Sazuna/UAT_keywords huggingface dataset:
Spatial Decorrelation of Young Stars and Dense Gas as a Probe of the Star Formation-Feedback Cycle in Galaxies. The spatial decorrelation of dense molecular gas and young stars observed on ≲1 kpc scales in nearby galaxies indicates rapid dispersal of star-forming regions by stellar feedback. We explore the sensitivity of this decorrelation to different processes controlling the structure of the interstellar medium, the abundance of molecular gas, star formation, and feedback in a suite of simulations of an isolated dwarf galaxy with structural properties similar to NGC 300 that self-consistently model radiative transfer and molecular chemistry. Our fiducial simulation reproduces the magnitude of decorrelation and its scale dependence measured in NGC 300, and we show that this agreement is due to different aspects of feedback, including H2 dissociation, gas heating by the locally variable UV field, early mechanical feedback, and supernovae. In particular, early radiative and mechanical feedback affects the correlation on ≲100 pc scales, while supernovae play a significant role on ≳ 100 pc scales. The correlation is also sensitive to the choice of the local star formation efficiency per free fall time, ϵff, which provides a strong observational constraint on ϵff when the global star formation rate is independent of its value. Finally, we explicitly show that the degree of correlation between the peaks of molecular gas and star formation density is directly related to the distribution of the lifetimes of star-forming regions.

Keywords: Hydrodynamical simulations, Interstellar dynamics, Disk galaxies, Stellar feedback, Star forming regions, Dwarf galaxies, Star formation, Interstellar medium, Radiative transfer simulations
Linear Polarization of the 21 cm Line from the Epoch of Reionization. The 21 cm linear polarization due to Thomson scattering off free electrons can probe the distribution of neutral hydrogen in the intergalactic medium during the epoch of reionization, complementary to the 21 cm temperature fluctuations. A previous study estimated the strength of polarization with a toy model and claimed that it can be detected with 1 month observation of the Square Kilometre Array (SKA). Here we revisit this investigation with account of nonlinear terms due to inhomogeneous reionization, using semi-numerical reionization simulations to provide the realistic estimation of the 21 cm TE and EE angular power spectra ( ${C}_{{\ell }}^{\mathrm{TE}}$ and ${C}_{{\ell }}^{\mathrm{EE}}$ ). We find that (1) both power spectra are enhanced on sub-bubble scales but suppressed on super-bubble scales, compared with previous results; (2) ${C}_{{\ell }}^{\mathrm{TE}}$ displays a zero crossing at ℓ &lt; 100, and its angular scale is sensitive to the scale dependence of H I bias on large scales; (3) the ratios of the power spectrum to its maximum value during reionization at a given ℓ, i.e., ${C}_{{\ell }}^{\mathrm{TE}}/{C}_{{\ell },\max }^{\mathrm{TE}}$ and ${C}_{{\ell }}^{\mathrm{EE}}/{C}_{{\ell },\max }^{\mathrm{EE}}$ , show robust correlations with the global ionized fraction. However, measurement of this signal will be very challenging not only because the overall strength is weaker than the sensitivity of SKA, but also because of the polarized foregrounds from diffuse synchrotron emission, and Faraday rotation, which modifies the observed polarization. Nevertheless, the 21 cm linear polarization signal may still likely be detectable through other approaches, e.g., its cross-correlation with other probes.

Keywords: Large-scale structure of the universe, H I line emission, Intergalactic medium, Reionization, Radio interferometry, Two-point correlation function
On the (Mis)Interpretation of the Scattering Polarization Signatures in the Ca II 8542 Å Line through Spectral Line Inversions. Scattering polarization tends to dominate the linear polarization signals of the Ca II 8542 Å line in weakly magnetized areas (B ≲ 100 G), especially when the observing geometry is close to the limb. In this paper, we evaluate the degree of applicability of existing non-LTE spectral line inversion codes (which assume that the spectral line polarization is due to the Zeeman effect only) at inferring the magnetic field vector and, particularly, its transverse component. To this end, we use the inversion code STiC to extract the strength and orientation of the magnetic field from synthetic spectropolarimetric data generated with the Hanle-RT code. The latter accounts for the generation of polarization through scattering processes as well as the joint actions of the Hanle and the Zeeman effects. We find that, when the transverse component of the field is stronger than ~80 G, the inversion code is able to retrieve accurate estimates of the transverse field strength as well as its azimuth in the plane of the sky. Below this threshold, the scattering polarization signatures become the major contributors to the linear polarization signals and often mislead the inversion code into severely over- or underestimating the field strength. Since the line-of-sight component of the field is derived from the circular polarization signal, which is not affected by atomic alignment, the corresponding inferences are always good.

