adsabs/SciX_UAT_keywords huggingface dataset:
Investigating the Origin of X-Ray Jets: A Case Study of Four Hybrid Morphology MOJAVE Blazars

We carried out Chandra, Hubble Space Telescope (HST), and Very Large Array observations of four MOJAVE blazars that have previously been classified as hybrid (FR I/II) blazars in terms of radio morphology but not total radio power. The motivation of this study is to determine the X-ray emission mechanism in jets, these being different in FR I and FR II jets. We detected X-ray jet emission with sufficient signal to noise in two blazars, viz. PKS 0215+015 and TXS 0730+504. We carried out spectral energy distribution modeling of the broadband emission from the jet regions in these sources and found that a single synchrotron emission model is ruled out due to the deep upper limits obtained from HST optical and IR data. The inverse Compton-cosmic microwave background model can reproduce the X-ray jet emission in both sources although the model requires extreme jet parameters. Both our sources possess FR II-like radio powers and our results are consistent with previous studies suggesting that radio power is more important than FR morphology in determining the emission mechanism of X-ray jets.

Keywords: bl lacertae objects; active galaxies; quasars; jets
A Systematic Search for the Reddest Far-infrared and Submillimeter Galaxies: Revealing Dust-embedded Starbursts at High Redshifts

We present the results of our systematic search for the reddest far-infrared (FIR) and submillimeter (sub-mm) galaxies using the data from the Herschel Multi-tiered Extragalactic Survey (HerMES) and the SCUBA2 Cosmological Legacy Survey (S2CLS). The red FIR galaxies are "500 μm risers," whose spectral energy distributions increase with wavelength across the three FIR passbands of the Spectral and Photometric Imaging REceiver (SPIRE) of Herschel. Within 106.5 deg2 of the HerMES fields, we have selected 629 500 μm risers. The red sub-mm galaxies are "SPIRE drop-outs," which are prominent detections in the S2CLS 850 μm data but are extremely weak or invisible in the SPIRE bands. Within the 2.98 deg2 common area of HerMES and S2CLS, we have selected 95 such objects. These very red sources could be dusty starbursts at high redshifts (z ≳ 4-6) because the peak of their cold-dust emission heated by star formation is shifted to the reddest FIR/sub-mm bands. The surface density of 500 μm risers is ∼8.2 deg-2 at the ≥20 mJy level in 500 μm, while that of SPIRE drop-outs is ∼19.3 deg-2 at the ≥5 mJy level in 850 μm. Both types of objects could span a wide range of redshifts, however. Using deep radio data in these fields to further select the ones likely at the highest redshifts, we find that the surface density of z > 6 candidates is 5.5 deg-2 among 500 μm risers and is 0.8-13.6 deg-2 among SPIRE drop-outs. If this is correct, the dust-embedded star formation processes in such objects could contribute comparably as Lyman-break galaxies to the global SFR density at z > 6.

Keywords: galaxy evolution; ultraluminous infrared galaxies; high-redshift galaxies; starburst galaxies; submillimeter astronomy; radio sources; blazars
Inferring the Magnetic Field from the Rayleigh-Taylor Instability

By extending the potential approach of Layzer and Goncharov to the magnetohydrodynamics equations, we find the nonlinear solutions to the single-mode Rayleigh-Taylor instability subjected to uniform magnetic fields at various inclinations. This allows us to derive the analytical prediction of the terminal bubble and spike velocities at arbitrary Atwood numbers, which are assessed against various 2D and 3D direct numerical simulations. Contrary to the linear phase, where the magnetic field inhibits or delays the instability, the growth rate may be enhanced in the nonlinear regime, exhibiting velocities faster than the Alfvén speed. This sheds light on the importance of the nondimensional number expressing the competition between the magnetic and buoyancy effects. Conversely, we show how the orientation and the intensity of the magnetic field can be simply inferred from these solutions.

Keywords: magnetohydrodynamics; magnetohydrodynamical simulations
Color Dependence of Planetary Transit Depths due to Large Starspots and Dust Clouds: Application to PTFO 8-8695

Although thousands of exoplanets have now been discovered, there is still a significant lack of observations of young planets only a few Myr old. Thus there is little direct evidence available to differentiate between various models of planet formation. The detection of planets of this age would provide much-needed data that could help constrain the planet formation process. To explore what transit observations of such planets may look like, we model the effects of large starspots and dust clouds on the depths of exoplanet transits across multiple wavelengths. We apply this model to the candidate planet PTFO 8-8695b, whose depths vary significantly across optical and infrared wavelengths. Our model shows that, while large starspots can significantly increase the color dependence of planetary transits, a combination of starspots and a large cloud surrounding the planet is required to reproduce the observed transit depths across four wavelengths.

