Sazuna/UAT_keywords huggingface dataset:
Nonaxisymmetric Precession of Magnetars and Fast Radio Bursts. The repeating fast radio bursts (FRBs) 180916.J0158 and 121102 are visible during periodically occurring windows in time. We consider the constraints on internal magnetic fields and geometries if the cyclical behavior observed for FRB 180916.J0158 and FRB 121102 is due to the precession of magnetars. In order to frustrate vortex line pinning we argue that internal magnetic fields must be stronger than about 1016 G, which is large enough to prevent superconductivity in the core and destroy the crustal lattice structure. We conjecture that the magnetic field inside precessing magnetars has three components: (1) a dipole component with characteristic strength ~ 1014 G; (2) a toroidal component with characteristic strength ~ 1015-1016 G that only occupies a modest fraction of the stellar volume; and (3) a disordered field with characteristic strength ~ 1016 G. The disordered field is primarily responsible for permitting precession, which stops once this field component decays away, which we conjecture happens after ~1000 yr. Conceivably, as the disordered component damps bursting activity diminishes and eventually ceases. We model the quadrupolar magnetic distortion of the star, which is due to its ordered components primarily, as triaxial and very likely prolate. We address the question of whether the spin frequency ought to be detectable for precessing, bursting magnetars by constructing a specific model in which bursts happen randomly in time with random directions distributed in or between cones relative to a single symmetry axis. Within the context of these specific models, we find that there are precession geometries for which detecting the spin frequency is very unlikely.

Keywords: Transient sources, High energy astrophysics
Testing the Momentum-driven Supernova Feedback Paradigm in M31. Momentum feedback from isolated supernova remnants (SNRs) have been increasingly recognized by modern cosmological simulations as a resolution-independent means to implement the effects of feedback in galaxies, such as turbulence and winds. However, the integrated momentum yield from SNRs is uncertain due to the effects of SN clustering and interstellar medium (ISM) inhomogeneities. In this paper, we use spatially resolved observations of the prominent 10 kpc star-forming ring of M31 to test models of mass-weighted ISM turbulence driven by momentum feedback from isolated, nonoverlapping SNRs. We use a detailed stellar age distribution (SAD) map from the Panchromatic Hubble Andromeda Treasury survey, observationally constrained SN delay-time distributions, and maps of the atomic and molecular hydrogen to estimate the mass-weighted velocity dispersion using the Martizzi et al. ISM turbulence model. Our estimates are within a factor of two of the observed mass-weighted velocity dispersion in most of the ring, but exceed observations at densities ≲0.2 cm-3 and SN rates &gt;2.1 × 10-4 SN yr-1 kpc-2, even after accounting for plausible variations in SAD models and ISM scale height assumptions. We conclude that at high SN rates the momentum deposited is most likely suppressed by the nonlinear effects of SN clustering, while at low densities, SNRs reach pressure equilibrium before the cooling phase. These corrections should be introduced in models of momentum-driven feedback and ISM turbulence.

Keywords: Stellar-interstellar interactions, Stellar feedback, Supernova remnants, Interstellar medium, Supernovae
Markov Chains for Horizons MARCH. I. Identifying Biases in Fitting Theoretical Models to Event Horizon Telescope Observations. We introduce a new Markov Chain Monte Carlo (MCMC) algorithm with parallel tempering for fitting theoretical models of horizon-scale images of black holes to the interferometric data from the Event Horizon Telescope (EHT). The algorithm implements forms of the noise distribution in the data that are accurate for all signal-to-noise ratios. In addition to being trivially parallelizable, the algorithm is optimized for high performance, achieving 1 million MCMC chain steps in under 20 s on a single processor. We use synthetic data for the 2017 EHT coverage of M87 that are generated based on analytic as well as General Relativistic Magnetohydrodynamic (GRMHD) model images to explore several potential sources of biases in fitting models to sparse interferometric data. We demonstrate that a very small number of data points that lie near salient features of the interferometric data exert disproportionate influence on the inferred model parameters. We also show that the preferred orientations of the EHT baselines introduce significant biases in the inference of the orientation of the model images. Finally, we discuss strategies that help identify the presence and severity of such biases in realistic applications.

