Sazuna/UAT_keywords huggingface dataset:
CALLIOPE: Pseudospectral Shearing Magnetohydrodynamics Code with a Pencil Decomposition. The pseudospectral method is a highly accurate numerical scheme suitable for turbulence simulations. We have developed an open-source pseudospectral code, CALLIOPE, which adopts the P3DFFT library to perform a fast Fourier transform with the two-dimensional (pencil) decomposition of numerical grids. CALLIOPE can solve incompressible magnetohydrodynamics (MHD), isothermal compressible MHD, and rotational reduced MHD with parallel computation using very large numbers of cores (&gt;105 cores for 20483 grids). The code can also solve for local magnetorotational turbulence in a shearing frame using the remapping method. CALLIOPE is currently the only pseudospectral code that can compute magnetorotational turbulence using pencil-domain decomposition. This paper presents the numerical scheme of CALLIOPE and the results of linear and nonlinear numerical tests, including compressible local magnetorotational turbulence with the largest grid number reported to date.

Keywords: Plasma astrophysics, Magnetohydrodynamical simulations
iPTF 16asu Revisited: A Rapidly Evolving Superluminous Broad-lined Ic Supernova?. In this paper, we fit the spectral energy distributions of iPTF 16asu, which has so far been classified as a luminous rapidly evolving broad-lined Ic supernova (SN Ic-BL), and reconstruct its postpeak bolometric light curve. We find that the luminosity of the postpeak bolometric light curve of iPTF 16asu is about 3 times that of the pseudobolometric light curve derived in the literature, and the extrapolated peak luminosity exceeds ~1044 erg s-1, which is higher than the threshold of superluminous supernovae (SLSNe). We then use the 56Ni model and the magnetar plus 56Ni model to fit the multiband light curves of iPTF 16asu, and construct the theoretical bolometric light curve using the best-fitting theoretical multiband light curves. We find that the magnetar plus 56Ni model can account for the photometry of iPTF 16asu, and the peak luminosity of its theoretical bolometric light curve is ~1.06 × 1044 erg s-1. We suggest that iPTF 16asu and similar SNe (e.g., SN 2018gep) constitute the class of rapidly evolving SLSNe Ic-BL.

Keywords: Type Ic supernovae, Spectral energy distribution, Magnetars
Plasma Emission versus Electron Cyclotron Maser Emission due to Power-law Energetic Electrons in Differently Magnetized Coronal Plasmas. By using self-consistent 2.5-dimensional particle-in-cell simulations, we study the excitation efficiency of electromagnetic waves by power-law energetic electrons with an anisotropic pitch-angle velocity distribution, which can simultaneously trigger the Langmuir and electron cyclotron maser instabilities, in differently magnetized coronal plasmas. It is found that the (transverse) electromagnetic waves can be excited much more efficiently in the case of strongly magnetized plasmas with ω ce &gt; ω pe than that of weakly magnetized plasmas with ω ce &lt; ω pe, where ω ce and ω pe are the electron cyclotron frequency and the electron plasma frequency, respectively. In particular, in a weakly magnetized plasma the electromagnetic wave is hardly excited effectively via the nonlinear coupling of Langmuir waves; although the Langmuir waves can be generated by the power-law energetic electrons, implying that the so-called plasma emission does not effectively work. These results can be helpful for us to better understand the physical mechanism of solar radio bursts.

Keywords: Solar radio emission, Solar corona, Plasma physics
HAWC Study of the Ultra-high-energy Spectrum of MGRO J1908+06. We report TeV gamma-ray observations of the ultra-high-energy source MGRO J1908+06 using data from the High Altitude Water Cherenkov Observatory. This source is one of the highest-energy known gamma-ray sources, with emission extending past 200 TeV. Modeling suggests that the bulk of the TeV gamma-ray emission is leptonic in nature, driven by the energetic radio-faint pulsar PSR J1907+0602. Depending on what assumptions are included in the model, a hadronic component may also be allowed. Using the results of the modeling, we discuss implications for detection prospects by multi-messenger campaigns.