Keywords: Starlight polarization, Solar magnetic fields, Radiative transfer
Orbital Decay of Short-period Exoplanets via Tidal Resonance Locking. A large fraction of known exoplanets have short orbital periods where tidal excitation of gravity waves within the host star causes the planets' orbits to decay. We study the effects of tidal resonance locking, in which the planet locks into resonance with a tidally excited stellar gravity mode. Because a star's gravity mode frequencies typically increase as the star evolves, the planet's orbital frequency increases in lockstep, potentially causing much faster orbital decay than predicted by other tidal theories. Due to nonlinear mode damping, resonance locking in Sun-like stars likely only operates for low-mass planets (M ≲ 0.1 MJup), but in stars with convective cores it can likely operate for all planetary masses. The orbital decay timescale with resonance locking is typically comparable to the star's main-sequence lifetime, corresponding to a wide range in effective stellar quality factor (103 ≲ Q' ≲ 109), depending on the planet's mass and orbital period. We make predictions for several individual systems and examine the orbital evolution resulting from both resonance locking and nonlinear wave dissipation. Our models demonstrate how short-period massive planets can be quickly destroyed by nonlinear mode damping, while short-period low-mass planets can survive, even though they undergo substantial inward tidal migration via resonance locking.

Keywords: Tidal interaction, Stellar oscillations, Exoplanets, Stellar evolution
Search for Dark Matter Annihilation Signals from Unidentified Fermi-LAT Objects with H.E.S.S.. Cosmological N-body simulations show that Milky Way-sized galaxies harbor a population of unmerged dark matter (DM) subhalos. These subhalos could shine in gamma-rays and eventually be detected in gamma-ray surveys as unidentified sources. We performed a thorough selection among unidentified Fermi-Large Area Telescope Objects (UFOs) to identify them as possible tera-electron-volt-scale DM subhalo candidates. We search for very-high-energy (E ≳ 100 GeV) gamma-ray emissions using H.E.S.S. observations toward four selected UFOs. Since no significant very-high-energy gamma-ray emission is detected in any data set of the four observed UFOs or in the combined UFO data set, strong constraints are derived on the product of the velocity-weighted annihilation cross section ⟨σv⟩ by the J factor for the DM models. The 95% confidence level observed upper limits derived from combined H.E.S.S. observations reach ⟨σv⟩J values of 3.7 × 10-5 and 8.1 × 10-6 GeV2 cm-2 s-1 in the W+W- and τ+τ- channels, respectively, for a 1 TeV DM mass. Focusing on thermal weakly interacting massive particles, the H.E.S.S. constraints restrict the J factors to lie in the range 6.1 × 1019-2.0 × 1021 GeV2 cm-5 and the masses to lie between 0.2 and 6 TeV in the W+W- channel. For the τ+τ- channel, the J factors lie in the range 7.0 × 1019-7.1 × 1020 GeV2 cm-5 and the masses lie between 0.2 and 0.5 TeV. Assuming model-dependent predictions from cosmological N-body simulations on the J-factor distribution for Milky Way-sized galaxies, the DM models with masses &gt;0.3 TeV for the UFO emissions can be ruled out at high confidence level.

