Sazuna/UAT_keywords huggingface dataset:
Measurement of Low-energy Cosmic-Ray Electron and Positron Spectra at 1 au with the AESOP-Lite Spectrometer. We report on a new measurement of the cosmic ray (CR) electron and positron spectra in the energy range of 20 MeV-1 GeV. The data were taken during the first flight of the balloon-borne spectrometer Anti Electron Sub Orbital Payload (AESOP-Lite), which was flown from Esrange, Sweden, to Ellesmere Island, Canada, in 2018 May. The instrument accumulated over 130 hr of exposure at an average altitude of 3 g cm-2 of residual atmosphere. The experiment uses a gas Cerenkov detector and a magnetic spectrometer, consisting of a permanent dipole magnet and silicon strip detectors (SSDs), to identify particle type and measure the rigidity. Electrons and positrons were detected against a background of protons and atmospheric secondary particles. The primary CR spectra of electrons and positrons, as well as the re-entrant albedo fluxes, were extracted between 20 MeV and 1 GeV during a positive solar magnetic polarity epoch. The positron fraction below 100 MeV appears flat, suggesting diffusion-dominated solar modulation at low rigidity. The all-electron spectrum is presented and compared with models from a heliospheric numerical transport code.

Keywords: Heliosphere, Cosmic ray detectors, Solar wind, High altitude balloons, Cosmic rays
Further Evidence for Significant Luminosity Evolution in Supernova Cosmology. Supernova (SN) cosmology is based on the assumption that the corrected luminosity of SNe Ia would not evolve with redshift. Recently, our age dating of stellar populations in early-type host galaxies (ETGs) from high-quality spectra has shown that this key assumption is most likely in error. It has been argued though that the age-Hubble residual (HR) correlation from ETGs is not confirmed from two independent age data sets measured from multiband optical photometry of host galaxies of all morphological types. Here we show, however, that one of the data sets is based on highly uncertain and inappropriate luminosity-weighted ages derived, in many cases, under serious template mismatch. The other data set employs more reliable mass-weighted ages, but the statistical analysis involved is affected by regression dilution bias, severely underestimating both the slope and significance of the age-HR correlation. Remarkably, when we apply regression analysis with a standard posterior sampling method to this data set comprising a large sample (N = 102) of host galaxies, very significant (&gt;99.99%) correlation is obtained between the global population age and HR with the slope (-0.047 ± 0.011 mag Gyr-1) highly consistent with our previous spectroscopic result from ETGs. For the local age of the environment around the site of SNe, a similarly significant (&gt;99.96%) correlation is obtained with a steeper slope (-0.057 ± 0.016 mag Gyr-1). Therefore, the SN luminosity evolution is strongly supported by the age dating based on multiband optical photometry and can be a serious systematic bias in SN cosmology.

Keywords: Observational cosmology, Type Ia supernovae, Dark energy
Global Energetics of Solar Flares. XII. Energy Scaling Laws. In this study we test 18 versions of five fundamental energy scaling laws that operate in large solar flares. We express scaling laws in terms of the magnetic potential field energy Ep, the mean potential field strength Bp, the free energy Efree, the dissipated magnetic flare energy Ediss, the magnetic length scale L, the thermal length scale Lth, the mean helically twisted flux tube radius R, the sunspot radius r, the emission-measure-weighted flare temperature Te, the electron density ne, and the total emission measure EM, measured from a data set of 173 GOES M- and X-class flare events. The five categories of physical scaling laws include (i) a scaling law of the potential field energy, (ii) a scaling law for helical twisting, (iii) a scaling law for Petschek-type magnetic reconnection, (iv) the Rosner-Tucker-Vaiana scaling law, and (v) the Shibata-Yokoyama scaling law. We test the self-consistency of these theoretical scaling laws with observed parameters by requiring two criteria: a cross-correlation coefficient of CCC &gt; 0.5 between the theoretically predicted scaling laws and observed values, and a linear regression fit with a slope of α ≈ 1 within one standard deviation σ. These two criteria enable us (i) to corroborate some existing (or modified) scaling laws, (ii) to reject other scaling laws that are not consistent with the observations, (iii) to probe the dimensionality of flare geometries, and (iv) to predict various energy parameters based on tested scaling laws.