Keywords: Gamma-ray sources, Pulsars, Supernova remnants, Gamma-ray astronomy, Gamma-rays
An Ultraluminous Supersoft Source in a Dwarf Galaxy of A85: An Intermediate-mass Black Hole Candidate. We study a large sample of dwarf galaxies using archival Chandra X-ray observations, with the aim of detecting accreting intermediate-mass black holes (IMBHs). IMBHs are expected to inhabit dwarf galaxies and to produce specific signatures in terms of luminosity and X-ray spectra. We report the discovery of an X-ray source associated with an A85 dwarf galaxy that fits the IMBH description. The stellar mass of the host galaxy is estimated to be 2 × 108  M ⊙, which makes it one of the least massive galaxies to potentially host an accreting black hole. The source is detected in the soft band, under 1 keV, and is undetected at higher energies. The X-ray luminosity is ≈1041 erg s-1, making it almost three orders of magnitude more luminous than the most luminous stellar-mass supersoft emitters. From the galaxy stellar mass versus black hole mass relation, we estimate the mass to be within the intermediate regime. Another method that resulted in an intermediate mass relies on the fact that supersoft emission is expected to be associated with high accretion rates, approaching the Eddington limit. We suggest that the observed offset of the X-ray source from the galactic center (≈1.8 kpc) is due to galaxy interactions, and we present evidence from the literature that supports the relation between black hole activity and galaxy interactions.

Keywords: Intermediate-mass black holes, Dwarf galaxies
Finite-time Response of Dynamo Mean-field Effects in Magnetorotational Turbulence. Accretion disk turbulence along with its effect on large-scale magnetic fields plays an important role in understanding disk evolution in general, and the launching of astrophysical jets in particular. Motivated by enabling a comprehensive subgrid description for global long-term simulations of accretions disks, we aim to further characterize the transport coefficients emerging in local simulations of magnetorotational disk turbulence. For the current investigation, we leverage a time-dependent version of the test-field method, which is sensitive to the turbulent electromotive force (EMF) generated as a response to a set of pulsating background fields. We obtain Fourier spectra of the transport coefficients as a function of oscillation frequency. These are well approximated by a simple response function, describing a finite-time buildup of the EMF as a result of a time-variable mean magnetic field. For intermediate timescales (i.e., slightly above the orbital frequency), we observe a significant phase lag of the EMF compared to the causing field. Augmented with our previous result on a nonlocal closure relation in space, and incorporated into a suitable mean-field description that we briefly sketch out here, the new framework will allow us to drop the restrictive assumption of scale separation.

Keywords: Magnetohydrodynamics, Magnetic fields, Magnetohydrodynamical simulations
Measurement of Galactic 26Al with the Compton Spectrometer and Imager. The Compton Spectrometer and Imager (COSI) is a balloon-borne compact Compton telescope designed to survey the 0.2-5 MeV sky. COSI's energy resolution of ~0.2% at 1.8 MeV, single-photon reconstruction, and wide field of view make it capable of studying astrophysical nuclear lines, particularly the 1809 keV γ-ray line from decaying Galactic 26Al. Most 26Al originates in massive stars and core-collapse supernova nucleosynthesis, but the path from stellar evolution models to Galaxy-wide emission remains unconstrained. In 2016, COSI had a successful 46 day flight on a NASA superpressure balloon. Here, we detail the first search for the 1809 keV 26Al line in the COSI 2016 balloon flight using a maximum-likelihood analysis. We find a Galactic 26Al flux of (8.6 ± 2.5) × 10-4 ph cm-2 s-1 within the Inner Galaxy (∣ℓ∣ ≤ 30°, ∣b∣ ≤ 10°) with 3.7σ significance above background. Within uncertainties, this flux is consistent with expectations from previous measurements by SPectrometer on INTEGRAL (SPI) and the Compton Telescope on the Compton Gamma-Ray Observatory (COMPTEL). This analysis demonstrates COSI's powerful capabilities for studies of γ-ray lines and underscores the scientific potential of future compact Compton telescopes. In particular, the next iteration of COSI as a NASA Small Explorer satellite has recently been approved for launch in 2025.

