Sazuna/UAT_keywords huggingface dataset:
Simulations of Stochastic Long-term Variability in Leptonic Models for External-Compton and Synchrotron Self-Compton Dominated Blazars. In this work we investigate the nature of multiwavelength variability of blazars from a purely numerical approach. We use a time-dependent one-zone leptonic blazar emission model to simulate multiwavelength variability by introducing stochastic parameter variations in the emission region. These stochastic parameter variations are generated by Monte Carlo methods and have a characteristic power-law index of α = -2 in their power spectral densities. We include representative blazar test cases for a flat spectrum radio quasar and a high-synchrotron peaked BL Lacertae object for which the high-energy component of the spectral energy distribution is dominated by external-Compton and synchrotron self-Compton emission, respectively. The simulated variability is analyzed in order to characterize the distinctions between the two blazar cases and the physical parameters driving the variability. We show that the variability's power spectrum is closely related to underlying stochastic parameter variations for both cases. Distinct differences between the different progenitor variations are present in the multiwavelength cross-correlation functions.

Keywords: Blazars, Jets, Radiative processes
Return of the TEDI: Revisiting the Triple Evolution Dynamical Instability Channel in Triple Stars. Triple-star systems exhibit a phenomenon known as triple evolution dynamical instability (TEDI), in which mass loss in evolving triples triggers short-term dynamical instabilities, potentially leading to collisions of stars, exchanges, and ejections. Previous work has shown that the TEDI is an important pathway to head-on stellar collisions in the Galaxy, significantly exceeding the rate of collisions due to random encounters in globular clusters. Here, we revisit the TEDI evolutionary pathway using state-of-the-art population synthesis methods that self-consistently take into account stellar evolution and binary interactions as well as gravitational dynamics and perturbations from passing stars in the field. We find Galactic TEDI-induced collision rates on the order of 10-4 yr-1, consistent with previous studies which were based on more simplified methods. The majority of TEDI-induced collisions involve main-sequence stars, potentially producing blue straggler stars. Collisions involving more evolved stars are also possible, potentially producing eccentric post-common-envelope systems, and white dwarfs collisions leading to Type Ia supernovae (although the latter with a negligible contribution to the Galactic rate). In our simulations, the TEDI is not only triggered by adiabatic wind mass loss, but also by Roche lobe overflow in the inner binary: when the donor star becomes less massive than the accretor, the inner binary orbit widens, triggering triple dynamical instability. We find that collision rates are increased by ~17% when flybys in the field are taken into account. In addition to collisions, we find that the TEDI produces ~10-4 yr-1 of unbound stars, although none with escape speeds in excess of 103 km s-1.

Keywords: Stellar dynamics, Stellar mergers, Stellar evolution
Refractive Index and Extinction Coefficient of Vapor-deposited Water Ice in the UV-vis Range. Laboratory results of the optical properties of vapor-deposited water ice, specifically the refractive index and extinction coefficient, are available mainly for a selective set of wavelengths and a limited number of deposition temperatures. Experimental limitations are the main reason for the lack of broadband data, which is unfortunate as these quantities are needed to interpret and predict astronomical and planetary observations. The goal of this work is to address these lacking data, using an experimental broadband method that is capable of rapidly providing reliable water ice data across the entire UV-visible range. This approach combines the simultaneous use of a monochromatic HeNe laser and a broadband Xe-arc lamp to record interference fringes of water ice during deposition at astronomically relevant ice temperatures. The ice thickness is typically more than 20 μm. Analyzing the period and intensity patterns combining both the monochromatic and broadband interference patterns allows the determination of the wavelength-dependent refractive index and extinction coefficient. We present accurate refractive index and extinction coefficient graphs for wavelengths between 250 and 750 nm and ices deposited between 30 and 160 K. From our data, we find a possible structural change in the ice in the 110-130 K region that has not been reported before. We also discuss that the data presented in this paper can be used to interpret astronomical observations of icy surfaces.