Keywords: Supermassive black holes, Very long baseline interferometry, Astrostatistics, Algorithms, Astrophysical black holes, Interferometry
Long-term North-South Asymmetry of the Heliospheric Current Sheet. In this paper, we evaluate the heliospheric current sheet (HCS) north-south asymmetry using the ecliptical sector structure of the interplanetary magnetic field (IMF) reconstructed since the second half of the 19th century. During the last five solar cycles, the inferred IMF polarities fairly reproduce the observed dominance of the sectors with the polarity of the northern solar hemisphere, i.e., the prolonged southward shift of the HCS. For the presatellite era, we found that the northward shift of the HCS was more common in cycles 10, 15, and 17-19, and the southward HCS shift was more common in cycles 9, 11-14, and 16. We also analyzed the north-south asymmetry in sunspot group numbers since 1749 and found that the northern hemisphere dominated in cycles 2-3, 7-9, and 15-20, and the southern hemisphere activity was stronger in cycles 4, 9-14, and 21-24. Moreover, other solar phenomena bear similar long-term asymmetry variations. The regularity of these variations is not clear. According to the available proxies of the solar data, the dominance of the northern hemisphere is found in the ascending phase of the secular solar cycle, and the dominance of the southern hemisphere coincides with the descending phase.

Keywords: Solar cycle, Sunspot groups, Solar physics, Solar magnetic fields, Solar activity
Embedded Young Massive Star Clusters in the Antennae Merger. The properties of young massive clusters (YMCs) are key to understanding the star formation mechanism in starburst systems, especially mergers. We present Atacama Large Millimeter/submillimeter Array high-resolution (~10 pc) continuum (100 and 345 GHz) data of YMCs in the overlap region of the Antennae galaxy. We identify six sources in the overlap region, including two sources that lie in the same giant molecular cloud (GMC). These YMCs correspond well with radio sources in lower-resolution continuum (100 and 220 GHz) images at GMC scales (~60 pc). We find most of these YMCs are bound clusters through virial analysis. We estimate their ages to be ~1 Myr and that they are either embedded or just beginning to emerge from their parent cloud. We also compare each radio source with a Paβ source, and find they have consistent total ionizing photon numbers, which indicates they are tracing the same physical source. By comparing the free-free emission at ~10 pc scale and ~60 pc scale, we find that ~50% of the free-free emission in GMCs actually comes from these YMCs. This indicates that roughly half of the stars in massive GMCs are formed in bound clusters. We further explore the mass correlation between YMCs and GMCs in the Antennae and find it generally agrees with the predictions of the star cluster simulations. The most massive YMC has a stellar mass that is 1%-5% of its host GMC mass.

Keywords: Starburst galaxies, Star formation, Interstellar medium, Star clusters
SDSS-IV MaNGA: Understanding Ionized Gas Turbulence Using Integral Field Spectroscopy of 4500 Star-forming Disk Galaxies. The Sloan Digital Sky Survey MaNGA program has now obtained integral field spectroscopy for over 10,000 galaxies in the nearby universe. We use the final MaNGA data release DR17 to study the correlation between ionized gas velocity dispersion and galactic star formation rate, finding a tight correlation in which σ Hα  from galactic H II regions increases significantly from ~18-30 km s-1, broadly in keeping with previous studies. In contrast, σ Hα  from diffuse ionized gas increases more rapidly from 20-60 km s-1. Using the statistical power of MaNGA, we investigate these correlations in greater detail using multiple emission lines and determine that the observed correlation of σ Hα  with local star formation rate surface density is driven primarily by the global relation of increasing velocity dispersion at higher total star formation rate, as are apparent correlations with stellar mass. Assuming H II region models consistent with our finding that σ [O III] &lt; σ Hα  &lt; σ [O I], we estimate the velocity dispersion of the molecular gas in which the individual H II regions are embedded, finding values σ Mol = 5-30 km s-1 consistent with ALMA observations in a similar mass range. Finally, we use variations in the relation with inclination and disk azimuthal angle to constrain the velocity dispersion ellipsoid of the ionized gas σ  z /σ  r  = 0.84 ± 0.03 and σ  ϕ /σ  r  = 0.91 ± 0.03, similar to that of young stars in the Galactic disk. Our results are most consistent with the theoretical models in which turbulence in modern galactic disks is driven primarily by star formation feedback.

