adsabs/SciX_UAT_keywords huggingface dataset:
Revealing the Gas Recycling in the Circumgalactic Medium (CGM) Utilizing a Luminous Lya Nebula around a Type II Quasar at z = 2.6 with the Keck Cosmic Web Imager (KCWI)

How galaxies acquire material from the circumgalactic medium is a key question in galaxy evolution. Recent observations and simulations show that gas recycling could be an important avenue for star formation. This paper presents Keck Cosmic Web Imager integral field unit spectroscopic observations on a type II quasar, Q1517 + 0055 at z = 2.65, a pilot study of our Lyα nebulae sample at z ≈ 2. We revealed diffuse emission of the Lyα 1216, He II 1640, and C IV 1549 on the projected physical scale of 122, 45, and 79 kpc, respectively. The total Lyα luminosity is L Lyα = 3.04 ± 0.02 × 1044 erg s-1. The line ratio diagnostics shows that He II/Lyα ≈ 0.08, and C IV/Lyα ≈ 0.28, consistent with the photoionization including recombination and photon pumping. We also identify the associated H I and C IV absorption from the spectra. By fitting the spectra, we derive both the column density and the velocity. We find that the velocity profile from both the absorption and the He II emission exhibit increasing trends. Moreover, both the line ratio diagnostic from the emission and the column density ratio from the absorption confirm that the cool gas metallicity is ≥Z ⊙. From detailed modeling and estimation, gas recycling might be a more plausible interpretation compared with the scenario of a powerful outflow.

Keywords: circumgalactic medium; galaxy accretion; high-redshift galaxies; quasars
Large-scale Molecular Gas Distribution in the M17 Cloud Complex: Dense Gas Conditions of Massive Star Formation?

The non-uniform distribution of gas and protostars in molecular clouds is caused by combinations of various physical processes that are difficult to separate. We explore this non-uniform distribution in the M17 molecular cloud complex that hosts massive star formation activity using the 12CO (J = 1-0) and 13CO (J = 1-0) emission lines obtained with the Nobeyama 45 m telescope. Differences in clump properties such as mass, size, and gravitational boundedness reflect the different evolutionary stages of the M17-H II and M17-IRDC clouds. Clumps in the M17-H II cloud are denser, more compact, and more gravitationally bound than those in M17-IRDC. While M17-H II hosts a large fraction of very dense gas (27%) that has a column density larger than the threshold of ∼1 g cm-2 theoretically predicted for massive star formation, this very dense gas is deficient in M17-IRDC (0.46%). Our HCO+ (J = 1-0) and HCN (J = 1-0) observations with the Taeduk Radio Astronomy Observatory 14 m telescope trace all gas with a column density higher than 3 × 1022 cm-2, confirming the deficiency of high-density (≳105 cm-3) gas in M17-IRDC. Although M17-IRDC is massive enough to potentially form massive stars, its deficiency of very dense gas and gravitationally bound clumps can explain the current lack of massive star formation.

Keywords: star formation; giant molecular clouds; diffuse molecular clouds; interstellar medium; protostars
Origin of Intense Electron Heating in Relativistic Blast Waves

The modeling of gamma-ray burst afterglow emission bears witness to strong electron heating in the precursor of Weibel-mediated, relativistic collisionless shock waves propagating in unmagnetized electron-ion plasmas. In this Letter, we propose a theoretical model, which describes electron heating via a Joule-like process caused by pitch-angle scattering in the decelerating, self-induced microturbulence and the coherent charge-separation field induced by the difference in inertia between electrons and ions. The emergence of this electric field across the precursor of electron-ion shocks is confirmed by large-scale particle-in-cell (PIC) simulations. Integrating the model using a Monte Carlo-Poisson method, we compare the main observables to the PIC simulations to conclude that the above mechanism can indeed account for the bulk of electron heating.

