Sazuna/UAT_keywords huggingface dataset:
Chemical Abundances in Sgr A East: Evidence for a Type Iax Supernova Remnant. Recent observations have shown a remarkable diversity of observational behaviors and explosion mechanisms in thermonuclear supernovae (SNe). An emerging class of peculiar thermonuclear SNe, called Type Iax, show photometric and spectroscopic behaviors distinct from normal Type Ia. Their origin remains highly controversial, but pure turbulent deflagration of white dwarfs (WDs) has been regarded as the leading formation theory. The large population of Type Iax indicates the existence of unidentified Galactic Type Iax supernova remnants (SNRs). We report evidence that SNR Sgr A East in the Galactic center resulted from a pure turbulent deflagration of a Chandrasekhar-mass carbon-oxygen WD, an explosion mechanism used for Type Iax SNe. Our X-ray spectroscopic study of Sgr A East using 3 Ms of Chandra data shows a low ratio of intermediate-mass elements to Fe and large Mn/Fe and Ni/Fe ratios. This abundance pattern does not accord with the core-collapse or normal Type Ia models. Sgr A East is thus the first Galactic SNR for which a likely Type Iax origin has been proposed and is the nearest target for studying this peculiar class. We compared Sgr A East with the Fe-rich SNRs 3C 397 and W49B, which also have high Mn and Cr abundances and were claimed to result from deflagration-to-detonation explosions of Chandrasekhar-mass WDs (although with disputes). Our study shows that they have distinct abundance patterns. The X-ray spectroscopic studies of thermonuclear SNRs provide observational evidence for the theories that there are diverse explosion channels and various metal outputs for Chandrasekhar-mass WDs.

Keywords: Galactic center, Explosive nucleosynthesis, White dwarf stars, Supernova remnants, Type Ia supernovae
Primordial Radius Gap and Potentially Broad Core Mass Distributions of Super-Earths and Sub-Neptunes. The observed radii distribution of Kepler exoplanets reveals two distinct populations: those that are more likely to be terrestrials (≲1.7R⊕) and those that are more likely to be gas-enveloped (≳2R⊕). There exists a clear gap in the distribution of radii that separates these two kinds of planets. Mass-loss processes like photoevaporation by high-energy photons from the host star have been proposed as natural mechanisms to carve out this radius valley. These models favor underlying core mass function of sub-Neptunes that is sharply peaked at ∼4-8M⊕, but the radial-velocity follow-up of these small planets hints at a more bottom-heavy mass function. By taking into account the initial gas accretion in gas-poor (but not gas-empty) nebula, we demonstrate that (1) the observed radius valley is a robust feature that is initially carved out at formation during late-time gas accretion; and (2) that it can be reconciled with core mass functions that are broad extending well into the sub-Earth regime. The maximally cooled isothermal limit prohibits cores lighter than ∼1-2M⊕ from accreting enough mass to appear gas-enveloped. The rocky-to-enveloped transition established at formation produces a gap in the radius distribution that shifts to smaller radii farther from the star, similar to that observed. For the best agreement with the data, our late-time gas accretion model favors dust-free accretion in hotter disks with cores slightly less dense than the Earth (∼0.8ρ⊕) drawn from a mass function that is as broad as ${dN}/{{dM}}_{\mathrm{core}}\propto {M}_{\mathrm{core}}^{-0.7}$ .

Keywords: Exoplanet astronomy, Exoplanet evolution, Exoplanet formation, Exoplanet structure
A Random Walk Model for Dark Matter Halo Concentrations. For idealized (spherical, smooth) dark matter halos described by single-parameter density profiles (such as the Navarro-Frenk-White profile), there exists a one-to-one mapping between the energy of the halo and the scale radius of its density profile. The energy therefore uniquely determines the concentration parameter of such halos. We exploit this fact to predict the concentrations of dark matter halos via a random walk in halo energy space. Given a full merger tree for a halo, the total internal energy of each halo in that tree is determined by summing the internal and orbital energies of progenitor halos. We show that, when calibrated, this model can accurately reproduce the mean of the concentration-mass relation measured in N-body simulations and reproduces more of the scatter in that relation than previous models. We further test this model by examining both the autocorrelation of scale radii across time and the correlations between halo concentration and spin, and comparing them to results measured from cosmological N-body simulations. In both cases, we find that our model closely matches the N-body results. Our model is implemented within the open-source GALACTICUS toolkit.

