Sazuna/UAT_keywords huggingface dataset:
Observation of S4716-a Star with a 4 yr Orbit around Sgr A*. The ongoing monitoring of the Galactic center and Sgr A*, the central supermassive black hole, produces surprising and unexpected findings. This goes hand in hand with the technical evolution of ground- and space-based telescopes and instruments, but also with the progression of image filter techniques such as the Lucy-Richardson algorithm. As we continue to trace the members of the S cluster close to Sgr A* on their expected trajectory around the supermassive black hole, we present the finding of a new stellar source, which we call S4716. The newly found star orbits Sgr A* in about 4.0 yr and can be detected with NIRC2 (Keck), OSIRIS (Keck), SINFONI (VLT), NACO (VLT), and GRAVITY (VLTI). With a periapse distance of about 100 au, S4716 shows an equivalent distance toward Sgr A* as S4711. These fast-moving stars undergo a similar dynamical evolution, since S4711-S4716 share comparable orbital properties. We will furthermore draw a connection between the recent finding of a new faint star called S300 and the data presented here. Additionally, we observed a blend-star event with S4716 and another newly identified S star S148 in 2017.

Keywords: Supermassive black holes, Galactic center, Stellar dynamics, Star clusters
The Physical Properties of Star-forming Galaxies with Strong [O III] Lines at z = 3.25. We present an analysis of physical properties of 34 [O III] emission-line galaxies (ELGs) at z = 3.254 ± 0.029 in the Extended Chandra Deep Field South (ECDFS). These ELGs are selected from deep narrow H2S(1) and broad K s imaging of 383 arcmin2 obtained with CFHT/WIRCam. We construct spectral energy distributions (SEDs) from U to K s to derive the physical properties of ELGs. These [O III] ELGs are identified as starburst galaxies with strong [O III] lines of L OIII  ~ 1042.6-1044.2 erg s-1 and have stellar masses of M * ~ 109.0-1010.6 M ⊙ and star formation rates of ~10-210 M ⊙ yr-1. Our results show that 24% of our sample galaxies are dusty with A V &gt; 1 mag and EW([O III])rest ~ 70-500 Å, which are often missed in optically selected [O III] ELG samples. Their rest-frame UV and optical morphologies from HST/ACS and HST/WFC3 deep imaging reveal that these [O III] ELGs are mostly multiple-component systems (likely mergers) or compact. And 20% of them are nearly invisible in the rest-frame UV owing to heavy dust attenuation. Interestingly, we find that our sample ELGs reside in an overdensity consisting of two components: one southeast (SE) with an overdensity factor of δ gal ~ 41 over a volume of 133 cMpc3, and the other northwest (NW) with δ gal ~ 38 over a volume of 103 cMpc3. The two overdense substructures are expected to be virialized at z = 0 with a total mass of ~ 1.1 × 1015 M ⊙ and ~ 4.8 × 1014 M ⊙ and probably merge into a Coma-like galaxy cluster.

Keywords: Galaxy formation, High-redshift galaxies, Galaxy evolution
Mapping Discrete Galaxies at Cosmic Dawn with 21 cm Observations. At cosmic dawn, the 21 cm signal from intergalactic hydrogen was driven by Ly-α photons from some of the earliest stars, producing a spatial pattern that reflected the distribution of galaxies at that time. Due to the large foreground, it is thought that at around redshift 20 it is only observationally feasible to detect 21 cm fluctuations statistically, yielding a limited indirect probe of early galaxies. Here, we show that 21 cm images at cosmic dawn should actually be dominated by large (tens of comoving megaparsecs) high-contrast bubbles surrounding individual galaxies. We demonstrate this using a substantially upgraded seminumerical simulation code that realistically captures the formation and 21 cm effects of the small galaxies expected during this era. Small number statistics associated with the rarity of early galaxies, combined with the multiple scattering of photons in the blue wing of the Ly-α line, create the large bubbles, and also enhance the 21 cm power spectrum by a factor of 2-7 and add to it a feature that measures the typical brightness of galaxies. These various signatures of discrete early galaxies are potentially detectable with planned experiments, such as the Square Kilometer Array and the Hydrogen Epoch of Reionization Array, even if the early stars prove to be formed in dark matter halos with masses as low as 108 M ⊙, 10,000 times smaller than the Milky Way halo.

