Sazuna/UAT_keywords huggingface dataset:
Detecting and Characterizing Young Quasars. II. Four Quasars at z   6 with Lifetimes &lt; 10<SUP>4</SUP> Yr. The extents of proximity zones of high-redshift quasars enable constraints on the timescales of quasar activity, which are fundamental for understanding the growth of the supermassive black holes (SMBHs) that power the quasars' emission. In this study, we obtain precise estimates for the ultraviolet (UV) luminous lifetimes of 10 quasars at 5.8 &lt; z &lt; 6.5. These objects were preselected to have short lifetimes based on preliminary measurements of their proximity zone sizes and were then targeted for high-quality follow-up submillimeter, optical, and infrared observations required to increase the measurements' precision and securely determine their lifetimes. By comparing these proximity zone sizes to mock quasar spectra generated from radiative transfer simulations at a range of different lifetimes, we deduce extremely short lifetimes tQ &lt; 104 yr for four objects in our sample, whereas the remaining quasars are consistent with longer lifetimes of tQ ≳ 105 yr. These young objects with small proximity zones represent ≲10% of the quasar population as a whole. We compare our results in detail to other studies on timescales of quasar activity, which point toward an average lifetime of tQ ~ 106 yr for the quasar population. This is consistent with finding newly turned-on quasars approximately ~1%-10% of the time. These young quasars represent a unique opportunity to study triggering and feedback mechanisms of SMBHs, since the onset of their UV-luminous quasar phase happened only recently, and therefore traces of this process might still be observable.

Keywords: Supermassive black holes, Early universe, Quasars, Intergalactic medium, Reionization
Detection of a Multiphase Ultrafast Wind in the Narrow-line Seyfert 1 Galaxy Mrk 1044. We present a detailed analysis of XMM-Newton X-ray spectra of the Narrow-Line Seyfert 1 galaxy Mrk 1044. We find robust evidence for a multiphase, ultrafast outflow, traced by four separate components in the grating spectrum. One component has high column density and ionization state, and is outflowing at ~0.15c. The other three wind components have lower temperature, lower column density, and have outflow velocities ~0.08c. This wind structure is strikingly similar to that found in IRAS 17020+4544, suggesting that stratified winds may be a common feature of ultrafast outflows. Such structure is likely produced by fluid instabilities that form when the nuclear wind shocks the ambient medium. We show that, in an energy-driven wind scenario, the wind in Mrk 1044 might carry enough energy to produce significant feedback on its host galaxy. We further discuss the implications of the presence of a fast wind in yet another NLS1 galaxy with high Eddington ratio.

Keywords: Active galactic nuclei, X-ray quasars, Quasar absorption line spectroscopy
The Critical Dark Matter Halo Mass for Population III Star Formation: Dependence on Lyman-Werner Radiation, Baryon-dark Matter Streaming Velocity, and Redshift. A critical dark matter halo mass (Mcrit) for Population III stars can be defined as the typical minimum halo mass that hosts sufficient cold-dense gas required for the formation of the first stars. The presence of Lyman-Werner (UV) radiation, which can dissociate molecular hydrogen, and the baryon-dark matter streaming velocity both delay the formation of Population III stars by increasing Mcrit. In this work, we constrain Mcrit as a function of Lyman-Werner flux (including self-shielding), baryon-dark matter streaming, and redshift using cosmological simulations with a large sample of halos utilizing the adaptive mesh refinement code ENZO. We provide a fit for Mcrit as a function of these quantities, which we expect to be particularly useful for semi-analytical models of early galaxy formation. In addition, we find (i) the measured redshift dependence of Mcrit in the absence of radiation or streaming is (1 + z)-1.58, consistent with a constant virial temperature; (ii) increasing the UV background increases Mcrit while steepening the redshift dependence, up to (1 + z)-5.7; (iii) baryon-dark matter streaming boosts Mcrit but flattens the dependence on redshift; (iv) the combination of the two effects is not simply multiplicative.