Keywords: Surface ices, Laboratory astrophysics, Experimental techniques
CLIMBER: Galaxy-Halo Connection Constraints from Next-generation Surveys. In the coming decade, a new generation of massively multiplexed spectroscopic surveys, such as the Prime Focus Spectrograph Galaxy Evolution Survey (PFS), Wide Area Vista Extragalactic Survey-Deep (WAVES), and Multi-Object Optical and Near-infrared Spectrograph (MOONS) for the Very Large Telescope, will probe galaxies in the distant universe in vastly greater numbers than was previously possible. In this work, we generate mock catalogs for each of these three planned surveys to help quantify and optimize their scientific output. To assign photometry into the UniverseMachine empirical model, we develop the Calibrating Light: Illuminating Mocks By Empirical Relations procedure using Ultra Deep Survey with the Visible and Infrared Survey Telescope for Astronomy (UltraVISTA) photometry. Using the published empirical selection functions for each aforementioned survey, we quantify the mass completeness of each survey. We compare different targeting strategies by varying the area and targeting completeness, and quantify how these survey parameters affect the uncertainty of the two-point correlation function. We demonstrate that the PFS and MOONS measurements will be primarily dominated by cosmic variance, not shot noise, motivating the need for increasingly large survey areas. On the other hand, the WAVES survey, which covers a much larger area, will strike a good balance between cosmic variance and shot noise. For a fixed number of targets, a 5% increased survey area (and ~5% decreased completeness) would decrease the uncertainty of the correlation function at intermediate scales by 0.15%, 1.2%, and 1.1% for our WAVES, PFS, and MOONS samples, respectively. Meanwhile, for a fixed survey area, 5% increased targeting completeness improves the same constraints by 0.7%, 0.25%, and 0.1%. All of the utilities used to construct our mock catalogs and many of the catalogs themselves are publicly available.

Keywords: Galaxy dark matter halos, Sky surveys, Galaxy cluster counts, Galactic and extragalactic astronomy, Stellar mass functions, Galaxy photometry, Star formation, Galaxy evolution, Galaxy counts, Galaxy spectroscopy, Redshift surveys, Two-point correlation function
High-resolution Simulations of the Inner Heliosphere in Search of the Kelvin-Helmholtz Waves. The Kelvin-Helmholtz instability (KHI) can be generated at velocity shears in plasmas. While shears are abundant in the solar wind, whether they generate KHI in situ remains an open question, because of the lack of models that can simultaneously resolve the global structure of the expanding solar wind and the local structure of much smaller-scale velocity shears. In this paper, we use the Grid Agnostic MHD for Extended Research Applications model whose high resolving power, in combination with a highly refined spatial grid, allowed us to extend the simulation from global scales roughly into the first decade of the inertial range (~1.5 × 105 km, which we refer to as mesoscale). We employ this computational capability to extract from the simulation the local properties of radial and azimuthal solar wind velocity shears and investigate their KH stability using a linear dispersion relation, which includes both the finite width of the shear and plasma compressibility. We find that radial shears, which dominate the global structure of the inner heliosphere, are stabilized by compressibility. However, depending on the local Alfvén speed, sound speed, shear thickness, and the strength of the stabilizing azimuthal magnetic field, the azimuthal shears generated inside stream interaction regions could be KH-unstable. While our highly resolved simulation allowed us to analyze the local properties of the velocity shears, its resolution was still insufficient to confirm the instability. We argue that even higher resolution simulations are required to reproduce in situ generation of KHI at velocity shears in the solar wind.

Keywords: Solar wind, Heliosphere, Magnetohydrodynamical simulations
The Implications of TeV-detected GRB Afterglows for Acceleration at Relativistic Shocks. Motivated by the detection of very-high-energy (VHE) gamma rays deep in the afterglow emission of a gamma-ray burst (GRB), we revisit predictions of the maximum energy to which electrons can be accelerated at a relativistic blast wave. Acceleration at the weakly magnetized forward shock of a blast wave can be limited by either the rapid damping of turbulence generated behind the shock, the effect of a large-scale ambient magnetic field, or radiation losses. Within the confines of a standard, single-zone, synchrotron self-Compton (SSC) model, we show that observations of GRB 190829A rule out a rapid damping of the downstream turbulence. Furthermore, simultaneous fits to the X-ray and TeV gamma-ray emission of this object are not possible unless the limit on acceleration imposed by the ambient magnetic field is comparable to or weaker than that imposed by radiation losses. This requires the dominant length scale of the turbulence behind the shock to be larger than that implied by particle-in-cell simulations. However, even then, Klein-Nishina effects prevent production of the hard VHE gamma-ray spectrum suggested by observations. Thus, TeV observations of GRB afterglows, though still very sparse, are already in tension with the SSC emission scenario.

