adsabs/SciX_UAT_keywords huggingface dataset:
High-resolution Near-infrared Spectroscopic Study of Galactic Supernova Remnants. I. Kinematic Distances

We have carried out high-resolution near-infrared spectroscopic observations toward 16 Galactic supernova remnants (SNRs) showing strong H2 emission features. A dozen bright H2 emission lines are clearly detected for individual SNRs, and we have measured their central velocities, line widths, and fluxes. For all SNRs except one (G9.9-0.8), the H2 line ratios are well consistent with that of thermal excitation at T ∼ 2000 K, indicating that the H2 emission lines are most likely from shock-excited gas and therefore that they are physically associated with the remnants. The kinematic distances to the 15 SNRs are derived from the central velocities of the H2 lines using a Galactic rotation model. We derive for the first time the kinematic distances to four SNRs: G13.5+0.2, G16.0-0.5, G32.1-0.9, and G33.2-0.6. Among the remaining 11 SNRs, the central velocities of the H2 emission lines for six SNRs are well consistent (±5 $\mathrm{km}\,{{\rm{s}}}^{-1}$ ) with those obtained in previous radio observations, while for the other five SNRs (G18.1-0.1, G18.9-1.1, Kes 69, 3C 396, W49B) they are significantly different. We discuss the velocity discrepancies in these five SNRs. In G9.9-0.8, the H2 emission shows nonthermal line ratios and narrow line width (∼4 $\mathrm{km}\,{{\rm{s}}}^{-1}$ ), and we discuss its origin.

Keywords: supernova remnants; distance measure; molecular clouds; high resolution spectroscopy; interstellar line emission
Assessing the Impact of Hydrogen Absorption on the Characteristics of the Galactic Center Excess

We present a new reconstruction of the distribution of atomic hydrogen in the inner Galaxy that is based on explicit radiation transport modeling of line and continuum emission and a gas-flow model in the barred Galaxy that provides distance resolution for lines of sight toward the Galactic center. The main benefits of the new gas model are (a) the ability to reproduce the negative line signals seen with the HI4PI survey and (b) the accounting for gas that primarily manifests itself through absorption. We apply the new model of Galactic atomic hydrogen to an analysis of the diffuse gamma-ray emission from the inner Galaxy, for which an excess at a few GeV was reported that may be related to dark matter. We find with high significance an improved fit to the diffuse gamma-ray emission observed with the Fermi-LAT, if our new H I model is used to estimate the cosmic-ray induced diffuse gamma-ray emission. The fit still requires a nuclear bulge at high significance. Once this is included there is no evidence of a dark-matter signal, be it cuspy or cored. But an additional so-called boxy bulge is still favored by the data. This finding is robust under the variation of various parameters, for example, the excitation temperature of atomic hydrogen, and a number of tests for systematic issues.

Keywords: gamma-rays; dark matter; galactic center
Magnetorotational Instability in Quantum Dusty Plasma

Magnetorotational instability (MRI) in complex quantum plasma, which comprises electron, ion, and dust grains, is investigated. Electrons are considered to be degenerate while ions and dust grains are taken as nondegenerate. The general dispersion relation for MRI with the effect of spin magnetization is derived using local approximations. The instability criteria for spin quantum plasma are derived using low-frequency approximations. Due to the complex nature of the dispersion relation, MHD assumptions are used to define the instability criteria. The dust mass plays a significant role in both the dispersion and growth rate of the magnetorotational mode. The complex mass of dust modifies the instability criteria. Spin magnetization force arises due to electron Pauli spin matrices and has an important role in low-temperature and highly dense plasmas that are found mainly in white dwarfs, neutron stars, and in core-collapse supernovae. It is found that spin magnetization influences the criteria for instability and hence the properties of MHD waves in the degenerate plasma.