Keywords: Cosmology, H I line emission
Evidence for Parametric Decay Instability in the Lower Solar Atmosphere. We find evidence for the first observation of the parametric decay instability (PDI) in the lower solar atmosphere. In particular, we find that the power spectrum of density fluctuations near the solar transition region resembles the power spectrum of the velocity fluctuations but with the frequency axis scaled up by about a factor of 2. These results are from an analysis of the Si IV lines observed by the Interface Region Imaging Spectrometer in the transition region of a polar coronal hole. We also find that the density fluctuations have radial velocity of about 75 km s-1 and that the velocity fluctuations are much faster with an estimated speed of 250 km s-1, as is expected for sound waves and Alfvén waves, respectively, in the transition region. Theoretical calculations show that this frequency relationship is consistent with those expected from PDI for the plasma conditions of the observed region. These measurements suggest an interaction between sound waves and Alfvén waves in the transition region, which is evidence for the parametric decay instability.

Keywords: Space plasmas, Magnetohydrodynamics, Solar atmosphere, Plasma physics, The Sun, Solar coronal heating, Plasma astrophysics, Solar physics, Alfven waves
Thomson Scattering above Solar Active Regions and an Ad Hoc Polarization Correction Method for the Emissive Corona. Thomson-scattered photospheric light is the dominant constituent of the lower solar corona's spectral continuum viewed off-limb at optical wavelengths. Known as the K-corona, it is also linearly polarized. We investigate the possibility of using the a priori polarized characteristics of the K-corona, together with polarized emission lines, to measure and correct instrument-induced polarized crosstalk. First we derive the Stokes parameters of the Thomson scattering of unpolarized light in an irreducible spherical tensor formalism. This allows forward synthesis of the Thomson-scattered signal for the more complex scenario that includes symmetry-breaking features in the incident radiation field, which could limit the accuracy of our proposed technique. For this, we make use of an advanced 3D radiative magnetohydrodynamic coronal model. Together with synthesized polarized signals in the Fe XIII 10746 Å emission line, we find that an ad hoc correction of telescope- and instrument-induced polarization crosstalk is possible under the assumption of a nondepolarizing optical system.

Keywords: Solar E corona, Spectropolarimetry, Solar K corona, Solar magnetic fields
Trends in Silicates in the β Pictoris Disk. While β Pic is known to host silicates in ring-like structures, whether the properties of these silicate dust vary with stellocentric distance remains an open question. We re-analyze the β Pictoris debris disk spectrum from the Spitzer Infrared Spectrograph (IRS) and a new Infrared Telescope Facility Spectrograph and Imager spectrum to investigate trends in Fe/Mg ratio, shape, and crystallinity in grains as a function of wavelength, a proxy for stellocentric distance. By analyzing a re-calibrated and re-extracted spectrum, we identify a new 18 μm forsterite emission feature and recover a 23 μm forsterite emission feature with a substantially larger line-to-continuum ratio than previously reported. We find that these prominent spectral features are primarily produced by small submicron-sized grains, which are continuously generated and replenished from planetesimal collisions in the disk and can elucidate their parent bodies' composition. We discover three trends about these small grains: as stellocentric distance increases, (1) small silicate grains become more crystalline (less amorphous), (2) they become more irregular in shape, and (3) for crystalline silicate grains, the Fe/Mg ratio decreases. Applying these trends to β Pic's planetary architecture, we find that the dust population exterior to the orbits of β Pic b and c differs substantially in crystallinity and shape. We also find a tentative 3-5 μm dust excess due to spatially unresolved hot dust emission close to the star. From our findings, we infer that the surfaces of large planetesimals are more Fe-rich and collisionally processed closer to the star but more Fe-poor and primordial farther from the star.

