Sazuna/UAT_keywords huggingface dataset:
Probing Interstellar Grain Growth through Polarimetry in the Taurus Cloud Complex. The optical and near-infrared (OIR) polarization of starlight is typically understood to arise from the dichroic extinction of that light by dust grains whose axes are aligned with respect to a local magnetic field. The size distribution of the aligned-grain population can be constrained by measurements of the wavelength dependence of the polarization. The leading physical model for producing the alignment is that of radiative alignment torques (RATs), which predicts that the most efficiently aligned grains are those with sizes larger than the wavelengths of light composing the local radiation field. Therefore, for a given grain-size distribution, the wavelength at which the polarization reaches a maximum ( ${\lambda }_{\max }$ ) should correlate with the characteristic reddening along the line of sight between the dust grains and the illumination source. A correlation between ${\lambda }_{\max }$ and reddening has been previously established for extinctions up to ${A}_{V}\approx 4$ mag. We extend the study of this relationship to a larger sample of stars in the Taurus cloud complex, including extinctions ${A}_{V}\gt 10$ mag. We confirm the earlier results for ${A}_{V}\lt 4$ mag but find that the ${\lambda }_{\max }$ versus AV relationship bifurcates above ${A}_{V}\approx 4$ mag, with part of the sample continuing the previously observed relationship. The remaining sample exhibits a steeper rise in ${\lambda }_{\max }$ versus AV. We propose that the data exhibiting the steep rise represent lines of sight of high-density "clumps," where grain coagulation has taken place. We present RAT-based modeling supporting these hypotheses. These results indicate that multiband OIR polarimetry is a powerful tool for tracing grain growth in molecular clouds, independent of uncertainties in the dust temperature and emissivity.

Keywords: Interstellar dust, Spectropolarimetry, Interstellar dust extinction, Starlight polarization, Interstellar clouds, Interstellar medium, Polarimetry
Formation of the Hub-Filament System G33.92+0.11: Local Interplay between Gravity, Velocity, and Magnetic Field. The formation of filaments in molecular clouds is an important process in star formation. Hub-filament systems (HFSs) are a transition stage connecting parsec-scale filaments and protoclusters. Understanding the origin of HFSs is crucial to reveal how star formation proceeds from clouds to cores. Here we report James Clerk Maxwell telescope POL-2 850 μm polarization and IRAM 30 m C18O (2-1) line observations toward the massive HFS G33.92+0.11. The 850 μm continuum map reveals four major filaments converging to the center of G33.92+0.11 with numerous short filaments connecting to the major filaments at local intensity peaks. We estimate the local orientations of filaments, magnetic field, gravity, and velocity gradients from observations, and we examine their correlations based on their local properties. In the high-density areas, our analysis shows that the filaments tend to align with the magnetic field and local gravity. In the low-density areas, we find that the local velocity gradients tend to be perpendicular to both the magnetic field and local gravity, although the filaments still tend to align with local gravity. A global virial analysis suggests that the gravitational energy overall dominates the magnetic and kinematic energy. Combining local and global aspects, we conclude that the formation of G33.92+0.11 is predominantly driven by gravity, dragging and aligning the major filaments and magnetic field on the way to the inner dense center. Traced by local velocity gradients in the outer diffuse areas, ambient gas might be accreted onto the major filaments directly or via the short filaments.

Keywords: Interstellar filaments, Interstellar dynamics, Infrared dark clouds, Star forming regions, Young massive clusters, Molecular clouds, Interstellar magnetic fields, Interstellar medium, Submillimeter astronomy, Polarimetry, Collapsing clouds
Nonuniversal Interstellar Density Spectra Probed by Pulsars. Galactic interstellar turbulence affects density distribution and star formation. We introduce a new method of measuring interstellar turbulent density spectra by using the dispersion measures (DMs) of a large sample of pulsars. Without the need of invoking multiple tracers, we obtain nonuniversal density spectra in the multiphase interstellar medium over different ranges of length scales. By comparing the analytical structure function of DMs with the observationally measured one in different areas of sky, we find a shallow density spectrum arising from the supersonic turbulence in cold interstellar phases, and a Kolmogorov-like density spectrum in the diffuse warm ionized medium (WIM). Both spectra extend up to hundreds of parsecs. On larger scales, we identify, for the first time, a steep density spectrum in the diffuse WIM extending up to several kiloparsecs. Our results show that the DMs of pulsars can provide unique new information on the interstellar turbulence.