Keywords: plasma astrophysics; plasma physics; magnetohydrodynamics; astrophysical fluid dynamics
Instability of Circumnuclear Gas Supply as an Origin of the "Changing-look" Phenomenon of Supermassive Black Holes

The origin of the "changing-look" (CL) phenomenon in supermassive black holes (SMBHs) remains an open issue. This study aims to shed light on this phenomenon by focusing on a sample that encompasses all known repeating CL active galactic nuclei (AGNs). Through the identification of a characteristic timescale for the CL phenomenon, it was observed that larger SMBHs possess shorter characteristic timescales, while smaller SMBHs exhibit longer timescales. These findings reveal a significant contrast to the traditional AGN variability that has been adequately explained by the AGN's disk instability model. This stark discrepancy highlights a distinct origin of the CL phenomenon, distinguishing it from traditional AGN variability. By properly predicting the characteristic timescale and its dependence on SMBH mass, we propose that the CL phenomenon is likely a result of a variation in accretion rate caused by a sudden change in the supply of circumnuclear gas during the transition between active and passive SMBH fueling stages.

Keywords: active galactic nuclei; time domain astronomy; spectroscopy; accretion; bondi accretion; galaxy evolution
The Atacama Cosmology Telescope: Detection of Millimeter-wave Transient Sources

We report on the serendipitous discovery of three transient millimeter-wave sources using data from the Atacama Cosmology Telescope. The first, detected at R.A. = 273.8138, decl. = -49.4628 at ~50σ total, brightened from less than 5 mJy to at least 1100 mJy at 150 GHz with an unknown rise time shorter than 13 days, during which the increase from 250 mJy to 1100 mJy took only 8 minutes. Maximum flux was observed on 2019 November 8. The source's spectral index in flux between 90-150 GHz was positive, α = 1.5 ± 0.2. The second, detected at R.A. = 105.1584, decl. = -11.2434 at ~20σ total, brightened from less than 20 mJy to at least 300 mJy at 150 GHz with an unknown rise time shorter than 8 days. Maximum flux was observed on 2019 December 15. Its spectral index was also positive, α = 1.8 ± 0.2. The third, detected at R.A. = 301.9952, decl. = 16.1652 at ~40σ total, brightened from less than 8 mJy to at least 300 mJy at 150 GHz over a day or less but decayed over a few days. Maximum flux was observed on 2018 September 11. Its spectrum was approximately flat, with a spectral index of α = -0.2 ± 0.1. None of the sources were polarized to the limits of these measurements. The two rising-spectrum sources are coincident in position with M and K stars, while the third is coincident with a G star.

Keywords: time domain astronomy; transient sources; ground-based astronomy; millimeter astronomy; stellar flares
Nature of Turbulence inside Small-scale Magnetic Flux Ropes near the Sun: Parker Solar Probe Observations

In this study, we probe the turbulence characteristic within the small-scale magnetic flux ropes (SSMFRs) close to the Sun using Parker Solar Probe (PSP) magnetic field data. The study includes 50 SSMFRs observed by PSP during Encounter 1, 2, and 3 between 35.74 R ☉ and 142.29 R ☉ distance from the Sun. We observed that the average spectral index for all the selected SSMFR events is -1.49 ± 0.21. In line with expectations, we also saw average ∣σ m ∣ values close to zero throughout the inertial range. We also observed that the size of the eddy at the highest frequency is much smaller than the size of the SSMFRs, indicating anisotropy within it. Thus, our finding supports anisotropic models that feature the Iroshnikov-Kraichnan index. Our findings agree with the turbulence properties of the solar wind near the Sun. We also observe low ~0.1 compressibility, indicating SSMFRs are dominant by Alfvénic fluctuations. In light of this, we believe such an incompressible MHD spectrum results from nonlinear interactions between Alfvénic fluctuations. As a result, our research contributes to understanding the energy cascade process and its transport in solar plasma within the inner heliosphere.