Keywords: exoplanets; transit photometry; starspots
Geodesic Model of HF QPOs Tested for Black Holes in Spacetimes Reflecting the Effect of Surrounding Dark Matter

Using the simple but robust model of a shell of dark matter (DM) around a Schwarzschild black hole (BH), represented by the mass ratio of the shell and BH ΔM/M, the shell extension Δr s and its inner radius r s, we study the influence of DM on the spacetime structure and geodesic motion, and provide a classification of the BH+DM shell spacetimes according to the properties of the stable circular geodesics governing Keplerian disks. We focus our attention on the epicyclic motion around circular geodesics that can be related to observational phenomena in X-ray radiation from Keplerian accretion disks, assumed to be influenced by the DM shell only gravitationally. We give the frequencies of the orbital and epicyclic motions and discuss their properties in terms of the parameters governing the DM shell. Using the frequencies in relevant variants of the standard geodesic model of high-frequency quasiperiodic oscillations (HF QPOs), we test the role of DM by fitting the HF QPO data from some microquasars and active galactic nuclei with supermassive BHs where no variant of the geodesic model applied in the standard vacuum BH background is able to explain the data. We thus provide a robust review of the applicability of the geodesic model of HF QPOs, and also provide limits on the amount of DM around a BH. We demonstrate that the geodesic model could be well applied to most observations of active galactic nuclei, with strong restrictions on the amount of invisible matter around BHs.

Keywords: supermassive black holes; dark matter
X-Ray View of Little Red Dots: Do They Host Supermassive Black Holes?

The discovery of Little Red Dots (LRDs)—a population of compact, high-redshift, dust-reddened galaxies—is one of the most surprising results from JWST. However, the nature of LRDs is still debated: does the near-infrared emission originate from accreting supermassive black holes (SMBHs), or intense star formation? In this work, we utilize ultra-deep Chandra observations and study LRDs residing behind the lensing galaxy cluster, A2744. We probe the X-ray emission from individual galaxies but find that they remain undetected and provide SMBH mass upper limits of ≲(1.5–16) × 106 M ⊙ assuming Eddington limited accretion. To increase the signal-to-noise ratios, we conduct a stacking analysis of the full sample with a total lensed exposure time of ≈87 Ms. We also bin the galaxies based on their stellar mass, lensing magnification, and detected broad-line Hα emission. For the LRDs exhibiting broad-line Hα emission, there is a hint of a stacked signal (∼2.6σ), corresponding to an SMBH mass of ∼3.2 × 106 M ⊙. Assuming unobscured, Eddington-limited accretion, this black hole (BH) mass is at least 1.5 orders of magnitude lower than that inferred from virial mass estimates using JWST spectra. Given galaxy-dominated stellar mass estimates, our results imply that LRDs do not host overmassive SMBHs and/or accrete at a few percent of their Eddington limit. However, alternative stellar mass estimates may still support that LRDs host overmassive BHs. The significant discrepancy between the JWST and Chandra data hints that the scaling relations used to infer the SMBH mass from the Hα line and virial relations may not be applicable for high-redshift LRDs.

Keywords: active galactic nuclei; james webb space telescope; x-ray active galactic nuclei; supermassive black holes
Inferring the Neutron Star Maximum Mass and Lower Mass Gap in Neutron Star-Black Hole Systems with Spin

Gravitational-wave (GW) detections of merging neutron star-black hole (NSBH) systems probe astrophysical neutron star (NS) and black hole (BH) mass distributions, especially at the transition between NS and BH masses. Of particular interest are the maximum NS mass, minimum BH mass, and potential mass gap between them. While previous GW population analyses assumed all NSs obey the same maximum mass, if rapidly spinning NSs exist, they can extend to larger maximum masses than nonspinning NSs. In fact, several authors have proposed that the ~2.6 M ⊙ object in the event GW190814-either the most massive NS or least massive BH observed to date-is a rapidly spinning NS. We therefore infer the NSBH mass distribution jointly with the NS spin distribution, modeling the NS maximum mass as a function of spin. Using four LIGO-Virgo NSBH events including GW190814, if we assume that the NS spin distribution is uniformly distributed up to the maximum (breakup) spin, we infer the maximum nonspinning NS mass is ${2.7}_{-0.4}^{+0.5}\,{M}_{\odot }$ (90% credibility), while assuming only nonspinning NSs, the NS maximum mass must be >2.53 M ⊙ (90% credibility). The data support the mass gap's existence, with a minimum BH mass at ${5.4}_{-1.0}^{+0.7}{M}_{\odot }$ . With future observations, under simplified assumptions, 150 NSBH events may constrain the maximum nonspinning NS mass to ±0.02 M ⊙, and we may even measure the relation between the NS spin and maximum mass entirely from GW data. If rapidly rotating NSs exist, their spins and masses must be modeled simultaneously to avoid biasing the NS maximum mass.