Keywords: Hydrodynamics, Theoretical techniques, Interstellar medium, Radio pulsars
Deterministic Aspect of the γ-Ray Variability in Blazars. Linear time series analysis, mainly the Fourier transform-based methods, has been quite successful in extracting information contained in the ever-modulating light curves of active galactic nuclei, and thereby contribute in characterizing the general features of supermassive black hole systems. In particular, the statistical properties of γ-ray variability of blazars are found to be fairly represented by flicker noise in the temporal frequency domain. However, these conventional methods have not been able to fully encapsulate the richness and the complexity displayed in the light curves of the sources. In this work, to complement our previous study on a similar topic, we perform nonlinear time series analysis of the decade-long Fermi/LAT observations of 20 γ-ray bright blazars. The study is motivated to address one of the most relevant queries: whether the dominant dynamical processes leading to the observed γ-ray variability are of deterministic or stochastic nature. For the purpose, we perform recurrence quantification analysis of the blazars and directly measure the quantities, which suggest that the dynamical processes in blazars could be a combination of deterministic and stochastic processes, while some of the source light curves revealed significant deterministic content. The result, with possible implication of strong disk-jet connection in blazars, could prove to be significantly useful in constructing models that can explain the rich and complex multiwavelength observational features in active galactic nuclei. In addition, we estimate the dynamical timescales, so-called trapping timescales, in the order of a few weeks.

Keywords: Supermassive black holes, High energy astrophysics, Blazars, Relativistic jets, Active galactic nuclei, Time domain astronomy, Gamma-ray transient sources, Time series analysis
GOES-class Estimation for Behind-the-limb Solar Flares Using MESSENGER SAX. Mercury mission MESSENGER's Solar Assembly for X-rays (SAX) observed almost 700 solar flares between 2007 May 28 and 2013 August 19, as cataloged by Dennis Brian et al. The SAX instrument, part of the X-ray Spectrometer, operated at 1-10 keV, partially overlapping the energy range of the GOES X-ray spectrometers. SAX provides viewing angles different from the Earth-Sun line and can therefore be used as a GOES proxy for partially or fully occulted flares as seen from Earth. For flares with GOES classes above C2 seen on-disk for both instruments, we found an empirical relationship between the soft X-ray (SXR) fluxes measured by both SAX and GOES. Due to the different energy response of the two SXR instruments, individual events can deviate on average by about a factor of 2 from the empirical relationship, implying that predictions of the GOES class of occulted flares from SAX data are therefore accurate to within the same factor. The distinctive GOES energy response in combination with the multithermal nature of flares makes it difficult for any instrument, even other soft X-ray spectrometers, to provide a GOES proxy more accurate than a factor of 2.

Keywords: Solar flares, Solar extreme ultraviolet emission, Solar x-ray flares
The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. IV. Unveiling the Embedded Intermediate-Mass Protostar and Disk within OMC2-FIR3/HOPS-370. We present ALMA (0.87 and 1.3 mm) and VLA (9 mm) observations toward the candidate intermediate-mass protostar OMC2-FIR3 (HOPS-370; Lbol ∼ 314 L☉) at ∼0"1 (40 au) resolution for the continuum emission and ∼0"25 (100 au) resolution of nine molecular lines. The dust continuum observed with ALMA at 0.87 and 1.3 mm resolves a near edge-on disk toward HOPS-370 with an apparent radius of ∼100 au. The VLA observations detect both the disk in dust continuum and free-free emission extended along the jet direction. The ALMA observations of molecular lines (H2CO, SO, CH3OH, 13CO, C18O, NS, and H13CN) reveal rotation of the apparent disk surrounding HOPS-370 orthogonal to the jet/outflow direction. We fit radiative transfer models to both the dust continuum structure of the disk and molecular line kinematics of the inner envelope and disk for the H2CO, CH3OH, NS, and SO lines. The central protostar mass is determined to be ∼2.5 M☉ with a disk radius of ∼94 au, when fit using combinations of the H2CO, CH3OH, NS, and SO lines, consistent with an intermediate-mass protostar. Modeling of the dust continuum and spectral energy distribution yields a disk mass of 0.035 M☉ (inferred dust+gas) and a dust disk radius of 62 au; thus, the dust disk may have a smaller radius than the gas disk, similar to Class II disks. In order to explain the observed luminosity with the measured protostar mass, HOPS-370 must be accreting at a rate of (1.7-3.2) × 10-5 M☉ yr-1.

