for the observed disk structures if transitional disks are created by exoplanets more massive than Jupiter and ring disks by exoplanets more massive than Neptune, under the assumption that most of those planets eventually migrate inwards. On the other hand, the known anticorrelation between transiting super-Earths and stellarmass implies those planets must form in the disks without observed structure, consistent with formation through pebble accretion in drift-dominated disks. These findings support an evolutionary scenario where the early formation of giant planets determines the disks dust evolution and its observational appearance.

Keywords: planet formation; protoplanetary disks; exoplanets
z 2-9 Galaxies Magnified by the Hubble Frontier Field Clusters. I. Source Selection and Surface Density-Magnification Constraints from >2500 Galaxies

We assemble a large comprehensive sample of 2534 z ~ 2, 3, 4, 5, 6, 7, 8, and 9 galaxies lensed by the six clusters from the Hubble Frontier Fields (HFF) program. Making use of the availability of multiple independent magnification models for each of the HFF clusters and alternatively treating one of the models as the "truth," we show that the median magnification factors from the v4 parametric models are typically reliable to values of 30-50, and in one case to 100. Using the median magnification factor from the latest v4 models, we estimate the UV luminosities of the 2534 lensed z ~ 2-9 galaxies, finding sources as faint as -12.4 mag at z ~ 3 and -12.9 mag at z ~ 7. We explicitly demonstrate the power of the surface density-magnification relations Σ(z) versus μ in the HFF clusters to constrain both distant galaxy properties and cluster lensing properties. Based on the Σ(z) versus μ relations, we show that the median magnification estimates from existing public models must be reliable predictors of the true magnification μ to μ < 15 (95% confidence). We also use the observed Σ(z) versus μ relations to derive constraints on the evolution of the luminosity function faint-end slope from z ~ 7 to z ~ 2, showing that faint-end slope results can be consistent with blank-field studies if, and only if, the selection efficiency shows no strong dependence on the magnification factor μ. This can only be the case if very low-luminosity galaxies are very small, being unresolved in deep lensing probes.

Keywords: strong gravitational lensing; dwarf galaxies; galaxy clusters; lyman-break galaxies
Mass Models of the Milky Way and Estimation of Its Mass from the Gaia DR3 Data Set

We use data from the Gaia DR3 data set to estimate the mass of the Milky Way (MW) by analyzing the rotation curve in the range of distances 5 to 28 kpc. We consider three mass models: The first model adds a spherical dark matter (DM) halo, following the Navarro-Frenk-White (NFW) profile, to the known stellar components. The second model assumes that DM is confined to the Galactic disk, following the idea that the observed density of gas in the Galaxy is related to the presence of a more massive DM disk (DMD), similar to the observed correlation between DM and gas in other galaxies. The third model only uses the known stellar-mass components and is based on the Modified Newton Dynamics (MOND) theory. Our results indicate that the DMD model is comparable in accuracy to the NFW and MOND models and fits the data better at large radii where the rotation curve declines but has the largest errors. For the NFW model, we obtain a virial mass M vir = (6.5 ± 0.3) × 1011 M ⊙ with concentration parameter c = 14.5, which is lower than what is typically reported. In the DMD case, we find that the MW mass is M d = (1.6 ± 0.5) × 1011 M ⊙ with a disk's characteristic radius of R d = 17 kpc.

Keywords: milky way galaxy
Dynamics of the Parker-Jeans Instability of Gaseous Disks Including the Effect of Cosmic Rays

The effect of cosmic rays on the Parker-Jeans instability in magnetized self-gravitating gaseous disks is studied using three-dimensional magnetohydrodynamic simulations with cosmic rays taken as a massless fluid with notable pressure. Cosmic-ray diffusion along the magnetic field is taken into account in the simulation. The initial configuration of the disk is a magnetized cold gas slab sandwiched between hot coronae (on top and bottom). We show that cosmic rays play an important role in the formation of filaments or clumps in some parameter regimes. In a certain range of the thickness of the gas slab, the cosmic-ray diffusion coefficient plays a decisive role in determining whether the filaments lie along or perpendicular to the magnetic field. We also consider the effect of rotation on the system.