Keywords: Cosmology, Population III stars, High-redshift galaxies
Recurring Planetary Debris Transits and Circumstellar Gas around White Dwarf ZTF J0328-1219. We present follow-up photometry and spectroscopy of ZTF J0328-1219, strengthening its status as a white dwarf exhibiting transiting planetary debris. Using TESS and Zwicky Transient Facility photometry, along with follow-up high-speed photometry from various observatories, we find evidence for two significant periods of variability at 9.937 and 11.2 hr. We interpret these as most likely the orbital periods of different debris clumps. Changes in the detailed dip structures within the light curves are observed on nightly, weekly, and monthly timescales, reminiscent of the dynamic behavior observed in the first white dwarf discovered to harbor a disintegrating asteroid, WD 1145+017. We fit previously published spectroscopy along with broadband photometry to obtain new atmospheric parameters for the white dwarf, with M⋆ = 0.731 ± 0.023 M☉, Teff = 7630 ± 140 K, and [Ca/He] = - 9.55 ± 0.12. With new high-resolution spectroscopy, we detect prominent and narrow Na D absorption features likely of circumstellar origin, with velocities 21.4 ± 1.0 km s-1 blueshifted relative to atmospheric lines. We attribute the periodically modulated photometric signal to dusty effluents from small orbiting bodies such as asteroids or comets, but we are unable to identify the most likely material that is being sublimated, or otherwise ejected, as the environmental temperatures range from roughly 400 to 700 K.

Keywords: Transits, White dwarf stars, Tidal disruption, Roche limit, Planetesimals, Circumstellar dust
Ions Measured by Voyager 1 Outside the Heliopause to 28 au and Implications Thereof. We report 40-139 keV in situ ion measurements from the Voyager 1/Low Energy Charged Particle (LECP) instrument, over the time period from 2000 to the first 3 months of 2020, toward assessing energetic ion flow properties inside the heliosheath (HS) and upstream of the heliopause (HP). We identify an average radial outflow of ions at ~46, 67, and 109 keV of ~2.33 × 10-3, ~1.37 × 10-3, and ~7.27 × 10-4 $({\mathrm{cm}}^{2}\,\mathrm{sr}\,{\rm{s}}\,\mathrm{keV})$ -1, respectively, from the beginning of 2013 up to 2020, i.e., over a spatial range of ~28 au past the HP. The raw 40-139 keV rates, uncorrected for background, show distinct intensity dropouts for particles with 90° pitch angles, in concert with the &gt;211 MeV Galactic cosmic-ray anisotropy events, reported after Voyager 1 exited the HS in 2012 August. The intensity spectrum is consistent with a power-law form in energy with a spectral index of ~-1.4, similar to energy spectra measured by both Voyager 1 and 2/LECP inside the HS, providing strong indication that these particles correspond to an ion population leaking from the HS into interstellar space, most likely due to the flux tube interchange instability at the boundary. Future modeling efforts should incorporate this ion population, which provides the framework for establishing a communication between the HS and the very local interstellar medium.

Keywords: Heliopause, Heliosphere, Termination shock, Interstellar magnetic fields, Interstellar medium, Heliosheath
Stellar Transits across a Magnetized Accretion Torus as a Mechanism for Plasmoid Ejection. The close neighborhood of a supermassive black hole contains not only the accreting gas and dust but also stellar-sized objects, such as late-type and early-type stars and compact remnants that belong to the nuclear star cluster. When passing through the accretion flow, these objects perturb it by the direct action of stellar winds, as well as their magnetic and gravitational effects. By performing general-relativistic magnetohydrodynamic simulations, we investigate how the passages of a star can influence the supermassive black hole gaseous environment. We focus on the changes in the accretion rate and the emergence of blobs of plasma in the funnel of an accretion torus. We compare results from 2D and 3D numerical computations that have been started with comparable initial conditions. We find that a quasi-stationary inflow can be temporarily inhibited by a transiting star, and the plasmoids can be ejected along the magnetic field lines near the rotation axis. We observe the characteristic signatures of the perturbing motion in the power spectrum of the accretion variability, which provides an avenue for a multi-messenger detection of these transient events. Finally, we discuss the connection of our results to multiwavelength observations of galactic nuclei, with the emphasis on ten promising sources (Sgr A*, OJ 287, J0849+5108, RE J1034+396, 1ES 1927+65, ESO 253-G003, GSN 069, RX J1301.9+2747, eRO-QPE1, and eRO-QPE2).