Keywords: Solar flares
Cosmological 3D H I Gas Map with HETDEX Lyα Emitters and eBOSS QSOs at z = 2: IGM-Galaxy/QSO Connection and a ∼40 Mpc Scale Giant H II Bubble Candidate. We present cosmological (30-400 Mpc) distributions of neutral hydrogen (H I) in the intergalactic medium (IGM) traced by Lyα emitters (LAEs) and QSOs at z = 2.1-2.5, selected with the data of the ongoing Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) and the eBOSS survey. Motivated by a previous study of Mukae et al., we investigate spatial correlations of LAEs and QSOs with H I tomography maps reconstructed from H I Lyα forest absorption in the spectra of background galaxies and QSOs obtained by the CLAMATO survey and this study, respectively. In the cosmological volume far from QSOs, we find that LAEs reside in regions of strong H I absorption, i.e., H I rich, which is consistent with results of previous galaxy-background QSO pair studies. Moreover, there is an anisotropy in the H I distribution plot of transverse and line-of-sight distances; on average the H I absorption peak is blueshifted by ∼200 km s-1 from the LAE Lyα redshift, reproducing the known average velocity offset between the Lyα emission redshift and the galaxy systemic redshift. We have identified a ∼40 Mpc scale volume of H I underdensity that is a candidate for a giant H II bubble, where six QSOs and an LAE overdensity exist at $\left\langle z\right\rangle =2.16$ . The coincidence of the QSO and LAE overdensities with the H I underdensity indicates that the ionizing photon radiation of the QSOs has created a highly ionized volume of multiple proximity zones in a matter overdensity. Our results suggest an evolutionary picture where H I gas in an overdensity of galaxies becomes highly photoionized when QSOs emerge in the galaxies.

Keywords: Large-scale structure of the universe, Galaxy formation, Intergalactic medium
Chasing Accreted Structures within Gaia DR2 Using Deep Learning. In previous work, we developed a deep neural network classifier that only relies on phase-space information to obtain a catalog of accreted stars based on the second data release of Gaia (DR2). In this paper, we apply two clustering algorithms to identify velocity substructure within this catalog. We focus on the subset of stars with line-of-sight velocity measurements that fall in the range of Galactocentric radii $r\in [6.5,9.5]\,{\rm{kpc}}$ and vertical distances $| z| \lt 3\,{\rm{kpc}}$ . Known structures such as Gaia Enceladus and the Helmi stream are identified. The largest previously unknown structure, Nyx, is a vast stream consisting of at least 200 stars in the region of interest. This study displays the power of the machine-learning approach by not only successfully identifying known features but also discovering new kinematic structures that may shed light on the merger history of the Milky Way.

Keywords: Neural networks, Galaxy dynamics, Milky Way dynamics, Astrometry, Star clusters
Constraints on Circumgalactic Media from Sunyaev-Zel'dovich Effects and X-Ray Data. We use observational measurements of thermal and kinetic Sunyaev-Zel'dovich effects, as well as soft X-ray emission associated with galaxy groups, to constrain the gas density and temperature in the circumgalactic medium for dark matter halos with masses above 1012.5 M⊙. A number of generic models are used together with a Bayesian scheme to make model inferences. We find that gas with a single temperature component cannot provide a consistent model to match the observational data. A simple two-phase model assuming a hot component and an ionized warm component can accommodate all three observations. The total amount of the gas in individual halos is inferred to be comparable to the universal baryon fraction corresponding to the halo mass. The inferred temperature of the hot component is comparable to the halo virial temperature. The fraction of the hot component increases from (15-40)% for 1012.5M⊙ halos to (40-60)% for 1014.5M⊙ halos, where the ranges reflect uncertainties in the assumed gas density profile. Our results suggest that a significant fraction of the halo gas is in a nonthermalized component with the temperature much lower than the virial temperature.