Keywords: magnetohydrodynamical simulations; interstellar clouds; cosmic rays; magnetic fields; collapsing clouds
Mapping the Imprints of Stellar and Active Galactic Nucleus Feedback in the Circumgalactic Medium with X-Ray Microcalorimeters

The Astro2020 Decadal Survey has identified the mapping of the circumgalactic medium (CGM; the gaseous plasma around galaxies) as a key objective. We explore the prospects for characterizing the CGM in and around nearby galaxy halos with a future large-grasp X-ray microcalorimeter. We create realistic mock observations from hydrodynamical simulations (EAGLE, IllustrisTNG, and Simba) that demonstrate a wide range of potential measurements, which will address the open questions in galaxy formation and evolution. By including all background and foreground components in our mock observations, we show why it is impossible to perform these measurements with current instruments, such as X-ray CCDs, and why only microcalorimeters will allow us to distinguish the faint CGM emission from the bright Milky Way (MW) foreground emission lines. We find that individual halos of MW mass can, on average and depending on star formation rate, be traced out to large radii, around R 500, and for larger galaxies even out to R 200, using prominent emission lines, such as O VII, or O VIII. Furthermore, we show that emission-line ratios for individual halos can reveal the radial temperature structure. Substructure measurements show that it will be possible to relate azimuthal variations to the feedback mode of the galaxy. We demonstrate the ability to construct temperature, velocity, and abundance ratio maps from spectral fitting for individual galaxy halos, which reveal rotation features, active galactic nucleus outbursts, and enrichment.

Keywords: circumgalactic medium; stellar feedback; active galactic nuclei
The Metallicity and Carbon-to-oxygen Ratio of the Ultrahot Jupiter WASP-76b from Gemini-S/IGRINS

Measurements of the carbon-to-oxygen (C/O) ratios of exoplanet atmospheres can reveal details about their formation and evolution. Recently, high-resolution cross-correlation analysis has emerged as a method of precisely constraining the C/O ratios of hot Jupiter atmospheres. We present two transits of the ultrahot Jupiter WASP-76b observed between 1.4 and 2.4 μm with the high-resolution Immersion GRating INfrared Spectrometer on the Gemini-S telescope. We detected the presence of H2O, CO, and OH at signal-to-noise ratios of 6.93, 6.47, and 3.90, respectively. We performed two retrievals on this data set. A free retrieval for abundances of these three species retrieved a volatile metallicity of , consistent with the stellar value, and a supersolar carbon-to-oxygen ratio of C/O . We also ran a chemically self-consistent grid retrieval, which agreed with the free retrieval within 1σ but favored a slightly more substellar metallicity and solar C/O ratio ( and C/O ). A variety of formation pathways may explain the composition of WASP-76b. Additionally, we found systemic (V sys) and Keplerian (K p ) velocity offsets which were broadly consistent with expectations from 3D general circulation models of WASP-76b, with the exception of a redshifted V sys for H2O. Future observations to measure the phase-dependent velocity offsets and limb differences at high resolution on WASP-76b will be necessary to understand the H2O velocity shift. Finally, we find that the population of exoplanets with precisely constrained C/O ratios generally trends toward super-solar C/O ratios. More results from high-resolution observations or JWST will serve to further elucidate any population-level trends.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; exoplanet atmospheric dynamics; observational astronomy
PHANGS-JWST First Results: The Influence of Stellar Clusters on Polycyclic Aromatic Hydrocarbons in Nearby Galaxies

We present a comparison of theoretical predictions of dust continuum and polycyclic aromatic hydrocarbon (PAH) emission with new JWST observations in three nearby galaxies: NGC 628, NGC 1365, and NGC 7496. Our analysis focuses on a total of 1063 compact stellar clusters and 2654 stellar associations previously characterized by the Hubble Space Telescope in the three galaxies. We find that the distributions and trends in the observed PAH-focused infrared colors generally agree with theoretical expectations, and that the bulk of the observations is more aligned with models of larger, ionized PAHs. These JWST data usher in a new era of probing interstellar dust and studying how the intense radiation fields near stellar clusters and associations play a role in shaping the physical properties of PAHs.