Keywords: solar wind; interplanetary turbulence; space plasmas; alfven waves
Demographics of Protoplanetary Disks: A Simulated Population of Edge-on Systems

The structure of protoplanetary disks plays an essential role in planet formation. A disk that is highly inclined, or "edge-on," is of particular interest since its geometry provides a unique opportunity to study the disk's vertical structure and radial extent. Candidate edge-on protoplanetary disks are typically identified via their unique spectral energy distributions (SEDs) and subsequently confirmed through high-resolution imaging. However, this selection process is likely biased toward the largest, most-massive disks, and the resulting sample may not accurately represent the underlying disk population. To investigate this, we generated a grid of protoplanetary disk models using radiative transfer simulations and determined which sets of disk parameters produce edge-on systems that could be recovered by the aforementioned detection techniques-i.e., identified by their SEDs and confirmed through follow-up imaging with the Hubble Space Telescope. In doing so, we adopt a quantitative working definition of "edge-on disks" (EODs) that is observation driven and agnostic about the disk inclination or other properties. Folding in empirical disk demographics, we predict an occurrence rate of 6.2% for EODs and quantify biases toward highly inclined, massive disks. We also find that EODs are underrepresented in samples of Spitzer-studied young stellar objects, particularly for disks with host masses of M ≲ 0.5 M ⊙. Overall, our analysis suggests that several dozen EODs remain undiscovered in nearby star-forming regions, and provides a universal selection process to identify EODs for consistent, population-level demographic studies.

Keywords: protoplanetary disks; circumstellar disks; planetary system formation; planet formation; radiative transfer; radiative transfer simulations; astronomical simulations; direct imaging
The Implications of Ultra-Faint Dwarf Galaxy Reticulum II on the Common Envelope Jets Supernova r-process Scenario

We show that the common envelope jets supernova (CEJSN) r-process scenario is compatible with very recent observationally determined properties of the stars in the ultra faint dwarf (UFD) galaxy Reticulum II that are strongly enhanced in r-process elements. These new results, like efficient mixing of the r-process elements in the Reticulum II galaxy, have some implications on the CEJSN r-process scenario for UFD galaxies. In particular, the energetic jets efficiently mix with the common envelope ejecta and then with the entire interstellar medium of Reticulum II. The compatibility that we find between the scenario and new observations suggests that the CEJSN r-process scenario supplies a non-negligible fraction of the r-process elements.

Keywords: r-process; neutron stars; core-collapse supernovae; stellar jets; massive stars; nucleosynthesis
Accretion History of AGNs. III. Radiative Efficiency and AGN Contribution to Reionization

The cosmic history of supermassive black hole (SMBH) growth is important for understanding galaxy evolution, reionization, and the physics of accretion. Recent NuSTAR, Swift-BAT, and Chandra hard X-ray surveys have provided new constraints on the space density of heavily obscured active galactic nuclei (AGNs). Using the new X-ray luminosity function derived from these data, we here estimate the accretion efficiency of SMBHs and their contribution to reionization. We calculate the total ionizing radiation from AGNs as a function of redshift, based on the X radiation and distribution of obscuring column density, converted to ultraviolet (UV) wavelengths. Limiting the luminosity function to unobscured AGNs only, our results agree with current UV luminosity functions of unobscured AGNs. For realistic assumptions about the escape fraction, the contribution of all AGNs to cosmic reionization is ∼4 times lower than the galaxy contribution (23% at z ∼ 6). Our results also offer an observationally constrained prescription that can be used in simulations or models of galaxy evolution. To estimate the average efficiency with which SMBHs convert mass to light, we compare the total radiated energy, converted from X-ray light using a bolometric correction, with the most recent local black hole mass density. The most likely value, η ∼ 0.3-0.34, approaches the theoretical limit for a maximally rotating Kerr black hole, η = 0.42, implying that on average growing SMBHs are spinning rapidly.

