Sazuna/UAT_keywords huggingface dataset:
Turbulence Sets the Length Scale for Planetesimal Formation: Local 2D Simulations of Streaming Instability and Planetesimal Formation. The trans-Neptunian object 2014 MU69, named Arrokoth, is the most recent evidence that planetesimals did not form by successive collisions of smaller objects, but by the direct gravitational collapse of a pebble cloud. But what process sets the physical scales on which this collapse may occur? Star formation has the Jeans mass, that is, when gravity is stronger than thermal pressure, helping us to understand the mass of our Sun. But what controls mass and size in the case of planetesimal formation? Both asteroids and Kuiper Belt objects show a kink in their size distribution at 100 km. Here we derive a gravitational collapse criterion for a pebble cloud to fragment to planetesimals, showing that a critical mass is needed for the clump to overcome turbulent diffusion. We successfully tested the validity of this criterion in direct numerical simulations of planetesimal formation triggered by the streaming instability. Our result can therefore explain the sizes for planetesimals found forming in streaming instability simulations in the literature, while not addressing the detailed size distribution. We find that the observed characteristic diameter of ∼100 km corresponds to the critical mass of a pebble cloud set by the strength of turbulent diffusion stemming from streaming instability for a wide region of a solar nebula model from 2 to 60 au, with a tendency to allow for smaller objects at distances beyond and at late times, when the nebula gas gets depleted.

Keywords: Hydrodynamical simulations, Solar system formation, Asteroids, Small Solar System bodies, Classical Kuiper belt objects, Protoplanetary disks, Planetesimals, Comets, Trans-Neptunian objects, Planet formation
The Sloan Digital Sky Survey Reverberation Mapping Project: Mg II Lag Results from Four Years of Monitoring. We present reverberation mapping results for the Mg II λ2800 Å broad emission line in a sample of 193 quasars at $0.35\lt z\lt 1.7$ with photometric and spectroscopic monitoring observations from the Sloan Digital Sky Survey Reverberation Mapping project during 2014-2017. We find significant time lags between the Mg II and continuum lightcurves for 57 quasars, and define a "gold sample" of 24 quasars with the most reliable lag measurements. We estimate false-positive rates for each lag that range from 1% to 24%, with an average false-positive rate of 11% for the full sample and 8% for the gold sample. There are an additional ∼40 quasars with marginal Mg II lag detections, which may yield reliable lags after additional years of monitoring. The Mg II lags follow a radius-luminosity relation with a best-fit slope that is consistent with $\alpha =0.5$ , but with an intrinsic scatter of 0.36 dex that is significantly larger than found for the Hβ radius-luminosity relation. For targets with SDSS-RM lag measurements of other emission lines, we find that our Mg II lags are similar to the Hβ lags and ∼2-3 times larger than the C IV lags. This work significantly increases the number of Mg II broad-line lags and provides additional reverberation-mapped black hole masses, filling the redshift gap at the peak of supermassive black hole growth between the Hβ and C IV emission lines in optical spectroscopy.

Keywords: Active galactic nuclei, Active galaxies, Quasars, Galaxy nuclei
Mapping the Galactic Disk with the LAMOST and Gaia Red Clump Sample. IV. The Kinematic Signature of the Galactic Warp. Using a sample of nearly 140,000 red clump stars selected from the LAMOST and Gaia Galactic surveys, we have mapped mean vertical velocity $\overline{{V}_{z}}$ in the X-Y plane for a large volume of the Galactic disk (6 &lt; R &lt; 16 kpc; -20 &lt; φ &lt; 50°; $| Z| \lt 1$ kpc). A clear signature where $\overline{{V}_{z}}$ increases with R is detected for the chemically thin disk. The signature for the thick disk, however, is not significant, in line with the hot nature of this disk component. For the thin disk, the warp signature shows significant variations in both the radial and azimuthal directions, in excellent agreement with the previous results of star counts. Fitting the two-dimensional distribution of $\overline{{V}_{z}}$ with a simple long-lived static warp model yields a line-of-node angle for this kinematic warp of about 12°5, again consistent with the previous results.

