Sazuna/UAT_keywords huggingface dataset:
Stability of Cool Cores during Galaxy Cluster Growth: A Joint Chandra/SPT Analysis of 67 Galaxy Clusters along a Common Evolutionary Track Spanning 9 Gyr. We present the results of a joint analysis of Chandra X-ray and South Pole Telescope (SPT) Sunyaev-Zel'dovich (SZ) observations targeting the first sample of galaxy clusters at 0.3 &lt; z &lt; 1.3, selected to be the progenitors of well-studied nearby clusters based on their expected accretion rate. We develop a new procedure in order to tackle the analysis challenge that is estimating the intracluster medium (ICM) properties of low-mass and high-redshift clusters with ~150 X-ray counts. One of the dominant sources of uncertainty on the ICM density profile estimated with a standard X-ray analysis with such shallow X-ray data is due to the systematic uncertainty associated with the ICM temperature obtained through the analysis of the background-dominated X-ray spectrum. We show that we can decrease the uncertainty on the density profile by a factor varying between 2 and 8 with a joint deprojection of the X-ray surface brightness profile measured by Chandra and the SZ-integrated Compton parameter available in the SPT cluster catalog. We apply this technique to the whole sample of 67 clusters in order to track the evolution of the ICM core density during cluster growth. We confirm that the evolution of the gas density profile is well modeled by the combination of a fixed core and a self-similarly evolving non-cool-core profile. We show that the fraction of cool cores in this sample is remarkably stable with redshift although clusters have gained a factor of ~4 in total mass over the past ~9 Gyr.

Keywords: Galaxy clusters, X-ray astronomy, High-redshift galaxy clusters, Sunyaev-Zeldovich effect, Cool cores, Intracluster medium
Kilonovae Across the Nuclear Physics Landscape: The Impact of Nuclear Physics Uncertainties on r-process-powered Emission. Merging neutron stars produce "kilonovae"-electromagnetic transients powered by the decay of unstable nuclei synthesized via rapid neutron capture (the r-process) in material that is gravitationally unbound during inspiral and coalescence. Kilonova emission, if accurately interpreted, can be used to characterize the masses and compositions of merger-driven outflows, helping to resolve a long-standing debate about the origins of r-process material in the Universe. We explore how the uncertain properties of nuclei involved in the r-process complicate the inference of outflow properties from kilonova observations. Using r-process simulations, we show how nuclear physics uncertainties impact predictions of radioactive heating and element synthesis. For a set of models that span a large range in both predicted heating and final abundances, we carry out detailed numerical calculations of decay product thermalization and radiation transport in a kilonova ejecta with a fixed mass and density profile. The light curves associated with our models exhibit great diversity in their luminosities, with peak brightness varying by more than an order of magnitude. We also find variability in the shape of the kilonova light curves and their color, which in some cases runs counter to the expectation that increasing levels of lanthanide and/or actinide enrichment will be correlated with longer, dimmer, redder emission.

Keywords: Neutron stars, R-process, Gravitational wave sources, Stellar mergers
Transmission Electron Microscopy Study of the Morphology of Ices Composed of H<SUB>2</SUB>O, CO<SUB>2</SUB>, and CO on Refractory Grains. It has been implicitly assumed that ices on grains in molecular clouds and protoplanetary disks are formed by homogeneous layers regardless of their composition or crystallinity. To verify this assumption, we observed the H2O deposition onto refractory substrates and the crystallization of amorphous ices (H2O, CO2, and CO) using an ultra-high-vacuum transmission electron microscope. In the H2O-deposition experiments, we found that three-dimensional islands of crystalline ice (Ic) were formed at temperatures above 130 K. The crystallization experiments showed that uniform thin films of amorphous CO and H2O became three-dimensional islands of polyhedral crystals; amorphous CO2, on the other hand, became a thin film of nano-crystalline CO2 covering the amorphous H2O. Our observations show that crystal morphologies strongly depend not only on the ice composition but also on the substrate. Using experimental data concerning the crystallinity of deposited ices and the crystallization timescale of amorphous ices, we illustrated the criteria for ice crystallinity in space and outlined the macroscopic morphology of icy grains in molecular clouds as follows: amorphous H2O covered the refractory grain uniformly, CO2 nano-crystals were embedded in the amorphous H2O, and a polyhedral CO crystal was attached to the amorphous H2O. Furthermore, a change in the grain morphology in a protoplanetary disk is shown. These results have important implications for the chemical evolution of molecules, nonthermal desorption, collision of icy grains, and sintering.

