Sazuna/UAT_keywords huggingface dataset:
The Green Bank North Celestial Cap Pulsar Survey. V. Pulsar Census and Survey Sensitivity. The Green Bank North Celestial Cap (GBNCC) pulsar survey will cover the entire northern sky (δ &gt; -40°) at 350 MHz, and is one of the most uniform and sensitive all-sky pulsar surveys to date. We have created a pipeline to reanalyze GBNCC survey data to take a 350 MHz census of all pulsars detected by the survey, regardless of their discovery survey. Of the 1413 pulsars in the survey region, we were able to recover 670. For these we present measured signal-to-noise ratios (S/N), flux densities, pulse widths, profiles, and where appropriate, refined measurements of dispersion measures (DMs) (656 out of 670) and new or improved spectral indices (339 out of 670 total, 47 new, 292 improved). We also measure the period-pulse width relation at 350 MHz to scale as W∝ P-0.27. Detection scans for several hundred sources were reanalyzed in order to inspect pulsars' single pulse behavior and 223 were found to exhibit evidence of nulling. With a detailed analysis of measured and expected S/N values and the evolving radio frequency interference environment at 350 MHz, we assess the GBNCC survey's sensitivity as a function of spin period, DM, and sky position. We find the sky-averaged limiting flux density of the survey to be 0.74 mJy. Combining this analysis with PsrPopPy pulsar population simulations, we predict 60/5 nonrecycled/MSP discoveries in the survey's remaining 21,000 pointings, and we begin to place constraints on population model parameters.

Keywords: Surveys, Radio astronomy, Radio pulsars
ZFIRE: Measuring Electron Density with [O II] as a Function of Environment at z = 1.62. The global star formation rates (SFR) of galaxies at fixed stellar masses increase with redshift and are known to vary with environment up to z ∼ 2. We explore here whether the changes in the SFRs also apply to the electron densities of the interstellar medium by measuring the [O II] (λ 3726, λ 3729) ratio for cluster and field galaxies at z ∼ 2. We measure a median electron density of ne = 366 ± 84 cm-3 for six galaxies (with 1σ scatter = 163 cm-3) in the Ultra-Deep Survey (UDS) protocluster at z = 1.62. We find that the median electron density of galaxies in the UDS protocluster environment is three times higher compared to the median electron density of field galaxies (ne = 113 ± 63 cm03 and 1 &amp;sigma scatter = 79 cm-3) at comparable redshifts, stellar mass, and SFR. However, we note that a sample of six protocluster galaxies is insufficient to reliably measure the electron density in the average protocluster environment at z ∼ 2. We conclude that the electron density increases with redshift in both cluster and field environments up to z ∼ 2 (ne = 30 ± 1 cm-3 for z ∼ 0 to ne = 254 ± 76 cm-3 for z ∼ 1.5). We find tentative evidence (∼2.6σ) for a possible dependence of electron density on environment, but the results require confirmation with larger sample sizes.

Keywords: High-redshift galaxies, Galaxy evolution, Emission line galaxies, High-redshift galaxy clusters
Black Hole Parameter Estimation from Its Shadow. The Event Horizon Telescope (EHT), a global submillimeter wavelength very long baseline interferometry array, unveiled event-horizon-scale images of the supermassive black hole M87* as an asymmetric bright emission ring with a diameter of 42 ± 3 μas, and it is consistent with the shadow of a Kerr black hole of general relativity. A Kerr black hole is also a solution of some alternative theories of gravity, while several modified theories of gravity admit non-Kerr black holes. While earlier estimates for the M87* black hole mass, depending on the method used, fall in the range ≈ 3× 109 M⊙ - 7×109 M⊙, the EHT data indicated a mass for the M87* black hole of (6.5 ± 0.7) × 109 M⊙. This offers another promising tool to estimate black hole parameters and to probe theories of gravity in its most extreme region near the event horizon. The important question arises: Is it possible by a simple technique to estimate black hole parameters from its shadow, for arbitrary models? In this paper, we present observables, expressed in terms of ordinary integrals, characterizing a haphazard shadow shape to estimate the parameters associated with black holes, and then illustrate its relevance to four different models: Kerr, Kerr-Newman, and two rotating regular models. Our method is robust, accurate, and consistent with the results obtained from existing formalism, and it is applicable to more general shadow shapes that may not be circular due to noisy data.