Keywords: Stellar kinematics, Milky Way disk, Milky Way dynamics, Red giant branch
The MAVERIC Survey: Chandra/ACIS Catalog of Faint X-Ray Sources in 38 Galactic Globular Clusters. Globular clusters host a variety of lower-luminosity (LX &lt; 1035 erg s-1) X-ray sources, including accreting neutron stars (NSs) and black holes (BHs), millisecond pulsars (MSPs), cataclysmic variables, and chromospherically active binaries. In this paper, we provide a comprehensive catalog of more than 1100 X-ray sources in 38 Galactic globular clusters (GCs) observed by the Chandra X-ray Observatory's Chandra/ACIS detector. The targets are selected to complement the MAVERIC survey's deep radio continuum maps of Galactic GCs. We perform photometry and spectral analysis for each source, determine a best-fit model, and assess the possibility of it being a foreground or background source based on its spectral properties and location in the cluster. We also provide basic assessments of variability. We discuss the distribution of X-ray binaries in GCs and their X-ray luminosity function, and we carefully analyze systems with LX &gt; 1033 erg s-1. Among these moderately bright systems, we discover a new source in NGC 6539 that may be a candidate accreting stellar-mass BH or a transitional MSP. We show that quiescent NS low-mass X-ray binaries in GCs may spend ∼2% of their lifetimes as transitional MSPs in their active (LX &gt; 1033 erg s-1) state. Finally, we identify a substantial underabundance of bright (LX &gt; 1033 erg s-1) intermediate polars in GCs compared to the Galactic field, in contrast with the literature of the past two decades.

Keywords: Globular star clusters, Neutron stars, Stellar accretion disks, Celestial objects catalogs, Low-mass x-ray binary stars, Astrophysical black holes
Probing Dark Low-mass Halos and Primordial Black Holes with Frequency-dependent Gravitational Lensing Dispersions of Gravitational Waves. We explore the possibility of using amplitude and phase fluctuations of gravitational waves due to gravitational lensing as a probe of the small-scale matter power spectrum. The direct measurement of the small-scale matter power spectrum is made possible by making use of the frequency dependence of such gravitational lensing dispersions originating from the wave optics nature of the propagation of gravitational waves. We first study the small-scale behavior of the matter power spectrum in detail taking the so-called halo model approach, including the effects of baryons and subhalos. We find that the matter power spectrum at the wavenumber k ∼ 106 hMpc-1 is mainly determined by the abundance of dark low-mass halos with mass $1{h}^{-1}{M}_{\odot }\lesssim M\lesssim {10}^{4}{h}^{-1}{M}_{\odot }$ and is relatively insensitive to baryonic effects. The matter power spectrum at this wavenumber is probed by gravitational lensing dispersions of gravitational waves at frequencies of f ∼ 0.1-1 Hz with predicted signals of ${ \mathcal O }({10}^{-3})$ . We also find that primordial black holes (PBHs) with MPBH ≳ 0.1 M⊙ can significantly enhance the matter power spectrum at k ≳ 105 hMpc-1 due to both the enhanced halo formation and the shot noise from PBHs. We find that gravitational lensing dispersions at f ∼ 10-100 Hz are particularly sensitive to PBHs and can be enhanced by more than an order of magnitude depending on the mass and abundance of PBHs.

Keywords: Cosmology, Gravitational waves, Dark matter, Weak gravitational lensing
Evolution of Dust and Water Ice in Cometary Comae by Radiative Torques. Comets provide unique information about the physical and chemical properties of the environment in which the solar system was formed. Understanding how cometary dust and ice evolve under the effect of sunlight is essential for constraining nuclear structure and triggering the mechanism of comet activity. In this paper, we first study the rotational disruption of dust grains lifted by outgassing from comet nuclei by radiative torques (RATs). We find that composite grains could be rapidly disrupted into small fragments by the RAT disruption mechanism. We then study rotational desorption of ice grains by RATs and find that icy grains could be desorbed from large heliocentric distances, beyond the sublimation radius of water at ${R}_{\mathrm{sub}}({{\rm{H}}}_{2}{\rm{O}})\sim 3\,\mathrm{au}$ . We also calculate the production rate of water vapor versus the heliocentric distance of comets due to rotational desorption. Our results could explain the variation of dust properties and the presence of small grains frequently observed from cometary comae. Finally, we suggest that the activity of distant comets could be triggered by rotational disruption of grains and desorption of water-ice grains at large heliocentric distances.