Keywords: Laboratory astrophysics, Experimental techniques, Ice formation
Mass, Spin, and Ultralight Boson Constraints from the Intermediate-mass Black Hole in the Tidal Disruption Event 3XMM J215022.4-055108. We simultaneously and successfully fit the multiepoch X-ray spectra of the tidal disruption event (TDE) 3XMM J215022.4-055108 using a modified version of our relativistic slim disk model that now accounts for angular momentum losses from radiation. We explore the effects of different disk properties and of uncertainties in the spectral hardening factor fc and redshift z on the estimation of the black hole mass M∙ and spin a∙. Across all choices of theoretical priors, we constrain M∙ to less than 2.2 × 104 M☉ at 1σ confidence. Assuming that the TDE host is a star cluster associated with the adjacent, brighter, barred lenticular galaxy at z = 0.055, we constrain M∙ and a∙ to be ${1.75}_{-0.05}^{+0.45}\times {10}^{4}$ M☉ and ${0.8}_{-0.02}^{+0.12}$ , respectively, at 1σ confidence. The high, but sub-extremal, spin suggests that, if this intermediate-mass black hole (IMBH) has grown significantly since formation, it has acquired its last e-fold in mass in a way incompatible with both the "standard" and "chaotic" limits of gas accretion. Ours is the first clear IMBH with a spin measurement. As such, this object represents a novel laboratory for astroparticle physics; its M∙ and a∙ place tight limits on the existence of ultralight bosons, ruling out those with masses from ~10-15 to 10-16 eV.

Keywords: Accretion, Black hole physics, Intermediate-mass black holes, Tidal disruption, X-ray transient sources
Limitations of the Ca II 8542 Å Line for the Determination of Magnetic Field Oscillations. Chromospheric umbral oscillations produce periodic brightenings in the core of some spectral lines, known as umbral flashes. They are also accompanied by fluctuations in velocity, temperature, and, according to several recent works, magnetic field. In this study, we aim to ascertain the accuracy of the magnetic field determined from inversions of the Ca II 8542 Å line. We have developed numerical simulations of wave propagation in a sunspot umbra. Synthetic Stokes profiles emerging from the simulated atmosphere were computed and then inverted using the NICOLE code. The atmospheres inferred from the inversions have been compared with the original parameters from the simulations. Our results show that the inferred chromospheric fluctuations in velocity and temperature match the known oscillations from the numerical simulation. In contrast, the vertical magnetic field obtained from the inversions exhibits an oscillatory pattern with a ~300 G peak-to-peak amplitude, which is absent in the simulation. We have assessed the error in the inferred parameters by performing numerous inversions with slightly different configurations of the same Stokes profiles. We find that when the atmosphere is approximately at rest, the inversion tends to favor solutions that underestimate the vertical magnetic field strength. On the contrary, during umbral flashes, the values inferred from most of the inversions are concentrated at stronger fields than those from the simulation. Our analysis provides a quantification of the errors associated with the inversions of the Ca II 8542 Å line and suggests caution with the interpretation of the inferred magnetic field fluctuations.

Keywords: Solar atmosphere, Sunspots, Computational methods, Solar oscillations, Solar chromosphere
Collisionless Equilibria in General Relativity: Stable Configurations beyond the First Binding Energy Maximum. We numerically study the stability of collisionless equilibria in the context of general relativity. More precisely, we consider the spherically symmetric, asymptotically flat Einstein-Vlasov system in Schwarzschild and maximal areal coordinates. Our results provide strong evidence against the well-known binding energy hypothesis, which states that the first local maximum of the binding energy along a sequence of isotropic steady states signals the onset of instability. We do, however, confirm the conjecture that steady states are stable at least up to the first local maximum of the binding energy. For the first time, we observe multiple stability changes for certain models. The equations of state used are piecewise linear functions of the particle energy and provide a rich variety of different equilibria.