Keywords: Galaxy formation, Bayesian statistics, Sunyaev-Zeldovich effect, Galaxy evolution, Circumgalactic medium
Application and Interpretation of Deep Learning for Identifying Pre-emergence Magnetic Field Patterns. Magnetic flux generated within the solar interior emerges to the surface, forming active regions (ARs) and sunspots. Flux emergence may trigger explosive events—such as flares and coronal mass ejections, and therefore understanding emergence is useful for space-weather forecasting. Evidence of any pre-emergence signatures will also shed light on subsurface processes responsible for emergence. In this paper, we present a first analysis of EARs from the Solar Dynamics Observatory/Helioseismic Emerging Active Regions dataset using deep convolutional neural networks (CNN) to characterize pre-emergence surface magnetic field properties. The trained CNN classifies between pre-emergence line-of-sight magnetograms and a control set of nonemergence magnetograms with a true skill statistic (TSS) score of approximately 85% about 3 hr prior to emergence and approximately 40% about 24 hr prior to emergence. Our results are better than a baseline classification TSS obtained using discriminant analysis (DA) of only the unsigned magnetic flux, although a multivariable DA produces TSS values consistent with the CNN. We develop a network-pruning algorithm to interpret the trained CNN and show that the CNN incorporates filters that respond positively as well as negatively to the unsigned magnetic flux of the magnetograms. Using synthetic magnetograms, we demonstrate that the CNN output is sensitive to the length scale of the magnetic regions, with small-scale and intense fields producing maximum CNN output and possibly a characteristic pre-emergence pattern. Given increasing popularity of deep learning, the techniques developed here to interpret the trained CNN—using network pruning and synthetic data—are relevant for future applications in solar and astrophysical data analysis.

Keywords: Solar active region magnetic fields, Convolutional neural networks, Solar magnetic flux emergence, Astronomy data analysis
The Depth and the Vertical Extent of the Energy Deposition Layer in a Medium-class Solar Flare. We analyze here variations of the position and the vertical extent of the energy deposition layer (EDL) in the C1.6 GOES-class solar flare observed at 10:20 UT on 2012 September 10. The variations of the EDL are contrasted with the variations of the spectra and emission intensities recorded in the Hα line with very high time resolution using the MSDP spectrograph at Białków Observatory. The flare radiated hard X-rays (HXR) detectable up to a energy of 70 keV. A numerical model of the flare used in the analysis assumes that the nonthermal electrons (NTEs) carried the external energy to the flare. The energy flux of the NTEs was derived from a nonthermal component seen in RHESSI spectra. The main geometrical parameters of the flare were derived using restored RHESSI imaging data. We found that the variations of the X-ray fluxes recorded in various energy bands and the variations of the Hα intensities were well-correlated in time during the pre-impulsive and impulsive phases of the flare, and they agreed with the variations of the calculated position and vertical extent of the EDL. The variations of the emission noticed in various parts of the Hα line profile were caused by individual episodes of energy deposition by the beams of NTEs of various energy spectra on various depths in the chromospheric plasma. These results supplement our previous findings for the solar flare on 2013 June 21, having nearly the same GOES class of C1.1 but HXR emission below 34 keV only.

Keywords: The Sun
Reconstructing the EUV Spectrum of Star-forming Regions from Millimeter Recombination Lines of H I, He I, and He II. The extreme ultraviolet (EUV) spectra of distant star-forming regions cannot be probed directly using either ground- or space-based telescopes due to the high cross section for interaction of EUV photons with the interstellar medium. This makes EUV spectra poorly constrained. The millimeter/submillimeter recombination lines of H and He, which can be observed from the ground, can serve as a reliable probe of the EUV. Here we present a study based on ALMA observations of three Galactic ultracompact H II regions and the starburst region Sgr B2(M), in which we reconstruct the key parameters of the EUV spectra using millimeter recombination lines of H I, He I, and He II. We find that in all cases the EUV spectra between 13.6 and 54.4 eV have similar frequency dependence: ${L}_{\nu }\propto {\nu }^{-4.5\pm 0.4}.$ We compare the inferred values of the EUV spectral slopes with the values expected for a purely single stellar evolution model (Starburst99) and the Binary Population and Spectral Synthesis code (BPASS). We find that the observed spectral slope differs from the model predictions. This may imply that the fraction of interacting binaries in H II regions is substantially lower than assumed in BPASS. The technique demonstrated here allows one to deduce the EUV spectra of star-forming regions, providing critical insight into photon production rates at $\lambda \leqslant 912\mathring{{\rm{A}}}$ , and can serve as calibration to starburst synthesis models, improving our understanding of star formation in the distant universe and the properties of ionizing flux during reionization.