Keywords: Silicate grains, Exozodiacal dust, Planetary system formation, Infrared astronomy, Spectroscopy, Planetesimals, Exoplanet formation, Debris disks
MHD Turbulent Power Anisotropy in the Inner Heliosphere. We study anisotropic magnetohydrodynamic (MHD) turbulence in the slow solar wind measured by Parker Solar Probe (PSP) and Solar Orbiter (SolO) during its first orbit from the perspective of variance anisotropy and correlation anisotropy. We use the Belcher &amp; Davis approach (M1) and a new method (M2) that decomposes a fluctuating vector into parallel and perpendicular fluctuating vectors. M1 and M2 calculate the transverse and parallel turbulence components relative to the mean magnetic field direction. The parallel turbulence component is regarded as compressible turbulence, and the transverse turbulence component as incompressible turbulence, which can be either Alfvénic or 2D. The transverse turbulence energy is calculated from M1 and M2, and the transverse correlation length from M2. We obtain the 2D and slab turbulence energy and the corresponding correlation lengths from those transverse turbulence components that satisfy an angle between the mean solar wind flow speed and mean magnetic field θ UB of either (i) 65° &lt; θ UB &lt; 115° or (ii) 0° &lt; θ UB &lt; 25° (155° &lt; θ UB &lt; 180°), respectively. We find that the 2D turbulence component is not typically observed by PSP near perihelion, but the 2D component dominates turbulence in the inner heliosphere. We compare the detailed theoretical results of a nearly incompressible MHD turbulence transport model with the observed results of PSP and SolO measurements, finding good agreement between them.

Keywords: Interplanetary turbulence, Solar wind, Slow solar wind
What It Takes to Measure Reionization with Fast Radio Bursts. Fast Radio Bursts (FRBs) are extragalactic radio transients that exhibit a distance-dependent dispersion of their signal, and thus can be used as cosmological probes. In this article we, for the first time, apply a model-independent approach to measure reionization from synthetic FRB data assuming these signals are detected beyond redshift 5. This method allows us to constrain the full shape of the reionization history as well as the CMB optical depth τ while avoiding the problems of commonly used model-based techniques. A total of 100 localized FRBs, originating from redshifts 5-15, could constrain (at 68% confidence level) the CMB optical depth to within 11%, and the midpoint of reionization to 4%, surpassing current state-of-the-art CMB bounds and quasar limits. Owing to the higher numbers of expected FRBs at lower redshifts, the τ constraints are asymmetric (+14%, -7%), providing a much stronger lower limit. Finally, we show that the independent constraints on reionization from FRBs will improve limits on other cosmological parameters, such as the amplitude of the power spectrum of primordial fluctuations.

Keywords: Cosmology, Reionization, Radio transient sources
Mass Matters: No Evidence for Ubiquitous Lithium Production in Low-mass Clump Giants. Known sources of lithium (Li) in the universe include the Big Bang, novae, asymptotic giant branch stars, and cosmic-ray spallation. During their longer-lived evolutionary phases, stars are not expected to add to the Li budget of the Galaxy, but to largely deplete it. In this context, recent analyses of Li data from GALAH and LAMOST for field red clump (RC) stars have concluded that there is the need for a new production channel of Li, ubiquitous among low-mass stars, and that would be triggered on the upper red giant branch (RGB) or at helium ignition. This is distinct from the Li-rich giant problem and reflects bulk RC star properties. We provide an analysis of the GALAH Li data that accounts for the distribution of progenitor masses of field RC stars observed today. Such progenitors are different than today's field RGB stars. Using standard post-main-sequence stellar evolution, we show that the distribution of Li among field RC giants as observed by GALAH is consistent with standard model predictions, and does not require new Li production mechanisms. Our model predicts a large fraction of very low Li abundances from low-mass progenitors, with higher abundances from higher mass ones. Moreover, there should be a large number of upper limits for RC giants, and higher abundances should correspond to higher masses. The most recent GALAH data indeed confirm the presence of large numbers of upper limits, and a much lower mean Li abundance in RC stars, in concordance with our interpretation.