Keywords: Black hole physics, Galactic center, Gravitation, Gravitational lensing, Astrophysical black holes
Sympathetic Eruptions of Two Filaments with an Identifiable Causal Link Observed by the Solar Dynamics Observatory. Filament eruptions occurring at different places within a relatively short time internal, but with a certain physical causal connection, are usually categorized as sympathetic eruptions. Studies of sympathetic eruptions are not uncommon. However, in these studies the causal links between sympathetic eruptions remain rather speculative. In this work, we present detailed observations of a sympathetic filament eruption event in which an identifiable causal link between two eruptive filaments is observed. On 2015 November 15, two filaments (F1 in the north and F2 in the south) were located at the southwestern quadrant of the solar disk. Their main axes were almost parallel to each other. Around 22:20 UT, F1 began to erupt, forming two flare ribbons. The southwestern ribbon apparently moved southwest and invaded the southeast part of F2. This continuous intrusion caused F2's eventual eruption. Accompanying the eruption of F2, flare ribbons and post-flare loops appeared in the northwest region of F2. Meanwhile, neither flare ribbons nor post-flare loops could be observed in the southeastern area of F2. In addition, the nonlinear force-free field extrapolations show that the magnetic fields above F2 in the southeast region are much weaker than those in the northwest region. These results imply that the overlying magnetic fields of F2 were not uniform. So we propose that the southwest ribbon formed from eruptive F1 invaded F2 from its southeast region with relatively weaker overlying magnetic fields relative to its northwest region, disturbing F2 and leading F2 to eventually erupt.

Keywords: Solar atmosphere, Solar physics, Solar filaments, Solar filament eruptions, Solar activity
The Turbulent Stress Spectrum in the Inertial and Subinertial Ranges. For velocity and magnetic fields, the turbulent pressure and, more generally, the squared fields such as the components of the turbulent stress tensor, play important roles in astrophysics. For both one and three dimensions, we derive the equations relating the energy spectra of the fields to the spectra of their squares. We solve the resulting integrals numerically and show that for turbulent energy spectra of Kolmogorov type, the spectral slope of the stress spectrum is also of Kolmogorov type. For shallower turbulence spectra, the slope of the stress spectrum quickly approaches that of white noise, regardless of how blue the spectrum of the field is. For fully helical fields, the stress spectrum is elevated by about a factor of two in the subinertial range, while that in the inertial range remains unchanged. We discuss possible implications for understanding the spectrum of primordial gravitational waves from causally generated magnetic fields during cosmological phase transitions in the early universe. We also discuss potential diagnostic applications to the interstellar medium, where polarization and scintillation measurements characterize the square of the magnetic field.

Keywords: Interplanetary turbulence, Magnetohydrodynamics, Gravitational waves, Hydrodynamics
Variable Accretion onto Protoplanet Host Star PDS 70. The PDS 70 system has been subject to many studies in the past year following the discovery of two accreting planets in the gap of its circumstellar disk. Nevertheless, the mass accretion rate onto the star is still not well known. Here, we determined the stellar mass accretion rate and its variability based on Transiting Exoplanet Survey Satellite and High-Accuracy Radial velocity Planetary Searcher (HARPS) observations. The stellar light curve shows a strong signal with a 3.03 ± 0.06 days period, which we attribute to stellar rotation. Our analysis of the HARPS spectra shows a rotational velocity of V sin I=16.0± 0.5 km s-1, indicating that the inclination of the rotation axis is 50° ± 8°. This implies that the rotation axes of the star and its circumstellar disk are parallel within the measurement error. We apply magnetospheric accretion models to fit the profiles of the Hα line and derive mass accretion rates onto the star in the range of (0.6-2.2)× 10-10 M☉ yr-1, varying over the rotation phase. The measured accretion rates are in agreement with those estimated from near-UV fluxes using accretion shock models. The derived accretion rates are higher than expected from the disk mass and planets' properties for the low values of the viscous parameter α suggested by recent studies, potentially pointing to an additional mass reservoir in the inner disk to feed the accretion, such as a dead zone. We find that the He I λ10830 line shows a blueshifted absorption feature, indicative of a wind. The mass-loss rate estimated from the line depth is consistent with an accretion-driven inner disk MHD wind.