Keywords: Interstellar molecules, Protostars, Young stellar objects, Interstellar medium
Atmosphere Models of Brown Dwarfs Irradiated by White Dwarfs: Analogs for Hot and Ultrahot Jupiters. Irradiated brown dwarfs (BDs) provide natural laboratories to test our understanding of substellar and irradiated atmospheres. A handful of short-period BDs around white dwarfs (WDs) have been observed, but the uniquely intense UV-dominated irradiation presents a modeling challenge. Here, we present the first fully self-consistent 1D atmosphere models that take into account the UV irradiation's effect on the object's temperature structure. We explore two BD-WD systems, namely WD-0137-349 and EPIC-212235321. WD-0137-349B has an equilibrium temperature that would place it in the transition between hot and ultra-hot Jupiters, while EPIC-212235321B has an equilibrium temperature higher than all ultra-hot Jupiters except KELT-9b. We explore some peculiar aspects of irradiated BD atmospheres and show that existing photometry can be well-fit with our models. Additionally, the detections of atomic emission lines from these BDs can be explained by a strong irradiation-induced temperature inversion, similar to inversions recently explored in ultra-hot Jupiters. Our models of WD-0137-349B can reproduce the observed equivalent width of many but not all of these atomic lines. We use the observed photometry of these objects to retrieve the temperature structure using the PHOENIX ExoplaneT Retrieval Algorithm and demonstrate that the structures are consistent with our models, albeit somewhat cooler at low pressures. We then discuss the similarities and differences between this class of irradiated brown dwarf and the lower-mass ultra-hot Jupiters. Lastly, we describe the behavior of irradiated BDs in color-magnitude space to show the difficulty in using otherwise well-tested methods for isolated objects to classify irradiated BDs.

Keywords: Brown dwarfs, Theoretical models, Binary stars, Infrared photometry, Stellar atmospheres, Spectroscopy, Broad band photometry, Exoplanet atmospheres
Deconstructing the Planck TT Power Spectrum to Constrain Deviations from ΛCDM. Consistency checks of Lambda cold dark matter (ΛCDM) predictions with current cosmological data sets may illuminate the types of changes needed to resolve cosmological tensions. To this end, we modify the CLASS Boltzmann code to create phenomenological amplitudes, similar to the lensing amplitude parameter AL, for the Sachs-Wolfe, Doppler, early Integrated Sachs-Wolfe (eISW), and polarization contributions to the cosmic microwave background temperature anisotropy, and then we include these additional amplitudes in fits to the Planck TT power spectrum. We find that allowing one of these amplitudes to vary at a time results in little improvement over ΛCDM alone suggesting that each of these physical effects are being correctly accounted for given the current level of precision. Further, we find that the only pair of phenomenological amplitudes that results in a significant improvement to the fit to Planck temperature data results from varying the amplitudes of the Sachs-Wolfe and Doppler effects simultaneously. However, we show that this model is really just refinding the ΛCDM + AL solution. We test adding our phenomenological amplitudes as well as Neff, YHe, and nrun to ΛCDM + AL and find that none of these model extensions provide significant improvement over ΛCDM + AL when fitting Planck temperature data. Finally, we quantify the contributions of both the eISW effect and lensing on the constraint of the physical matter density from Planck temperature data by allowing the phenomenological amplitude from each effect to vary. We find that these effects play a relatively small role (the uncertainty increases by 3.5% and 16% respectively) suggesting that the overall photon envelope has the greatest constraining power.