Keywords: Astronomy data modeling, Gamma-ray lines, Gamma-ray telescopes, High altitude balloons, Stellar nucleosynthesis
Mid- and Far-infrared Color-Color Relations within Local Galaxies. We present an extensive archival analysis of a sample of local galaxies, combining multiwavelength data from GALEX, Spitzer, and Herschel to investigate "blue-side" mid-infrared (MIR) and "red-side" far-infrared (FIR) color-color correlations within the observed infrared spectral energy distributions. Our sample largely consists of the KINGFISH galaxies, with the important addition of a select few including NGC 5236 (M83) and NGC 4449. With data from the far-ultraviolet (~0.15 μm) through 500 μm convolved to common angular resolution, we measure the photometry of kiloparsec-scale star-forming regions 36″ × 36″ in size. Star formation rates (SFRs), stellar masses, and metallicity distributions are derived throughout our sample. Focusing on the f 70/f 500 "FIR" and f 8/f 24 "MIR" flux density ratios (colors), we find that a subsample of galaxies demonstrate a strong IR color-color correlation within their star-forming regions, while others demonstrate uncorrelated colors. This division is driven by two main effects: (1) the local strength of star formation (SF) and (2) the metal content of the interstellar medium (ISM). Galaxies uniformly dominated by high surface densities of SF (e.g., NGC 5236) demonstrate strong IR color-color correlations, while galaxies that exhibit lower levels of SF and mixed environments (e.g., NGC 5457) demonstrate weaker or no correlation-explained by the increasing effect of varying ISM heating and metal content on the IR colors, specifically in the MIR. We find large dispersion in the SFR-L 8 (8 μm luminosity) relation that is traced by the metallicity distributions, consistent with extant studies, highlighting its problematic use as an SFR indicator across diverse systems/samples.

Keywords: Polycyclic aromatic hydrocarbons, Galaxy environments, Star forming regions, Star formation, Spectral energy distribution, Interstellar medium
Using Single-view Observations of Cometary Plasma Tails to Infer Solar Wind Speed. A comet plasma tail is a product of the interaction between the solar wind and the comet's coma, and has long been studied as a natural probe of the solar wind condition. We previously developed a method to derive the solar wind speed from dual-view observations of comet plasma tails. Here we improve the method to use single-view observations by assuming a radially propagating solar wind and apply it to two comets, C/2011 W3 (Lovejoy) and C/2012 S1 (ISON) observed by coronagraphs on board the Solar and Heliospheric Observatory and STEREO. We compare the results to the solar wind simulations and tomography and to the results from our previous dual-view method, and find they are generally consistent, especially when the comets were far away from the Sun or far away from the ecliptic plane and when the observer is high above the comet's orbital plane. Meanwhile, we notice that this method may suffer from a large error for comets near the ecliptic plane and close to the Sun, where a nonradial component of the solar wind is significant. Using the observations from the first seven orbits of the Parker Solar Probe, we show that the solar wind deviates from a radial direction significantly within around 35 R s. We also notice that, when the nonradial solar wind component is presented, the error may be even larger if the observer is closer to the comet's orbital plane. This method provides a potentially useful tool to estimate the solar wind speed around comets from only single-view imaging observations.