Keywords: Gamma-ray bursts, High energy astrophysics
TeV and keV-MeV Excesses as Probes for Hadronic Process in BL Lacertaes. A hard TeV γ-ray component excess over the single-zone leptonic model prediction (TeV excess) is observed in the spectral energy distributions (SEDs) of some BL Lacs. Its origin is uncertain. We revisit this issue with four BL Lacs (1ES 0229+200, 1ES 0347-121, 1ES 1101-232, and H2356-309), in which the TeV excess is detected in their intrinsic SEDs. We represent their SEDs with a single-zone leptohadronic model, where radiations of the electrons and protons as well as the cascade electrons produced by the γγ and pγ interactions within their jets are considered. We show that the observed SEDs below the GeV gamma-ray band are attributed to the synchrotron radiations and self-Compton process of the primary electrons, and the TeV excess is explained with the γ-ray emission from the pγ process via the π 0 decay. The cascade emission of the electrons produced via the γγ and pγ interactions results in a keV-MeV excess in the SEDs, illustrated as a bump or plateau. This extra photon field enhances the production of TeV photons from the p γ process, resulting in a reduction of the proton power by about one order of magnitude. However, the derived powers are still 3-4 orders of magnitude larger than the Eddington limit, being challenged by the current black hole accretion physics. Applying our model to Mrk 421, we propose that synergic observations with current and upcoming TeV and keV-MeV telescopes for its tentative TeV and MeV excesses can give insights to the hadronic process in its jet.

Keywords: Blazars, Relativistic jets, Non-thermal radiation sources
Helium Fluxes Measured by the PAMELA Experiment from the Minimum to the Maximum Solar Activity for Solar Cycle 24. Time-dependent energy spectra of galactic cosmic rays (GCRs) carry fundamental information regarding their origin and propagation. When observed at the Earth, these spectra are significantly affected by the solar wind and the embedded solar magnetic field that permeates the heliosphere, changing significantly over an 11 yr solar cycle. Energy spectra of GCRs measured during different epochs of solar activity provide crucial information for a thorough understanding of solar and heliospheric phenomena. The PAMELA experiment collected data for almost 10 years (2006 June 15-2016 January 23), including the minimum phase of solar cycle 23 and the maximum phase of solar cycle 24. In this paper, we present new spectra for helium nuclei measured by the PAMELA instrument from 2010 January to 2014 September over a three-Carrington-rotation time basis. These data are compared to the PAMELA spectra measured during the previous solar minimum, providing a picture of the time dependence of the helium-nuclei fluxes over a nearly full solar cycle. Time and rigidity dependencies are observed in the proton-to-helium flux ratios. The force-field approximation of the solar modulation was used to relate these dependencies to the shapes of the local interstellar proton and helium-nuclei spectra.

Keywords: Cosmic ray detectors, Cosmic ray astronomy, Heliosphere
Streaming Instabilities in Accreting and Magnetized Laminar Protoplanetary Disks. The streaming instability (SI) is one of the most promising pathways to the formation of planetesimals from pebbles. Understanding how this instability operates under realistic conditions expected in protoplanetary disks (PPDs) is therefore crucial to assess the efficiency of planet formation. Contemporary models of PPDs show that magnetic fields are key to driving gas accretion through large-scale, laminar magnetic stresses. However, the effect of such magnetic fields on the SI has not been examined in detail. To this end, we study the stability of dusty, magneftized gas in a protoplanetary disk. We find the SI can be enhanced by passive magnetic torques and even persist in the absence of a global radial pressure gradient. In this case, instability is attributed to the azimuthal drift between dust and gas, unlike the classical SI, which is driven by radial drift. This suggests that the SI can remain effective inside dust-trapping pressure bumps in accreting disks. When a live vertical field is considered, we find the magneto-rotational instability can be damped by dust feedback, while the classic SI can be stabilized by magnetic perturbations. We also find that Alfvén waves can be destabilized by dust-gas drift, but this instability requires nearly ideal conditions. We discuss the possible implications of these results for dust dynamics and planetesimal formation in PPDs.