Keywords: shocks; plasma astrophysics; gamma-ray bursts; relativistic jets; high energy astrophysics; particle astrophysics
Black Hole Parameter Estimation from Its Shadow

The Event Horizon Telescope (EHT), a global submillimeter wavelength very long baseline interferometry array, unveiled event-horizon-scale images of the supermassive black hole M87* as an asymmetric bright emission ring with a diameter of 42 ± 3 μas, and it is consistent with the shadow of a Kerr black hole of general relativity. A Kerr black hole is also a solution of some alternative theories of gravity, while several modified theories of gravity admit non-Kerr black holes. While earlier estimates for the M87* black hole mass, depending on the method used, fall in the range ≈ 3× 109 M⊙ - 7×109 M⊙, the EHT data indicated a mass for the M87* black hole of (6.5 ± 0.7) × 109 M⊙. This offers another promising tool to estimate black hole parameters and to probe theories of gravity in its most extreme region near the event horizon. The important question arises: Is it possible by a simple technique to estimate black hole parameters from its shadow, for arbitrary models? In this paper, we present observables, expressed in terms of ordinary integrals, characterizing a haphazard shadow shape to estimate the parameters associated with black holes, and then illustrate its relevance to four different models: Kerr, Kerr-Newman, and two rotating regular models. Our method is robust, accurate, and consistent with the results obtained from existing formalism, and it is applicable to more general shadow shapes that may not be circular due to noisy data.

Keywords: astrophysical black holes; galactic center; black hole physics; gravitation; gravitational lensing
Inflation from Multiple Pseudo-scalar Fields: Primordial Black Hole Dark Matter and Gravitational Waves

We study a model of inflation with multiple pseudo-scalar fields coupled to a U(1) gauge field through Chern-Simons interactions. Because of parity-violating interactions, one polarization of the gauge field is amplified, yielding to an enhanced curvature perturbation power spectrum. Inflation proceeds in multiple stages, as each pseudo-scalar field rolls toward its minimum, yielding to distinct multiple peaks in the curvature perturbation power spectra at various scales during inflation. The localized peaks in the power spectra generate primordial black holes that can furnish a large fraction of dark matter abundance. In addition, gravitational waves with nontrivial spectra are generated that are in the sensitivity ranges of various forthcoming GW observatories.

Keywords: cosmic inflation; gravitational waves; primordial black holes; cosmological perturbation theory
Numerical Modeling of Energetic Charged-particle Transport with SPECTRUM Software: General Approach and Artificial Effects due to Field Discretization

Test-particle simulations are an important tool for magnetospheric and heliophysics research. In this paper, we present the Space Plasma and Energetic Charged particle TRansport on Unstructured Meshes (SPECTRUM) software as a novel tool for performing these types of simulations in arbitrary astrophysical environments, specified either analytically or numerically (i.e., on a grid). We discuss and benchmark SPECTRUM's interface with meshed magnetohydrodynamic backgrounds, including output from the Block Adaptive Tree Solar-wind Roe-type Upwind Scheme (BATS-R-US) code. We also investigate the effects of field discretization on both deterministic and stochastic particle motion, with emphasis on space science applications, concluding that the discretization error typically enhances the diffusive behavior of the ensemble.

Keywords: distributed computing; monte carlo methods; heliosphere; cosmic rays
Building a High-resolution Digital Terrain Model of Bennu from Laser Altimetry Data

The Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft orbited the near-Earth asteroid (101955) Bennu to characterize the asteroid prior to sampling. One important aspect of this characterization was the creation of a high-resolution (5-7 cm) global shape model using the OSIRIS-REx Laser Altimeter (OLA). We describe the data collected by OLA, along with the approach used to register overlapping topography using keypoints and keypoint descriptors in order to produce a globally self-consistent set of data. These globally registered sets of topographic scans were used to generate digital terrain models at both global and regional scales. We also describe efforts to correct for a change in behavior of the scanning mirror after the launch and highlight the improvements to the data after implementing an updated calibration of the mirror. The resulting model represents the highest-fidelity global OLA data set.

Keywords: asteroids; near-earth objects; remote sensing; astronomy data modeling; calibration
Molecular Gas and Dust Heating in Active Galaxies: Growing Black Holes or Tidal Shocks?