Keywords: Comet tails, Solar wind
Optical to X-Ray Signatures of Dense Circumstellar Interaction in Core-collapse Supernovae. Progenitors of core-collapse supernovae (SNe) can shed significant mass to circumstellar material (CSM) in the months to years preceding core collapse. The ensuing SN explosion launches ejecta that may subsequently collide with this CSM, producing shocks that can power emissions across the electromagnetic spectrum. In this work we explore the thermal signatures of dense CSM interaction when the CSM density profile is truncated at some outer radius. CSM with optical depth &gt;c/v (where v is the shock velocity) will produce primarily ~blackbody optical/UV emission, whereas lower optical depth CSM will power bremsstrahlung X-ray emission. Focusing on the latter, we derive light curves and spectra of the resulting X-ray transients that include a detailed treatment of Comptonization. Due to strong photoelectric absorption, the X-ray light curve is dominated by the postinteraction phase that occurs after the shock reaches the CSM truncation radius. We treat this regime here for the first time. Using these results, we present the phase space of optical, UV, and X-ray transients as a function of CSM properties, and discuss detectability prospects. We find that ROSAT would not have been sensitive to CSM X-ray transients but that eROSITA is expected to detect many such events. Future wide-field UV missions such as the Ultraviolet Transient Astronomy Satellite will dramatically enhance sensitivity to large optical depth CSM configurations. Finally, we present a framework within which CSM properties may be directly inferred from observable features of X-ray transients. This can serve as an important tool for studying stellar mass loss using SN X-ray detections.

Keywords: Core-collapse supernovae, High energy astrophysics, X-ray transient sources, Time domain astronomy, Ultraviolet transient sources
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: Uranian satellites, Natural satellite formation
Search for Lensing Signatures from the Latest Fast Radio Burst Observations and Constraints on the Abundance of Primordial Black Holes. The possibility that primordial black holes (PBHs) form some part of dark matter has been considered for a long time but poorly constrained over a wide mass range. Fast radio bursts (FRBs) are bright radio transients with millisecond duration. Their lensing effect has been proposed to be one of the cleanest probes for constraining the presence of PBHs in the stellar-mass window. In this paper, we first apply the normalized cross-correlation algorithm to search and identify candidates for lensed FRBs in the latest public FRB observations, i.e., 593 FRBs, which mainly consist of the first Canadian Hydrogen Intensity Mapping Experiment FRB catalog, and then derive constraints on the abundance of PBHs from the null search result of the lensing signature. For a monochromatic mass distribution, the fraction of dark matter made up of PBHs could be constrained to ≤87% for ≥500 M ⊙ at the 95% confidence level by assuming signal-to-noise ratios dependent on the flux ratio threshold for each FRB and that apparently one-off events are intrinsic single bursts. This result would be improved by a factor of 3 when a conventional constant flux ratio threshold is considered. Moreover, we derive constraints on PBHs with a log-normal mass function naturally predicted by some popular inflation models and often investigated with gravitational-wave detections. We find that, in this mass distribution scenario, the constraint from the current public FRB observations is relatively weaker than the one from gravitational-wave detections. It is foreseen that upcoming complementary multimessenger observations will yield considerable constraints on the possibilities of PBHs in this intriguing mass window.

Keywords: Radio bursts, Primordial black holes, Strong gravitational lensing
Density Turbulence and the Angular Broadening of Outer Heliospheric Radio Sources at High Latitudes and in the Ecliptic Plane. Density irregularities are responsible for the scattering of radio waves in the solar wind and astrophysical plasmas. These irregularities significantly affect the inferred physical properties of radio sources, such as size, direction, and intensity. We present here a theory of angular broadening due to the scattering of radio waves by density irregularities that improves the existing formalism used to investigate radio wave scattering in the outer heliosphere and the very local interstellar medium. The model includes an inner scale and both latitudinal and radial dependencies for the density fluctuation spectra and propagation paths for the radiation both near and out of the ecliptic plane. Based on the pickup-ion-mediated solar wind model (PUI model) of Zank et al., we estimate the turbulence and solar wind quantities for the high-latitude fast solar wind. The predictions include the density variance, inner/dissipation scale, velocity correlation length, mean magnetic field, and proton temperature. The density turbulence amplitude is estimated in two ways. First, a simple scaling technique is used to extend the theoretical predictions of the PUI model for the high-latitude wind beyond the heliospheric termination shock. Second, the solar wind and turbulence quantities are calculated near the ecliptic plane using plasma and magnetometer data from the Voyager 2 spacecraft over the period 1977-2018. Based on the turbulence models and observations, we calculate the scattering angle of the radio sources in the high-latitude and near-ecliptic wind. Finally, we compare the numerical results with the analytic predictions from Cairns and Armstrong et al. and the observed source sizes.