Keywords: gravitational waves; neutron stars; black holes
On Ganymede's Magnetic Quadrupolar Strength

Ganymede is the only moon in our solar system known to have a large-scale intrinsic magnetic field, likely generated in the moon's metallic core. Initial analyses of Galileo spacecraft measurements concluded that Ganymede's intrinsic magnetic field is dominated by a magnetic dipole and that quadrupolar contributions are exceptionally weak. These findings have influenced the development of models for Ganymede's core dynamo over the past two decades, some concluding that Ganymede's dynamo is limited to the innermost part of Ganymede's core. Here, we reassess Ganymede's internal field contributions based on the magnetic measurements from close Galileo flybys of Ganymede (G1, G2, G7, G8, G28, and G29), adding the recent Juno flyby. We find that presently available data cannot constrain Ganymede's quadrupole moment, as we demonstrate by constructing models with a range of quadrupole moments, including relative values comparable to those at the Earth. As a consequence, global analysis of available data cannot constrain the spatial limits of Ganymede's core dynamo. Incorporating ocean induction for a range of Ganymede ocean models indicates that ocean induction may be present, but that available magnetic data cannot discern between end-member cases for Ganymede ocean models.

Keywords: ganymede; magnetic fields; planetary cores
Quijote-PNG: Simulations of Primordial Non-Gaussianity and the Information Content of the Matter Field Power Spectrum and Bispectrum

Primordial non-Gaussianity (PNG) is one of the most powerful probes of the early universe, and measurements of the large-scale structure of the universe have the potential to transform our understanding of this area. However, relating measurements of the late-time universe to the primordial perturbations is challenging due to the nonlinear processes that govern the evolution of the universe. To help address this issue, we release a large suite of N-body simulations containing four types of PNG: QUIJOTE-PNG. These simulations were designed to augment the QUIJOTE suite of simulations that explored the impact of various cosmological parameters on large-scale structure observables. Using these simulations, we investigate how much information on PNG can be extracted by extending power spectrum and bispectrum measurements beyond the perturbative regime at z = 0.0. This is the first joint analysis of the PNG and cosmological information content accessible with power spectrum and bispectrum measurements of the nonlinear scales. We find that the constraining power improves significantly up to ${k}_{\max }\approx 0.3h\,{\mathrm{Mpc}}^{-1}$ , with diminishing returns beyond as the statistical probes signal-to-noise ratios saturate. This saturation emphasizes the importance of accurately modeling all the contributions to the covariance matrix. Further, we find that combining the two probes is a powerful method of breaking the degeneracies with the ΛCDM parameters.

Keywords: non-gaussianity; cosmology; large-scale structure of the universe; cosmological parameters from large-scale structure; cosmological parameters
Removal of Hot Saturns in Mass-Radius Plane by Runaway Mass Loss

The hot Saturn population exhibits a boundary in mass-radius space, such that no planets are observed at a density less than ~0.1 g cm-3. Yet, planet interior structure models can readily construct such objects as the natural result of radius inflation. Here, we investigate the role X-ray and extreme UV irradiation (XUV)-driven mass loss plays in sculpting the density boundary by constructing interior structure models that include radius inflation, photoevaporative mass loss, and a simple prescription of Roche lobe overflow. We demonstrate that planets puffier than ~0.1 g cm-3 experience a runaway mass loss caused by adiabatic radius expansion as the gas layer is stripped away, providing a good explanation of the observed edge in mass-radius space. The process is also visible in the radius-period and mass-period spaces, though smaller, high-bulk-metallicity planets can still survive at short periods, preserving a partial record of the population distribution at formation.