Keywords: Gamma-ray sources, Dark matter, High energy astrophysics, Gamma-ray telescopes
Accessing Intermediate-mass Black Holes in 728 Globular Star Clusters in NGC 4472. Intermediate-mass black holes (IMBHs) by definition have masses of MIMBH ~ 102-5 M⊙, a range with few observational constraints. Finding IMBHs in globular star clusters (GCs) would validate a formation channel for massive black-hole seeds in the early universe. Here, we simulate a 60 hr observation with the next-generation Very Large Array (ngVLA) of 728 GC candidates in the Virgo Cluster galaxy NGC 4472. Interpreting the radio detection thresholds as signatures of accretion onto IMBHs, we benchmark IMBH mass thresholds in three scenarios and find the following: (1) radio analogs of ESO 243-49 HLX-1, a strong IMBH candidate with ${M}_{\mathrm{IMBH}}^{\mathrm{HLX}}\sim {10}^{4-5}\,\,{M}_{\odot }$ in a star cluster, are easy to access in all 728 GC candidates. (2) For the 30 GC candidates with extant X-ray detections, the empirical fundamental-plane relation involving black-hole mass plus X-ray and radio luminosities suggests access to ${M}_{\mathrm{IMBH}}^{\mathrm{FP}}\sim {10}^{1.7-3.6}\,\,{M}_{\odot }$ , with an uncertainty of 0.44 dex. (3) A fiducial Bondi accretion model was applied to all 728 GC candidates and to radio stacks of the GC candidates. This model suggests access to IMBH masses, with a statistical uncertainty of 0.39 dex, of ${M}_{\mathrm{IMBH}}^{{\rm{B}}}\sim {10}^{4.9-5.1}\,{M}_{\odot }$ for individual GC candidates, and ${M}_{\mathrm{IMBH}}^{{\rm{B}},\mathrm{stack}}\sim {10}^{4.5}\,{M}_{\odot }$ for radio stacks of about 100-200 GC candidates. The fiducial Bondi model offers initial guidance, but is subject to additional systematic uncertainties and should be superseded by hydrodynamical simulations of gas flows in GCs.

Keywords: Globular star clusters, Intermediate-mass black holes, Accretion
Symbiotic Stars in the Apache Point Observatory Galactic Evolution Experiment Survey: The Case of LIN 358 and SMC N73 (LIN 445a). LIN 358 and SMC N73 are two symbiotic binaries in the halo of the Small Magellanic Cloud, each composed of a hot white dwarf accreting from a cool giant companion. In this work, we characterize these systems using a combination of spectral energy distribution (SED)-fitting to the extant photometric data spanning a broad wavelength range (X-ray/ultraviolet to near-infrared), detailed analysis of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra for the giant stars, and orbit fitting to high quality radial velocities from the APOGEE database. Using the calculated Roche lobe radius for the giant component and the mass ratio for each system, it is found that LIN 358 is likely undergoing mass transfer via wind Roche lobe overflow, while the accretion mechanism for SMC N73 remains uncertain. This work presents the first orbital characterization for both of these systems (yielding periods of &gt;270 and &gt;980 days, respectively, for SMC N73 and LIN 358) and the first global SED fitting for SMC N73. In addition, variability was identified in APOGEE spectra of LIN 358 spanning 17 epochs over two years that may point to a time variable accretion rate as the product of an eccentric orbit.

Keywords: Symbiotic binary stars
Learning How to Surf: Reconstructing the Propagation and Origin of Gravitational Waves with Gaussian Processes. Soon, the combination of electromagnetic and gravitational signals will open the door to a new era of gravitational-wave (GW) cosmology. It will allow us to test the propagation of tensor perturbations across cosmic time and study the distribution of their sources over large scales. In this work, we show how machine-learning techniques can be used to reconstruct new physics by leveraging the spatial correlation between GW mergers and galaxies. We explore the possibility of jointly reconstructing the modified GW propagation law and the linear bias of GW sources, as well as breaking the slight degeneracy between them by combining multiple techniques. We show predictions roughly based on a network of Einstein Telescopes combined with a high-redshift galaxy survey (z ≲ 3). Moreover, we investigate how these results can be rescaled to other instrumental configurations. In the long run, we find that obtaining accurate and precise luminosity distance measurements (extracted directly from the individual GW signals) will be the most important factor to consider when maximizing the constraining power.

