Sazuna/UAT_keywords huggingface dataset:
The Ultraluminous X-Ray Sources Population of the Galaxy NGC 7456. Ultraluminous X-ray sources (ULXs) are a class of accreting compact objects with X-ray luminosities above 1039 erg s-1. The ULX population counts several hundred objects but only a fraction are well studied. Here we present a detailed analysis of all ULXs hosted in the galaxy NGC 7456. It was observed in X-rays only once in the past (in 2005) by XMM-Newton. but the observation was short and strongly affected by high background. In 2018, we obtained a new, deeper (∼90 ks) XMM-Newton observation that allowed us to perform a detailed characterization of the ULXs hosted in the galaxy. ULX-1 and ULX-2, the two brightest objects (LX ∼ 6-10 × 1039 erg s-1), have spectra that can be described by a model with two thermal components, as often found in ULXs. ULX-1 also shows one order of magnitude in flux variability on short-term timescales (hundreds to thousands of kiloseconds). The other sources (ULX-3 and ULX-4) show flux changes of at least an order of magnitude, and these objects may be candidate transient ULXs, although longer X-ray monitoring or further studies are required to ascribe them to the ULX population. In addition, we found a previously undetected source that might be a new candidate ULX (labeled as ULX-5), with a luminosity of ∼1039 erg s-1 and hard power-law spectral shape, whose nature is still unclear and for which a background active galactic nucleus cannot be excluded. We discuss the properties of all the ULXs in NGC 7456 within the framework of super-Eddington accretion onto stellar-mass compact objects. Although no pulsations were detected, we cannot exclude that the sources host neutron stars.

Keywords: X-ray astronomy, Neutron stars, X-ray binary stars, Pulsars, X-ray sources
The Fifth Candidate for an Intermediate-mass Black Hole in the Galactic Center. We report the results of high-resolution molecular line observations of the high-velocity compact cloud HCN-0.085-0.094 with the Atacama Large Millimeter/submillimeter Array. The HCN J = 4-3, HCO+ J = 4-3, and CS J = 7-6 line images reveal that HCN-0.085-0.094 consists mainly of three small clumps with extremely broad velocity widths. Each of the three clumps has a 5.5 GHz radio continuum counterpart in its periphery toward Sgr A*. The positional relationship indicates that their surfaces have been ionized by ultraviolet photons from young stars in the central cluster, suggesting the clumps are in close proximity to the Galactic nucleus. One of the three clumps has a ring-like structure with a very steep velocity gradient. This kinematical structure suggests an orbit around a point-like object with a mass of ∼104 M⊙. The absence of stellar counterparts indicates that the point-like object may be a quiescent black hole. This discovery adds another intermediate-mass black hole candidate in the central region of our Galaxy.

Keywords: Submillimeter astronomy, Intermediate-mass black holes, Galactic center, Molecular clouds
The Gravitational Lensing Signatures of BOSS Voids in the Cosmic Microwave Background. We report a $5.3\sigma $ detection of the gravitational lensing effect of cosmic voids from the Baryon Oscillation Spectroscopic Data Release 12 seen in the Planck 2018 cosmic microwave background (CMB) lensing convergence map. To make this detection, we introduce new optimal techniques for void stacking and filtering of the CMB maps, such as binning voids by a combination of their observed galaxy density and size to separate those with distinctive lensing signatures. We calibrate theoretical expectations for the void lensing signal using mock catalogs generated in a suite of 108 full-sky lensing simulations from Takahashi et al. Relative to these templates, we measure the lensing amplitude parameter in the data to be AL = 1.10 ± 0.21 using a matched-filter stacking technique and confirm it using an alternative Wiener-filtering method. We demonstrate that the result is robust against thermal Sunyaev-Zel'dovich contamination and other sources of systematics. We use the lensing measurements to test the relationship between the matter and galaxy distributions within voids and show that the assumption of linear bias with a value consistent with galaxy clustering results is discrepant with observation at ∼3σ; we explain why such a result is consistent with simulations and previous results, and is expected as a consequence of void selection effects. We forecast the potential for void CMB lensing measurements in future data from the Advanced ACT, Simons Observatory, and CMB-S4 experiments, showing that, for the same number of voids, the achievable precision improves by a factor of more than 2 compared to Planck.