Keywords: Comet nuclei, Comet volatiles , Comae, Coma dust
Can Chondrules Be Produced by the Interaction of Jupiter with the Protosolar Disk?. Chondrules are crystallized droplets of silicate melt formed by rapid heating to high temperatures (&gt;1800 K) of solid precursors followed by hours or days of cooling. The time interval of chondrule formation is consistent with the formation timescale of Jupiter in the core-accretion model (1-4 Myr). Here we investigate if the shocks generated by a massive planet could generate flash heating episodes necessary to form chondrules using high-resolution 2D simulations with the multifluid code RoSSBi. We use different radiative cooling prescriptions, planet masses, orbits, and disk models. Temperatures reached during flash heating can be deduced from chondrule observations and are achieved in a Minimum Mass Solar Nebula (MMSN) for a massive protoplanet (&gt;0.75 M♃) but only in cases in which radiative cooling is low enough to lead to nearly adiabatic conditions. More realistic thermodynamics undershoot the temperatures required in shocks for chondrule formation. However, these temperatures are reached when considering more massive disks (e.g., five MMSN), but these conditions lead to fast planet migration and too low cooling rates compared to those deduced from chondrule textures. Thus, it seems unlikely that shocks from Jupiter can form chondrules in most cases. Independent of the nebular mass, the simulations demonstrate that a massive planet that forms a gap triggers vortices, which act as dust traps for chondrule precursors. These vortices also provide a high-pressure environment consistent with cosmochemical evidence from chondrules. They only lack the flash heating source for a potential chondrule formation environment.

Keywords: Cosmochemistry, Chondrules, Jupiter, Protoplanetary disks, Astrophysical fluid dynamics, Planet formation
Four (Super)luminous Supernovae from the First Months of the ZTF Survey. We present photometry and spectroscopy of four hydrogen-poor luminous supernovae discovered during the 2-month long science commissioning and early operations of the Zwicky Transient Facility (ZTF) survey. Three of these objects, SN 2018bym (ZTF18aapgrxo), SN 2018avk (ZTF18aaisyyp), and SN 2018bgv (ZTF18aavrmcg), resemble typical SLSN-I spectroscopically, while SN 2018don (ZTF18aajqcue) may be an object similar to SN 2007bi experiencing considerable host galaxy reddening, or an intrinsically long-lived, luminous, and red SN Ic. We analyze the light curves, spectra, and host galaxy properties of these four objects and put them in context of the population of SLSN-I. SN 2018bgv stands out as the fastest-rising SLSN-I observed to date, with a rest-frame g-band rise time of just 10 days from explosion to peak—if it is powered by magnetar spin-down, the implied ejecta mass is only ≃1 M⊙. SN 2018don also displays unusual properties—in addition to its red colors and comparatively massive host galaxy, the light curve undergoes some of the strongest light-curve undulations postpeak seen in an SLSN-I, which we speculate may be due to interaction with circumstellar material. We discuss the promises and challenges of finding SLSNe in large-scale surveys like ZTF given the observed diversity in the population.

Keywords: Surveys, Magnetars, Supernovae, Stellar mass loss
Evidence for Dense Gas Heated by the Explosion in Orion KL. We mapped the kinetic temperature structure of Orion KL in a ∼20″ (∼8000 au) sized region with para-H2CS 707 - 606, 726 - 625, and 725 - 624 making use of Atacama Large Millimeter/submillimeter Array Band 6 Science Verification data. The kinetic temperatures obtained with a resolution of 1"65 × 1"14 (∼550 au) are deduced by modeling the measured averaged velocity-integrated intensity ratios of para-H2CS 726 - 625/707 - 606 and 725 - 624/707 - 606 with a RADEX non-LTE model. The kinetic temperatures of the dense gas, derived from the para-H2CS line ratios at a spatial density of 107 cm-3, are high, ranging from 43 to &gt;500 K with an unweighted average of ∼170 K. There is no evidence for internal sources playing an important role in the heating of the various structures identified in previous work, namely the elongated ridge, the northwestern clump, and the eastern region of the compact ridge, while the high temperatures in the western region of the compact ridge may be dominated by internal massive star formation. Significant gradients of kinetic temperature along molecular filaments traced by H2CS indicate that the dense gas is heated by the shocks induced by the enigmatic explosive event which occurred several hundred years ago and greatly affected the energetics of the Orion KL region. Thus, with the notable exception of the western region of the compact ridge, the high temperatures of the dense gas in Orion KL are probably caused by shocks from the explosive event, leading to a dominant component of externally heated dense gas.