Keywords: Cosmological models, Cosmological parameters, Cosmic microwave background radiation, Observational cosmology, Hubble constant
Hot Plasma Flows and Oscillations in the Loop-top Region During the 2017 September 10 X8.2 Solar Flare. In this study, we investigate motions in the hot plasma above the flare loops during the 2017 September 10 X8.2 flare event. We examine the region to the south of the main flare arcade, where there is data from the Interface Region Imaging Spectrograph (IRIS) and the Extreme ultraviolet Imaging Spectrometer (EIS) on Hinode. We find that there are initial blueshifts of 20-60 km s-1 observed in this region in the Fe XXI line in IRIS and the Fe XXIV line in EIS, and that the locations of these blueshifts move southward along the arcade over the course of about 10 minutes. The cadence of IRIS allows us to follow the evolution of these flows, and we find that at each location where there is an initial blueshift in the Fe XXI line, there are damped oscillations in the Doppler velocity with periods of ∼400 s. We conclude that these periods are independent of loop length, ruling out magnetoacoustic standing modes as a possible mechanism. Microwave observations from the Expanded Owens Valley Solar Array (EOVSA) indicate that there are nonthermal emissions in the region where the Doppler shifts are observed, indicating that accelerated particles are present. We suggest that the flows and oscillations are due to motions of the magnetic field that are caused by reconnection outflows disturbing the loop-top region.

Keywords: Active solar corona, Solar flares, Solar magnetic reconnection
Integral Field Spectroscopy of Fast Outflows in Dwarf Galaxies with AGNs. Feedback likely plays a vital role in the formation of dwarf galaxies. While stellar processes have long been considered the main source of feedback, recent studies have revealed tantalizing signs of active galactic nucleus (AGN) feedback in dwarf galaxies. In this paper, we report the results from an integral field spectroscopic study of a sample of eight dwarf galaxies with known AGNs and suspected outflows. Outflows are detected in seven of them. The outflows are fast, with 50th-percentile (median) velocity of up to ∼240 km s-1 and 80th-percentile line width reaching ∼1200 km s-1, in clear contrast with the more quiescent kinematics of the host gas and stellar components. The outflows are generally spatially extended on a scale of several hundred parsecs to a few kiloparsecs, although our data do not clearly resolve the outflows in three targets. The outflows appear to be primarily photoionized by the AGN rather than shocks or young, massive stars. The kinematics and energetics of these outflows suggest that they are primarily driven by the AGN, although the star formation activity in these objects may also contribute to the energy input. A small but nonnegligible portion of the outflowing material likely escapes the main body of the host galaxy and contributes to the enrichment of the circumgalactic medium. Overall, the impact of these outflows on their host galaxies is similar to those taking place in the more luminous AGNs in the low-redshift universe.

Keywords: AGN host galaxies, Dwarf galaxies, Active galactic nuclei, Galaxy winds, Galaxy kinematics, Galaxy evolution, Extragalactic astronomy
Figuring Out Gas &amp; Galaxies in Enzo (FOGGIE). IV. The Stochasticity of Ram Pressure Stripping in Galactic Halos. We study ram pressure stripping in simulated Milky Way-like halos at $z\geqslant 2$ from the Figuring Out Gas &amp; Galaxies in Enzo (FOGGIE) project. These simulations reach subkiloparsec resolution throughout the gas in their circumgalactic medium (CGM) owing to FOGGIE's novel refinement scheme. The CGM of each halo spans a wide dynamic range in density and velocity over its volume—roughly 6 dex and 1000 km s-1, respectively—translating into a 5 dex range in ram pressure imparted to interacting satellites. The local ram pressure of the simulated CGM at z = 2 is highly stochastic, owing to kiloparsec-scale variations of the density and velocity fields of the CGM gas. As a result, the efficacy of ram pressure stripping depends strongly on the specific path a satellite takes through the CGM. The ram pressure history of a single satellite is generally unpredictable and not well correlated with its approach vector with respect to the host galaxy. The cumulative impact of ram pressure on the simulated satellites is dominated by only a few short, strong impulses—on average, 90% of the total surface momentum gained through ram pressure is imparted in 20% or less of the total orbital time. These results reveal an erratic mode of ram pressure stripping in Milky Way-like halos at high redshift—one that is not captured by a smooth, spherically averaged hydrostatic model of the circumgalactic medium.