Keywords: exoplanet evolution; exoplanet structure; exoplanets; hot jupiters; hot neptunes
The Inner 2 pc of Sagittarius A*: Simulations of the Circumnuclear Disk and Multiphase Gas Accretion in the Galactic Center

The inner few parsecs of the Milky Way's Galactic center contain the central accreting supermassive black hole, over a million stars, and multiple large gaseous structures. In the past, the structures at these length scales have generally been modeled independently of each other. It is consequently not well understood how these complex features interact with each other, nor how gas flows between the outer few parsecs and the inner subarcsecond region (1″ ≈ 0.04 pc). In this work, we present hydrodynamic simulations of the inner few parsecs of the Galactic center that, for the first time, combine a realistic treatment of stellar winds and the circumnuclear disk (CND) as they interact with the gravitational potential of the nuclear star cluster and Sagittarius A*. We observe interactions of the stellar winds with the inner edge of the CND, which leads to the growth of instabilities, induced accretion of cool gas from the inner edge of the disk, and the eventual formation of a small accretion disk of ~104-105 K within r ~ 0.1 pc. The formation of an inner disk qualitatively agrees with observations. This disk grows in radial extent and mass with time on ≳10 kyr timescales, with a growth rate of $M\propto {t}_{\mathrm{kyr}}^{3.5}$ . We discuss additional physical mechanisms not yet included in this work that can improve our model.

Keywords: galactic center; galaxy circumnuclear disk; stellar winds
The Chocolate Chip Cookie Model: Dust-to-metal Ratio of H II Regions

Using a sample of face-on star-forming galaxies selected from the Sloan Digital Sky Survey, we statistically derive the typical optical depth τ cl of individual H II regions based on the "Chocolate Chip Cookie" model of Lu et al. (2022). By binning galaxies into stellar mass and gas-phase metallicity bins and interpreting τ cl as the dust-to-gas ratio (DGR) of H II regions, we further investigate the correlations between DGR and stellar mass and between DGR and gas-phase metallicity, respectively. We find that DGR increases monotonically with the stellar mass of galaxies. At a given stellar mass, DGR shows a linear correlation with the gas-phase metallicity, which implies a constant dust-to-metal ratio (DTM) of galaxies at a given stellar mass. These results adequately indicate that the DTM of galaxies is simply a function of their stellar masses. In terms of gas-phase metallicity, because of the mass-metallicity relation, DTM increases with increasing metallicity with a power-law index 1.45 in the low-metallicity region, while it remains constant at the high-metallicity end.

Keywords: disk galaxies; extinction; interstellar dust; interstellar dust extinction; h ii regions; gas-to-dust ratio
JWST Transmission Spectroscopy of HD 209458b: A Supersolar Metallicity, a Very Low C/O, and No Evidence of CH4, HCN, or C2H2

We present the transmission spectrum of the original transiting hot Jupiter HD 209458b from 2.3 to 5.1 μm as observed with the NIRCam instrument on the James Webb Space Telescope (JWST). Previous studies of HD 209458b's atmosphere have given conflicting results on the abundance of H2O and the presence of carbon- and nitrogen-bearing species, which have significant ramifications on the inferences of the planet's metallicity (M/H) and carbon-to-oxygen (C/O) ratio. We detect strong features of H2O and CO2 in the JWST transmission spectrum, which when interpreted using a retrieval that assumes thermochemical equilibrium and fractional gray cloud opacity yields ${3}_{-1}^{+4}$ × solar metallicity and C/O = ${0.11}_{-0.06}^{+0.12}$ . The derived metallicity is consistent with the atmospheric metallicity–planet mass trend observed in solar gas giants. The low C/O ratio suggests that this planet has undergone significant contamination by evaporating planetesimals while migrating inward. We are also able to place upper limits on the abundances of CH4, C2H2, and HCN of log( ${\chi }_{{\mathrm{CH}}_{4}}$ ) = ‑5.6, log( ${\chi }_{{{\rm{C}}}_{2}{{\rm{H}}}_{2}}$ ) = ‑5.7, and log( ${\chi }_{\mathrm{HCN}}$ ) = ‑5.1, which are in tension with the recent claim of a detection of these species using ground-based cross-correlation spectroscopy. We find that HD 209458b has a weaker CO2 feature size than WASP-39b when comparing their scale-height-normalized transmission spectra. On the other hand, the size of HD 209458b's H2O feature is stronger, thus reinforcing the low C/O inference.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; exoplanet atmospheric structure
High-energy Neutrinos from Stellar Explosions in Active Galactic Nuclei Accretion Disks

