Sazuna/UAT_keywords huggingface dataset:
Astrophysical Limits on Very Light Axion-like Particles from Chandra Grating Spectroscopy of NGC 1275. Axions/axion-like particles (ALPs) are a well-motivated extension of the Standard Model and are generic within String Theory. The X-ray transparency of the intracluster medium (ICM) in galaxy clusters is a powerful probe of light ALPs (with mass $\lt {10}^{-11}\mathrm{eV}$ ); as X-ray photons from an embedded or background source propagate through the magnetized ICM, they may undergo energy-dependent quantum mechanical conversion into ALPs (and vice versa), imprinting distortions on the X-ray spectrum. We present Chandra data for the active galactic nucleus NGC 1275 at the center of the Perseus cluster. Employing a 490 ks High Energy Transmission Gratings exposure, we obtain a high-quality 1-9 keV spectrum free from photon pileup and ICM contamination. Apart from iron-band features, the spectrum is described by a power-law continuum, with any spectral distortions at the &lt;3% level. We compute photon survival probabilities as a function of ALP mass ma and ALP-photon coupling constant ${g}_{a\gamma }$ for an ensemble of ICM magnetic field models, and then use the NGC 1275 spectrum to constrain the $({m}_{a},{g}_{a\gamma })$ -plane. Marginalizing over magnetic field realizations, the 99.7% credible region limits the ALP-photon coupling to ${g}_{a\gamma }\lt 6-8\times {10}^{-13}\,{\mathrm{GeV}}^{-1}$ (depending upon magnetic field model) for masses ${m}_{a}\lt 1\times {10}^{-12}\mathrm{eV}$ . These are the most stringent limit to date on ${g}_{a\gamma }$ for these light ALPs, and have already reached the sensitivity limits of next-generation helioscopes and light-shining-through-wall experiments. We highlight the potential of these studies with the next-generation X-ray observatories Athena and Lynx, but note the critical importance of advances in relative calibration of these future X-ray spectrometers.

Keywords: X-ray active galactic nuclei, Intracluster medium, Dark matter, Particle astrophysics, Extragalactic magnetic fields
Initial Evaluation of SNEMO2 and SNEMO7 Standardization Derived from Current Light Curves of Type Ia Supernovae. To determine if the SuperNova Empirical Model (SNEMO) can improve Type Ia supernova (SN Ia) standardization of several currently available photometric data sets, we perform an initial test, comparing results with the much-used SALT2 approach. We fit the SNEMO light-curve parameters and pass them to the Bayesian hierarchical model UNITY1.2 to estimate the Tripp-like standardization coefficients, including a host-mass term as a proxy for redshift-dependent astrophysical systematics. We find that, among the existing large data sets, only the Carnegie Supernova Project data set consistently provides the signal-to-noise and time sampling necessary to constrain the additional five parameters that SNEMO7 incorporates beyond SALT2. This is an important consideration for future SN Ia surveys like LSST and WFIRST. Although the SNEMO7 parameters are poorly constrained by most of the other available data sets of light curves, we find that the SNEMO2 parameters are just as well constrained as the SALT2 parameters. In addition, SNEMO2 and SALT2 have comparable unexplained intrinsic scatter when fitting the same data. When looking at the total scatter, SNEMO7 reduces the Hubble-Lemaître diagram rms from 0.148 to 0.141 mag. It is not then the SNEMO methodology, but the interplay of data quality and the increased number of degrees of freedom that is behind these reduced constraints. With this in mind, we recommend further investigation into the data required to use SNEMO7 and the possibility of fitting the poorer photometry data with intermediate SNEMO-like models with three to six components.