Keywords: Cosmology, Weak gravitational lensing, Large-scale structure of the universe, Cosmic microwave background radiation, Voids
Model-independent Constraints on Lorentz Invariance Violation: Implication from Updated Gamma-Ray Burst Observations. Astrophysical observations provide a unique opportunity to test possible signatures of Lorentz invariance violation (LIV), due to the high energies and long distances involved. In quantum theory of gravity, one may expect the modification of the dispersion relation between energy and momentum for photons, which can be probed with the time lag (the arrival time delay between light curves in different energy bands) of gamma-ray bursts (GRBs). In this paper, by using the detailed time delay measurements of GRB 160625B at different energy bands, as well as 23 time delay GRBs covering the redshift range of z = 0.168-2.5 (which were measured at different energy channels from the light curves), we propose an improved model-independent method (based on the newly compiled sample of H(z) measurements) to probe the energy-dependent velocity due to the modified dispersion relation for photons. In the framework of a more complex and reasonable theoretical expression to describe the time delays, our results imply that the intrinsic time lags can be better described with more GRB time delay data. More importantly, through direct fitting of the time delay measurements of a sample of GRBs, our limit on the LIV energy scale is comparable to that with unknown constant for the intrinsic time lag, much lower than the Planck energy scale in both linear LIV and quadratic LIV cases.

Keywords: Gamma-ray bursts, Gravitation, Distance indicators, General relativity, Particle astrophysics
Collisional Evolution of Meter- to Kilometer-sized Planetesimals in Mean Motion Resonances: Implications for Inward Planet Shepherding. Small particles (meter to kilometer sized) can drift inward through a protoplanetary disk owing to their interaction with a gaseous nebula. If planets exist, these particles can get captured in mean motion resonance (MMR) and, if massive, exchange angular momentum with the planets. While dependent on the total mass in small inward-drifting particles captured, the main result out of such resonant angular momentum exchange is inward planet shepherding. However, it is not clear what the real dynamics of a large number of massive particles in MMR would be when collisional effects are included. Therefore, we studied the capture mechanism and collisional evolution of a swarm of massive inward-drifting particles in MMRs with planets. Due to the confined space of an MMR, captured massive particles can rapidly collisionally evolve. Our main results show that, if massive particles are assumed to be rocky, collisions make the swarm of particles decrease in size. In this case, as their gas drag properties change (smaller particles drift faster through the gas nebula), they eventually leave the MMR. On the other hand, if massive particles are assumed to be 10, 100, or 1000 times stronger (harder to break) than rocky particles, they instead grow. In this situation, the drifting particles slow down (r ≳ 1-5 km) or even stop (r ≳ 5-10 km) their inward drift. We conclude that, although some angular momentum exchange may exist, in no cases studied here did the massive inward-drifting particles significantly change the orbit of the planet.

Keywords: Planetary system formation, Planet formation, Dynamical evolution
The Redshift and Star Formation Mode of AzTEC2: A Pair of Massive Galaxies at z = 4.63. We combine observations from the Atacama Large Millimeter/submillimeter Array and the NOrthern Extended Millimeter Array to assess the redshift and to study the star formation conditions in AzTEC2, one of the brightest submillimeter galaxies (SMGs) in the COSMOS field ( ${S}_{1.1\mathrm{mm}}=10.5\pm 1.4$ mJy). Our high-resolution observations confirm that AzTEC2 splits into two components (namely AzTEC2-A and AzTEC2-B) for which we detect [C II] and 12CO(5 → 4) line emission, implying a redshift of 4.626 ± 0.001 (4.633 ± 0.001) for AzTEC2-A (AzTEC2-B) and ruling out previous associations with a galaxy at $z\sim 1$ . We use the 12CO(5 → 4) line emission and adopt typical SMG-like gas excitation conditions to estimate the molecular gas mass, which is ${M}_{\mathrm{gas}}({\alpha }_{\mathrm{CO}}/2.5)=2.1\pm 0.4\,\times \,{10}^{11}\,{M}_{\odot }$ for AzTEC2-A, and a factor four lower for AzTEC2-B. With the infrared-derived star formation rate of AzTEC2-A ( $1920\pm 100\,{M}_{\odot }$ yr-1) and AzTEC2-B ( $710\pm 35\,{M}_{\odot }$ yr-1), they both will consume their current gas reservoir within (30-200) Myr. We find evidence of a rotation-dominated [C II] disk in AzTEC2-A, with a deprojected rotational velocity of ${V}_{\mathrm{rot}}(I=39^\circ )=660\pm 130$ km s-1, velocity dispersion $\lesssim 100$ km s-1, and dynamical mass of ${M}_{\mathrm{dyn}}(I=39^\circ )={2.6}_{-0.9}^{+1.2}\times {10}^{11}\,{M}_{\odot }$ . We propose that an elevated gas accretion rate from the cosmic web might be the main driver of the intense levels of star formation in AzTEC2-A, which might be further enhanced by gravitational torques induced by its minor companion (AzTEC2-B). These results strengthen the picture whereby the population of single-dish selected SMGs is rather heterogeneous, including a population of pairs of massive, highly active galaxies in a pre-coalescence phase.