Keywords: Galaxy kinematics, Disk galaxies
X-Ray Emission from the Jets and Lobes of the Spiderweb. Deep Chandra and Very Large Array imaging reveals a clear correlation between X-ray and radio emission on scales ~100 kpc in the Spiderweb radio galaxy at z = 2.16. The X-ray emission associated with the extended radio source is likely dominated by inverse Compton upscattering of cosmic microwave background photons by the radio-emitting relativistic electrons. For regions dominated by high surface brightness emission, such as hot spots and jet knots, the implied magnetic fields are ~50-70 μG. The nonthermal pressure in these brighter regions is then ~9 × 10-10 dynes cm-2, or three times larger than the nonthermal pressure derived assuming minimum energy conditions, and an order of magnitude larger than the thermal pressure in the ambient cluster medium. Assuming ram pressure confinement implies an average advance speed for the radio source of ~2400 km s-1 and a source age of ~3 × 107 yr. Considering the lower surface brightness, diffuse radio-emitting regions, we identify an evacuated cavity in the Lyα emission coincident with the tail of the eastern radio lobe. Making reasonable assumptions for the radio spectrum, we find that the relativistic electrons and fields in the lobe are plausibly in pressure equilibrium with the thermal gas and close to a minimum energy configuration. The radio morphology suggests that the Spiderweb is a high-z example of the rare class of hybrid morphology radio sources (or HyMoRS), which we attribute to interaction with the asymmetric gaseous environment indicated by the Lyα emission.

Keywords: Cosmic microwave background radiation, Radio galaxies, Radio jets, High-energy cosmic radiation
Measuring the Virial Factor in SDSS DR5 Quasars with Redshifted Hβ and Fe II Broad Emission Lines. Under the hypothesis of gravitational redshift induced by a central supermassive black hole, and based on line widths and shifts of redward-shifted Hβ and Fe II broad emission lines for a sample of 1973 z &lt; 0.8 Sloan Digital Sky Survey DR5 quasars, we measured the virial factor in determining supermassive black hole masses, usually estimated by the reverberation mapping method or the relevant secondary methods. The virial factor had been believed to be from the geometric effect of the broad-line region. The measured virial factor of Fe II is larger than that of Hβ for 98% of these quasars. The virial factor is very different from object to object and for different emission lines. For most of these quasars, the virial factor of Hβ is larger than these averages that were usually used in determining the masses of black holes. There are three positive correlations among the measured virial factor of Hβ, dimensionless accretion rate, and Fe II/Hβ line ratio. A positive three-dimensional correlation is found among these three quantities, and this correlation indicates that the virial factor is likely dominated by the dimensionless accretion rate and metallicity. A negative correlation is found between the redward shift of Hβ and the scaled size of the broad-line region radius in units of the gravitational radius of the black hole. This negative correlation will be expected naturally if the redward shift of Hβ is mainly from the gravity of the black hole. Radiation pressure from the accretion disk may be a significant contributor to the virial factor.

Keywords: Black hole physics, Supermassive black holes, Quasars, Emission line galaxies, Active galactic nuclei
A 16 au Binary in the Class 0 Protostar L1157 MMS. We present Very Large Array observations toward the Class 0 protostar L1157 MMS at 6.8 and 9 mm with a resolution of ~0.″04 (14 au). We detect two sources within L1157 MMS and interpret these sources as a binary protostar with a separation of ~16 au. The material directly surrounding the binary system within the inner 50 au radius of the system has an estimated mass of 0.11 M ☉, calculated from the observed dust emission. We interpret the observed binary system in the context of previous observations of its flattened envelope structure, low rates of envelope rotation from 5000 to 200 au scales, and an ordered, poloidal magnetic field aligned with the outflow. Thus, L1157 MMS is a prototype system for magnetically regulated collapse, and the presence of a compact binary within L1157 MMS demonstrates that multiple star formation can still occur within envelopes that likely have dynamically important magnetic fields.

