adsabs/SciX_UAT_keywords huggingface dataset:
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: elliptical galaxies; galaxies; giant elliptical galaxies; galaxy dynamics; galaxy kinematics; galaxy structure; black holes; supermassive black holes
Generation of Vertical Flows by Torsional Alfvén Pulses in Zero-beta Tubes with a Transitional Layer

Spicule activity in the chromosphere is modeled via the perturbation resulting from the propagation of an Alfvén wave pulse in a magnetic flux tube. Building on previous work, the model is augmented by the inclusion of a finite transitional layer in which the atmospheric density decreases exponentially. This additional complexity of the density stratification provides a more physical representation of the solar atmosphere and improves on the existing model. The wave pulse is introduced at the lower boundary of the flux tube and interacts with the transitional layer, also being partially reflected. The total mass flux induced by the pulse, and the proportion of this pulse that is transmitted through the layer, is calculated and examined in the context of spicules and the solar wind using an example solution. We find that the inclusion of the transitional layer results in more plasma flux being transferred into the upper solar atmosphere when compared with the case of a discontinuity. We examine how varying the parameters of this transitional layer affects the ratio of the flux above and below the layer.

Keywords: solar atmosphere; solar physics; solar chromosphere; solar transition region; solar magnetic fields; alfven waves; magnetohydrodynamics; solar magnetic bright points; theoretical models; solar spicules; plasma jets; jets
Exploring the Coronal Magnetic Field with Galactic Cosmic Rays: The Sun Shadow Observed by HAWC

Galactic cosmic rays (GCRs) are charged particles that reach the heliosphere almost isotropically in a wide energy range. In the inner heliosphere, the GCR flux is modulated by solar activity so that only energetic GCRs reach the lower layers of the solar atmosphere. In this work, we propose that high-energy GCRs can be used to explore the solar magnetic fields at low coronal altitudes. We used GCR data collected by the High-Altitude Water Cherenkov observatory to construct maps of GCR flux coming from the Sun's sky direction and studied the observed GCR deficit, known as Sun shadow (SS), over a 6 yr period (2016–2021) with a time cadence of 27.3 days. We confirm that the SS is correlated with sunspot number, but we focus on the relationship between the photospheric solar magnetic field measured at different heliolatitudes and the relative GCR deficit at different energies. We found a linear relationship between the relative deficit of GCRs represented by the depth of the SS and the solar magnetic field. This relationship is evident in the observed energy range of 2.5–226 TeV, but is strongest in the range of 12.4 33.4 TeV, which implies that this is the best energy range to study the evolution of magnetic fields in the low solar atmosphere.

Keywords: active solar corona; solar magnetic fields; solar physics
Radio Pulsar B0950+08: Radiation in the Magnetosphere and Sparks above the Surface

We observed the nearby radio pulsar B0950+08, which has a 100% duty cycle, using the Five-hundred-meter Aperture Spherical Radio Telescope. We obtained the polarization profile for its entire rotation, which enabled us to investigate its magnetospheric radiation geometry and the sparking pattern of the polar cap. After we excluded part of the profile in which the linear polarization factor is low (≲30%) and potentially contaminated by jumps in position angle, the rest of the swing in polarization position angle fits a classical rotating vector model (RVM) well. The best-fit RVM indicates that the inclination angle, α, and the impact angle, β, of this pulsar, are 100.°5 and ‑33.°2, respectively, suggesting that the radio emission comes from two poles. We find that, in such RVM geometry, either the annular vacuum gap model or the core vacuum gap model would require that the radio emissions come from a high-altitude magnetosphere with heights from ∼0.25 R LC to ∼0.56 R LC, with R LC being the light cylinder radius. Both the main and interpulses' sparking points are located away from the magnetic pole, which could relate to the physical conditions on the pulsar surface.

Keywords: radio pulsars; magnetospheric radio emissions
The Rise and Fall of the Eclipsing Binary HS Hydrae

HS Hydrae is a short period eclipsing binary (Porb = 1.57 day) that belongs to a rare group of systems observed to have rapidly changing inclinations. This evolution is due to a third star on an intermediate orbit, and results in significant differences in eclipse depths and timings year to year. Zasche & Paschke revealed that HS Hydrae's eclipses were rapidly fading from view, predicting they would cease around 2022. Using 25 days of photometric data from Sector 009 of the Transiting Exoplanet Survey Satellite (TESS), we find that the primary eclipses for HS Hydrae were only 0.00173 &PlusMinus; 0.00007 mag in depth in March 2019. This data from TESS likely represents the last eclipses detected from HS Hydrae. We also searched the Digitization of the Harvard Astronomical Plate Collection archive for historic data from the system. With a total baseline of over 125 yr, this unique combination of data sets-from photographic plates to precision space-based photometry-allows us to trace the emergence and decay of eclipses from HS Hydrae, and further constrain its evolution. Recent TESS observations from Sector 035 confirm that eclipses have ceased for HS Hya, and we estimate they will begin again in 2195.