Keywords: Magnetohydrodynamics, Hydrodynamics, Protoplanetary disks, Astrophysical fluid dynamics, Planet formation
Triaxial Orbit-based Dynamical Modeling of Galaxies with Supermassive Black Holes and an Application to Massive Elliptical Galaxy NGC 1453. Most stellar-dynamical determinations of the masses of nearby supermassive black holes (SMBHs) have been obtained with the orbit superposition technique under the assumption of axisymmetry. However, few galaxies-in particular massive early-type galaxies-obey exact axisymmetry. Here we present a revised orbit superposition code and a new approach for dynamically determining the intrinsic shapes and mass parameters of triaxial galaxies based on spatially resolved stellar kinematic data. The triaxial TriOS code described here corrects an error in the original van den Bosch et al. code that gives rise to incorrect projections for most orbits in triaxial models and can significantly impact parameter search results. The revised code also contains significant improvements in orbit sampling, mass constraints, and run time. Furthermore, we introduce two new parameter-searching strategies-a new set of triaxial shape parameters and a novel grid-free sampling technique-that together lead to a remarkable gain in efficiency in locating the best-fit model. We apply the updated code and search method to NGC 1453, a fast-rotating massive elliptical galaxy. A full 6D parameter search finds $p=b/a={0.933}_{-0.015}^{+0.014}$ and q = c/a = 0.779 ± 0.012 for the intrinsic axis ratios and T = 0.33 ± 0.06 for the triaxiality parameter. Despite the deviations from axisymmetry, the best-fit SMBH mass, stellar mass-to-light ratio, and dark matter enclosed mass for NGC 1453 are consistent with the axisymmetric results. More comparisons between axisymmetric and triaxial modeling are needed before drawing general conclusions.

Keywords: Supermassive black holes, Black holes, Galaxy dynamics, Galaxy structure, Giant elliptical galaxies, Galaxy kinematics, Elliptical galaxies, Galaxies
The Intrinsic Structure of Sagittarius A* at 1.3 cm and 7 mm. Sagittarius A* (Sgr A*), the Galactic Center supermassive black hole (SMBH), is one of the best targets in which to resolve the innermost region of an SMBH with very long baseline interferometry (VLBI). In this study, we have carried out observations toward Sgr A* at 1.349 cm (22.223 GHz) and 6.950 mm (43.135 GHz) with the East Asian VLBI Network, as a part of the multiwavelength campaign of the Event Horizon Telescope (EHT) in 2017 April. To mitigate scattering effects, the physically motivated scattering kernel model from Psaltis et al. (2018) and the scattering parameters from Johnson et al. (2018) have been applied. As a result, a single, symmetric Gaussian model well describes the intrinsic structure of Sgr A* at both wavelengths. From closure amplitudes, the major-axis sizes are ~704 ± 102 μas (axial ratio ~ ${1.19}_{-0.19}^{+0.24}$ ) and ~300 ± 25 μas (axial ratio ~1.28 ± 0.2) at 1.349 cm and 6.95 mm, respectively. Together with a quasi-simultaneous observation at 3.5 mm (86 GHz) by Issaoun et al. (2019), we show that the intrinsic size scales with observing wavelength as a power law, with an index ~1.2 ± 0.2. Our results also provide estimates of the size and compact flux density at 1.3 mm, which can be incorporated into the analysis of the EHT observations. In terms of the origin of radio emission, we have compared the intrinsic structures with the accretion flow scenario, especially the radiatively inefficient accretion flow based on the Keplerian shell model. With this, we show that a nonthermal electron population is necessary to reproduce the source sizes.