Keywords: Observational cosmology, Type Ia supernovae, Distance indicators
Mechanisms for Limiting the Depth of Zonal Winds in the Gas Giant Planets. Gravity signatures observed by the Juno and Cassini missions that are associated with the strong zonal winds in Jupiter's and Saturn's outer envelopes suggest that these flows extend for several thousand kilometers into the interior. It has been noted that the winds seem to abate at a depth where electrical conductivity becomes significant, suggesting that electromagnetic effects play a key role for confining the winds to the outer weakly conducting region. Here, we explore the possible mechanisms for braking the zonal flow at depth in two model setups with depth-dependent conductivity and forced jet flow, I.e., in axisymmetric shell models and in more simple linearized box models that allow the exploration of a wide parameter range. Braking of the winds directly by Lorentz forces does not reduce their speed in the conducting region enough to be compatible with the inferred secular variation of Jupiter's field. Stable stratification above the depth where conductivity becomes significant can solve the problem. Electromagnetic forces drive a weak meridional circulation that perturbs the density distribution in the stable region such that the wind speed decreases strongly with depth, due to a thermal wind balance. For this mechanism to be effective, the stable layer must extend upward into a region of low conductivity. Applying the results of the linearized calculations to Jupiter suggests that the dissipation associated with the zonal winds can be limited to a fraction of the internal heat flow and that the jets may drop off over a depth range of 150-300 km.

Keywords: Planetary structure
Deep XMM-Newton Observations Reveal the Origin of Recombining Plasma in the Supernova Remnant W44. Recent X-ray studies have revealed overionized recombining plasmas in a dozen mixed-morphology (MM) supernova remnants (SNRs). However, the physical process of the overionization has not yet been fully understood. Here we report on spatially resolved spectroscopy of X-ray emission from W44, one of the overionized MM SNRs, using XMM-Newton data from deep observations, with the aim of clarifying the physical origin of the overionization. We find that combination of low electron temperature and low recombination timescale is achieved in the region interacting with dense molecular clouds. Moreover, a clear anticorrelation between the electron temperature and the recombination timescale is obtained from each of the regions with and without the molecular clouds. The results are well explained if the plasma was overionized by rapid cooling through thermal conduction with the dense clouds hit by the blast wave of W44. Given that a few other overionized SNRs show evidence for adiabatic expansion as the major driver of the rapid cooling, our new result indicates that both processes can contribute to overionization in SNRs, with the dominant channel depending on the evolutionary stage.

Keywords: Supernova remnants, X-ray astronomy, Plasma astrophysics, Molecular clouds
xGASS: H I Fueling of Star Formation in Disk-dominated Galaxies. We introduce a method to estimate the H I mass within the optical radius of disk galaxies from integrated H I spectra, with an uncertainty of 0.09 dex. We use these estimates to study how inner H I fuels star formation in late-type disk galaxies. We find that star formation rate (SFR) at a given stellar mass (M*) is well correlated with the inner H I surface density ( ${{\rm{\Sigma }}}_{{\rm{H}}{\rm{I}},\mathrm{in}}$ ) and inner H I mass-to-stellar mass ratio. For the massive (M* &gt; 1010M⊙) disk galaxies, higher SFR at a given stellar mass is also related to higher efficiency of converting inner H I to molecular gas, but no such correlation is found for the total H I mass. The highest ${{\rm{\Sigma }}}_{{\rm{H}}{\rm{I}},\mathrm{in}}$ and the fastest depletion of the total neutral gas within the optical disks are found in the most compact and star-forming disk galaxies at a given stellar mass. These results highlight the important role of inner H I as an intermediate step of fueling star formation in disk galaxies.

Keywords: Late-type galaxies, Galaxy evolution, Interstellar atomic gas
Application of Convolutional Neural Networks to Identify Stellar Feedback Bubbles in CO Emission. We adopt the deep learning method called the Convolutional Approach to Shell Identification (casi) and extend it to 3D (casi-3d) to identify signatures of stellar feedback in molecular line spectra. We use magnetohydrodynamics simulations modeling the impact of stellar winds in a turbulent molecular cloud to generate synthetic 13CO (J = 1 - 0) observations. We train two casi-3d models: ME1 predicts only the position of feedback, while MF predicts the fraction of the mass coming from feedback in each voxel. We adopt 75% of the synthetic observations as the training set and assess the accuracy of the two models with the remaining data. Both models identify bubbles in simulated data within 5% error. We use bubbles previously visually identified in Taurus in 13CO to validate the models and show that both perform well on the highest confidence bubbles. Models ME1 and MF predict total feedback gas mass of 2894 M⊙ and 302 M⊙, respectively. After correcting for missing energy due to the limited velocity range, model ME1 predicts feedback kinetic energies of 4.0 × 1046 erg and 1.5 × 1047 erg with and without subtracting the cloud velocity gradient. Model MF predicts feedback kinetic energies of 9.6 × 1045 erg and 2.8 × 1046 erg with and without subtracting the cloud velocity gradient. Model ME1 predicts bubble locations and properties consistent with previous visual identifications. However, model MF demonstrates that feedback properties computed using visual identifications significantly overestimate feedback impact, due to line-of-sight confusion and contamination from background and foreground gas.