We investigate if and how growing supermassive black holes (SMBH) known as active galactic nuclei (AGN) and gravitational interactions affect the warm molecular gas and dust of galaxies. Our analysis focuses on the morphologies and warm ISM properties of 630 galaxies at z < 0.1. We use grizy images from the Pan-STARRS survey to classify the galaxies into mergers, early mergers, and non-mergers. We use MIR spectroscopic measurements of emission from rotational H2 transitions, dust, and polycyclic aromatic hydrocarbon (PAH) features, and silicate emission or absorption lines at 9.7 μm to study how gravitational interactions impact the warm ISM in AGN and non-AGN hosts. We find that in AGN-hosts, the ISM is warmer, the ratios of H2 to PAHs are larger, the PAH emission-line ratios and silicate strengths have a wider range of values than in non-AGN hosts. We find some statistical differences between the H2 emission of mergers and non-mergers, but those differences are less statistically significant than those between AGN and non-AGN hosts. Our results do not establish a relation between the rate of BH growth and the warm ISM but point to highly statistically significant differences between AGN hosts and non-AGN hosts, differences that are not present with the same statistical significance between mergers and non-mergers. We speculate that the combination of triggering mechanisms, AGN orientations, and evolutionary stages that allow AGN to be classified as such in the MIR indicate that those AGN are energetically coupled on kiloparsec scales to their host galaxies's warm ISM. Future optical and IR, spatially resolved spectroscopic studies are best suited to characterize this connection.

Keywords: active galactic nuclei; agn host galaxies
X-PSI Parameter Recovery for Temperature Map Configurations Inspired by PSR J0030+0451

In the last few years, the NICER collaboration has provided mass and radius inferences, via pulse profile modeling, for two pulsars: PSR J0030+0451 and PSR J0740+6620. Given the importance of these results for constraining the equation of state of dense nuclear matter, it is crucial to validate them and test their robustness. We therefore explore the reliability of these results and their sensitivity to analysis settings and random processes, including noise, focusing on the specific case of PSR J0030+0451. We use X-ray Pulse Simulation and Inference (X-PSI), one of the two main analysis pipelines currently employed by the NICER collaboration for mass and radius inferences. With synthetic data that mimic the PSR J0030+0451 NICER data set, we evaluate the recovery performances of X-PSI under conditions not previously tested, including complex modeling of the thermally emitting neutron star surface. For the test cases explored, our results suggest that X-PSI is capable of recovering the true mass and radius within reasonable credible intervals. This work also reveals the main vulnerabilities of the analysis: a significant dependence on noise and the presence of multimodal structure in the posterior surface. Noise particularly impacts our sensitivity to the analysis settings and widths of the posterior distributions. The multimodal structure in the posterior suggests that biases could be present if the analysis is unable to exhaustively explore the parameter space. Convergence testing, to ensure an adequate coverage of the parameter space and a suitable representation of the posterior distribution, is one possible solution to these challenges.

Keywords: neutron stars; nuclear astrophysics; astronomical simulations; astronomy data analysis; high energy astrophysics; x-ray astronomy
Betelgeuse as a Merger of a Massive Star with a Companion

We investigate the merger between a 16M ⊙ star, on its way to becoming a red supergiant (RSG), and a 4M ⊙ main-sequence companion. Our study employs three-dimensional hydrodynamic simulations using the state-of-the-art adaptive mesh refinement code OCTO-TIGER. The initially corotating binary undergoes interaction and mass transfer, resulting in the accumulation of mass around the companion and its subsequent loss through the second Lagrangian point (L2). The companion eventually plunges into the envelope of the primary, leading to its spin-up and subsequent merger with the helium core. We examine the internal structural properties of the post-merger star, as well as the merger environment and the outflow driven by the merger. Our findings reveal the ejection of approximately ∼0.6 M ⊙ of material in an asymmetric and somewhat bipolar outflow. We import the post-merger stellar structure into the MESA stellar evolution code to model its long-term nuclear evolution. In certain cases, the post-merger star exhibits persistent rapid equatorial surface rotation as it evolves in the H–R diagram toward the observed location of Betelgeuse. These cases demonstrate surface rotation velocities of a similar magnitude to those observed in Betelgeuse, along with a chemical composition resembling that of Betelgeuse. In other cases, efficient rotationally induced mixing leads to slower surface rotation. This pioneering study aims to model stellar mergers across critical timescales, encompassing dynamical, thermal, and nuclear evolutionary stages.