Keywords: Gravitational instability, Galaxy dynamics, General relativity, Gravitational collapse
Reverberation Mapping Measurements of Black Hole Masses and Broad-line Region Kinematics in Mrk 817 and NGC 7469. We present the results from a spectroscopic monitoring campaign to obtain reverberation mapping measurements and investigate the broad-line region (BLR) kinematics for active galactic nuclei (AGNs) of Mrk 817 and NGC 7469. This campaign was undertaken with the Lijiang 2.4 m telescope. The median spectroscopic sampling is 2.0 days for Mrk 817 and 1.0 day for NGC 7469. We detect time lags of the broad emission lines, including Hβ, Hγ, He II, and He I for both AGNs, including Fe II for Mrk 817 with respect to the varying AGN continuum at 5100 Å. Investigating the relationship between line widths and time lags of the broad emission lines, we find that the BLR dynamics of Mrk 817 and NGC 7469 are consistent with the virial prediction. We estimate the masses of central supermassive black holes (SMBHs) and the accretion rates of both AGNs. Using the data of this campaign, we construct the velocity-resolved lag profiles of the broad Hγ, Hβ, and He I lines for Mrk 817, which show almost the same kinematic signatures in that the time lags in the red wing are slightly larger than the time lags in the blue wing. For NGC 7469, we only clearly construct the velocity-resolved lag profiles of the broad Hγ and Hβ, which show very similar kinematic signatures to the BLR of Mrk 817. These signatures indicate that the BLR of Keplerian motion in both AGNs seemingly has outflowing components during the monitoring period. We discuss the kinematics of the BLR and the measurements, including SMBH mass and accretion rates.

Keywords: Supermassive black holes, Reverberation mapping, Seyfert galaxies, Time domain astronomy
The Energy Conversion Rate of an Active Region Transient Brightening Estimated by Hinode Spectroscopic Observations. We statistically estimate the conversion rate of the energy released during an active region transient brightening to Doppler motion and thermal and nonthermal energies. We used two types of data sets for the energy estimation and detection of transient brightenings. One includes spectroscopic images of Fe XIV, Fe XV, and Fe XVI lines observed by the Hinode/EUV Imaging Spectrometer. The other includes images obtained from the 211 Å channel of the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA). The observed active region was NOAA 11890 on 2013 November 9 and 10. As a result, the released Doppler motion and nonthermal energies were found to be approximately 0.1%-1% and 10%-100% of the change in the amount of thermal energy in each enhancement, respectively. Using this conversion rate, we estimated the contribution of the total energy flux of AIA transient brightenings to the active region heating to be at most 2% of the conduction and radiative losses.

Keywords: Solar active region velocity fields, Solar flares, The Sun, Active sun, Solar flare spectra, Solar physics, Solar active regions, Spectroscopy
GRB 170817A Afterglow from a Relativistic Electron-Positron Pair Wind Observed Off-axis. A relativistic electron-positron (e+e-) pair wind from a rapidly rotating, strongly magnetized neutron star (NS) would interact with a gamma-ray burst (GRB) external shock and reshape afterglow emission signatures. Assuming that the merger remnant of GW170817 is a long-lived NS, we show that a relativistic e+e- pair wind model with a simple top-hat jet viewed off-axis can reproduce multiwavelength afterglow lightcurves and superluminal motion of GRB 170817A. The Markov Chain Monte Carlo (MCMC) method is adopted to obtain the best-fitting parameters, which give the jet half-opening angle θj ≈ 0.12 rad, and the viewing angle θv ≈ 0.23 rad. The best-fitting value of θv is close to the lower limit of the prior that is chosen based on the gravitational-wave and electromagnetic observations. In addition, we also derive the initial Lorentz factor Γ0 ≈ 49 and the isotropic kinetic energy EK,iso ≈ 1× 1052 erg. Consistency between the corrected on-axis values for GRB 170817A and typical values observed for short GRBs indicates that our model can also reproduce the prompt emission of GRB 170817A. An NS with a magnetic field strength Bp ≈ 1.6 × 1013 G is obtained in our fitting, indicating that a relatively low thermalization efficiency η ≲ 10-3 is needed to satisfy observational constraints on the kilonova. Furthermore, our model is able to reproduce a late-time shallow decay in the X-ray lightcurve, and predicts that the X-ray and radio flux will continue to decline in the coming years.