Keywords: Stellar feedback, Stellar wind bubbles, Neural networks, Convolutional neural networks, Astronomy data analysis, Molecular clouds, Astrostatistics, Interstellar clouds, Star formation, Interstellar medium, Interdisciplinary astronomy, Astronomical methods
Searching for z &gt; 6.5 Analogs Near the Peak of Cosmic Star Formation. Strong [O III]λλ4959,5007 + Hβ emission appears to be typical in star-forming galaxies at z &gt; 6.5. As likely contributors to cosmic reionization, these galaxies and the physical conditions within them are of great interest. At z &gt; 6.5, where Lyα is greatly attenuated by the intergalactic medium, rest-UV metal emission lines provide an alternative measure of redshift and constraints on the physical properties of star-forming regions and massive stars. We present the first statistical sample of rest-UV line measurements in z ∼ 2 galaxies selected as analogs of those in the reionization era based on [O III]λλ4959,5007 equivalent width (EW) or rest-frame U - B color. Our sample is drawn from the 3D-HST Survey and spans the redshift range $1.36\leqslant z\leqslant 2.49$ . We find that the median Lyα and C III]λλ1907,1909 EWs of our sample are significantly greater than those of z ∼ 2 UV-continuum-selected star-forming galaxies. Measurements from both individual and composite spectra indicate a monotonic, positive correlation between C III] and [O III], while a lack of trend is observed between Lyα and [O III] at EW[O III] ≲ 1000 Å. At higher EW[O III], extreme Lyα emission starts to emerge. Using stacked spectra, we find that Lyα and C III] are significantly enhanced in galaxies with lower metallicity. Two objects in our sample appear comparable to z &gt; 6.5 galaxies with exceptionally strong rest-UV metal line emission. These objects have significant C IVλλ1548,1550, He IIλ1640, and O III]λλ1661,1665 emission in addition to intense Lyα or C III]. Detailed characterization of these lower-redshift analogs provides unique insights into the physical conditions in z &gt; 6.5 star-forming regions, motivating future observations of reionization-era analogs at lower redshifts.

Keywords: High-redshift galaxies, H II regions, Emission line galaxies
Are Faint Supernovae Responsible for Carbon-enhanced Metal-poor Stars?. Mixing and fallback models in faint supernova models are supposed to reproduce the abundance patterns of observed carbon-enhanced metal-poor (CEMP) stars in the Galactic halo. A fine-tuning of the model parameters for individual stars is required to reproduce the observed ratios of carbon to iron. We focus on extremely metal-poor stars formed out of the ejecta from the mixing and fallback models using a chemical evolution model. Our chemical evolution models take into account the contribution of individual stars to chemical enrichment in host halos, together with their evolution in the context of the hierarchical clustering. Parameterized models of mixing and fallback models for Population III faint supernovae are implemented in the chemical evolution models with merger trees to reproduce the observed CEMP stars. A variety of choices for model parameters on star formation and metal pollution by faint supernovae are unable to reproduce the observed stars with $[\mathrm{Fe}/{\rm{H}}]\lesssim -4$ and $[{\rm{C}}/{\rm{H}}]\gtrsim -2$ , which are the majority of CEMP stars among the lowest-metallicity stars. Only possible solution is to form stars from small ejecta mass, which produces an inconsistent metallicity distribution function. We conclude that not all the CEMP stars are explicable by the mixing and fallback models. We also tested the contribution of binary mass transfers from AGB stars that are also supposed to reproduce the abundances of known CEMP stars. This model reasonably reproduces the distribution of carbon and iron abundances simultaneously only if we assume that long-period binaries are favored at $[\mathrm{Fe}/{\rm{H}}]\lesssim -3.5$ .