Keywords: star clusters; polycyclic aromatic hydrocarbons; spiral galaxies
The GALAH Survey: A New Sample of Extremely Metal-poor Stars Using a Machine-learning Classification Algorithm

Extremely metal-poor (EMP) stars provide a valuable probe of early chemical enrichment in the Milky Way. Here we leverage a large sample of ~600,000 high-resolution stellar spectra from the GALAH survey plus a machine-learning algorithm to find 54 candidates with estimated [Fe/H] ≤-3.0, six of which have [Fe/H] ≤-3.5. Our sample includes ~20% main-sequence EMP candidates, unusually high for EMP star surveys. We find the magnitude-limited metallicity distribution function of our sample is consistent with previous work that used more complex selection criteria. The method we present has significant potential for application to the next generation of massive stellar spectroscopic surveys, which will expand the available spectroscopic data well into the millions of stars.

Keywords: galactic archaeology; stellar abundances; stellar classification; classification; cemp stars; population ii stars; population iii stars; galaxy stellar content; high resolution spectroscopy
The Anisotropic Circumgalactic Medium of Massive Early-type Galaxies

Using measurements of the [O III], Hα, and [N II] emission line fluxes originating in the cool (T ~104 K) gas that populates the halos of massive early-type galaxies with stellar masses greater than 1010.4 M ⊙, we explore the recent conjecture that active galactic nucleus (AGN) activity preferentially removes the circumgalactic medium (CGM) along the polar (minor-axis) direction. We find deficits in the mean emission line flux of [O III] and Hα (65% and 43%, respectively) along the polar versus planar directions, although due to the large uncertainties in these difficult measurements the results are of marginal statistical significance (1.5σ). More robustly (97%-99.9% confidence depending on the statistical test), diagnostic line ratios show stronger AGN ionization signatures along the polar direction at small radii than at other angles or radii. Our results are consistent with the conjecture of an anisotropic CGM in massive early-type galaxies, suggested on independent grounds, that is tied to AGN activity and begin to show the potential of CGM mapping using emission lines.

Keywords: circumgalactic medium; active galactic nuclei; galaxy structure
The Closure Relations in Optical Afterglow of Gamma-Ray Bursts

Gamma-ray bursts (GRBs) are extremely high-energy events that can be observed at very high redshift. In addition to γ rays, they can emit in X-ray, optical, and sometimes radio wavelengths. Here, following the approach in Srinivasaragavan et al.; Dainotti et al.; and Dainotti et al., we consider 82 GRBs from Dainotti et al. that have been observed in optical wavelengths and fitted with a broken power law. We consider the relations between the spectral and temporal indices (closure relations; CRs) according to the synchrotron forward-shock model evolving in the constant-density interstellar medium (ISM; k = 0) and the stellar wind environment (k = 2) in both slow- and fast-cooling regimes, where the density profile is defined as n ∝ r -k . We find the $\nu \gt \max \{{\nu }_{{\rm{c}}},{\nu }_{{\rm{m}}}\}$ regime is most favored, where ν c and ν m are the cooling and characteristic frequencies, respectively. Finally, we test the 2D Dainotti correlation between the rest-frame end time of the plateau and the luminosity at that time on GRBs that fulfill the most-favored CRs. When we compare the intrinsic scatter σ int of those 2D correlations to the scatter presented in Dainotti et al., we see the scatters of our correlations generally agree with the previous values within 1σ, both before and after correction for selection bias. This new information has helped us to pinpoint subsamples of GRBs with features that could drive the GRB emission mechanism, and eventually allow for GRBs to be used as standard candles.