Keywords: Interstellar clouds, Interstellar medium
The Role of Peak Temperatures in Solar X-Ray Flare Associations with CME Speeds and Widths and in Flare Size Distributions. Recently, we reported that solar X-ray flares with relatively low peak (0.05-0.3 nm)/(0.1-0.8 nm) ratios R, a proxy for peak flare temperature T, were preferentially associated not only with solar energetic (E &gt; 10 MeV) particle (SEP) events, but also with fast (Vcme ≥ 1000 km s-1) coronal mass ejections (CMEs) that produce the SEP events. Flares associated with a characteristic CME speed Vcme range from small and cool to large and hot, and cooler X-ray flares were preferentially associated with broader CME widths. Here we increase the list of analyzed Geostationary Operational Environmental Satellite flares from the previous 450 to 588 and validate the earlier results with flare peak X-ray temperatures T from the TEBBS (Temperature and Emission measure-based Background Subtraction) method catalog. Power-law size distributions of flare peak fluxes Fp are increasingly steeper for X-ray flares with (1) fast (Vcme ≥ 1000 km s-1); (2) slow (Vcme &lt; 1000 km s-1); and (3) no CMEs; in each case flares of larger Fp are characteristically hotter. The power-law size distribution of SEP event peak intensities Ip is flatter than any of the X-ray Fp distributions or a distribution formed from the product of the steep SEP Ip dependence on Vcme and the Vcme number distributions.

Keywords: Solar energetic particles, Solar coronal mass ejection shocks, Solar flare spectra, Solar x-ray flares
Active Region Irradiance during Quiescent Periods: New Insights from Sun-as-a-star Spectra. How much energy do solar active regions (ARs) typically radiate during quiescent periods? This is a fundamental question for storage and release models of flares and ARs, yet it is presently poorly answered by observations. Here we use the "Sun-as-a-point-source" spectra from the EUV Variability Experiment (EVE) on the Solar Dynamics Observatory to provide a novel estimate of radiative energy losses of an evolving AR. Although EVE provides excellent spectral (5-105 nm) and temperature (2-25 MK) coverage for AR analysis, to our knowledge, these data have not been used for this purpose due to the lack of spatial resolution and the likelihood of source confusion. Here we present a way around this problem. We analyze EVE data time series, when only one large AR 11520 was present on the disk. By subtracting the quiet-Sun background, we estimate the radiative contribution in EUV from the AR alone. We estimate the mean AR irradiance and cumulative AR radiative energy losses in the 1-300 Å and astronomical standard ROSAT-PSPC, 3-124 Å, passbands and compare these to the magnetic energy injection rate through the photosphere, and to variations of the solar cycle luminosity. We find that while AR radiative energy losses are ∼100 times smaller than typical magnetic energy injection rates at the photosphere, they are an order of magnitude larger or similar to the bolometric radiated energies associated with large flares. This study is the first detailed analysis of AR thermal properties using EVE Sun-as-a-star observations, opening doors to AR studies on other stars.

Keywords: Solar active region magnetic fields, Solar atmosphere, Solar flares, Solar spectral irradiance, Solar flare spectra, Stellar activity, Solar coronal lines, Solar active regions, Solar physics, Solar activity, Active solar corona, Stellar spectral lines
Termination Shock as a Source of Unusual Solar Radio Bursts. Using centimeter-wave and decimeter-wave solar radio spectral observations of the flares of 2003 November 18 and 2004 September 12, we have discussed two type-II-like bursts at the meter waves. The radio bursts show that the ordinary frequency drift from high to low frequencies slows down and stops, and a frequency drift from low to high frequencies appears. An analysis of all data on the corresponding flares provides evidence of the formation of quasi-standing fast-mode shocks (termination shocks, TSs). TSs are able to generate energetic electrons, responsible for the appearance of new sources of hard X-ray radiation and generation of fast radio bursts (spikes), fibers, and zebra structures. The sources of the radio emission bands with the unusual frequency drift are situated above the top of the post-flare loops (lower TS) or are connected with the erupting prominence or coronal mass ejection (upper TS). Estimations of the critical Mach numbers for the ordinary plasma parameters in the solar flares give the values Mcr = 1.1-1.3 easily realized in the flare events. The conditions necessary for the generation of unusual radio bursts are likely to occur in the helmet-shaped magnetic structures in the solar corona.