Keywords: Space plasmas, Heliosphere, Interplanetary turbulence, Solar wind, Solar radio emission
LEGA-C: Analysis of Dynamical Masses from Ionized Gas and Stellar Kinematics at z   0.8. We compare dynamical mass estimates based on spatially extended stellar and ionized gas kinematics (M  dyn,* and M dyn,eml, respectively) of 157 star-forming galaxies at 0.6 ≤ z &lt; 1. Compared with z ~ 0, these galaxies have enhanced star formation rates, with stellar feedback likely affecting the dynamics of the gas. We use LEGA-C DR3, the highest-redshift data set that provides sufficiently deep measurements of a K  s -band limited sample. For M  dyn,*, we use Jeans anisotropic multi-Gaussian expansion models. For M dyn,eml, we first fit a custom model of a rotating exponential disk with uniform dispersion, whose light is projected through a slit and corrected for beam smearing. We then apply an asymmetric drift correction based on assumptions common in the literature to the fitted kinematic components to obtain the circular velocity, assuming hydrostatic equilibrium. Within the half-light radius, M dyn,eml is on average lower than M  dyn,*, with a mean offset of -0.15 ± 0.016 dex and galaxy-to-galaxy scatter of 0.19 dex, reflecting the combined random uncertainty. While data of higher spatial resolution are needed to understand this small offset, it supports the assumption that the galaxy-wide ionized gas kinematics do not predominantly originate from disruptive events such as star formation-driven outflows. However, a similar agreement can be obtained without modeling from the integrated emission line dispersions for axis ratios q &lt; 0.8. This suggests that our current understanding of gas kinematics is not sufficient to efficiently apply asymmetric drift corrections to improve dynamical mass estimates compared with observations lacking the signal-to-noise ratio required for spatially extended dynamics.

Keywords: Galaxy dynamics, High-redshift galaxies, Galaxy evolution
How to Obtain the Redshift Distribution from Probabilistic Redshift Estimates. A reliable estimate of the redshift distribution n(z) is crucial for using weak gravitational lensing and large-scale structures of galaxy catalogs to study cosmology. Spectroscopic redshifts for the dim and numerous galaxies of next-generation weak-lensing surveys are expected to be unavailable, making photometric redshift (photo-z) probability density functions (PDFs) the next best alternative for comprehensively encapsulating the nontrivial systematics affecting photo-z point estimation. The established stacked estimator of n(z) avoids reducing photo-z PDFs to point estimates but yields a systematically biased estimate of n(z) that worsens with a decreasing signal-to-noise ratio, the very regime where photo-z PDFs are most necessary. We introduce Cosmological Hierarchical Inference with Probabilistic Photometric Redshifts (CHIPPR), a statistically rigorous probabilistic graphical model of redshift-dependent photometry that correctly propagates the redshift uncertainty information beyond the best-fit estimator of n(z) produced by traditional procedures and is provably the only self-consistent way to recover n(z) from photo-z PDFs. We present the chippr prototype code, noting that the mathematically justifiable approach incurs computational cost. The CHIPPR approach is applicable to any one-point statistic of any random variable, provided the prior probability density used to produce the posteriors is explicitly known; if the prior is implicit, as may be the case for popular photo-z techniques, then the resulting posterior PDFs cannot be used for scientific inference. We therefore recommend that the photo-z community focus on developing methodologies that enable the recovery of photo-z likelihoods with support over all redshifts, either directly or via a known prior probability density.

Keywords: Bayesian statistics, Posterior distribution, Observational cosmology, Redshift surveys, Astrostatistics, Galaxy photometry, Hierarchical models, Markov chain Monte Carlo, Broad band photometry, Prior distribution, Astronomical methods, Two-point correlation function