Keywords: close binary stars; stellar mergers; common envelope binary stars; hydrodynamical simulations; red supergiant stars; stellar evolution; stellar physics; interacting binary stars; binary stars; computational methods; computational astronomy
The Importance of Horizontal Poynting Flux in the Solar Photosphere

The electromagnetic energy flux in the lower atmosphere of the Sun is a key tool to describe the energy balance of the solar atmosphere. Current investigations on energy flux in the solar atmosphere focus primarily on the vertical electromagnetic flux through the photosphere, ignoring the Poynting flux in other directions and its possible contributions to local heating. Based on a realistic Bifrost simulation of a quiet-Sun (coronal hole) atmosphere, we find that the total electromagnetic energy flux in the photosphere occurs mainly parallel to the photosphere, concentrating in small regions along intergranular lanes. Thereby, it was possible to define a proxy for this energy flux based on only variables that can be promptly retrieved from observations, namely, horizontal velocities of the small-scale magnetic elements and their longitudinal magnetic flux. Our proxy accurately describes the actual Poynting flux distribution in the simulations, with the electromagnetic energy flux reaching 1010 erg cm-2 s-1. To validate our findings, we extended the analysis to SUNRISE/IMaX data. First, we show that Bifrost realistically describes photospheric quiet-Sun regions, as the simulation presents similar distributions for line-of-sight magnetic flux and horizontal velocity field. Second, we found very similar horizontal Poynting flux proxy distributions for the simulated photosphere and observational data. Our results also indicate that the horizontal Poynting flux in the observations is considerably larger than the vertical electromagnetic flux from previous observational estimates. Therefore, our analysis confirms that the electromagnetic energy flux in the photosphere is mainly horizontal and is most intense in localized regions along intergranular lanes.

Keywords: solar chromospheric heating; magnetohydrodynamics; solar surface; solar magnetic fields; solar granulation
Radial Distributions of Dwarf Satellite Systems in the Local Volume

The radial spatial distribution of low-mass satellites around a Milky Way (MW)-like host is an important benchmark for simulations of small-scale structure. The distribution is sensitive to the disruption of subhalos by the central disk and can indicate whether the disruption observed in simulations of MW analogs is artificial (i.e., numerical) or physical in origin. We consider a sample of 12 well-surveyed satellite systems of MW-like hosts in the Local Volume (D < 12 Mpc) that are complete to MV < -9 and within 150 projected kpc. We investigate the radial distribution of satellites and compare with ΛCDM cosmological simulations, including big-box cosmological simulations and high-resolution zoom-in simulations of MW-sized halos. We find that the observed satellites are significantly more centrally concentrated than the simulated systems. Several of the observed hosts, including the MW, are ∼2σ outliers relative to the simulated hosts in being too concentrated, while none of the observed hosts are less centrally concentrated than the simulations. This result is robust to different ways of measuring the radial concentration. We find that this discrepancy is more significant for bright, MV < -12 satellites, suggestive that this is not the result of observational incompleteness. We argue that the discrepancy is possibly due to artificial disruption in the simulations, but, if so, this has important ramifications for what relation between stellar mass and halo mass is allowed in the low-mass regime by the observed abundance of satellites.

Keywords: dark matter; local group; milky way galaxy; dwarf galaxies
Interplay between Young Stars and Molecular Clouds in the Ophiuchus Star-forming Complex

We present spatial and kinematic correlation between the young stellar population and the cloud clumps in the Ophiuchus star-forming region. The stellar sample consists of known young objects at various evolutionary stages, taken from the literature, some of which are diagnosed with Gaia EDR3 parallax and proper-motion measurements. The molecular gas is traced by the 850 μm Submillimetre Common-User Bolometer Array-2 image, reaching ~2.3 mJy beam-1, the deepest so far for the region, stacked from the James Clerk Maxwell Telescope/Transient program aiming to detect submillimeter outburst events. Our analysis indicates that the more evolved sources, namely the class II and III young stars, are located further away from clouds than class I and flat-spectrum sources that have ample circumstellar matter and are closely associated with natal clouds. Particularly the class II and III population is found to exhibit a structured spatial distribution indicative of passage of shock fronts from the nearby Sco-Cen OB association thereby compressing clouds to trigger star formation, with the latest starbirth episode occurring now in the densest cloud filaments. The young stars at all evolutionary stages share similar kinematics. This suggests that the stellar patterns trace the relics of parental cloud filaments that now have been dispersed.