Keywords: Gravitational wave astronomy, Non-standard theories of gravity, Gaussian Processes regression, Large-scale structure of the universe
Coronal Hole Detection and Open Magnetic Flux. Many scientists use coronal hole (CH) detections to infer open magnetic flux. Detection techniques differ in the areas that they assign as open, and may obtain different values for the open magnetic flux. We characterize the uncertainties of these methods, by applying six different detection methods to deduce the area and open flux of a near-disk center CH observed on 2010 September 19, and applying a single method to five different EUV filtergrams for this CH. Open flux was calculated using five different magnetic maps. The standard deviation (interpreted as the uncertainty) in the open flux estimate for this CH ≈ 26%. However, including the variability of different magnetic data sources, this uncertainty almost doubles to 45%. We use two of the methods to characterize the area and open flux for all CHs in this time period. We find that the open flux is greatly underestimated compared to values inferred from in situ measurements (by 2.2-4 times). We also test our detection techniques on simulated emission images from a thermodynamic MHD model of the solar corona. We find that the methods overestimate the area and open flux in the simulated CH, but the average error in the flux is only about 7%. The full-Sun detections on the simulated corona underestimate the model open flux, but by factors well below what is needed to account for the missing flux in the observations. Under-detection of open flux in coronal holes likely contributes to the recognized deficit in solar open flux, but is unlikely to resolve it.

Keywords: Solar coronal holes, Interplanetary magnetic fields, Solar magnetic fields
The Sizes of Quasar Host Galaxies in the Hyper Suprime-Cam Subaru Strategic Program. The relationship between quasars and their host galaxies provides clues on how supermassive black holes (SMBHs) and massive galaxies are jointly assembled. To elucidate this connection, we measure the structural and photometric properties of the host galaxies of ~5000 Sloan Digital Sky Survey quasars at 0.2 &lt; z &lt; 1 using five-band (grizy) optical imaging from the Hyper Suprime-Cam Subaru Strategic Program. An automated analysis tool is used to forward-model the blended emission of the quasar as characterized by the point-spread function and the underlying host galaxy as a two-dimensional Sérsic profile. We find that quasars are preferentially hosted by massive star-forming galaxies with disklike light profiles. Furthermore, the size distribution of quasar hosts is broad at a given stellar mass and the average values exhibit a size-stellar mass relation as seen with inactive galaxies. In contrast, the sizes of quasar hosts are more compact than those of inactive star-forming galaxies on average, but not as compact as those of quiescent galaxies of similar stellar masses. This is true irrespective of quasar properties, including the bolometric luminosity, Eddington ratio, and black hole mass. These results are consistent with a scenario in which galaxies are concurrently fueling an SMBH and building their stellar bulge from a centrally concentrated gas reservoir. Alternatively, quasar hosts may be experiencing a compaction process in which stars from the disk and inflowing gas are responsible for growing the bulge. In addition, we confirm that the host galaxies of type 1 quasars have a bias of being closer to face-on systems, suggesting that galactic-scale dust can contribute to obscuring the broad-line region.

Keywords: AGN host galaxies, Supermassive black holes, Quasars, Galaxy structure, Active galactic nuclei
Galaxy Properties at the Faint End of the H I Mass Function. The Survey of H I in Extremely Low-mass Dwarfs (SHIELD) includes a volumetrically complete sample of 82 gas-rich dwarfs with ${M}_{{\rm{H}}\,{\rm\small{I}}}\lesssim {10}^{7.2}$ ${M}_{\odot }$ selected from the ALFALFA survey. We are obtaining extensive follow-up observations of the SHIELD galaxies to study their gas, stellar, and chemical content, and to better understand galaxy evolution at the faint end of the H I mass function. Here, we investigate the properties of 30 SHIELD galaxies using Hubble Space Telescope imaging of their resolved stars and Westerbork Synthesis Radio Telescope observations of their neutral hydrogen. We measure tip of the red giant branch (TRGB) distances, star formation activity, and gas properties. The TRGB distances are up to 4× greater than estimates from flow models, highlighting the importance of velocity-independent distance indicators in the nearby universe. The SHIELD galaxies are in underdense regions, with 23% located in voids; one galaxy appears paired with a more massive dwarf. We quantify galaxy properties at low masses including stellar and H I masses, star formation rate (SFRs), specific SFRs, star formation efficiencies, birth-rate parameters, and gas fractions. The lowest-mass systems lie below the mass thresholds where stellar mass assembly is predicted to be impacted by reionization. Even so, we find the star formation properties follow the same trends as higher-mass gas-rich systems, albeit with a different normalization. The H I disks are small ( $ \langle r \rangle \lt 0.7\,{\rm{kpc}}$ ), making it difficult to measure the H I rotation using standard techniques; we develop a new methodology and report the velocity extent, and its associated spatial extent, with robust uncertainties.