Keywords: Galaxy formation, Disk galaxies, Galaxy evolution, High-redshift galaxies, Galaxies
Assessment of Systematic Uncertainties in the Cosmological Analysis of the SDSS Supernovae Photometric Sample. Improvements to the precision of measurements of cosmological parameters with Type Ia supernovae (SNe Ia) are expected to come from large photometrically identified (photometric) supernova (SN) samples. Here we reanalyze the Sloan Digital Sky Survey (SDSS) photometric SN sample, with roughly 700 high-quality, likely but unconfirmed SNe Ia light curves, to develop new analysis tools aimed at evaluating systematic uncertainties on the dark energy equation-of-state parameter w. Since we require a spectroscopically measured host-galaxy redshift for each SN, we determine the associated selection efficiency of host galaxies in order to simulate bias corrections. We determine that the misassociation rate of host galaxies is 0.6%; ignoring this effect in simulated bias corrections leads to a w-bias of Δw = +0.0007, where w is evaluated from SNe Ia and priors from measurements of baryon acoustic oscillations and the cosmic microwave background. We assess the uncertainty in our modeling of the host-galaxy selection efficiency and find the associated w uncertainty to be -0.0072. Finally, we explore new core-collapse (CC) models in simulated training samples and find that adjusting the CC luminosity distribution to be in agreement with previous Pan-STARRS analyses yields a better match to the SDSS data. The impact of ignoring this adjustment is Δw = -0.0109; the impact of replacing the new CC models with those used by Pan-STARRS is Δw = -0.0028. These systematic uncertainties are subdominant to the statistical constraints from the SDSS sample, but must be considered in future photometric analyses of large SN samples such as those from the Dark Energy Survey (DES), the Large Synoptic Survey Telescope (LSST), and the Wide Field Infrared Survey Telescope (WFIRST).

Keywords: Cosmology, Type Ia supernovae, Dark energy
The Formation of Exponential Disk Galaxies in MOND. The formation and evolution of galaxies are highly dependent on the dynamics of stars and gas, which is governed by the underlying law of gravity. To investigate how the formation and evolution of galaxies take place in Milgromian gravity (MOND), we present full hydrodynamical simulations with the Phantom of Ramses code. These are the first-ever galaxy formation simulations done in MOND with detailed hydrodynamics, including star formation, stellar feedback, radiative transfer, and supernovae. These models start from simplified initial conditions, in the form of isolated, rotating gas spheres in the early universe. These collapse and form late-type galaxies obeying several scaling relations, which was not a priori expected. The formed galaxies have a compact bulge and a disk with exponentially decreasing surface mass density profiles and scale lengths consistent with observed galaxies, as well as vertical stellar mass distributions with distinct exponential profiles (thin and thick disk). This work thus shows for the first time that disk galaxies with exponential profiles in both gas and stars are a generic outcome of collapsing gas clouds in MOND. These models have a slight lack of stellar angular momentum because of their somewhat compact stellar bulge, which is connected to the simple initial conditions and the negligible later gas accretion. We also analyze how the addition of more complex baryonic physics changes the resulting main properties of the models and find this to be negligibly so in the Milgromian framework.