Keywords: High-redshift galaxies, Galaxies, Galaxy environments
Formation of Chromospheric Spicules in Magnetic Bright Points: An Analytical Approach Using Cartesian Slab Geometry. We aim to provide insight into chromospheric spicules by suggesting a new formation mechanism. A magnetic field boundary condition is imposed, generating an Alfvén wave that shears a magnetic slab and propagates up the slab. The resulting Lorentz force accelerates material vertically, potentially nonlinearly driving a jet-like feature. This formation mechanism is applied to take place in a magnetic bright point embedded in the photosphere, providing motivation to use the simplifying assumption of a zero-β plasma. After deriving an analytical expression describing the vertical mass flux that constitutes the spicular jet, further understanding is gained by examining a model example of a magnetic field boundary condition in terms of standard functions. By visualizing the vertical mass flux through 3D plots, we demonstrate that the jet properties capture the observed properties of chromospheric spicules during their formation. This vindicates the model and simplifying assumptions used. Although we do not provide insight into the full evolution of a spicule, we show that the role of Alfvén waves triggered by shear in fact could be a viable formation mechanism for at least some chromospheric spicules. Consequently, we provide a starting point for further studies of this formation mechanism, which will lead to a greater understanding of the vast variety of chromospheric jets.

Keywords: Magnetohydrodynamics, Solar photosphere, The Sun, Solar spicules, Solar physics, Alfven waves, Solar chromosphere, Solar magnetic bright points
The Influence of the Secular Perturbation of an Intermediate-mass Companion. I. Eccentricity Excitation of Disk Stars at the Galactic Center. There is a dense group of OB and Wolf-Rayet stars within a fraction of a parsec from the supermassive black hole (SMBH) at the Galactic Center. These stars appear to be coeval and relatively massive. A subgroup of these stars orbits on the same plane. If they emerged with low- to modest-eccentricity orbits from a common gaseous disk around the central SMBH, their inferred life span would not be sufficiently long to account for the excitation of their high orbital eccentricity through dynamical relaxation. Here we analyze the secular perturbation of Galactic Center stars by an intermediate-mass companion (IMC) as a potential mechanism to account for these young disk stars' high eccentricity. This IMC may be either an intermediate-mass black hole or a compact cluster such as IRS 13E. If its orbital angular momentum vector is antiparallel to that of the disk stars, this perturbation would be effective in exciting the eccentricity of stars with orbital precession rates that resonate with the IMC's precession rate. If it orbits around the SMBH in the same direction as the disk stars, the eccentricity of the young stars can still be highly excited by the IMC during the depletion of their natal disk, possibly associated with the launch of the Fermi bubble. In this scenario, the IMC's precession rate decreases, and its secular resonance sweeps through the proximity of the young stars. We carry out numerical simulations with various inclination angles between the orbits of the IMC and the disk stars and show that this secular interaction is a robust mechanism to excite the eccentricity and inclination of some disk stars.

Keywords: Early-type stars, Galactic center, Stellar kinematics, Stellar dynamics, Galaxy stellar content, Celestial mechanics, Computational methods, Galaxy circumnuclear disk
Galaxy Sizes Since z = 2 from the Perspective of Stellar Mass Distribution within Galaxies. How stellar mass assembles within galaxies is still an open question. We present measurements of the stellar mass distribution on kiloparsec-scales for ∼5500 galaxies with stellar masses above $\mathrm{log}({M}_{* }/{M}_{\odot })\geqslant 9.8$ up to redshift 2.0. We create stellar mass maps from Hubble Space Telescope observations by means of the pixel-by-pixel spectral energy distribution fitting method. These maps are used to derive radii encompassing 20%, 50%, and 80% (r20, r50, and r80) of the total stellar mass from the best-fit Sérsic models. The reliability and limitations of the structural parameter measurements are checked extensively using a large sample (∼3000) of simulated galaxies. The size-mass relations and redshift evolution of r20, r50, and r80 are explored for star-forming and quiescent galaxies. At fixed mass, the star-forming galaxies do not show significant changes in their r20, r50, and r80 sizes, indicating self-similar growth. Only above the pivot stellar mass of $\mathrm{log}({M}_{* }/{M}_{\odot })\simeq 10.5$ does r80 evolve as r80 ∝ (1 + z)-0.85±0.20, indicating that mass builds up in the outskirts of these systems (inside-out growth). The Sérsic values also increase for the massive star-forming galaxies toward late cosmic time. Massive quiescent galaxies show stronger size evolution at all radii, in particular, the r20 sizes. For these massive galaxies, Sérsic values remain almost constant since at least z ∼ 1.3, indicating that the strong size evolution is related to the changes in the outer parts of these galaxies. We make all the structural parameters publicly available.

Keywords: Galaxy mass distribution, Galaxy structure, Galaxy evolution, Galaxy radii