Keywords: gamma-ray bursts
Coaccretion + Giant-impact Origin of the Uranus System: Tilting Impact

The origin of the Uranian satellite system remains uncertain. The four major satellites have nearly circular, coplanar orbits, and the ratio of the satellite system to planetary mass resembles Jupiter's satellite system, suggesting the Uranian system was similarly formed within a disk produced by gas coaccretion. However, Uranus is a retrograde rotator with a high obliquity. The satellites orbit in its highly tilted equatorial plane in the same sense as the planet's retrograde rotation, a configuration that cannot be explained by coaccretion alone. In this work, we investigate the first stages of the coaccretion + giant-impact scenario proposed by Morbidelli et al. (2012) for the origin of the Uranian system. In this model, a satellite system formed by coaccretion is destabilized by a giant impact that tilts the planet. The primordial satellites collide and disrupt, creating an outer debris disk that can reorient to the planet's new equatorial plane and accrete into Uranus' four major satellites. The needed reorientation out to distances comparable to outermost Oberon requires that the impact creates an inner disk with ≥1% of Uranus' mass. We here simulate giant impacts that appropriately tilt the planet and leave the system with an angular momentum comparable to that of the current system. We find that such impacts do not produce inner debris disks massive enough to realign the outer debris disk to the post-impact equatorial plane. Although our results are inconsistent with the apparent requirements of a coaccretion + giant-impact model, we suggest alternatives that merit further exploration.

Keywords: natural satellite formation; uranian satellites
Can the Violent Merger of White Dwarfs Explain the Slowest Declining Type Ia Supernova SN 2011aa?

We present optical observations and Monte Carlo radiative transfer modeling of the Type Ia supernova (SN Ia) SN 2011aa. With a Δm 15(B) of 0.59 ± 0.07 mag and a peak magnitude M B of -19.30 ± 0.27 mag, SN 2011aa has the slowest decline rate among SNe Ia. The secondary maximum in the I band is absent or as equally bright as the primary maximum. The velocity of C II is lower than the velocity of Si II. This indicates either the presence of C at lower velocities than Si or a line-of-sight effect. Application of Arnett's radiation diffusion model to the bolometric light curve indicates a massive ejecta M ej 1.8-2.6 M ⊙. The slow decline rate and large ejecta mass, with a normal peak magnitude, are well explained by a double degenerate, violent merger explosion model. The synthetic spectra and light curves generated with SEDONA considering a violent merger density profile match the observations.

Keywords: supernovae
KMTNet Nearby Galaxy Survey II. Searching for Dwarf Galaxies in Deep and Wide-field Images of the NGC 1291 System

We present newly discovered dwarf galaxy candidates in deep and wide-field images of NGC 1291 obtained with the Korea Microlensing Telescope Network. We identify 15 dwarf galaxy candidates by visual inspection. Using imaging simulations, we demonstrate that the completeness rate of our detection is greater than 70% for the central surface-brightness value of μ0,R ≲ 26 mag arcsec-2 and for magnitudes MR ≲ -10 mag. The structural and photometric properties of the dwarf galaxy candidates appear to be broadly consistent with those of ordinary dwarf galaxies in nearby groups and clusters, with μ0,R ∼ 22.5 to 26.5 mag arcsec-2 and effective radii of 200 pc to 1 kpc. The dwarf galaxy candidates show a concentration toward NGC 1291 and tend to be redder the closer they are to the center, possibly indicating that they are associated with NGC 1291. The dwarf candidates presented in this paper appear to be bluer than those in denser environments, revealing that the quenching of star formation in dwarf galaxies is susceptible to the environment, while the morphology shaping is not.

Keywords: dwarf galaxies