Keywords: Accretion, Supermassive black holes, Very long baseline interferometry, Galactic center
Photometric Objects Around Cosmic Webs (PAC) Delineated in a Spectroscopic Survey. II. Morphology, Color, and Size Dependences of the Stellar-Halo Mass Relation for Massive Galaxies. In this paper, we report a robust measurement of the morphology, color, and galaxy size dependences of the stellar-halo mass relation (SHMR) at the high-mass end (1011.3 M ⊙ &lt; M ⋆ &lt; 1011.7 M ⊙) at redshift z  s  ~ 0.6. 3 3 Throughout the paper, we use z  s  for redshift and z for the z-band magnitude. Applying our method, Photometric objects Around Cosmic webs (PAC), developed in a previous work to Baryon Oscillation Spectroscopic Survey and Hyper Suprime-cam Subaru Strategic Program observations, we measure the excess surface density ( ${\bar{n}}_{2}{w}_{p}({r}_{p})$ ) of satellites around massive central galaxies with different morphologies indicated by the Sérsic index n. We find that more compact (larger n) central galaxies are surrounded by more satellites. With the abundance matching method, we estimate the halo mass for the central galaxies and find that it increases monotonically with n, solid evidence for a morphology dependence of the SHMR. Specifically, our results show that most compact galaxies (n &gt; 6) have a halo mass around 5.5 times larger than disk galaxies (n &lt; 2). Similarly, using the effective radius R  e  and the rest-frame u - r color, we find that red (large) galaxies reside in halos that are in average 2.6 (2.3) times more massive than those hosting blue (small) galaxies.

Keywords: Galaxy dark matter halos, Galaxy formation
On the Formation of Solar Wind and Switchbacks, and Quiet Sun Heating. The solar coronal heating in quiet Sun (QS) and coronal holes (CHs), including solar wind formation, are intimately tied by magnetic field dynamics. Thus, a detailed comparative study of these regions is needed to understand the underlying physical processes. CHs are known to have subdued intensity and larger blueshifts in the corona. This work investigates the similarities and differences between CHs and QS in the chromosphere using the Mg II h and k, C II line, and transition region using Si IV line, for regions with identical absolute magnetic flux density (∣B∣). We find CHs to have subdued intensity in all of the lines, with the difference increasing with line formation height and ∣B∣. The chromospheric lines show excess upflows and downflows in CH, while Si IV shows excess upflows (downflows) in CHs (QS), where the flows increase with ∣B∣. We further demonstrate that the upflows (downflows) in Si IV are correlated with both upflows and downflows (only downflows) in the chromospheric lines. CHs (QS) show larger Si IV upflows (downflows) for similar flows in the chromosphere, suggesting a common origin to these flows. These observations may be explained due to impulsive heating via interchange (closed-loop) reconnection in CHs (QS), resulting in bidirectional flows at different heights, due to differences in magnetic field topologies. Finally, the kinked field lines from interchange reconnection may be carried away as magnetic field rotations and observed as switchbacks. Thus, our results suggest a unified picture of solar wind emergence, coronal heating, and near-Sun switchback formation.

Keywords: Slow solar wind, Solar magnetic reconnection, Quiet solar chromosphere, Fast solar wind, Solar chromospheric heating, Quiet sun, Solar wind, Solar coronal heating, Solar magnetic fields, Solar transition region, Solar coronal holes, Solar chromosphere
The 3D Kinematics of the Orion Nebula Cluster: NIRSPEC-AO Radial Velocities of the Core Population. The kinematics and dynamics of stellar and substellar populations within young, still-forming clusters provide valuable information for constraining theories of formation mechanisms. Using Keck II NIRSPEC+AO data, we have measured radial velocities for 56 low-mass sources within 4' of the core of the Orion Nebula Cluster (ONC). We also remeasure radial velocities for 172 sources observed with SDSS/APOGEE. These data are combined with proper motions measured using HST ACS/WFPC2/WFC3IR and Keck II NIRC2, creating a sample of 135 sources with all three velocity components. The velocities measured are consistent with a normal distribution in all three components. We measure intrinsic velocity dispersions of ( ${\sigma }_{{v}_{\alpha }}$ , ${\sigma }_{{v}_{\delta }}$ , ${\sigma }_{{v}_{r}}$ ) = (1.64 ± 0.12, 2.03 ± 0.13, ${2.56}_{-0.17}^{+0.16}$ ) km s-1. Our computed intrinsic velocity dispersion profiles are consistent with the dynamical equilibrium models from Da Rio et al. (2014) in the tangential direction but not in the line-of-sight direction, possibly indicating that the core of the ONC is not yet virialized, and may require a nonspherical potential to explain the observed velocity dispersion profiles. We also observe a slight elongation along the north-south direction following the filament, which has been well studied in previous literature, and an elongation in the line-of-sight to tangential velocity direction. These 3D kinematics will help in the development of realistic models of the formation and early evolution of massive clusters.

Keywords: Stellar kinematics, Star forming regions, Open star clusters, Star formation, Radial velocity, Stellar associations