Keywords: Hydrodynamical simulations, Disk galaxies, Gravitation, Non-standard theories of gravity, Galaxies
Helios-r2: A New Bayesian, Open-source Retrieval Model for Brown Dwarfs and Exoplanet Atmospheres. We present an improved, hybrid CPU-GPU atmospheric retrieval code, Helios-r2, which is applicable to medium-resolution emission spectra of brown dwarfs, in preparation for precision atmospheric spectroscopy in the era of the James Webb Space Telescope. The model is available as open-source code on the Exoclimes Simulation Platform. We subject Helios-r2 to a battery of tests of varying difficulty. The simplest test involves a mock retrieval on a forward model generated using the same radiative transfer technique, the same implementation of opacities, and the same chemistry model. The least trivial test involves a mock retrieval on synthetic spectra from the Sonora model grid, which uses a different radiative transfer technique, a different implementation of opacities, and a different chemistry model. A calibration factor, which is included to capture uncertainties in the brown dwarf radius, distance to the brown dwarf and flux calibration of the spectrum, may compensate, sometimes erroneously, for discrepancies in modeling choices and implementation. We analyze spectra of the benchmark brown dwarf GJ 570 D and the binary brown dwarf companions in the Epsilon Indi system. The retrieved surface gravities are consistent with previous studies and/or values inferred from dynamical masses (for Epsilon Indi Ba and Bb only). There remains no clear criterion on how to reject unphysical values of the retrieved brown dwarf radii. The inferred radii and corresponding masses should be taken with great caution. The retrieved carbon-to-oxygen ratios and metallicity depend on whether chemical equilibrium is assumed.

Keywords: Brown dwarfs, Bayesian statistics, Radiative transfer, Exoplanet atmospheres
Mass Segregation in Eccentric Nuclear Disks: Enhanced Tidal Disruption Event Rates for High-mass Stars. Eccentric nuclear disks (ENDs) are a type of star cluster in which the stars lie on eccentric, apsidally aligned orbits in a disk around a central supermassive black hole. These disks can produce a high rate of tidal disruption events via secular gravitational torques. Previous studies of ENDs have included stars with only one mass. Here, we present the first study of an END with two stellar species. We show that ENDs show radial mass segregation consistent with previous results from other cluster types. Additionally, ENDs show vertical mass segregation by which the heavy stars sink to lower inclinations than light stars. These two effects cause heavy stars to be more susceptible to tidal disruption, which can be seen in the higher fraction of heavy stars that are disrupted compared to light stars.

Keywords: Celestial mechanics, Tidal disruption, Black holes, Galaxy nuclei
Global Chemistry and Thermal Structure Models for the Hot Jupiter WASP-43b and Predictions for JWST. The James Webb Space Telescope (JWST) is expected to revolutionize the field of exoplanets. The broad wavelength coverage and the high sensitivity of its instruments will allow characterization of exoplanetary atmospheres with unprecedented precision. Following the Call for the Cycle 1 Early Release Science Program, the Transiting Exoplanet Community was awarded time to observe several targets, including WASP-43b. The atmosphere of this hot Jupiter has been intensively observed but still harbors some mysteries, especially concerning the day-night temperature gradient, the efficiency of the atmospheric circulation, and the presence of nightside clouds. We will constrain these properties by observing a full orbit of the planet and extracting its spectroscopic phase curve in the 5-12 μm range with JWST/MIRI. To prepare for these observations, we performed extensive modeling work with various codes: radiative transfer, chemical kinetics, cloud microphysics, global circulation models, JWST simulators, and spectral retrieval. Our JWST simulations show that we should achieve a precision of 210 ppm per 0.1 μm spectral bin on average, which will allow us to measure the variations of the spectrum in longitude and measure the nightside emission spectrum for the first time. If the atmosphere of WASP-43b is clear, our observations will permit us to determine if its atmosphere has an equilibrium or disequilibrium chemical composition, eventually providing the first conclusive evidence of chemical quenching in a hot Jupiter atmosphere. If the atmosphere is cloudy, a careful retrieval analysis will allow us to identify the cloud composition.

Keywords: Exoplanet structure, Exoplanet atmospheric composition , Exoplanet atmospheres
A New Method to Classify Type IIP/IIL Supernovae Based on Their Spectra. Type IIP and Type IIL supernovae are defined on the basis of their light curves, but the spectral criteria for distinguishing these two types of supernovae (SNe) remain unclear. We propose a spectral classification method. First, we subtract the principal components of different wavelength bands in the spectra based on the functional principal components analysis method. Then, we use support vector machine and artificial neural network to classify these two types of SNe. The best F1_Score of our classifier is 0.871 for SNe IIL, and 0.974 for SNe IIP. We found that by only using the Hα line at 6150-6800 Å for classification, the F1_Score up to 0.961 for Type IIP, and 0.818 for Type IIL SNe can be obtained. These results indicate that the profile of the Hα spectral line is the key to distinguishing the two types of SNe.