Keywords: Compact H II region, Radiative recombination, Star forming regions, Star formation, Astrophysicists, Interstellar medium
SOFIA/FIFI-LS Full-disk [C II] Mapping and CO-dark Molecular Gas across the Nearby Spiral Galaxy NGC 6946. We present SOFIA/FIFI-LS observations of the [C II] 158 μm cooling line across the nearby spiral galaxy NGC 6946. We combine these with UV, IR, CO, and H I data to compare [C II] emission to dust properties, star formation rate (SFR), H2, and H I at 560 pc scales via stacking by environment (spiral arms, interarm, and center), radial profiles, and individual, beam-sized measurements. We attribute 73% of the [C II] luminosity to arms, and 19% and 8% to the center and interarm region, respectively. [C II]/TIR, [C II]/CO, and [C II]/PAH radial profiles are largely constant, but rise at large radii (≳ 8 kpc) and drop in the center ("[C II] deficit"). This increase at large radii and the observed decline with the 70 μm/100 μm dust color are likely driven by radiation field hardness. We find a near proportional [C II]-SFR scaling relation for beam-sized regions, though the exact scaling depends on methodology. [C II] also becomes increasingly luminous relative to CO at low SFR (interarm or large radii), likely indicating more efficient photodissociation of CO and emphasizing the importance of [C II] as an H2 and SFR tracer in such regimes. Finally, based on the observed [C II] and CO radial profiles and different models, we find αCO to increase with radius, in line with the observed metallicity gradient. The low αCO (galaxy average ≲ 2 M⊙ pc-2 (K km s-1)-1) and low [C II]/CO ratios (∼400 on average) imply little CO-dark gas across NGC 6946, in contrast to estimates in the Milky Way.

Keywords: Interstellar dust, Interstellar line emission, Spiral galaxies, Galaxy structure, Interstellar medium
Double-peaked Balmer Emission Indicating Prompt Accretion Disk Formation in an X-Ray Faint Tidal Disruption Event. We present the multiwavelength analysis of the tidal disruption event (TDE) AT 2018hyz (ASASSN-18zj). From follow-up optical spectroscopy, we detect the first unambiguous case of resolved double-peaked Balmer emission in a TDE. The distinct line profile can be well-modeled by a low eccentricity (e ≈ 0.1) accretion disk extending out to ∼100 Rp and a Gaussian component originating from non-disk clouds, though a bipolar outflow origin cannot be completely ruled out. Our analysis indicates that in AT 2018hyz, disk formation took place promptly after the most-bound debris returned to pericenter, which we estimate to be roughly tens of days before the first detection. Redistribution of angular momentum and mass transport, possibly through shocks, must occur on the observed timescale of about a month to create the large Hα-emitting disk that comprises ≲5% of the initial stellar mass. With these new insights from AT 2018hyz, we infer that circularization is efficient in at least some, if not all optically bright, X-ray faint TDEs. In these efficiently circularized TDEs, the detection of double-peaked emission depends on the disk inclination angle and the relative strength of the disk contribution to the non-disk component, possibly explaining the diversity seen in the current sample.