Keywords: Galaxy dark matter halos
Precision Weak Gravitational Lensing Using Velocity Fields: Fisher Matrix Analysis. Weak gravitational lensing measurements based on photometry are limited by shape noise: the variance in the unknown unlensed orientations of the source galaxies. If the source is a disk galaxy with a well-ordered velocity field, however, velocity field data can support simultaneous inference of the shear, inclination, and position angle, virtually eliminating shape noise. We use the Fisher information matrix formalism to forecast the precision of this method in the idealized case of a perfectly ordered velocity field defined on an infinitesimally thin disk. For nearly face-on targets, one shear component, γ×, can be constrained to $0.003\tfrac{90}{{I}_{0}}\tfrac{25}{{n}_{\mathrm{pix}}}$ , where I0 is the signal-to-noise ratio of the central intensity pixel and npix is the number of pixels across a diameter enclosing 80% of the light. This precision degrades with inclination angle by a factor of 3 by i = 50°. The uncertainty on the other shear component, γ+, is about 1.5 (7) times larger than the γ× uncertainty for targets at i = 10° (50°). For an arbitrary galaxy position angle on the sky, these forecasts apply not to γ+ and γ× as defined on the sky but to two eigenvectors in (γ+, γ×, μ) space, where μ is the magnification. We also forecast the potential of less expensive partial observations of the velocity field, such as slit spectroscopy. We conclude by outlining some ways in which real galaxies depart from our idealized model and thus create random or systematic uncertainties not captured here. In particular, our forecast γ× precision is currently limited only by the data quality rather than scatter in galaxy properties because the relevant type of scatter has yet to be measured.

Keywords: Weak gravitational lensing, Fisher's Information, Gravitational lensing, Galaxy kinematics, Gravitational lensing shear
Dependence of the IBEX Ribbon Geometry on Pitch-Angle Scattering outside the Heliopause. Interstellar Boundary Explorer (IBEX) observations of the "ribbon" of enhanced energetic neutral atom (ENA) fluxes show that it is a persistent feature that approximately forms a circle in the sky, likely formed from secondary ENAs whose source lies outside the heliopause. The IBEX ribbon's geometry (radius and center) depends on ENA energy and is believed to be influenced by the draping of the ISMF and the latitudinal structure of the SW. In this study, we demonstrate that the ribbon's geometry also depends on the pitch-angle scattering rate of ions outside the heliopause, which we simulate under strong and weak-scattering limits. The ribbon radius in the weak-scattering model is ∼4° larger than IBEX observations at most energies, and the strong-scattering model produces radii statistically consistent with IBEX at 1.1-2.7 keV. The simulated ribbon center is shifted between ∼2° and 5° along the B-V plane away from the IBEX center for the weak and strong limits, respectively, suggesting that the pristine ISMF far from the heliosphere is shifted ∼2°-5° away from our simulated ISMF toward the VLISM inflow direction. However, the magnitude needs to be decreased from ∼3 to 2 μG for the weak-scattering model to be consistent with the IBEX ribbon radius, which seems unlikely. We also find that the presence of interstellar He does not significantly affect the ribbon in the strong-scattering limit but yields weaker agreement with data in the weak limit. Our results slightly favor the strong-scattering limit for the ribbon's origin.