Keywords: Supernovae, Astronomy data analysis
Water in the Star-forming Region NGC 7129 FIRS 2. Observations of intermediate mass (IM) star formation are expected to highlight the transition between the formation processes of its low and high-mass (HM) counterparts. ${{\rm{H}}}_{2}^{18}{\rm{O}}$ and ${{\rm{H}}}_{2}^{16}{\rm{O}}$ observations of the IM star formation region NGC 7129 FIRS 2 were obtained with the Heterodyne Instrument for the Far-Infrared aboard the Herschel Space Observatory; most as part of the WISH key-program. The radiative transfer program RATRAN was used to model water emission from the envelope of this star-forming region. We consider the envelope in two regions, inner and outer envelope, which are separated by the water freeze-out radius. An outer envelope ortho-H ${}_{2}^{18}$ O/H2 abundance was determined to be 3.5 ± 0.3 × 10-11, and an outer turbulent velocity was determined to be 2.25 ± 0.25 km s-1. The outer envelope ortho-H216O/H2 and para-H216O/H2 abundances were determined to be 1.5 ± 0.5 × 10-8 and 4.5 ± 0.5 × 10-9, respectively. The inner envelope abundances and turbulent velocity could not be constrained due to increased optical depth. The derived values are consistent with those found by low-mass (LM) and HM young stellar object studies of water. While the line shapes and intensities of these lines are more similar to the spectral lines found for LM objects, the turbulent velocity is closer to that seen in HM objects. Lastly, we present a simple visualization tool that we created to show that these abundance results, particularly the limited extent probed by these lines, should not have been a surprise. This tool can be very useful in planning future molecular line observations.

Keywords: Interstellar molecules, Interstellar abundances, Star formation, Astrochemistry
An Extremely Massive Quiescent Galaxy at z = 3.493: Evidence of Insufficiently Rapid Quenching Mechanisms in Theoretical Models. We present spectra of the most massive quiescent galaxy yet spectroscopically confirmed at z &gt; 3, verified via the detection of Balmer absorption features in the H- and K-bands of Keck/MOSFIRE. The spectra confirm a galaxy with no significant ongoing star formation, consistent with the lack of rest-frame UV flux and overall photometric spectral energy distribution. With a stellar mass of ${3.1}_{-0.2}^{+0.1}\times {10}^{11}\,{M}_{\odot }$ at z = 3.493, this galaxy is nearly three times more massive than the highest redshift spectroscopically confirmed absorption-line-identified galaxy known. The star formation history of this quiescent galaxy implies that it formed &gt;1000 M⊙ yr-1 for almost 0.5 Gyr beginning at z ∼ 7.2, strongly suggestive that it is the descendant of massive dusty star-forming galaxies at 5 &lt; z &lt; 7 recently observed with ALMA. While galaxies with similarly extreme stellar masses are reproduced in some simulations at early times, such a lack of ongoing star formation is not seen there. This suggests the need for a quenching process that either starts earlier or is more rapid than that currently prescribed, challenging our current understanding of how ultra-massive galaxies form and evolve in the early universe.

Keywords: Extragalactic astronomy, Galaxy formation, High-redshift galaxies, Galaxy evolution
Onset of Turbulent Fast Magnetic Reconnection Observed in the Solar Atmosphere. Fast magnetic reconnection powers explosive events throughout the universe, from gamma-ray bursts to solar flares. Despite its importance, the onset of astrophysical fast reconnection is the subject of intense debate and remains an open question in plasma physics. Here we report high-cadence observations of two reconnection-driven solar microflares obtained by the Interface Region Imaging Spectrograph that show persistent turbulent flows preceding flaring. The speeds of these flows are comparable to the local sound speed initially, suggesting the onset of fast reconnection in a highly turbulent plasma environment. Our results are in close quantitative agreement with the theory of turbulence-driven reconnection as well as with numerical simulations in which fast magnetic reconnection is induced by turbulence.

Keywords: Solar atmosphere, Magnetohydrodynamics, Solar flares, Solar magnetic reconnection, Solar ultraviolet emission, Plasma physics, Solar active regions, Solar magnetic fields, Spectroscopy, Solar transition region, Solar chromosphere