Keywords: Neutron stars, Gamma-ray bursts
Star Formation and Quenching of Central Galaxies from Stacked HI Measurements. We quantitatively investigate the dependence of central galaxy HI mass (MHI) on the stellar mass (M*), halo mass (Mh), star formation rate (SFR), and central stellar surface density within 1 kpc (Σ1), taking advantage of the HI spectra stacking technique using both the Arecibo Fast Legacy ALFA Survey and the Sloan Digital Sky Survey. We find that the shapes of MHI-Mh and MHI-M* relations are remarkably similar for both star-forming and quenched galaxies, with massive quenched galaxies having constantly lower HI masses of around 0.6 dex. This similarity strongly suggests that neither halo mass nor stellar mass is the direct cause of quenching, but rather the depletion of the HI reservoir. While the HI reservoir for low-mass galaxies of M* &lt; 1010.5 M⊙ strongly increases with Mh, more massive galaxies show no significant dependence of MHI with Mh, indicating that the main effect of halo is to determine the smooth cold gas accretion. We find that the star formation and quenching of central galaxies are directly regulated by the available HI reservoir, with an average relation of $\mathrm{SFR}\propto {M}_{{\rm{H}}\,{\rm\small{I}}}^{2.75}/{M}_{* }^{0.40}$ , implying a quasi-steady state of star formation. We further confirm that galaxies are depleted of their HI reservoir once they drop off the star formation main sequence and there is a very tight and consistent correlation between MHI and Σ1 in this phase, with ${M}_{{\rm{H}}\,{\rm\small{I}}}\propto {{\rm{\Sigma }}}_{1}^{-2}$ . This result is consistent with the compaction-triggered quenching scenario, with galaxies going through three evolutionary phases of cold gas accretion, compaction and post-compaction, and quenching.

Keywords: Galaxy dark matter halos, Quenched galaxies, Interstellar atomic gas, H I line emission, Star formation, Galaxy evolution, Circumgalactic medium, Galaxy quenching
EMPRESS. III. Morphology, Stellar Population, and Dynamics of Extremely Metal-poor Galaxies (EMPGs): Are EMPGs Local Analogs of High-z Young Galaxies?. We present the morphology and stellar population of 27 extremely metal-poor galaxies (EMPGs) at z ~ 0 with metallicities of 0.01-0.1 Z⊙. We conduct multicomponent surface brightness (SB) profile fitting for the deep Subaru/Hyper Suprime-Cam i-band images of the EMPGs with the GALFIT software, carefully removing the SB contributions of tails. We find that the EMPGs with a median stellar mass of $\mathrm{log}({M}_{* }/{M}_{\odot })=6.0$ have a median Sérsic index of n = 1.1 and a median effective radius of re = 200 pc, suggesting that typical EMPGs have a very compact disk. We compare the EMPGs with z ~ 6 galaxies and local galaxies on the size-mass (re-M*) diagram, and identify that the majority of the EMPGs have an re-M* relation similar to z ~ 0 star-forming galaxies rather than z ~ 6 galaxies. Not every EMPG is a local analog of high-z young galaxies in the re-M* relation. A spectrum of one pair of EMPG and tail, so far available, indicates that the tail is dynamically related to the EMPG with a median velocity difference of ΔV = 101 ± 32 km s-1. This moderately large ΔV cannot be explained by the dynamics of the tail, but likely by the infall on the tail. For the first time, we may identify the metal-poor star-forming system just now infalling into the tail. * Released on.

Keywords: Galaxy formation, Galaxy structure, Dwarf galaxies, Star formation, Galaxy kinematics
NOEMA Observations of CO Emission in Arp 142 and Arp 238. Previous studies have shown significant differences in the enhancement of the star formation rate (SFR) and star formation efficiency (SFE = SFR/Mmol) between spiral-spiral and spiral-elliptical mergers. In order to shed light on the physical mechanism of these differences, we present NOEMA observations of the molecular gas distribution and kinematics (linear resolutions of ~2 kpc) in two representative close major-merger star-forming pairs: the spiral-elliptical pair Arp 142 and the spiral-spiral pair Arp 238. The CO in Arp 142 is widely distributed over a highly distorted disk without any nuclear concentration, and an off-center ringlike structure is discovered in channel maps. The SFE varies significantly within Arp 142, with a starburst region (region 1) near the eastern tip of the distorted disk showing an SFE ~ 0.3 dex above the mean of the control sample of isolated galaxies and the SFE of the main disk (region 4) 0.43 dex lower than the mean of the control sample. In contrast, the CO emission in Arp 238 is detected only in two compact sources at the galactic centers. Compared to the control sample, Arp 238-E shows an SFE enhancement of more than 1 dex, whereas Arp 238-W has an enhancement of ~0.7 dex. We suggest that the extended CO distribution and large SFE variation in Arp 142 are due to an expanding large-scale ring triggered by a recent high-speed head-on collision between the spiral galaxy and the elliptical galaxy, and the compact CO sources with high SFEs in Arp 238 are associated with nuclear starbursts induced by gravitational tidal torques in a low-speed coplanar interaction.