Keywords: Accretion, Supermassive black holes, Low-luminosity active galactic nuclei, Magnetohydrodynamical simulations
The Complex Organic Molecular Content in the L1498 Starless Core. Observations carried out toward starless and prestellar cores have revealed that complex organic molecules are prevalent in these objects, but it is unclear what chemical processes are involved in their formation. Recently, it has been shown that complex organics are preferentially produced at an intermediate-density shell within the L1544 prestellar core at radial distances of ~4000 au with respect to the core center. However, the spatial distribution of complex organics has only been inferred toward this core, and it remains unknown whether these species present a similar behavior in other cores. We report high-sensitivity observations carried out toward two positions in the L1498 starless core, the dust peak and a position located at a distance of ~11,000 au from the center of the core where the emission of CH3OH peaks. Similarly to L1544, our observations reveal that small O-bearing molecules and N-bearing species are enhanced by factors of ~4-14 toward the outer shell of L1498. However, unlike L1544, large O-bearing organics such as CH3CHO, CH3OCH3, or CH3OCHO are not detected within our sensitivity limits. For N-bearing organics, these species are more abundant toward the outer shell of the L1498 starless core than toward the one in L1544. We propose that the differences observed between O-bearing and N-bearing species in L1498 and L1544 are due to the different physical structure of these cores, which in turn is a consequence of their evolutionary stage, with L1498 being younger than L1544.

Keywords: Interstellar molecules, Molecular clouds, Interstellar medium, Astrochemistry
Evidence of Solar-cycle-related Structural Changes in the Solar Convection Zone. While it has been relatively easy to determine solar-cycle related changes in solar dynamics, determining changes in structure in the deeper layers of the Sun has proved to be difficult. By using helioseismic data obtained over two solar cycles, and sacrificing resolution in favor of lower uncertainties, we show that there are significant changes in the solar convection zone, and perhaps even below it. Using Michelson Doppler Imager (MDI) data, we find a relative squared sound-speed difference of (2.56 ± 0.71) × 10-5 at the convection-zone base between the maximum of solar Cycle 23 and the minimum between Cycles 23 and 24. The squared sound-speed difference for the maximum of Cycle 24 obtained with Helioseismic and Magnetic Imager (HMI) data is (1.95 ± 0.69) × 10-5. Global Oscillation Network Group (GONG) data support these results. We also find that the sound speed in the solar convection zone decreases compared to the sound speed in the layers below it as the Sun becomes more active. We find evidence of changes in the radial derivative of the sound-speed difference between the solar minimum and other epochs at the base of the convection zone, implying possible small changes in the position of the convection-zone base; however, the results are too noisy to make any definitive estimates of the change.

Keywords: Solar cycle, Solar activity, Helioseismology, Solar interior
Heavy Magnetic Neutron Stars. We systematically study the properties of pure nucleonic and hyperonic magnetic stars using a density-dependent relativistic mean-field (DD-RMF) equations of state. We explore several parameter sets and hyperon coupling schemes within the DD-RMF formalism. We focus on sets that are in better agreement with nuclear and other astrophysical data while generating heavy neutron stars. Magnetic field effects are included in the matter equation of state and in general relativity solutions, which in addition fulfill Maxwell's equations. We find that pure nucleonic matter, even without magnetic field effects, generates neutron stars that satisfy the potential GW 190814 mass constraint; however, this is not the case for hyperonic matter, which instead only satisfies the more conservative 2.1 M⊙ constraint. In the presence of strong but still somehow realistic internal magnetic fields ≈1017 G, the stellar charged particle population re-leptonizes and de-hyperonizes. As a consequence, magnetic fields stiffen hyperonic equations of state and generate more massive neutron stars, which can satisfy the possible GW 190814 mass constraint but present a large deformation with respect to spherical symmetry.

Keywords: Neutron stars, Magnetars
Shocked Molecular Hydrogen and Broad CO Lines from the Interacting Supernova Remnant HB 3. We present the detections of shocked molecular hydrogen (H2) gas in near- and mid-infrared and broad CO in millimeter from the mixed-morphology supernova remnant (SNR) HB 3 (G132.7+1.3) using the Palomar Wide-field InfraRed Camera, the Spitzer GLIMPSE360 and Wide-field Infrared Survey Explorer (WISE) surveys, and the Heinrich Hertz Submillimeter Telescope. Our near-infrared narrow-band filter H2 2.12 μm images of HB 3 show that both Spitzer Infrared Array Camera and WISE 4.6 μm emission originates from shocked H2 gas. The morphology of H2 exhibits thin filamentary structures and a large scale of interaction sites between the HB 3 and nearby molecular clouds. Half of HB 3, the southern and eastern shell of the SNR, emits H2 in a shape of a butterfly or W, indicating the interaction sites between the SNR and dense molecular clouds. Interestingly, the H2 emitting region in the southeast is also co-spatial to the interacting area between HB 3 and the H II regions of the W3 complex, where we identified star-forming activity. We further explore the interaction between HB 3 and dense molecular clouds with detections of broad CO(3-2) and CO(2-1) molecular lines from the southern and southeastern shell along the H2 emitting region. The widths of the broad lines are 8-20 km s-1; the detection of such broad lines is unambiguous, dynamic evidence of the interactions between the SNR and clouds. The CO broad lines are from two branches of the bright, southern H2 shell. We apply the Paris-Durham shock model to the CO line profiles, which infer the shock velocities of 20-40 km s-1, relatively low densities of 103-4 cm-3, and strong (&gt;200 μG) magnetic fields.