Keywords: Luminosity function, Dwarf irregular galaxies, Distance measure, Galaxy rotation, H I line emission, Star formation, Hertzsprung Russell diagram
Fermi-LAT Detection of GeV γ-Ray Emission from the Type Ia Supernova Remnant G272.2-3.2. A new γ-ray source with a significance level of approximately 5σ was reported in the region of the supernova remnant (SNR) G272.2-3.2 by analyzing the approximately 12.4 yr of observation data from the Fermi Large Area Telescope. Its γ-ray spatial distribution did not show an extended feature, and it had a soft spectrum with a spectral index of 2.56 ± 0.01 in the power-law model. No significant variability of its light curve with 10 time bins was identified, and its spatial positions in the X-ray and GeV bands overlapped. We suggest that the new γ-ray source is a likely counterpart of SNR G272.2-3.2. Analyzing its spectrum, we discussed the likely origins of the γ-ray emission.

Keywords: Gamma-ray observatories, Gamma-ray astronomy, Type Ia supernovae
Observation of the Apoapsis of S62 in 2019 with NIRC2 and SINFONI. Given the increased attention toward the detection of faint stars in the Galactic center, we would like to address the detectability of S62 in its apoapsis with the Spectrograph for INtegral Field Observations in the Near Infrared at the Very Large Telescope (SINFONI; VLT) and the Near-Infrared Camera 2 (NIRC2; KECK) in this work. Because of the nearby stars and the chance of confusion, we are using Lucy-Richardson deconvolved images to detect S62 on its Keplerian orbit around Sgr A* with a period of less than 10 yr. We use the same data set as for S62 to trace additionally the S-cluster star S29 at the expected position based on the orbital elements presented in this work. To verify the results of the filtering technique, we are analyzing K-band continuum data of the same epoch independently observed with NIRC2/KECK. Based on the well-derived orbit of S62, we find the star in projection at the expected position in 2019.4 and 2019.5. By analyzing the SINFONI data of 2019.5, we confirm the 16.1 ± 0.2 mag for S62 that was formerly derived with NAOS-CONICA (NACO; VLT). We base our NACO imaging analysis on the robust data set that was previously used to investigate the Schwarzschild precision of S2. We also present a critical discussion of the elsewhere proposed linear trajectory of S62 and its disputed identification with a 19 mag star found with GRAVITY mounted at the VLT Interferometer.

Keywords: Keplerian orbit, Galactic center, Black holes
Photoionized Herbig-Haro Objects in the Orion Nebula through Deep High Spectral Resolution Spectroscopy. II. HH 204. We analyze the physical conditions, chemical composition, and other properties of the photoionized Herbig-Haro (HH) object HH 204 through Very Large Telescope echelle spectroscopy and Hubble Space Telescope imaging. We kinematically isolate the high-velocity emission of HH 204 from the emission of the background nebula and study the subarcsecond distribution of physical conditions and ionic abundances across the HH object. We find that low- and intermediate-ionization emission arises exclusively from gas at photoionization equilibrium temperatures, whereas the weak high-ionization emission from HH 204 shows a significant contribution from higher-temperature shock-excited gas. We separately derive the ionic abundances of HH 204, the emission of the Orion Nebula, and the fainter diffuse blue layer. In HH 204, the O+ abundance determined from collisional excited lines matches the one based on recombination lines, while the O2+ abundance is very low, so that the oxygen abundance discrepancy is zero. The ionic abundances of Ni and Fe in HH 204 have similar ionization and depletion patterns, with total abundances that are a factor of 3.5 higher than in the rest of the Orion Nebula due to dust destruction in the bow shock. We show that a failure to resolve the kinematic components in our spectra would lead to significant error in the determination of chemical abundances (for instance, a 40% underestimate of O), mainly due to incorrect estimation of the electron density.

Keywords: Herbig-Haro objects, H II regions, Chemical abundances, Interstellar medium