Keywords: Accretion, H I line emission, T Tauri stars, Protoplanetary disks, Stellar accretion
Proper Motions of the Radio Source Orion MR, Formerly Known as Orion n, and New Sources with Large Proper Motions in Orion BN/KL. The infrared source known as Orion n was detected in 1980. About two decades later, sensitive observations made with the Very Large Array (VLA) revealed the presence of a spatially coincident millijansky double source that appeared to be its radio counterpart. However, over the years it has been concluded that the radio source shows large proper motions to the south while the infrared source n is stationary. Here we reanalyze the proper motions of the radio source adding both older and newer VLA observations than previously used. We confirm the proper motions of the double radio source that at present no longer coincides positionally with the infrared source. We propose that the infrared source is stationary while the radio source is moving as a result of the explosion that took place in this region some 500 yr ago. Considering the paper where it was first reported, we refer to this double radio source as Orion MR. Additionally, we use these new observations to fully confirm the large proper motions of the sources IRc23 and Zapata 11. Together with sources BN, I, Orion MR, and X, there are at least six compact sources that recede from a common point in Orion BN/KL. However, IRc23 is peculiar in that its ejection age appears to be only 300 yr. The relatively large number of sources rules out as a possible mechanism the classic three-body scenario since then only two escaping bodies are expected: a tight binary plus the third star involved in the encounter.

Keywords: Radio astrometry, Star formation, Radio sources
Model of a Gap Formed by a Planet with Fast Inward Migration. A planet is formed within a protoplanetary disk. Recent observations have revealed substructures such as gaps and rings, which may indicate forming planets within the disk. Due to disk-planet interaction, the planet migrates within the disk, which can affect the shape of a planet-induced gap. In this paper, we investigate effects of fast inward migration of the planet on the gap shape, by carrying out hydrodynamic simulations. We found that when the migration timescale is shorter than the timescale of the gap-opening, the orbital radius is shifted inward as compared to the radial location of the gap. We also found a scaling relation between the radial shift of the locations of the planet and the gap as a function of the ratio of the timescale of the migration and gap-opening. Our scaling relation also enables us to constrain the gas surface density and the viscosity when the gap and the planet are observed. Moreover, we also found the scaling relation between the location of the secondary gap and the aspect ratio. By combining the radial shift and the secondary gap, we may constrain the physical condition of the planet formation and how the planet evolves in the protoplanetary disk, from the observational morphology.

Keywords: Protoplanetary disks, Planet formation
Dust Destruction by Charging: A Possible Origin of Gray Extinction Curves of Active Galactic Nuclei. Observed extinction curves of active galactic nuclei (AGNs) are significantly different from those observed in the Milky Way. The observations require preferential removal of small grains at the AGN environment; however, the physics for this remains unclear. In this paper, we propose that dust destruction by charging, or Coulomb explosion, may be responsible for AGN extinction curves. Harsh AGN radiation makes a dust grain highly charged through photoelectric emission, and grain fission via Coulomb explosion occurs when the electrostatic tensile stress of a charge grain exceeds its tensile strength. We show that Coulomb explosion can preferentially remove both small silicate and graphite grains and successfully reproduce both flat extinction curve and the absence of 2175 Å bump.