Keywords: Stellar interiors, Sky surveys, Evolved stars, Stellar populations, Red giant clump, Chemical abundances, Red giant stars, Asteroseismology, Stellar evolution
Inferring the Thermal History of the Intergalactic Medium from the Properties of the Hydrogen and Helium Lyα Forest. The filamentary network of intergalactic medium (IGM) gas that gives origin to the Lyα forest in the spectra of distant quasars encodes information on the physics of structure formation and the early thermodynamics of diffuse baryonic material. Here we use a massive suite of more than 400 high-resolution cosmological hydrodynamical simulations run with the Graphics Processing Unit-accelerated code Cholla to study the IGM at high spatial resolution maintained over the entire computational volume. The simulations capture a wide range of possible IGM thermal histories by varying the photoheating and photoionizing background produced by star-forming galaxies and active galactic nuclei. A statistical comparison of synthetic spectra with the observed 1D flux power spectra of hydrogen at redshifts 2.2 ≤ z ≤ 5.0 and with the helium Lyα opacity at redshifts 2.4 &lt; z &lt; 2.9 tightly constrains the photoionization and photoheating history of the IGM. By leveraging the constraining power of the available Lyα forest data to break model degeneracies, we find that the IGM experienced two main reheating events over 1.2 Gyr of cosmic time. For our best-fit model, hydrogen reionization completes by z  R  ≍ 6.0 with a first IGM temperature peak of T 0 ≃ 1.3 × 104 K and is followed by the reionization of He II that completes by z R ≍ 3.0 and yields a second temperature peak of T 0 ≃ 1.4 × 104 K. We discuss how our results can be used to obtain information on the timing and the sources of hydrogen and helium reionization.

Keywords: Hydrodynamical simulations, Computational methods, Lyman alpha forest, Large-scale structure of the universe
Surveying the Giant H II Regions of the Milky Way with SOFIA. IV. Sgr D, W42, and a Reassessment of the Giant H II Region Census. This is the fourth paper exploring the infrared properties of giant H II regions with the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy (SOFIA). Our survey utilizes the census of 56 Milky Way giant H II regions identified by Conti &amp; Crowther, and in this paper we present the 20 and 37 μm imaging data we obtained from SOFIA for sources Sgr D and W42. Based upon the SOFIA data and other multiwavelength data, we derive and discuss the detailed physical properties of the individual compact sources and subregions as well as the large-scale properties of Sgr D and W42. However, improved measurements have revealed much closer distances to both regions than previously believed, and consequently, both sources are not powerful enough to be considered giant H II regions any longer. Motivated by this, we revisit the census of giant H II regions, performing a search of the last two decades of literature to update each source with the most recent and/or most accurate distance measurements. Based on these new distance estimates, we determine that 14 sources in total (25%) are at sufficiently reliable and closer distances that they are not powerful enough to be considered giant H II regions. We briefly discuss the observational and physical characteristics specific to Sgr D and W42 and show that they have properties distinct from the giant H II regions previously studied as a part of this survey.

Keywords: Star forming regions, Young star clusters, H II regions, Infrared sources
SDSS-IV MaNGA: Cannibalism Caught in the Act-On the Frequency of Occurrence of Multiple Cores in Brightest Cluster Galaxies. Although it is generally accepted that massive galaxies form in a two-phased fashion, beginning with a rapid mass buildup through intense starburst activities followed by primarily dry mergers that mainly deposit stellar mass at outskirts, the late time stellar mass growth of brightest cluster galaxies (BCGs), the most massive galaxies in the universe, is still not well understood. Several independent measurements have indicated a slower mass growth rate than predictions from theoretical models. We attempt to resolve the discrepancy by measuring the frequency of BCGs with multiple cores, which serve as a proxy of the merger rates in the central region and facilitate a more direct comparison with theoretical predictions. Using 79 BCGs at z = 0.06-0.15 with integral field spectroscopic data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) project, we obtain a multiple-core fraction of 0.11 ± 0.04 at z ≈ 0.1 within an 18 kpc radius from the center, which is comparable to the value of 0.08 ± 0.04 derived from mock observations of 218 simulated BCGs from the cosmological hydrodynamical simulation IllustrisTNG. We find that most cores that appear close to the BCGs from imaging data turn out to be physically associated systems. Anchoring on the similarity in the multiple-core frequency between the MaNGA and IllustrisTNG, we discuss the mass growth rate of BCGs over the past 4.5 Gyr.