Keywords: Population III stars, Galaxy chemical evolution, Chemical enrichment, Halo stars, Population II stars
The Role of Pressure Anisotropy in Cosmic-Ray Hydrodynamics. The mean free path of cosmic rays in diffuse interstellar and intracluster gas is determined primarily by pitch angle scattering from hydromagnetic waves with wavelength of order the cosmic-ray gyroradius. In the theory of cosmic-ray self confinement, the waves are generated by instabilities driven by the cosmic rays themselves. The dominant instability is due to bulk motion, or streaming, of the cosmic rays, parallel to the background magnetic field ${\boldsymbol{B}}$ , and transfers cosmic-ray momentum and energy to the thermal gas as well as confining the cosmic rays. Classical arguments and recent numerical simulations show that self confinement due to the streaming instability breaks down unless the cosmic-ray pressure and thermal gas density gradients parallel to ${\boldsymbol{B}}$ are aligned, a condition that is unlikely to always be satisfied We investigate an alternative mechanism for cosmic-ray self confinement and heating of thermal gas based on pressure anisotropy instability. Although pressure anisotropy is demonstrably less effective than streaming instability as a self-confinement and heating mechanism on global scales, it may be important on mesoscales, particularly near sites of cosmic-ray injection.

Keywords: Galactic winds, Plasma astrophysics, Interstellar medium, Cosmic rays
Possible Formation Scenarios of ZTF J153932.16+502738.8—A Gravitational Source Close to the Peak of LISA's Sensitivity. ZTF J153932.16+502738.8 (ZTFJ1539) is an eclipsing double-white-dwarf system with an orbital period of 6.91 minutes, and a significant source for LISA detection of gravitational waves. However, the massive white dwarf (WD), with a mass of about 0.61 M⊙, has a high effective temperature (48,900 K), and the lower-mass WD, with a mass of about 0.21 M⊙, has a low effective temperature (&lt;10,000 K). This discrepancy challenges the popular theory of binary evolution. We investigate the formation of ZTFJ1539 via nova and Algol scenarios. Assuming that the massive WD in ZTFJ1539 just experiences a thermonuclear runaway, the nova scenario can explain the effective temperatures of the two WDs in ZTFJ1539. However, in order to enlarge a semi-detached orbit of about 4-5 minutes to a detached orbit of about 7 minutes, the nova scenario needs a much higher kick velocity of about 200 km s-1 during nova eruption. The high kick velocity can result in a high eccentricity of about 0.2-0.6. The Algol scenario can also produce ZTFJ1539 if we take a high efficient parameter for ejecting the common envelope and enhance the mass-loss rate via stellar wind trigger by tidal effect.

Keywords: Close binary stars, White dwarf stars, Classical novae
Studying the Anisotropy of Compressible Magnetohydrodynamic Turbulence by Synchrotron Polarization Intensity. Based on statistical analysis of synchrotron polarization intensity, we study the anisotropic properties of compressible magnetohydrodynamic (MHD) turbulence. The second-order normalized structure function, quadrupole ratio modulus, and anisotropic coefficient are synergistically used to characterize the anisotropy of the polarization intensity. On the basis of predecomposition data cubes, we first explore the anisotropy of the polarization intensity in different turbulence regimes and find that the most significant anisotropy occurs in the sub-Alfvénic regime. Using postdecomposition data cubes in this regime, we then study the anisotropy of the polarization intensity from Alfvén, slow, and fast modes. The statistics of the polarization intensity from Alfvén and slow modes demonstrate the significant anisotropy, while the statistics of the polarization intensity from fast modes show isotropic structures. This is consistent with earlier results provided in Cho &amp; Lazarian. As a result, both quadrupole ratio modulus and anisotropic coefficient for polarization intensities can quantitatively recover the anisotropy of underlying compressible magnetohydrodynamic turbulence. The synergistic use of the two methods helps enhance the reliability of the magnetic field measurement.

Keywords: Interstellar magnetic fields, Magnetohydrodynamics, Interstellar synchrotron emission
Broad-line Region of the Quasar PG 2130+099 from a Two-year Reverberation Mapping Campaign with High Cadence. As one of the most interesting Seyfert 1 galaxies, PG 2130+099 has been the target of several reverberation mapping (RM) campaigns over the years. However, its measured broad Hβ line responses have been inconsistent, with time lags of ∼200 days, ∼25 days, and ∼10 days being reported for different epochs while its optical luminosity changed no more than 40%. To investigate this issue, we conducted a new RM-campaign with homogenous and high cadence (about ∼3 days) for two years during 2017-2019 to measure the kinematics and structure of the ionized gas. We successfully detected time lags of broad Hβ, He II, He I, and Fe II lines with respect to the varying 5100 Å continuum, revealing a stratified structure that is likely virialized with Keplerian kinematics in the first year of observations, but an inflow kinematics of the broad-line region from the second year. With a central black hole mass of ${0.97}_{-0.18}^{+0.15}\times {10}^{7}{M}_{\odot }$ , PG 2130+099 has an accretion rate of ${10}^{2.1\pm 0.5}{L}_{\mathrm{Edd}}{c}^{-2}$ , where LEdd is the Eddington luminosity and c is speed of light, implying that it is a super-Eddington accretor and likely possesses a slim, rather than thin, accretion disk. The fast changes of the ionization structures of the three broad lines remain puzzling.