Keywords: The Sun
The Correlation of Outflow Kinematics with Star Formation Rate. VI. Gas Outflows in AGNs. We investigate the connection between ionized gas outflows and star formation activity using a large sample of type 1 and 2 active galactic nuclei (AGNs) with far-infrared detections or star formation rate (SFR) estimates. The strength of ionized gas outflows, measured by the velocity dispersion and velocity shift of the [O III] emission line, clearly shows a correlation with SFR. The connection between specific star formation rate (sSFR) and [O III] gas velocity dispersion indicates that AGNs with stronger outflows are hosted by galaxies with higher SFR. Compared with star-forming galaxies in the main sequence, both type 1 and type 2 AGNs show sSFRs similar to that of non-AGN galaxies, indicating no instantaneous AGN feedback, while sSFR is higher (lower) for AGNs with stronger (weaker) outflows than that of main-sequence galaxies. These results are consistent with a delayed AGN feedback scenario. However, it is also possible that a decease/increase of gas fraction may cause the correlation without AGN feedback.

Keywords: AGN host galaxies, Supermassive black holes, Galaxy formation, Star formation
Monitoring the Morphology of M87* in 2009-2017 with the Event Horizon Telescope. The Event Horizon Telescope (EHT) has recently delivered the first resolved images of M87*, the supermassive black hole in the center of the M87 galaxy. These images were produced using 230 GHz observations performed in 2017 April. Additional observations are required to investigate the persistence of the primary image feature—a ring with azimuthal brightness asymmetry—and to quantify the image variability on event horizon scales. To address this need, we analyze M87* data collected with prototype EHT arrays in 2009, 2011, 2012, and 2013. While these observations do not contain enough information to produce images, they are sufficient to constrain simple geometric models. We develop a modeling approach based on the framework utilized for the 2017 EHT data analysis and validate our procedures using synthetic data. Applying the same approach to the observational data sets, we find the M87* morphology in 2009-2017 to be consistent with a persistent asymmetric ring of ∼40 μas diameter. The position angle of the peak intensity varies in time. In particular, we find a significant difference between the position angle measured in 2013 and 2017. These variations are in broad agreement with predictions of a subset of general relativistic magnetohydrodynamic simulations. We show that quantifying the variability across multiple observational epochs has the potential to constrain the physical properties of the source, such as the accretion state or the black hole spin.

Keywords: Supermassive black holes, Astronomy data modeling, Black holes, Very long baseline interferometry, Galaxy accretion disks, Low-luminosity active galactic nuclei, Active galactic nuclei, Galaxy accretion, Radio interferometry
X-Ray Spectroscopy in the Microcalorimeter Era. I. Effects of Fe XXIV Resonant Auger Destruction on Fe XXV Kα Spectra. We discuss the importance of Fe23+ in determining the line intensities of the Fe XXV Kα complex in an optically thick cloud, and investigate resonant auger destruction (RAD) with CLOUDY. Although initially motivated by the Perseus cluster, our calculations are extended to the wide range of column densities encountered in astronomy. A Fe XXV line photon can change/lose its identity upon absorption by three-electron iron as a result of "line interlocking." This may lead to the autoionization of the absorbing ion, ultimately destroying the Fe XXV Kα photon by RAD. Out of the four members in the Fe XXV Kα complex, a significant fraction of the x line photons are absorbed by Fe23+ and destroyed, causing the x line intensity to decrease. For example, at a hydrogen column density of 1025 cm-2, ∼32% of x photons are destroyed due to RAD while w is mostly unaffected. The line intensity of y is slightly (≤2%) reduced. z is not directly affected by RAD, but the contrasting behavior between z and x line intensities points toward the possible conversion of a tiny fraction (∼2%) of x photons into z photons. The change in line intensities due to electron scattering escape off fast thermal electrons is also discussed.

Keywords: Galaxy clusters, High resolution spectroscopy, X-ray astronomy, Radiative transfer, X-ray observatories, Intracluster medium