Keywords: Infrared observatories, Interstellar line emission, CO line emission, Infrared dark clouds, Core-collapse supernovae, Supernova remnants, Molecular physics, Infrared telescopes, Interstellar medium, Nebulae, Collisional broadening, Line intensities
Meterwavelength Single-pulse Polarimetric Emission Survey. V. Flux Density, Component Spectral Variation, and Emission States. We present the flux density measurements of the pulsars observed in the Meterwavelength Single-pulse Polarimetric Emission Survey. The average flux densities were estimated in 113 pulsars at two frequencies of 325 and 610 MHz using interferometric imaging. The average profile and single-pulse emission in each pulsar were calibrated using the estimated flux density. We have used the flux-calibrated average profile to study the variation of the spectral index across the emission beam in 21 pulsars where the core, inner cone, and the outer conal components could be clearly identified. The central core component showed a steeper increase in emission at the lower frequency compared with conal emission, with an average difference in spectral index δαcore-cone ~ -0.7 between the core and the conal components in this frequency range. In contrast, the inner conal components had positive difference in their spectral index compared to the outer cones with average difference δαin-out ~ +0.3. The variation in the spectral index across the pulse window should provide valuable inputs for constraining the radio emission processes. The single-pulse emission showed the presence of emission mode changing in 12 pulsars, with three cases where the phenomenon is being reported for the first time. In addition, we have also detected enhanced emission for short durations or flaring, in parts or across the entire emission window in 14 pulsars. The sudden changes in the emission during mode changing, as well as these bursting states, are unrelated to the emission mechanism and suggest the presence of rapid and repetitive changes during the plasma generation process.

Keywords: Radio pulsars
H<SUB>2</SUB> Formation on Interstellar Grains and the Fate of Reaction Energy. Molecular hydrogen is the most abundant molecular species in the universe. While no doubts exist that it is mainly formed on the interstellar dust grain surfaces, many details of this process remain poorly known. In this work, we focus on the fate of the energy released by the H2 formation on the dust icy mantles: how it is partitioned between the substrate and the newly formed H2, a process that has a profound impact on the interstellar medium. We carried out state-of-the-art ab initio molecular dynamics simulations of H2 formation on periodic crystalline and amorphous ice surface models. Our calculations show that up to two-thirds of the energy liberated in the reaction (~300 kJ mol-1 ~3.1 eV) is absorbed by the ice in less than 1 ps. The remaining energy (~140 kJ mol-1 ~1.5 eV) is kept by the newly born H2. Since it is 10 times larger than the H2 binding energy on the ice, the new H2 molecule will eventually be released into the gas phase. The ice water molecules within ~4 Å from the reaction site acquire enough energy, between 3 and 14 kJ mol-1 (360-1560 K), to potentially liberate other frozen H2 and, perhaps, frozen CO molecules. If confirmed, the latter process would solve the long standing conundrum of the presence of gaseous CO in molecular clouds. Finally, the vibrational state of the newly formed H2 drops from highly excited states (ν = 6) to low (ν ≤ 2) vibrational levels in a timescale of the order of picoseconds.