Keywords: binary stars; eclipsing binary stars
MHD Mode Composition in the Inner Heliosphere from the Parker Solar Probe’s First Perihelion

Field and plasma variations during the first perihelion pass of the Parker Solar Probe (PSP) from 53 into 35 solar radii (R S ) from the Sun and over a frequency range in the spacecraft frame (f SC) from 0.0002 to 0.2 Hz are decomposed into constituent magnetohydrodynamic (MHD) modes. The analysis operates on measurements of the MHD variables recorded between impulsive, large amplitude rotations of the magnetic field to reveal the dominance of a broad spectrum of shear Alfvén waves propagating antiparallel (backward) to the background magnetic field ( B 0) with a significant fraction of spectral energy density in the backward slow mode and, to a lesser extent, fast mode waves. While all three MHD modes provide Poynting flux directed outward from the Sun the impulsive rotations of B 0 from inward to outward radial orientations provide intervals of outward and inward propagation in the plasma frame, respectively. This morphology is suggestive of outward wave propagation from a near Sun source along kinked field lines that provide alternating radial B 0 orientations as the magnetic field is advected with the flow over the spacecraft. Shear Alfvén and slow mode spectral energy density is generally largest within intervals of reversed radial B 0, while the fast mode tends to occur outside these regions, albeit with lower intensity. The spectral energy density in the forward propagating modes increases with f SC above 0.01 Hz, which is suggestive of back scatter in the plasma frame of the dominant backward modes from the radial field reversals and associated inhomogeneities of the embedded plasmas.

Keywords: magnetohydrodynamics; slow solar wind; solar coronal holes
Determining the Pyroxene Mineralogies of Vestoids

Bulk pyroxene compositions were calculated for a number of V-type asteroid spectra using formulae derived by Burbine et al. These formulae were derived by analyzing HED (howardite, eucrite, and diogenite) meteorites and calculate bulk Fs (mol%) and Wo (mol%) contents using derived band centers. Using HEDs with known bulk pyroxene compositions, the uncertainty in the predicted Fs contents was determined to be ±3 mol%, and the uncertainty in the predicted Wo contents was ±2 mol%. V-type asteroids tend to have interpreted pyroxene mineralogies consistent primarily with eucrites and howardites. We investigate why diogenitic mineralogies appear so rare among ~5-10 km V-type asteroids but are much more commonly present among HED meteorites. One possibility is that diogenitic intrusions are extremely "thin" but widespread in Vesta's eucritic crust. In this scenario, Vestoids (V-type asteroids thought to be derived from Vesta) would be expected to be solid fragments of Vesta. Another possibility is that Vesta's upper crust has been significantly shattered and diogenitic material would be much less common than the eucritic material in the crust. Vestoids would then be expected to be rubble piles. The belief that most asteroid families were shattered at least twice would argue that Vesta's crust is also shattered and that Vestoids are rubble piles.

Keywords: meteorites; asteroids; vesta; main belt asteroids
Extension of the Synchrotron Radiation of Electrons to Very High Energies in Clumpy Environments

The synchrotron cooling of relativistic electrons is one of the most effective radiation mechanisms in astrophysics. It not only accompanies the process of particle acceleration, but also has feedback on the formation of the energy distribution of the parent electrons. The radiative cooling time of electrons decreases with energy as tSYN ∝ 1/E; correspondingly, the overall radiation efficiency increases with energy. However, this effect strictly limits the maximum energy of individual photons. Even in the so-called extreme accelerators, where the acceleration proceeds at the highest possible rate, ${t}_{{\rm\small{ACC}}}^{-1}={eBc}/E$ , allowed in an ideal magnetohydrodynamic plasma, the synchrotron radiation cannot extend well beyond the characteristic energy determined by the electron mass and the fine-structure constant: $h{\nu }^{{\rm\small{MAX}}}\sim {m}_{{\rm{e}}}{c}^{2}/\alpha \sim 70\,\mathrm{MeV}$ . In this paper, we propose a model in which the formation of synchrotron radiation takes place in compact magnetic blobs located inside the particle accelerator and develop a formalism for calculations of synchrotron radiation emerging from such systems. We demonstrate that for certain combinations of parameters characterizing the accelerator and the magnetic blobs, the synchrotron radiation can extend beyond this limit by a several orders of magnitude. This scenario requires a weak magnetization of the particle accelerator, and an efficient conversion of gas internal energy into magnetic energy in sufficiently small blobs. The required size of the blobs is constrained by the magnetic mirroring effect, which can prevent particle penetration into the regions of strong magnetic field under certain conditions.