Keywords: Slow solar wind, Heliosphere, Interstellar magnetic fields, Pickup ions, Interstellar medium, Heliosheath
Spectral Shapes of the Lyα Emission from Galaxies. I. Blueshifted Emission and Intrinsic Invariance with Redshift. We demonstrate the redshift evolution of the spectral profile of H I Lyα emission from star-forming galaxies. In this first study we pay special attention to the contribution of blueshifted emission. At redshift z = 2.9-6.6, we compile spectra of a sample of 229 Lyα-selected galaxies identified with the Multi-Unit Spectroscopic Explorer at the Very Large Telescope, while at low z ( &lt; 0.44) we use a sample of 74 ultraviolet-selected galaxies observed with the Cosmic Origin Spectrograph on board the Hubble Space Telescope. At low z, where absorption from the intergalactic medium (IGM) is negligible, we show that the ratio of Lyα luminosity blueward and redward of line center (LB/R) increases rapidly with increasing equivalent width (WLyα). This correlation does not, however, emerge at z = 3-4, and we use bootstrap simulations to demonstrate that trends in LB/R should be suppressed by variations in IGM absorption. Our main result is that the observed blueshifted contribution evolves rapidly downward with increasing redshift: LB/R ≍ 30% at z ≍ 0, but dropping to 15% at z ≍ 3, and to below 3% by z ≍ 6. Applying further simulations of the IGM absorption to the unabsorbed COS spectrum, we demonstrate that this decrease in the blue-wing contribution can be entirely attributed to the thickening of intervening Lyα absorbing systems, with no need for additional H I opacity from local structure, companion galaxies, or cosmic infall. We discuss our results in light of the numerical radiative transfer simulations, the evolving total Lyα and ionizing output of galaxies, and the utility of resolved Lyα spectra in the reionization epoch. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Keywords: Starburst galaxies, H I line emission, Galaxy evolution, Radiative transfer, Intergalactic medium, Lyman-alpha galaxies, High-redshift galaxies
Analysis of the Unconcentrated Background of the EPIC pn Camera on Board XMM-Newton. Our understanding of the background of the EPIC/pn camera on board XMM-Newton is incomplete. This affects the study of extended sources and can influence the predictions of the expected background of future X-ray missions, such as the Advanced Telescope for High Energy Astrophysics (ATHENA). Here we provide new results based on the analysis of the largest data set ever used. We focus on the unconcentrated component of the EPIC/pn background, supposedly related to cosmic rays interacting with detector and telescope structures. We show that the so-called out field-of-view region of the pn detector is actually exposed to the sky. After carefully cleaning from the sky contamination, the unconcentrated background measured in the out field-of-view region does not show significant spatial variations, and its time behavior is anticorrelated with the solar cycle. We find a very tight linear correlation between unconcentrated backgrounds detected in the EPIC/pn and EPIC/MOS2 cameras. This relationship permits the correct evaluation of the pn unconcentrated background of each exposure on the basis of MOS2 data, avoiding the use of the contaminated out field-of-view region of the pn, as done in standard techniques. We find a tight linear correlation between the pn unconcentrated background and the proton flux in the 630-970 MeV energy band, as measured by the EPHIN instrument on board SOHO. Through this relationship, we quantify the contribution of cosmic-ray interaction to the pn unconcentrated background. This reveals a second source that contributes to the pn unconcentrated background for a significant fraction (30%-70%). This agent does not depend on the solar cycle or vary with time and is roughly isotropic. After having ruled out several candidates, we find that the hard X-ray photons of the cosmic X-ray background satisfy all known properties of the constant component. Our findings provide an important observational confirmation of simulation results on ATHENA and suggest that a high-energy particle monitor could contribute decisively to the reproducibility of the background for both experiments on ATHENA.

Keywords: X-ray astronomy, X-ray detectors, Astronomy data analysis, Diffuse x-ray background, Particle astrophysics
Three-dimensional Supernova Models Provide New Insights into the Origins of Stardust. We present the isotope yields of two post-explosion, three-dimensional 15 ${M}_{\odot }$ core-collapse supernova models, 15S and 15A, and compare them to the carbon, nitrogen, silicon, aluminum, sulfur, calcium, titanium, iron, and nickel isotopic compositions of SiC stardust. We find that these core-collapse supernova models predict similar carbon and nitrogen compositions to SiC X grains and grains with 12C/13C &lt; 20 and 14N/15N &lt; 60, which we will hereafter refer to as SiC 'D' grains. Material from the interior of a 15 ${M}_{\odot }$ explosion reaches high enough temperatures shortly after core collapse to produce the large enrichments of 13C and 15N necessary to replicate the compositions of SiC D grains. The innermost ejecta in a core-collapse supernova is operating in the neutrino-driven regime and undergoes fast proton capture after being heated by the supernova shockwave. Both 3D models predict 0.3 $\lt {}^{26}$ Al/27Al &lt; 1.5, comparable to the ratios seen in SiC X, C, and D grains. Models 15S and 15A, in general, predict very large anomalies in calcium isotopes but do compare qualitatively with the SiC X grain measurements that show 44Ca and 43Ca excesses. The titanium isotopic compositions of SiC X grains are well reproduced. The models predict 57Fe excesses and depletions that are observed in SiC X grains, and in addition predict accurately the 60Ni/58Ni, 61Ni/58Ni, and 62Ni/58Ni ratios in SiC X grains, as a result of fast neutron captures initiated by the propagation of the supernova shockwave. Finally, symmetry has a noticeable effect on the production of silicon, sulfur, and iron isotopes in the SN ejecta.