Some catastrophic stellar explosions, such as supernovae (SNe), compact binary coalescences, and microtidal disruption events, are believed to be embedded in the accretion disks of active galactic nuclei (AGNs). We show high-energy neutrinos can be produced efficiently through pp interactions between shock-accelerated cosmic rays and AGN disk materials shortly after the explosion ejecta shock breaks out of the disk. AGN stellar explosions are ideal targets for joint neutrino and electromagnetic (EM) multimessenger observations. Future EM follow-up observations of neutrino bursts can help us search for yet-discovered AGN stellar explosions. We suggest that AGN stellar explosions could potentially be important astrophysical neutrino sources. The contribution from AGN stellar explosions to the observed diffuse neutrino background depends on the uncertain local event rate densities of these events in AGN disks. By considering thermonuclear SNe, core-collapse SNe, gamma-ray burst associated SNe, kilonovae, and choked GRBs in AGN disks with known theoretical local event rate densities, we show that these events may contribute to ≲10% of the observed diffuse neutrino background.

Keywords: cosmological neutrinos; high energy astrophysics; active galactic nuclei; supernovae
X-Ray Sources in the 1.75 Ms Ultra Narrow Deep Field Observed by XMM-Newton

In this work, we present the results of the survey carried out on one of the deepest X-ray fields observed by the XMM-Newton satellite. The 1.75 Ms Ultra Narrow Deep Field (XMM175UNDF) survey is made by 13 observations taken over 2 yr with a total exposure time of 1.75 Ms (1.372 Ms after flare-filtered) in a field of 30' × 30' centered around the blazar 1ES 1553+113. We stacked the 13 observations reaching flux limits of 4.03 × 10-16, 1.3 × 10-15, and 9.8 × 10-16 erg s-1 cm-2 in the soft (0.2-2 keV), hard (2-12 keV), and full (0.2-12 keV) bands, respectively. Using a conservative threshold of Maximum Likelihood significance of ML ≥ 6, corresponding to 3σ, we detected 301 point-sources for which we derived positions, fluxes in different bands, and hardness ratios. Thanks to an optical follow-up that was carried out using the 10.4m the Gran Telescopio Canarias on the same field in the u'g'r'i'z' bands, combined with WISE/2MASS IR data, we identified 244 optical/IR counterpart candidates for our X-ray sources and estimated their X-ray luminosities, redshift distribution, X-ray/optical-X-ray/IR flux ratios, and absolute magnitudes. Finally, we divided this subsample into 40 non-active sources and 204 active galactic nuclei, of which 139 are classified as Seyfert galaxies and 41 as Quasars.

Keywords: x-ray active galactic nuclei; x-ray surveys; catalogs
An Excess of Active Galactic Nuclei Triggered by Galaxy Mergers in MaNGA Galaxies of Stellar Mass ∼1011 M ⊙

To facilitate new studies of galaxy-merger-driven fueling of active galactic nuclei (AGNs), we present a catalog of 387 AGNs that we have identified in the final population of over 10,000 z < 0.15 galaxies observed by the Sloan Digital Sky Survey-IV (SDSS-IV) integral field spectroscopy survey Mapping Nearby Galaxies at Apache Point Observatory (MaNGA). We selected the AGNs via mid-infrared Wide-field Infrared Survey Explorer colors, Swift/Burst Alert Telescope ultra-hard X-ray detections, NRAO Very Large Array Sky Survey and Faint Images of the Radio Sky at Twenty centimeters radio observations, and broad emission lines in SDSS spectra. By combining the MaNGA AGN catalog with a new SDSS catalog of galaxy mergers that were identified based on a suite of hydrodynamical simulations of merging galaxies, we study the link between galaxy mergers and nuclear activity for AGNs above a limiting bolometric luminosity of 1044.4 erg s‑1. We find an excess of AGNs in mergers, relative to nonmergers, for galaxies with stellar mass ∼1011 M ⊙, where the AGN excess is somewhat stronger in major mergers than in minor mergers. Further, when we combine minor and major mergers and sort by merger stage, we find that the highest AGN excess occurs in post-coalescence mergers in the highest-mass galaxies. However, we find no evidence of a correlation between galaxy mergers and AGN luminosity or accretion rate. In summary, while galaxy mergers overall do appear to trigger or enhance AGN activity more than nonmergers, they do not seem to induce higher levels of accretion or higher luminosities. We provide the MaNGA AGN Catalog and the MaNGA Galaxy Merger Catalog for the community here.

Keywords: active galactic nuclei; active galaxies; radio active galactic nuclei; x-ray active galactic nuclei; galaxy mergers; galaxy interactions