Keywords: gamma-ray sources; non-thermal radiation sources; theoretical models
A Tale of Three Dwarfs: No Extreme Cluster Formation in Extreme Star-forming Galaxies

Nearly all current simulations predict that outcomes of the star formation process, such as the fraction of stars that form in bound clusters (Γ), depend on the intensity of star formation activity (ΣSFR) in the host galaxy. The exact shape and strength of the predicted correlations, however, vary from simulation to simulation. Observational results also remain unclear at this time, because most works have mixed estimates made from very young clusters for galaxies with higher ΣSFR with those from older clusters for galaxies with lower ΣSFR. The three blue compact dwarf (BCD) galaxies ESO 185-IG13, ESO 338-IG04, and Haro 11 have played a central role on the observational side because they have some of the highest known ΣSFR and published values of Γ. We present new estimates of Γ for these BCDs in three age intervals (1-10 Myr, 10-100 Myr, 100-400 Myr), based on age-dating, which includes Hα photometry to better discriminate between clusters younger and older than ≈10 Myr. We find significantly lower values for Γ(1-10 Myr) than published previously. The likely reason for the discrepancy is that previous estimates appear to be based on age-reddening results that underestimated ages and overestimated reddening for many clusters, artificially boosting Γ(1-10 Myr). We also find that fewer stars remain in clusters over time, with ≈15%-39% in 1-10 Myr clusters, ≈5%-7% in 10-100 Myr clusters, and ≈1%-2% in 100-400 Myr clusters. We find no evidence that Γ increases with ΣSFR. These results imply that cluster formation efficiency does not vary with star formation intensity in the host galaxy. If confirmed, our results will help guide future assumptions in galaxy-scale simulations of cluster formation and evolution.

Keywords: blue compact dwarf galaxies; star clusters; young massive clusters
Discovery of a Young Stellar Snake with Two Dissolving Cores in the Solar Neighborhood

We report the discovery of a young (only 30-40 Myr) snake-like structure (dubbed a stellar snake) in the solar neighborhood from Gaia DR2. The average distance of this structure is about 310 pc from us. Both the length and width are over 200 pc, but the thickness is only about 80 pc. The snake has one tail and two dissolving cores, which can be clearly distinguished in the 6D phase space. The whole structure includes thousands of members with a total mass of larger than 2000 M⊙ in a uniform population. The population is so young that it cannot be well explained with the classical theory of tidal tails. We therefore suspect that the snake is hierarchically primordial, rather than the result of dynamically tidal stripping, even if the snake is probably expanding. The coherent 5D phase information and the ages suggest that the snake was probably born in the same environment as the filamentary structure of Beccari et al. If so, the snake could extend the sky region of the Vela OB2 association by a factor of ∼2 and supplement the census of its coeval structures. This finding is useful to understanding the history of the formation and evolution of the Vela OB2 complex. The age of the snake well matches with that of the Gould Belt. In the sky region of our interest, we detect one new open cluster, which is named Tian 1 in this work.

Keywords: stellar kinematics; stellar associations; stellar dynamics; open star clusters; gould belt; ob associations; young stellar objects; pre-main sequence stars; solar neighborhood; proper motions; tidal tails; filamentary nebulae
The Carina Nebula and Gum 31 Molecular Complex. III. The Distribution of the 1-3 GHz Radio Continuum across the Whole Nebula

We report the most detailed 1-3 GHz radio continuum emission map of the nearest region of massive-star formation, the Carina Nebula. As part of a large program with the Australia Telescope Compact Array, we have covered ∼12 deg2, achieving an angular resolution of ∼16″, representing the largest and most complete map of the radio continuum to date. Our continuum map shows a spectacular and complex distribution of emission across the nebula, with multiple structures such as filaments, shells, and fronts across a wide range of size scales. The ionization fronts have advanced far into the southern and northern region of the Galactic plane, as fronts are clearly detected at distances of ∼80 pc from the stellar clusters in the center. We estimated an ionization photon luminosity QH = (7. 8 ± 0.8) × 1050 s-1, which corresponds to ∼85% of the total value obtained from stellar population studies. Thus, approximately 15% of the ionizing flux has escaped from the nebula into the diffuse Galactic interstellar medium. Comparison between radio continuum and the hydrogen atomic and molecular gas maps offers a clear view of the bipolar outflow driven by the energy released by the massive stellar clusters that also affects the fraction of molecular gas across the nebula. Comparison between 8 μm and 70 μm emission maps and the radio continuum reveals how the hot gas permeates through the molecular cloud; shapes the material into features such as pillars, small shells, and arc-like structures; and ultimately escapes.