Keywords: Chondrites, Meteorite composition, Core-collapse supernovae, Asteroids, Small Solar System bodies, Type II supernovae, Theoretical models, Laboratory astrophysics, Stellar evolutionary models, Stellar winds, Meteorites, Stellar evolution
Modeling the Prompt Optical Emission of GRB 180325A: The Evolution of a Spike from the Optical to Gamma Rays. The transition from prompt to afterglow emission is one of the most exciting and least understood phases in gamma-ray bursts (GRBs). Correlations among optical, X-ray, and gamma-ray emission in GRBs have been explored, to attempt to answer whether the earliest optical emission comes from internal and/or external shocks. We present optical photometric observations of GRB 180325A collected with the TAROT and RATIR ground-based telescopes. These observations show two strong optical flashes with separate peaks at ∼50 and ∼120 s, followed by a temporally extended optical emission. We also present X-rays and gamma-ray observations of GRB 180325A, detected by the Burst Alert Telescope and X-ray Telescope, on the Neil Gehrels Swift observatory, which both observed a narrow flash at ∼80 s. We show that the prompt gamma-ray and X-ray early emission shares similar temporal and spectral features consistent with internal dissipation within the relativistic outflow (e.g., by internal shocks or magnetic reconnection), while the early optical flashes are likely generated by the reverse shock that decelerates the ejecta as it sweeps up the external medium.

Keywords: Optical observation, Gamma-ray bursts, Theoretical models, Ground telescopes
The Dynamics of a High Mach Number Quasi-perpendicular Shock: MMS Observations. Shock parameters at Earth's bow shock in rare instances can approach the Mach numbers predicted at supernova remnants. We present our analysis of a high Alfvén Mach number (MA = 27) shock utilizing multipoint measurements from the Magnetospheric Multiscale spacecraft during a crossing of Earth's quasi-perpendicular bow shock. We find that the shock dynamics are mostly driven by reflected ions, perturbations that they generate, and nonlinear amplification of the perturbations. Our analyses show that reflected ions create modest magnetic enhancements upstream of the shock, which evolve in a nonlinear manner as they traverse the shock foot. They can transform into proto-shocks that propagate at small angles to the magnetic field and toward the bow shock. The nonstationary bow shock shows signatures of both reformation and surface ripples. Our observations indicate that although shock reformation occurs, the main shock layer never disappears. These observations are at high plasma β, a parameter regime that has not been well explored by numerical models.

Keywords: Shocks, Solar wind, Space plasmas, Plasma physics
Laboratory Study of the Torus Instability Threshold in Solar-relevant, Line-tied Magnetic Flux Ropes. Coronal mass ejections (CMEs) occur when long-lived magnetic flux ropes (MFRs) anchored to the solar surface destabilize and erupt away from the Sun. This destabilization is often described in terms of an ideal magnetohydrodynamic instability called the torus instability. It occurs when the external magnetic field decreases sufficiently fast such that its decay index, ${n}_{}=-z\,\partial (\mathrm{ln}{B}_{})/\partial z$ , is larger than a critical value, $n\gt {n}_{\mathrm{cr}}^{}$ , where ${n}_{\mathrm{cr}}^{}=1.5$ for a full, large aspect ratio torus. However, when this is applied to solar MFRs, a range of conflicting values for ${n}_{\mathrm{cr}}^{}$ is found in the literature. To investigate this discrepancy, we have conducted laboratory experiments on arched, line-tied flux ropes and applied a theoretical model of the torus instability. Our model describes an MFR as a partial torus with foot points anchored in a conducting surface and numerically calculates various magnetic forces on it. This calculation yields better predictions of ${n}_{\mathrm{cr}}^{}$ that take into account the specific parameters of the MFR. We describe a systematic methodology to properly translate laboratory results to their solar counterparts, provided that the MFRs have a sufficiently small edge safety factor or, equivalently, a large enough twist. After this translation, our model predicts that ${n}_{\mathrm{cr}}^{}$ in solar conditions falls near ${n}_{\mathrm{cr}}^{\mathrm{solar}}\sim 0.9$ and within a larger range of ${n}_{\mathrm{cr}}^{\mathrm{solar}}\sim (0.7,1.2)$ , depending on the parameters. The methodology of translating laboratory MFRs to their solar counterparts enables quantitative investigations of CME initiation through laboratory experiments. These experiments allow for new physics insights that are required for better predictions of space weather events but are difficult to obtain otherwise.