Keywords: Supermassive black holes, Quasars, Reverberation mapping, Seyfert galaxies, Active galactic nuclei, Time domain astronomy
Optical Variability of the TeV Blazar 1ES 0806+524 on Diverse Timescales. We report the results of our optical (VRI) photometric observations of the TeV blazar 1ES 0806+524 on 153 nights during 2011-2019 using seven optical telescopes in Europe and Asia. We investigated the variability of the blazar on intraday as well as on long-term timescales. We examined 18 intraday light curves for flux and color variations using the most reliable power-enhanced F-test and the nested ANOVA test. Only on one night was a small, but significant, variation found, in both V-band and R-band light curves. The V-R color index was constant on every one of those nights. Flux density changes of around 80% were seen over the course of these eight years in multiple bands. We found a weighted mean optical spectral index of 0.639 ± 0.002 during our monitoring period by fitting a power law ( ${F}_{\nu }\propto {\nu }^{-\alpha }$ ) in 23 optical (VRI) spectral energy distributions of 1ES 0806+524. We discuss different possible mechanisms responsible for blazar variability on diverse timescales.

Keywords: Observational astronomy, CCD photometry, Optical observation, BL Lacertae objects, Blazars, Active galaxies, Relativistic jets, Radio loud quasars, Active galactic nuclei, Optical telescopes
The Prospects of Observing Tidal Disruption Events with the Large Synoptic Survey Telescope. The upcoming Large Synoptic Survey Telescope (LSST) will observe 18,000 deg2 of the southern sky and is expected to discover thousands of transients every night due to its large coverage area and its observing strategy. In this work, we address the prospects for the LSST in discovering tidal disruption events (TDEs) and in probing the supermassive black hole (SMBH) mass distribution in the universe. We used the LSST simulation framework and defined TDE catalogs on 20 fields of 20.25 deg2 size. TDE properties were defined by randomly chosen impact factors and SMBH masses drawn from six different mass distributions. Observations of TDEs over 10 years of LSST operation were simulated by querying the simulated observing strategy database minion_1016. Based on the results of our simulations, we estimate that the LSST should discover between 35,000 and 80,000 TDEs in 10 years of operation, depending on the assumed SMBH mass distribution. We also find that probing the SMBH mass distribution with TDE observations will not be straightforward, due to the fact that TDEs caused by low-mass black holes (105M⊙) are expected to be less luminous and shorter than TDEs by heavier SMBHs (&gt; 106M⊙), and therefore will mostly be missed by the irregular LSST cadence minion_1016.

Keywords: Supermassive black holes, Tidal disruption, Sky surveys
Applying Information Theory to Design Optimal Filters for Photometric Redshifts. In this paper we apply ideas from information theory to create a method for the design of optimal filters for photometric redshift estimation. We show the method applied to a series of simple example filters in order to motivate an intuition for how photometric redshift estimators respond to the properties of photometric passbands. We then design a realistic set of six filters covering optical wavelengths that optimize photometric redshifts for z &lt;= 2.3 and I &lt; 25.3. We create a simulated catalog for these optimal filters and use our filters with a photometric redshift estimation code to show that we can improve the standard deviation of the photometric redshift error by 7.1% overall and improve outliers 9.9% over the standard filters proposed for the Large Synoptic Survey Telescope (LSST). We compare features of our optimal filters to the LSST and find that the LSST filters incorporate key features for optimal photometric redshift estimation. Finally, we describe how information theory can be applied to a range of optimization problems in astronomy.

Keywords: Galaxy distances, Surveys, Astronomy data analysis, Astrostatistics, Galaxy photometry