Keywords: accretion; reionization; active galactic nuclei; x-ray active galactic nuclei; high energy astrophysics
The Causes of Peripheral Coronal Loop Contraction and Disappearance Revealed in a Magnetohydrodynamic Simulation of Solar Eruption

The phenomenon of peripheral coronal loop contraction during solar flares and eruptions, recently discovered in observations, has gradually drawn the attention of solar physicists. However, its underlying physical mechanism is still uncertain. One possible mechanism is Hudson's implosion conjecture, which attributes the contraction of peripheral coronal loops to magnetic pressure reduction in the magnetic energy liberation core, while other researchers proposed alternative explanations. In previous observational studies we also note the disappearance of peripheral shrinking loops in the late phase, of which there is a lack of investigation and interpretation. In this paper, we exploit a full MHD simulation of solar eruption to study the causes of the two phenomena. It is found that the loop motion in the periphery is well correlated with magnetic energy accumulation and dissipation in the core, and the loop shrinkage is caused by a more significant reduction in magnetic pressure gradient force than in magnetic tension force, consistent with the implosion conjecture. The peripheral contracting loops in the late phase act as inflow to reconnect with central erupting structures, which destroys their identities and naturally explains their disappearance. We also propose a positive feedback between the peripheral magnetic reconnection and the central eruption.

Keywords: solar active region magnetic fields; magnetohydrodynamics; magnetohydrodynamical simulations; solar corona
Numerical Research on the Effect of the Initial Parameters of CME Flux-rope Model on Simulation Results. III. Different Initial Energy of CMEs

In numerical studies, the initial parameters of coronal mass ejections (CMEs) have great influence on the simulation results. In our previous work, it has been proved that when the initial velocity is constant, the initial total mass mainly determines the propagation of the CME. On this basis, we carry out further research from the perspective of CME initial energy. We introduced a graduated cylindrical shell model into a 3D interplanetary total variation diminishing magnetohydrodynamic model to study the effect of different parameters of CMEs on simulation results. In this paper, we simulate several CME cases with different initial parameters and study the simulation results with a different initial energy composition. Actually, in interplanetary space, the kinetic energy of the CME always plays a dominant role. In order to study the effect of the initial thermal energy and magnetic energy on the propagation process of the CME, in this simulation, we adjust the initial parameters to make the thermal energy and magnetic energy reach the same level as the kinetic energy or an even higher level. Our results show that the initial total energy of the CME basically determines its arrival time at Earth, which indicates that the kinetic energy, thermal energy, and magnetic energy have similar effects on the propagation of the CMEs. Moreover, when the total energy keeps constant, the decrease of initial density will lead to the enhancement of CME expansion, which may make the front of the CME reach Earth earlier.

Keywords: solar coronal mass ejections; magnetohydrodynamical simulations; space weather
A Study of the Accretion State of Magnetically Arrested Disks across Black Hole Spins for Radiatively Inefficient Accretion Flows

The study of magnetically arrested disks (MAD) has attracted strong interest in recent years because these disk configurations were found to generate strong jets, as observed in many accreting systems. Here, we present the results of 14 general relativistic magnetohydrodynamic simulations of advection-dominated accretion flow in the MAD state across black hole (BH) spins, carried out with cuHARM. Our main findings are as follows. (i) The jets transport a significant amount of angular momentum to infinity in the form of Maxwell stresses. For positive, high spin, the rate of angular momentum transport is about five times higher than for negative spin. This contribution is nearly absent for a nonrotating BH. (ii) The mass accretion rate and the MAD parameter, both calculated at the horizon, are not correlated. However, their time derivatives are anticorrelated for every spin. (iii) For zero spin, the contribution of the toroidal component of the magnetic field to the magnetic pressure is negligible, while for a fast-spinning BH, it is on the same order as the contribution of the radial magnetic component. For high positive spin, the toroidal component even dominates. (iv) For negative spins, the jets are narrower than their positive-spin counterparts, while their fluctuations are stronger. The weak jet from the nonrotating BH is the widest with the weakest fluctuations. Our results highlight the complex nonlinear connection between the black hole spin and the resulting disk and jet properties in the MAD regime.