Keywords: Solar flares, Space weather, Laboratory astrophysics, Solar magnetic fields, Solar coronal mass ejections
Dynamical Masses and Stellar Evolutionary Model Predictions of M Stars. In this era of Gaia and ALMA, dynamical stellar mass measurements, derived from spatially and spectrally resolved observations of the Keplerian rotation of circumstellar disks, provide benchmarks that are independent of observations of stellar characteristics and their uncertainties. These benchmarks can then be used to validate and improve stellar evolutionary models, the latter of which can lead to both imprecise and inaccurate mass predictions for pre-main-sequence, low-mass (≤0.5 M⊙) stars. We present the dynamical stellar masses derived from disks around three M stars (FP Tau, J0432+1827, and J1100-7619) using ALMA observations of 12CO (J = 2-1) and 13CO (J = 2-1) emission. These are the first dynamical stellar mass measurements for J0432+1827 and J1100-7619 (0.192 ± 0.005 M⊙ and 0.461 ± 0.057 M⊙, respectively) and the most precise measurement for FP Tau (0.395 ± 0.012 M⊙). Fiducial stellar evolutionary model tracks, which do not include any treatment of magnetic activity, agree with the dynamical stellar mass measurement of J0432+1827 but underpredict the mass by ∼60% for FP Tau and by ∼80% for J1100-7619. Possible explanations for the underpredictions include inaccurate assumptions of stellar effective temperature, undetected binarity for J1100-7619, and that fiducial stellar evolutionary models are not complex enough to represent these stars. In the former case, the stellar effective temperatures would need to be increased by amounts ranging from ∼40 to ∼340 K to reconcile the fiducial stellar evolutionary model predictions with the dynamically measured masses. In the latter case, we show that the dynamical masses can be reproduced using results from stellar evolutionary models with starspots, which incorporate fractional starspot coverage to represent the manifestation of magnetic activity. Folding in low-mass M stars from the literature and assuming that the stellar effective temperatures are imprecise but accurate, we find tentative evidence of a relationship between fractional starspot coverage and observed effective temperature for these young, cool stars.

Keywords: Stellar evolutionary models, Protoplanetary disks, CO line emission, Stellar masses
Universal Conditional Distribution Function of [O II] Luminosity of Galaxies, and Prediction for the [O II] Luminosity Function at Redshift z &lt; 3. The star-forming emission line galaxies (ELGs) with a strong [O II] doublet are one of the main spectroscopic targets for the ongoing and upcoming fourth-generation galaxy redshift surveys. In this work, we measure the [O II] luminosity L[O II] and the absolute magnitude in the near-ultraviolet (NUV) band MNUV for a large sample of galaxies in the redshift range 0.6 ≤ z &lt; 1.45 from the Public Data Release 2 (PDR-2) of the VIMOS Public Extragalactic Redshift Survey (VIPERS). We aim to construct the intrinsic relationship between L[O II] and MNUV through Bayesian analysis. In particular, we develop two different methods to properly correct for the incompleteness effect and observational errors in the [O II] emission line measurement. Our results indicate that the conditional distribution of L[O II] at a given MNUV can be well described by a universal probability distribution function (PDF), which is independent of MNUV and redshift. Convolving the L[O II] conditional PDF with the NUV luminosity function (LF) available in the literature, we make a prediction for [O II] LFs at z &lt; 3. The predicted [O II] LFs are in good agreement with the observational results from the literature. Finally, we utilize the predicted [O II] LFs to estimate the number counts of [O II] emitters for the Subaru Prime Focus Spectrograph survey. This universal conditional PDF of L[O II] provides a novel way to optimize the source targeting strategy for [O II] emitters in future galaxy redshift surveys, and to model [O II] emitters in theories of galaxy formation.

Keywords: Luminosity function, Redshift surveys, Emission line galaxies, Dark energy