Keywords: Protostars, Young stellar objects, Radio interferometry
Mushroom-instability-driven Magnetic Reconnections in Collisionless Relativistic Jets. We study the kinetic plasma dynamics in collisionless relativistic jets with velocity shear, by carrying out particle-in-cell simulations in the transverse plane of a jet. It is discovered that intermittent magnetic reconnections (MRs) are driven by mushroom instability (MI), which is an important kinetic-scale plasma instability in the plasma shear flows with relativistic bulk speed. We refer to this sequence of kinetic plasma phenomena as "MI-driven MR." The MI-driven MRs intermittently occur with moving the location of the reconnection points from the vicinity of the initial velocity-shear surface toward the center of the jet. As a consequence, the number density of high-energy electrons that are accelerated by MI-driven MRs increases with time in the region inside the initial velocity-shear surface with the accompanying generation and subsequent amplification of magnetic fields by MI. The maximum Lorentz factor of electrons increases with initial bulk Lorentz factor of the jet. A possible relation of MI-driven MR to the bright synchrotron emission in the jet spine of an active galactic nucleus jet is also discussed.

Keywords: Radio jets, High energy astrophysics, Plasma jets, Plasma physics, Relativistic jets, Plasma astrophysics, Active galactic nuclei
AT 2019avd: A Tidal Disruption Event with a Two-phase Evolution. Tidal disruption events (TDEs) can uncover the quiescent supermassive black holes (SMBHs) at the center of galaxies and also offer a promising method to study them. After the disruption of a star by an SMBH, the highly elliptical orbit of the debris stream will be gradually circularized due to the self-crossing, and then the circularized debris will form an accretion disk. The recent TDE candidate AT 2019avd has double peaks in its optical light curve, and the X-ray emerges near the second peak. The durations of the peaks are ~400 and 600 days, respectively, and the separation between them is ~700 days. We fit its spectral energy distribution and analyze its light curves in the optical/UV, mid-infrared, and X-ray bands. We find that this source can be interpreted as a two-phase scenario in which the first phase is dominated by the stream circularization, and the second phase is the delayed accretion. We use the succession of the self-crossing model and delayed accretion model to fit the first and second peaks, respectively. The fitting result implies that AT 2019avd can be interpreted by the partial disruption of a 0.9 M ⊙ star by a 7 × 106 M ⊙ SMBH, but this result is sensitive to the stellar model. Furthermore, we find that the large-amplitude (by factors up to ~5) X-ray variability in AT 2019avd can be interpreted as the rigid-body precession of the misaligned disk due to the Lense-Thirring effect of a spinning SMBH, with a precession period of 10-25 days.

Keywords: Accretion, Black hole physics, Tidal disruption, Galaxy nuclei
Analytic Solution to the Dynamical Friction Acting on Circularly Moving Perturbers. We present an analytic approach to the dynamical friction (DF) acting on a circularly moving point mass perturber in a gaseous medium. We demonstrate that, when the perturber is turned on at t = 0, steady state (infinite time perturbation) is achieved after exactly one sound-crossing time. At low Mach numbers ${ \mathcal M }\,\ll 1$ , the circular-motion steady-state DF converges to the linear-motion, finite time perturbation expression. The analytic results describe both the radial and tangential forces on the perturbers caused by the backreaction of the wake propagating in the medium. The radial force is directed inward, toward the motion center, and is dominant at large Mach numbers. For subsonic motion, this component is negligible. For moderate and low Mach numbers, the tangential force is stronger and opposes the motion of the perturber. The analytic solution to the circular-orbit DF suffers from a logarithmic divergence in the supersonic regime. This divergence appears at short distances from the perturber solely (unlike the linear-motion result, which is also divergent at large distances) and can be encoded in a maximum multipole. This is helpful to assess the resolution dependence of numerical simulations implementing DF at the level of Liénard-Wiechert potentials. We also show how our approach can be generalized to calculate the DF acting on a compact circular binary.