Keywords: Astrophysical dust processes, Active galactic nuclei, Ultraviolet extinction
Electron Firehose Instabilities in High-β Intracluster Shocks. The preacceleration of electrons through reflection and shock drift acceleration (SDA) is essential for the diffusive shock acceleration of nonthermal electrons in collisionless shocks. Previous studies suggested that, in weak quasi-perpendicular (Q\bot) shocks in the high-β (β = Pgas/PB) intracluster medium (ICM), the temperature anisotropy due to SDA-reflected electrons can drive the electron firehose instability, which excites oblique nonpropagating waves in the shock foot. In this paper, we investigate, through a linear analysis and particle-in-cell simulations, the firehose instabilities driven by an electron temperature anisotropy (ETAFI) and also by a drifting electron beam (EBFI) in β ∼ 100 ICM plasmas. The EBFI should be more relevant to describing the self-excitation of upstream waves in Q\bot-shocks, since backstreaming electrons in the shock foot behave more like an electron beam rather than an anisotropic bi-Maxwellian population. We find that the basic properties of the two instabilities, such as the growth rate, γ, and the wavenumber of fast-growing oblique modes, are similar in the ICM environment, with one exception; while the waves excited by the ETAFI are nonpropagating (ωr = 0), those excited by the EBFI have a nonzero frequency (ωr ≠ 0). However, the frequency is small with ωr &lt; γ. Thus, we conclude that the interpretation of previous studies for the nature of upstream waves based on the ETAFI remains valid in Q\bot-shocks in the ICM.

Keywords: Galaxy clusters, Shocks, Plasma astrophysics, Cosmic rays
Gamma-Ray and Neutrino Emissions due to Cosmic-Ray Protons Accelerated at Intracluster Shocks in Galaxy Clusters. We examine the cosmic-ray protons (CRp) accelerated at collisionless shocks in galaxy clusters using cosmological structure formation simulations. We find that in the intracluster medium (ICM) within the virial radius of simulated clusters, only ∼7% of shock kinetic energy flux is dissipated by the shocks that are expected to accelerate CRp - that is, supercritical, quasi-parallel (Q∥) shocks with sonic Mach number Ms ≥ 2.25. The rest is dissipated at subcritical shocks and quasi-perpendicular shocks, both of which may not accelerate CRp. Adopting the diffusive shock acceleration (DSA) model recently presented in Ryu et al., we quantify the DSA of CRp in simulated clusters. The average fraction of the shock kinetic energy transferred to CRp via DSA is assessed at ∼(1-2) × 10-4. We also examine the energization of CRp through reacceleration using a model based on the test-particle solution. Assuming that the ICM plasma passes through shocks three times on average through the history of the universe and that CRp are reaccelerated only at supercritical Q∥-shocks, the CRp spectrum flattens by ∼0.05-0.1 in slope and the total amount of CRp energy increases by ∼40%-80% from reacceleration. We then estimate diffuse γ-ray and neutrino emissions, resulting from inelastic collisions between CRp and thermal protons. The predicted γ-ray emissions from simulated clusters lie mostly below the upper limits set by Fermi-LAT for observed clusters. The neutrino fluxes toward nearby clusters would be ≲10-4 of the IceCube flux at Eν = 1 PeV and ≲10-6 of the atmospheric neutrino flux in the energy range of Eν ≤ 1 TeV.

Keywords: Galaxy clusters, Neutrino astronomy, Shocks, Gamma-rays, Cosmic rays
The Variability of the Star Formation Rate in Galaxies. I. Star Formation Histories Traced by EW(Hα) and EW(Hδ<SUB>A</SUB>). To investigate the variability of the star formation rate (SFR) of galaxies, we define a star formation change parameter, SFR5 Myr/SFR800 Myr, which is the ratio of the SFR averaged within the last 5 Myr to the SFR averaged within the last 800 Myr. We show that this parameter can be determined from a combination of Hα emission and Hδ absorption, plus the 4000 Å break, with an uncertainty of ∼0.07 dex for star-forming galaxies. We then apply this estimator to MaNGA galaxies, both globally within Re and within radial annuli. We find that the global SFR5 Myr/SFR800 Myr, which indicates by how much a galaxy has changed its specific SFR (sSFR), is nearly independent of its sSFR, I.e., of its position relative to the star formation main sequence (SFMS) as defined by SFR800 Myr. Also, at any sSFR, there are as many galaxies increasing their sSFR as decreasing it, as required if the dispersion in the SFMS is to stay the same. The SFR5 Myr/SFR800 Myr of the overall galaxy population is very close to that expected for the evolving main sequence. Both of these provide a reassuring check on the validity of our calibration of the estimator. We find that galaxies with higher global SFR5 Myr/SFR800 Myr appear to have higher SFR5 Myr/SFR800 Myr at all galactic radii, I.e., that galaxies with a recent temporal enhancement in overall SFR have enhanced star formation at all galactic radii. The dispersion of the SFR5 Myr/SFR800 Myr at a given relative galactic radius and a given stellar mass decreases with the (indirectly inferred) gas depletion time: locations with short gas depletion time appear to undergo bigger variations in their star formation rates on Gyr or less timescales. In Wang et al., we showed that the dispersion in star formation rate surface densities σSFR in the galaxy population appears to be inversely correlated with the inferred gas depletion timescale and interpreted this in terms of the dynamical response of a gas-regulator system to changes in the gas inflow rate. In this paper, we can now prove directly with SFR5 Myr/SFR800 Myr that these effects are indeed due to genuine temporal variations in the SFR of individual galaxies on timescales between 107 and 109 yr rather than possibly reflecting intrinsic, non-temporal, differences between different galaxies.