Keywords: h ii regions; radio continuum emission; interstellar radiation field; massive stars; ionization; photoionization; radio astronomy
Variability and the Size-Luminosity Relation of the Intermediate-mass AGN in NGC 4395

We present a variability study of the lowest-luminosity Seyfert 1 nucleus of the galaxy NGC 4395 based on photometric monitoring campaigns in 2017 and 2018. Using 22 ground-based and space telescopes, we monitored NGC 4395 with a ∼5-minute cadence during a period of 10 days and obtained light curves in the ultraviolet (UV), V, J, H, and K/Ks bands, as well as narrowband Hα. The rms variability is ∼0.13 mag in the Swift UVM2 and V filter light curves, decreasing down to ∼0.01 mag in the K filter. After correcting for the continuum contribution to the Hα narrow band, we measured the time lag of the Hα emission line with respect to the V-band continuum as 55-31+27 - 122-67+33 minutes in 2017 and 49-14+15 - 83-14+13 minutes in 2018, depending on assumptions about the continuum variability amplitude in the Hα narrow band. We obtained no reliable measurements for the continuum-to-continuum lag between UV and V bands and among near-IR bands, owing to the large flux uncertainty of UV observations and the limited time baseline. We determined the active galactic nucleus (AGN) monochromatic luminosity at 5100 Å, λ{Lλ}=(5.75± 0.40)× 1039 erg s-1, after subtracting the contribution of the nuclear star cluster. While the optical luminosity of NGC 4395 is two orders of magnitude lower than that of other reverberation-mapped AGNs, NGC 4395 follows the size-luminosity relation, albeit with an offset of 0.48 dex (≥2.5σ) from the previous best-fit relation of Bentz et al.

Keywords: reverberation mapping; active galactic nuclei; active galaxies; galaxy nuclei; low-luminosity active galactic nuclei; intermediate-mass black holes; seyfert galaxies
Revisiting the Complex Nuclear Region of NGC 6240 with Chandra

We present a reanalysis of the cumulative ACIS-S Chandra data set pointed at the double active galactic nuclei (AGNs) of the NGC 6240 merging galaxy, focusing on the hard energy bands containing the hard spectral continuum (5.5-5.9 keV), the redshifted Fe I Kα line (6.0-6.4 keV), and the redshifted Fe XXV line (6.4-6.7 keV). We have used the full Chandra telescope angular resolution and modeled the Chandra point-spread function (PSF) by comparing a preflight calibration model to the data for the two bright AGNs. With two complementary approaches—(1) studying the residuals after PSF subtraction and (2) producing reconstructed Expectation through Markov Chain Monte Carlo (EMC2) images—we are able to resolve structures extending from ∼1 kpc to <200 pc in the S AGN. The latter are within the sphere of influence of this BH. We find significant extended emission in both continuum and Fe lines in the ∼2″ (∼1 kpc) region surrounding the nuclei, in the region between the N and S AGN, and in a sector of PA 120-210 deg. extending to the SE from the centroid of the S AGN surface brightness. The extended Fe I Kα emission is likely to originate from the fluorescence of X-ray photons interacting with dense molecular clouds, providing a complementary view to recent high-resolution Atacama Large Millimeter/submillimeter Array (ALMA) studies. The nonthermal emission is more prevalent in the region in between the two active X-ray nuclei and in the N AGN. We do not find strong evidence of X-ray emission associated with the third nucleus recently proposed for NGC 6240.

Keywords: x-ray active galactic nuclei
"Super GZK" Particles in a Classic Kramers' Diffusion-over-a-barrier Model. I. The Case of Protons

In interactions of ultra-high-energy cosmic ray (UHECR) protons with cosmic microwave background photons, we focus in this work on photopion production reactions and the effects of the measured, broad, energy-loss distributions in these reactions on the evolution of the protons' density functions in energy space. We rely on a Fokker-Planck transport equation in energy space whose transport coefficients are calculated using laboratory measurements. We also derive a Fokker-Planck potential that accounts for both systematic (drift) and stochastic (dispersive) energy losses due to photopion production reactions. Our results show that dispersive energy losses have significant effects on estimating the protons' horizon distance and their energy spectrum, as well as to elucidate a broadness in the GZK cutoff. We use the derived Fokker-Planck potential to assign a characteristic probability for a proton to clear the potential barrier as a function of energy. This estimate of probability can be used to assist observations in distinguishing between protons and heavy ions as charged particles. Our model is able to account for the so-called super GZK particles as a classic diffusion-over-a-barrier manifestation of the transport of UHECR protons in energy space in quantifying the extent and broadness of the GZK cutoff.

Keywords: ultra-high-energy cosmic radiation