Keywords: Black hole physics, Galaxy accretion disks, High energy astrophysics
First Results from SMAUG: Uncovering the Origin of the Multiphase Circumgalactic Medium with a Comparative Analysis of Idealized and Cosmological Simulations. We examine the properties of the circumgalactic medium (CGM) at low redshift in a range of simulated Milky Way mass halos. The sample is comprised of seven idealized simulations, an adaptive mesh refinement cosmological zoom-in simulation, and two groups of 50 halos with star-forming or quiescent galaxies taken from the TNG100 simulation. The simulations have very different setups, resolution, and feedback models, but are analyzed in a uniform manner. By comparing median radial profiles and mass distributions of CGM properties, we isolate key similarities and differences. In doing so, we advance the efforts of the Simulating Multiscale Astrophysics to Understand Galaxies project that aims to understand the inherently multiscale galaxy formation process. In the cosmological simulations, the CGM exhibits nearly flat temperature distributions, and broad pressure and radial velocity distributions. In the idealized simulations, similar distributions are found in the inner CGM ( $\lesssim 0.5\,{r}_{200{\rm{c}}}$ ) when strong galactic feedback models are employed, but the outer CGM ( $\gtrsim 0.5\,{r}_{200{\rm{c}}}$ ) has a much less prominent cold phase, and narrower pressure and velocity distributions even in models with strong feedback. This comparative analysis demonstrates the dominant role feedback plays in shaping the inner CGM and the increased importance of cosmological effects, such as nonspherical accretion and satellite galaxies, in the outer CGM. Furthermore, our findings highlight that, while cosmological simulations are required to capture the multiphase structure of the CGM at large radii, idealized simulations provide a robust framework to study how galactic feedback interacts with the inner CGM, and thereby provide a reliable avenue to constrain feedback prescriptions.

Keywords: Galactic winds, Galaxy physics, Galaxy evolution, Circumgalactic medium, Galaxies
A Multilevel Empirical Bayesian Approach to Estimating the Unknown Redshifts of 1366 BATSE Catalog Long-duration Gamma-Ray Bursts. We present a catalog of probabilistic redshift estimates for 1366 individual Long-duration Gamma-ray Bursts (LGRBs) detected by the Burst And Transient Source Experiment (BATSE). This result is based on a careful selection and modeling of the population distribution of 1366 BATSE LGRBs in the five-dimensional space of redshift and the four intrinsic prompt gamma-ray emission properties: the isotropic 1024 ms peak luminosity ( ${\text{}}{L}_{\mathrm{iso}}$ ), the total isotropic emission ( ${\text{}}{E}_{\mathrm{iso}}$ ), the spectral peak energy ( ${\text{}}{E}_{\mathrm{pz}}$ ), as well as the intrinsic duration ( ${\text{}}{T}_{90{\rm{z}}}$ ), while carefully taking into account the effects of sample incompleteness and the LGRB-detection mechanism of BATSE. Two fundamental plausible assumptions underlie our purely probabilistic approach: (1) LGRBs trace, either exactly or closely, the cosmic star formation rate, with a possibility of the excess rates of LGRBs in the nearby universe, and (2) the joint four-dimensional distribution of the aforementioned prompt gamma-ray emission properties is well described by a multivariate log-normal distribution. Our modeling approach enables us to constrain the redshifts of individual BATSE LGRBs to within 0.36 and 0.96 average uncertainty ranges at 50% and 90% confidence levels, respectively. Our redshift predictions are completely at odds with the previous redshift estimates of BATSE LGRBs that were computed via the proposed phenomenological high-energy relations, specifically, the apparently strong correlation of LGRBs' peak luminosity with the spectral peak energy, lightcurve variability, and spectral lag. The observed discrepancies between our predictions and the previous works can be explained by the strong influence of detector threshold and sample incompleteness in shaping these phenomenologically proposed high-energy correlations in the literature. Finally, we also discuss the potential effects of an excess cosmic rate of LGRBs at low redshifts and the possibility of a luminosity evolution of LGRBs on our results.

Keywords: Luminosity function, Gamma-ray bursts, Astronomy data modeling, Bayesian statistics, Astronomical simulations, Gamma-ray detectors, Astronomy data analysis, Markov chain Monte Carlo, Hierarchical models, Catalogs