Keywords: Circular orbits, Dynamical friction, Hydrodynamics, Compact binary stars
Full-sky, Arcminute-scale, 3D Models of Galactic Microwave Foreground Dust Emission Based on Filaments. We present the DUSTFILAMENTS code, a full-sky model for the millimeter Galactic emission of thermal dust. Our model, composed of millions of filaments that are imperfectly aligned with the magnetic field, is able to reproduce the main features of the dust angular power spectra at 353 GHz as measured by the Planck mission. Our model is made up of a population of filaments with sizes following a Pareto distribution $\propto {L}_{a}^{-2.445}$ , with an axis ratio between short and long semiaxes ϵ ~ 0.16 and an angle of magnetic field misalignment with a dispersion rms(θ LH) = 10°. On large scales, our model follows a Planck-based template. On small scales, our model produces spectra that behave like power laws up to ℓ ~ 4000 or smaller scales by considering even smaller filaments, limited only by computing power. We can produce any number of Monte Carlo realizations of small-scale Galactic dust. Our model will allow tests of how the small-scale non-Gaussianity affects CMB weak lensing and the consequences for the measurement of primordial gravitational waves or relativistic light relic species. Our model also can generate frequency decorrelation on the modified blackbody spectrum of dust and is freely adjustable to different levels of decorrelation. This can be used to test the performance of component separation methods and the impact of frequency spectrum residuals on primordial B-mode surveys. The filament density we paint in the sky is also able to reproduce the general level of non-Gaussianities measured by Minkowski functionals in the Planck 353 GHz channel map.

Keywords: Cosmology, Observational cosmology, Astrophysical dust processes, Milky Way magnetic fields
In Situ Measurement of the Energy Fraction in Suprathermal and Energetic Particles at ACE, Wind, and PSP Interplanetary Shocks. The acceleration of charged particles by interplanetary shocks (IPs) can drain a nonnegligible fraction of the plasma pressure. In this study, we have selected 17 IPs observed in situ at 1 au by the Advanced Composition Explorer and the Wind spacecraft, and 1 shock at 0.8 au observed by Parker Solar Probe. We have calculated the time-dependent partial pressure of suprathermal and energetic particles (smaller and greater than 50 keV for protons and 30 keV for electrons, respectively) in both the upstream and downstream regions. The particle fluxes were averaged for 1 hr before and 1 hr after the shock time to remove short timescale effects. Using the MHD Rankine-Hugoniot jump conditions, we find that the fraction of the total upstream energy flux transferred to suprathermal and energetic downstream particles is typically ≲16%, in agreement with previous observations and simulations. Notably, by accounting for errors on all measured shock parameters, we have found that for any given fast magnetosonic Mach number, M  f  &lt; 7, the angle between the shock normal and average upstream magnetic field, θ Bn, is not correlated with the energetic particle pressure; in particular, the partial pressure of energized particles does not decrease for θ Bn ≳ 45°. The downstream electron-to-proton energy ratio in the range ≳ 140 eV for electrons and ≳ 70 keV for protons exceeds the expected ~1% and nears equipartition (&gt;0.1) for the Wind events.

Keywords: Space plasmas, Interplanetary particle acceleration, Interplanetary shocks
A Detection of Red Noise in PSR J1824-2452A and Projections for PSR B1937+21 Using NICER X-Ray Timing Data. We have used X-ray data from the Neutron Star Interior Composition Explorer (NICER) to search for long-timescale temporal correlations ("red noise") in the pulse times of arrival (TOAs) from the millisecond pulsars PSR J1824-2452A and PSR B1937+21. These data more closely track intrinsic noise because X-rays are unaffected by the radio-frequency-dependent propagation effects of the interstellar medium. Our search yields strong evidence (natural log Bayes factor of 9.634 ± 0.016) for red noise in PSR J1824-2452A, but the search is inconclusive for PSR B1937+21. In the interest of future X-ray missions, we devise and implement a method to simulate longer and higher-precision X-ray data sets to determine the timing baseline necessary to detect red noise. We find that the red noise in PSR B1937+21 can be reliably detected in a 5 yr mission with a TOA error of 2 μs and an observing cadence of 20 observations per month compared to the 5 μs TOA error and 11 observations per month that NICER currently achieves in PSR B1937+21. We investigate detecting red noise in PSR B1937+21 with other combinations of observing cadences and TOA errors. We also find that time-correlated red noise commensurate with an injected stochastic gravitational-wave background having an amplitude of A GWB = 2 × 10-15 and spectral index of timing residuals of γ GWB = 13/3 can be detected in a pulsar with similar TOA precision to PSR B1937+21. This is with no additional red noise in a 10 yr mission that observes the pulsar 15 times per month and has an average TOA error of 1 μs.

Keywords: X-ray astronomy, Pulsar timing method, Millisecond pulsars, Pulsars, Red noise