Keywords: Astrochemistry
Cosmological Simulations of Quasar Fueling to Subparsec Scales Using Lagrangian Hyper-refinement. We present cosmological hydrodynamic simulations of a quasar-mass halo (Mhalo ≈ 1012.5 M⊙ at z = 2) that for the first time resolve gas transport down to the inner 0.1 pc surrounding the central massive black hole. We model a multiphase interstellar medium including stellar feedback by supernovae, stellar winds, and radiation, and a hyper-Lagrangian refinement technique increasing the resolution dynamically approaching the black hole. We do not include black hole feedback. We show that the subpc inflow rate (1) can reach ~6 M⊙ yr-1 roughly in steady state during the epoch of peak nuclear gas density (z ~ 2), sufficient to power a luminous quasar, (2) is highly time variable in the pre-quasar phase, spanning 0.001-10 M⊙ yr-1 on Myr timescales, and (3) is limited to short (~2 Myr) active phases (0.01-0.1 M⊙ yr-1) followed by longer periods of inactivity at lower nuclear gas density and late times (z ~ 1), owing to the formation of a hot central cavity. Inflowing gas is primarily cool, rotational support dominates over turbulence and thermal pressure, and star formation can consume as much gas as provided by inflows across 1 pc-10 kpc. Gravitational torques from multiscale stellar non-axisymmetries dominate angular momentum transport over gas self-torquing and pressure gradients, with accretion weakly dependent on black hole mass. Subpc inflow rates correlate with nuclear (but decouple from global) star formation and can exceed the Eddington rate by ×10. The black hole can move ~10 pc from the galaxy center on ~0.1 Myr. Accreting gas forms pc-scale, rotationally supported, obscuring structures often misaligned with the galaxy-scale disk. These simulations open a new avenue to investigate black hole-galaxy coevolution.

Keywords: AGN host galaxies, Black hole physics, Galaxy formation, Cosmological evolution, Supermassive black holes, Quasars, Galaxy nuclei, Galaxy evolution
The Sun's Magnetic (Hale) Cycle and 27 Day Recurrences in the aa Geomagnetic Index. We construct a new solar cycle phase clock which maps each of the last 18 solar cycles onto a single normalized epoch for the approximately 22 yr Hale (magnetic polarity) cycle, using the Hilbert transform of daily sunspot numbers (SSNs) since 1818. The occurrences of solar maxima show almost no discernible Hale cycle dependence, consistent with the clock being synchronized to polarity reversals. We reengineer the Sargent R27 index and combine it with our epoch analysis to obtain a high time resolution parameter for 27 day recurrence in aa, ⟨acv(27)⟩. This reveals that the transition to recurrence, that is, to an ordered solar wind dominated by high-speed streams, is fast, with an upper bound of a few solar rotations. It resolves an extended late declining phase which is approximately twice as long on even Schwabe cycles as odd. Galactic cosmic ray flux rises in step with ⟨acv(27)⟩ but then stays high. Our analysis also identifies a slow-timescale trend in SSN that simply tracks the Gleissberg cycle. We find that this trend is in phase with the slow-timescale trend in the modulus of sunspot latitudes, and in antiphase with that of the R27 index.

Keywords: Solar cycle, Space weather, Sunspot cycle
Efficiencies of Magnetic Field Amplification and Electron Acceleration in Young Supernova Remnants: Global Averages and Kepler's Supernova Remnant. Particle acceleration to suprathermal energies in strong astrophysical shock waves is a widespread phenomenon, generally explained by diffusive shock acceleration. Such shocks can also amplify the upstream magnetic field considerably beyond simple compression. The complex plasma physics processes involved are often parameterized by assuming that shocks put some fraction ϵe of their energy into fast particles and another fraction ϵB into the magnetic field. Modelers of shocks in supernovae, supernova remnants (SNRs), and gamma-ray bursters, among other locations, often assume typical values for these fractions, presumed to remain constant in time. However, it is rare that enough properties of a source are independently constrained that values of the epsilons can be inferred directly. SNRs can provide such circumstances. Here we summarize results from global fits to spatially integrated emission in six young SNRs, finding 10-4 ≲ ϵe ≲ 0.05 and 0.001 ≲ ϵB ≲ 0.1. These large variations might be put down to the differing ages and environments of these SNRs, so we conduct a detailed analysis of a single remnant, that of Kepler's supernova. Both epsilons can be determined at seven different locations around the shock, and we find even larger ranges for both epsilons, as well as for their ratio (thus independent of the shock energy itself). We conclude that unknown factors have a large influence on the efficiency of both processes. Shock obliquity, upstream neutral fraction, or other possibilities need to be explored, while calculations assuming fixed values of the epsilons should be regarded as provisional.

Keywords: Supernova remnants, Shocks, Magnetic fields, Cosmic rays