Keywords: accretion; magnetohydrodynamical simulations; relativistic jets; black hole physics
The Hyper-inflation Stage in the Coronal Mass Ejection Formation: A Missing Link That Connects Flares, Coronal Mass Ejections, and Shocks in the Low Corona

We analyze the formation and three-dimensional (3D) evolution of two coronal mass ejections (CMEs) and their associated waves in the low corona via a detailed multi-viewpoint analysis of extreme-ultraviolet observations. We analyze the kinematics in the radial and lateral directions and identify three stages in the early evolution of the CME: (1) a hyper-inflation stage, when the CME laterally expands at speeds of ~1000 km s-1, followed by (2) a shorter and slower expansion stage of a few minutes and ending with (3) a self-similar phase that carries the CME into the middle corona. The first two stages coincide with the impulsive phase of the accompanying flare, the formation and separation of an EUV wave from the CME, and the start of the metric type II radio burst. Our 3D analysis suggests that the hyper-inflation phase may be a crucial stage in the CME formation with wide-ranging implications for solar eruption research. It likely represents the formation stage of the magnetic structure that is eventually ejected into the corona, as the white-light CME. It appears to be driven by the injection of poloidal flux into the ejecting magnetic structure, which leads to the lateral (primarily) growth of the magnetic flux rope. The rapid growth results in the creation of EUV waves and eventually shocks at the CME flanks that are detected as metric type II radio bursts. In other words, the hyper-inflation stage in the early CME evolution may be the "missing" link between CMEs, flares, and coronal shocks.

Keywords: solar coronal waves; solar activity; solar coronal mass ejections
HETDEX Public Source Catalog 1: 220 K Sources Including Over 50 K Lyα Emitters from an Untargeted Wide-area Spectroscopic Survey

We present the first publicly released catalog of sources obtained from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). HETDEX is an integral field spectroscopic survey designed to measure the Hubble expansion parameter and angular diameter distance at 1.88 < z < 3.52 by using the spatial distribution of more than a million Lyα-emitting galaxies over a total target area of 540 deg2. The catalog comes from contiguous fiber spectra coverage of 25 deg2 of sky from 2017 January through 2020 June, where object detection is performed through two complementary detection methods: one designed to search for line emission and the other a search for continuum emission. The HETDEX public release catalog is dominated by emission-line galaxies and includes 51,863 Lyα-emitting galaxy (LAE) identifications and 123,891 [O II]-emitting galaxies at z < 0.5. Also included in the catalog are 37,916 stars, 5274 low-redshift (z < 0.5) galaxies without emission lines, and 4976 active galactic nuclei. The catalog provides sky coordinates, redshifts, line identifications, classification information, line fluxes, [O II] and Lyα line luminosities where applicable, and spectra for all identified sources processed by the HETDEX detection pipeline. Extensive testing demonstrates that HETDEX redshifts agree to within Δz < 0.02, 96.1% of the time to those in external spectroscopic catalogs. We measure the photometric counterpart fraction in deep ancillary Hyper Suprime-Cam imaging and find that only 55.5% of the LAE sample has an r-band continuum counterpart down to a limiting magnitude of r ~ 26.2 mag (AB) indicating that an LAE search of similar sensitivity to HETDEX with photometric preselection would miss nearly half of the HETDEX LAE catalog sample. Data access and details about the catalog can be found online at http://hetdex.org/. A copy of the catalogs presented in this work (Version 3.2) is available to download at Zenodo doi:10.5281/zenodo.7448504. * Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly.

Keywords: redshift surveys; catalogs; emission line galaxies; lyman-alpha galaxies
Refinement of the Parameters of the Negative Polarization Branch of Asteroid 419 Aurelia in the R Filter

Asteroid 419 Aurelia is of particular interest due to its unusual optical properties. But the lack of observational data, especially in the R filter, did not allow one to accurately determine the parameters of the negative polarization branch of this asteroid. We carried out the precise measurements of the Aurelia's degree of linear polarization at different phase angles. The data obtained made it possible to accurately approximate a complete branch of the negative polarization. Thanks to this, it was possible to obtain refined values of the parameters of the negative polarization branch.

Keywords: asteroids; polarimetry