Keywords: Star formation, Galaxy evolution, Galaxies
Coronal Electron Temperature Inferred from the Strahl Electrons in the Inner Heliosphere: Parker Solar Probe and Helios Observations. The shape of the electron velocity distribution function plays an important role in the dynamics of the solar wind acceleration. Electrons are normally modeled with three components, the core, the halo, and the strahl. We investigate how well the fast strahl electrons in the inner heliosphere preserve the information about the coronal electron temperature at their origin. We analyzed the data obtained by two missions, Helios, spanning the distances between 65 and 215 RS, and Parker Solar Probe (PSP), reaching down to 35 RS during its first two orbits around the Sun. The electron strahl was characterized with two parameters: pitch-angle width (PAW) and the strahl parallel temperature (Ts∥). PSP observations confirm the already reported dependence of strahl PAW on core parallel plasma beta (βec\parallel). Most of the strahl measured by PSP appear narrow with PAW reaching down to 30°. The portion of the strahl velocity distribution function aligned with the magnetic field is for the measured energy range well described by a Maxwellian distribution function. Ts∥ was found to be anticorrelated with the solar wind velocity and independent of radial distance. These observations imply that Ts∥ carries the information about the coronal electron temperature. The obtained values are in agreement with coronal temperatures measured using spectroscopy, and the inferred solar wind source regions during the first orbit of PSP agree with the predictions using a PFSS model.

Keywords: Space vehicle instruments, Space plasmas, Solar atmosphere, Solar wind, Astronomy data analysis, Solar physics, Solar corona
On Frequency-dependent Dispersion Measures and Extreme Scattering Events. Radio emission propagating over an Earth-pulsar line of sight provides a unique probe of the intervening ionized interstellar medium (ISM). Variations in the integrated electron column density along this line of sight, or dispersion measure (DM), have been observed since shortly after the discovery of pulsars. As early as 2006, frequency-dependent DMs have been observed and attributed to several possible causes. Ray-path averaging over different effective light-cone volumes through the turbulent ISM contributes to this effect, as will DM misestimation due to radio propagation across compact lensing structures such as those caused by "extreme scattering events (ESEs)." We present methods to assess the variations in frequency-dependent DMs due to the turbulent ISM versus these compact lensing structures along the line of sight. We analyze recent Low-Frequency Array observations of PSR J2219+4754 to test the underlying physical mechanism of the observed frequency-dependent DM. Previous analyses have indicated the presence of strong lensing due to compact overdensities halfway between the Earth and pulsar. Instead, we find the frequency dependence of the DM time series for PSR J2219+4754 is consistent with being due solely to ISM turbulence and there is no evidence for any ESE or small-scale lensing structure. The data show possible deviations from a uniform turbulent medium, suggesting that there may be an enhanced scattering screen near one of the two ends of the line of sight. We present this analysis as an example of the power of low-frequency observations to distinguish the underlying mechanisms in frequency-dependent propagation effects.

Keywords: Pulsar timing method, Interstellar plasma, Interstellar medium, Radio pulsars