Keywords: Galaxy clusters, Galaxy formation, Elliptical galaxies, Galaxy mergers
Climate Outcomes of Earth-similar Worlds as a Function of Obliquity and Rotation Rate. A set of simulations with a 3D global climate model are performed to investigate the roles of obliquity and rotation period in the habitability of Earthlike exoplanets. The simulations cover the obliquity-rotation parameter space, from 0° to 90° in obliquity and 1-128 days in rotation period. The simulated global mean temperatures are warmest at 45° obliquity with fast rotations, due to the modification of the greenhouse effect from the spatial redistribution of clouds and water vapor. The slow-moving insolation-cloud mechanism, previously found in simulations with slow rotations and zero obliquity, also produces a cooling trend from intermediate obliquity to high obliquity, with the coldest climate occurring at 90° obliquity for all rotation periods. At low obliquities and fast rotation, persistent snow and sea ice can form, producing cooler temperatures. A Climate Habitability metric is defined, based on temperature and precipitation, which compares well with observations when applied to a simulation using Earth's obliquity and rotation. Over a wider range of obliquity and rotation period, the Climate Habitability ranges from 10% to 70% of the terrestrial area. Overall, the simulated global mean surface temperature shows a much larger spread across the range of simulated rotation periods at 45° obliquity compared to 0° obliquity. Therefore, we conclude that 3D exoplanet simulations using intermediate obliquities (e.g., 45°) instead of 0° will reveal a wider range of possible climate conditions for specific orbital configurations. In addition, Earth's climate habitability can increase by 25% if the obliquity increases from 23.°5 to 45°.

Keywords: Exoplanet atmospheric variability, Planetary climates
Evaluating the Evidence for Water World Populations Using Mixture Models. Water worlds have been hypothesized as an alternative to photoevaporation in order to explain the gap in the radius distribution of Kepler exoplanets. We explore water worlds within the framework of a joint mass-radius-period distribution of planets fit to a sample of transiting Kepler exoplanets, a subset of which have radial velocity mass measurements. We employ hierarchical Bayesian modeling to create a range of ten mixture models that include multiple compositional subpopulations of exoplanets. We model these subpopulations-including planets with gaseous envelopes, evaporated rocky cores, evaporated icy cores, intrinsically rocky planets, and intrinsically icy planets-in different combinations in order to assess which combinations are most favored by the data. Using cross-validation, we evaluate the support for models that include planets with icy compositions compared to the support for models that do not, finding broad support for both. We find significant population-level degeneracies between subpopulations of water worlds and planets with primordial envelopes. Among models that include one or more icy-core subpopulations, we find a wide range for the fraction of planets with icy compositions, with a rough upper limit of 50%. Improved data sets or alternative modeling approaches may be able to better distinguish between these subpopulations of planets.

Keywords: Bayesian statistics, Exoplanet catalogs, Model selection, Astrostatistics, Exoplanet structure, Mixture model, Exoplanet formation, Hierarchical models
The Detection of Deuterated Water in the Large Magellanic Cloud with ALMA. We report the first detection of deuterated water (HDO) toward an extragalactic hot core. The HDO 211-212 line has been detected toward hot cores N 105-2 A and 2 B in the N 105 star-forming region in the low-metallicity Large Magellanic Cloud (LMC) dwarf galaxy with the Atacama Large Millimeter/submillimeter Array (ALMA). We have compared the HDO line luminosity (L HDO) measured toward the LMC hot cores to those observed toward a sample of 17 Galactic hot cores covering three orders of magnitude in L HDO, four orders of magnitude in bolometric luminosity (L bol), and a wide range of Galactocentric distances (thus metallicities). The observed values of L HDO for the LMC hot cores fit very well into the L HDO trends with L bol and metallicity observed toward the Galactic hot cores. We have found that L HDO seems to be largely dependent on the source luminosity, but metallicity also plays a role. We provide a rough estimate of the H2O column density and abundance ranges toward the LMC hot cores by assuming that HDO/H2O toward the LMC hot cores is the same as that observed in the Milky Way; the estimated ranges are systematically lower than Galactic values. The spatial distribution and velocity structure of the HDO emission in N 105-2 A is consistent with HDO being the product of the low-temperature dust grain chemistry. Our results are in agreement with the astrochemical model predictions that HDO is abundant regardless of the extragalactic environment and should be detectable with ALMA in external galaxies.

Keywords: Star forming regions, Chemical abundances, Astrochemistry, Star formation, Protostars, Magellanic Clouds