Keywords: Galaxy collisions, Galaxy pairs, Galaxy mergers, Interacting galaxies, Galaxies
Prospects for Constraining Interacting Dark Energy Models with 21 cm Intensity Mapping Experiments. We forecast constraints on cosmological parameters in the interacting dark energy models using the mock data generated for neutral hydrogen intensity mapping (IM) experiments. In this work, we only consider the interacting dark energy models with energy transfer rate Q = βHρc and take BINGO, FAST, SKA1-MID, and Tianlai as typical examples of the 21 cm IM experiments. We find that the Tianlai cylinder array will play an important role in constraining the interacting dark energy model. Assuming perfect foreground removal and calibration and using the Tianlai-alone data, we obtain σ(H0) = 0.19 km s-1 Mpc-1, σ(Ωm) = 0.0033, and σ(σ8) = 0.0033 in the IΛCDM model, which are much better than the results of Planck+optical BAO (i.e., optical galaxy surveys). However, the Tianlai-alone data cannot provide a very tight constraint on the coupling parameter β compared with Planck+optical BAO, while the Planck+Tianlai data can give a rather tight constraint of σ(β) = 0.00023 due to the parameter degeneracies being well broken by the data combination. In the IwCDM model, we obtain σ(β) = 0.00079 and σ(w) = 0.013 from Planck+Tianlai. In addition, we also make a detailed comparison among BINGO, FAST, SKA1-MID, and Tianlai in constraining the interacting dark energy models. We show that future 21 cm IM experiments will provide a useful tool for exploring the nature of dark energy and play a significant role in measuring the coupling between dark energy and dark matter.

Keywords: Cosmology, Cosmological parameters, Dark energy, H I line emission
Observations of Bright Pulses from Pulsar B0031-07 at 4.82 GHz. We report on the detection of 146 (0.96%) bright pulses with a peak flux density &gt;0.86 Jy from PSR B0031-07 in 4 hr of continuous observations made at 4.82 GHz, with a bandwidth of 1 GHz, using the Shanghai Tian Ma 65 m radio telescope. We find that the peak flux density distribution follows a power law with index α = -3.6 ± 0.2, while the pulse energy appears to follow a logarithmic normal distribution. The bright pulses from PSR B0031-07 were observed to repeat in an irregular fashion. The intervals between bright pulses can be described with an exponentiated Weibull distribution. Furthermore, the sensitive observations at higher frequency with a short time resolution of 65.54 μs form a reliable basis for detailed microstructure studies. Close inspection of the detected bright pulses reveals that 38 pulses exhibit well-defined quasi-periodicities. No unanimous period for the quasi-periodicities is found, and the peak flux density is independent of the micropulse width. Finally, possible physical mechanisms are discussed.

Keywords: Radio pulsars
Period Bouncer Cataclysmic Variable EZ Lyn in Quiescence. We report the study of the accretion disk structure of the period bouncer cataclysmic variable EZ Lyn (SDSS J080434.20+510349.2) in quiescence based on our new time-resolved photometric and spectroscopic observations and data extracted from archives. The object magnitude now is V = 17.95(5), close to its brightest before the first superoutburst in 2006. We confirmed the presence of the small eclipse in the optical light curve. The spectra obtained in quiescence at different epochs look similar. However, the contribution of the disk and intensities of emission lines are strongly varied. We singled out pure accretion disk spectra and found that the Balmer decrement Hα:Hβ:Hγ:Hδ = 1.61:1.0:0.76:0.59 is comparable with one at bright accretion disks in longer period cataclysmic variables. The decrement suggests that emission lines are excited collisionally in an optical thin part of the disk with average density and temperature of logN0 = 12.5(2) and T = (10-15) × 103 K. Based on the photometric data and our modeling techniques, we redetermined the mass of MWD = 0.85(1) M⊙ and the current effective temperature TWD,eff = 11,250(50) K of the white dwarf. The secondary has mass of M2 = 0.042(14) M⊙. The system inclination is 79.0°(2). The mass accretion rate is about $\dot{M}\approx (0.3\mbox{--}3.0)\times {10}^{-12}\ {M}_{\odot }$ yr-1. The disk luminosity, together with results from light-curve modeling, suggests a low effective temperature ~2500 K of the continuum emitting region, where also the spiral arm pattern is hosted.

Keywords: WZ Sagittae stars, Cataclysmic variable stars, Dwarf novae