Keywords: star formation; molecular clouds; young stellar objects; young star clusters; star forming regions
Ionized Outflows in Nearby Quasars Are Poorly Coupled to Their Host Galaxies

We analyze Multi-Unit Spectroscopic Explorer observations of nine low-redshift (z < 0.1) Palomar-Green quasar host galaxies to investigate the spatial distribution and kinematics of the warm, ionized interstellar medium, with the goal of searching for and constraining the efficiency of active galactic nucleus (AGN) feedback. After separating the bright AGN from the starlight and nebular emission, we use pixel-wise, kpc-scale diagnostics to determine the underlying excitation mechanism of the line emission, and we measure the kinematics of the narrow-line region (NLR) to estimate the physical properties of the ionized outflows. The radial size of the NLR correlates with the AGN luminosity, reaching scales of ~5 kpc and beyond. The geometry of the NLR is well-represented by a projected biconical structure, suggesting that the AGN radiation preferably escapes through the ionization cone. We find enhanced velocity dispersions (≳100 km s-1) traced by the Hα emission line in localized zones within the ionization cones. Interpreting these kinematic features as signatures of interaction between an AGN-driven ionized gas outflow and the host galaxy interstellar medium, we derive mass-outflow rates of ~0.008-1.6 M ⊙ yr-1 and kinetic injection rates of ~1039-1042 erg s-1, which yield extremely low coupling efficiencies of ≲10-3. These findings add to the growing body of recent observational evidence that AGN feedback is highly ineffective in the host galaxies of nearby AGNs.

Keywords: agn host galaxies; quasars
Eight Blue E+A Galaxy Candidates Located inside a Large-scale Filament in the Coma Cluster

E+A galaxies are post-starburst galaxies that have recently undergone quenching of their star formation, making them a valuable source for studying the evolution of galaxies. Using the SDSS Data Release 16, we found 13 "blue" E+A galaxy candidates and 117 "green" E+A galaxy candidates in and around the Coma cluster of galaxies. Blue E+A galaxies tend to be younger than green E+A galaxies, giving us a picture of how young galaxies transform into E+A galaxies. Based on their positions in R.A./decl./velocity space, we found that 8 of the blue E+A galaxy candidates seem to be located inside a large-scale galactic filament emanating from the center of the Coma Cluster. Their locations suggest there is an unusually high number of E+A galaxies throughout the filament. We have not yet determined whether these E+A galaxy candidates formed through merging or ram pressure stripping.

Keywords: e+a galaxies; post-starburst galaxies; coma cluster; intergalactic filaments; sloan photometry
Transport of Protostellar Cosmic Rays in Turbulent Dense Cores

Recent studies have suggested that low-energy cosmic rays (CRs) may be accelerated inside molecular clouds by the shocks associated with star formation. We use a Monte Carlo transport code to model the propagation of CRs accelerated by protostellar accretion shocks through protostellar cores. We calculate the CR attenuation and energy losses and compute the resulting flux and ionization rate as a function of both radial distance from the protostar and angular position. We show that protostellar cores have nonuniform CR fluxes that produce a broad range of CR ionization rates, with the maximum value being up to two orders of magnitude higher than the radial average at a given distance. In particular, the CR flux is focused in the direction of the outflow cavity, creating a "flashlight" effect and allowing CRs to leak out of the core. The radially averaged ionization rates are less than the measured value for the Milky Way of ζ ≈ 10-16 s-1; however, within r ≈ 0.03 pc from the protostar, the maximum ionization rates exceed this value. We show that variation in the protostellar parameters, particularly in the accretion rate, may produce ionization rates that are a couple of orders of magnitude higher or lower than our fiducial values. Finally, we use a statistical method to model unresolved subgrid magnetic turbulence in the core. We show that turbulence modifies the CR spectrum and increases the uniformity of the CR distribution but does not significantly affect the resulting ionization rates.

Keywords: cosmic rays; star formation; astrochemistry; magnetic fields; ionization; protostars; high energy astrophysics