Sazuna/UAT_keywords huggingface dataset:
Electron Holography Details the Tagish Lake Parent Body and Implies Early Planetary Dynamics of the Solar System. The degree of aqueous alteration of small bodies in the solar system depends on the time of their formation, their size, and collisions with other bodies, among other factors. Therefore, a knowledge of the aqueous alterations recorded in meteorites is crucial to understanding the history of our solar system. The Tagish Lake meteorite, believed to have formed in the cold outer solar system, contains framboidal magnetite, a major product of the aqueous process. By in situ annealing experiments on the magnetic properties of the magnetite by electron holography and by numerical simulations, we show that the interior temperature of the parent body of the Tagish Lake meteorite reached ~250°C as a result of radiogenic heating and an energetic impact. Our nanometer-scale magnetic study suggested that the parent body grew to &gt;160 km in diameter in the Kuiper Belt at ~3 Myr after the first solar system minerals formed and then experienced an energetic impact from a smaller body with a diameter of ~10 km at a speed of ~5 km s-1 about 4-5 Myr after the first minerals. The probability of such a high-impact-velocity event would have increased during travel of the parent body from the Kuiper Belt to the asteroid belt, triggered by the formation and migration of the giant planets. Our results imply the early dynamics of solar system bodies that occurred several million years after the formation of the solar system and a highly efficient formation of the outer bodies of the solar system, including Jupiter.

Keywords: Meteorites, Planetary dynamics
Machine Learning of Interstellar Chemical Inventories. The characterization of interstellar chemical inventories provides valuable insight into the chemical and physical processes in astrophysical sources. The discovery of new interstellar molecules becomes increasingly difficult as the number of viable species grows combinatorially, even when considering only the most thermodynamically stable. In this work, we present a novel approach for understanding and modeling interstellar chemical inventories by combining methodologies from cheminformatics and machine learning. Using multidimensional vector representations of molecules obtained through unsupervised machine learning, we show that identification of candidates for astrochemical study can be achieved through quantitative measures of chemical similarity in this vector space, highlighting molecules that are most similar to those already known in the interstellar medium. Furthermore, we show that simple, supervised learning regressors are capable of reproducing the abundances of entire chemical inventories, and predict the abundance of not-yet-seen molecules. As a proof-of-concept, we have developed and applied this discovery pipeline to the chemical inventory of a well-known dark molecular cloud, the Taurus Molecular Cloud 1, one of the most chemically rich regions of space known to date. In this paper, we discuss the implications and new insights machine learning explorations of chemical space can provide in astrochemistry.

Keywords: Interdisciplinary astronomy, Chemical abundances, Astrochemistry
Dynamics and Morphology of Cold Gas in Fast, Radiatively Cooling Outflows: Constraining AGN Energetics with Horseshoes. Warm ionized and cold neutral outflows with velocities exceeding 100 km s-1 are commonly observed in galaxies and clusters. However, theoretical studies indicate that ram pressure from a hot wind, driven either by the central active galactic nucleus (AGN) or a starburst, cannot accelerate existing cold gas to such high speeds without destroying it. In this work we explore a different scenario, where cold gas forms in a fast, radiatively cooling outflow with temperature T ≲ 107 K. Using 3D hydrodynamic simulations, we demonstrate that cold gas continuously fragments out of the cooling outflow, forming elongated filamentary structures extending tens of kiloparsecs. For a range of physically relevant temperature and velocity configurations, a ring of cold gas perpendicular to the direction of motion forms in the outflow. This naturally explains the formation of transverse cold gas filaments such as the blue loop and the horseshoe filament in the Perseus cluster. Based on our results, we estimate that the AGN outburst responsible for the formation of these two features drove bipolar outflows with velocity &gt;2000 km s-1 and total kinetic energy &gt;8 × 1057 erg about ~10 Myr ago. We also examine the continuous cooling in the mixing layer between hot and cold gas, and find that radiative cooling only accounts for ~10% of the total mass cooling rate, indicating that observations of soft X-ray and far-ultraviolet emission may significantly underestimate the growth of cold gas in the cooling flow of galaxy clusters.

Keywords: Cooling flows, Active galactic nuclei, Galaxy winds, Intracluster medium, Filamentary nebulae
Collisional Growth within the Solar System's Primordial Planetesimal Disk and the Timing of the Giant Planet Instability. The large-scale structure of the solar system has been shaped by a transient dynamical instability that may have been triggered by the interaction of the giants planets with a massive primordial disk of icy debris. In this work, we investigate the conditions under which this primordial disk could have coalesced into planets using analytic and numerical calculations. In particular, we perform numerical simulations of the solar system's early dynamical evolution that account for the viscous stirring and collisional damping within the disk. We demonstrate that if collisional damping would have been sufficient to maintain a temperate velocity dispersion, Earth-mass trans-Neptunian planets could have emerged within a timescale of 10 Myr. Therefore, our results favor a scenario wherein the dynamical instability of the outer solar system began immediately upon the dissipation of the gaseous nebula to avoid the overproduction of Earth-mass planets in the outer solar system.

Keywords: Astrodynamics, Solar system formation, Trans-Neptunian objects
Compact Elliptical Galaxies Hosting Active Galactic Nuclei in Isolated Environments. We present the discovery of rare active galactic nuclei (AGNs) in nearby (z &lt; 0.05) compact elliptical galaxies (cEs) located in isolated environments. Using spectroscopic data from the Sloan Digital Sky Survey (SDSS) Data Release 12, four AGNs were identified based on the optical emission-line diagnostic diagram. SDSS optical spectra of AGNs show the presence of distinct narrow-line emissions. Utilizing the black hole (BH) mass-stellar velocity dispersion scaling relation and the correlation between the narrow L([O III])/L(Hβ) line ratio and the width of the broad Hα emission line, we estimated the BH masses of the cEs to be in the range of 7 × 105-8 × 107 M☉. The observed surface brightness profiles of the cEs were fitted with a double Sérsic function using the Dark Energy Camera Legacy Survey r-band imaging data. Assuming the inner component as the bulge, the K-band bulge luminosity was also estimated from the corresponding Two Micron All Sky Survey images. We found that our cEs follow the observed BH mass-stellar velocity dispersion and BH mass-bulge luminosity scaling relations, albeit there was a large uncertainty in the derived BH mass of one cE. In view of the observational properties of BHs and those of the stellar populations of cEs, we discuss the proposition that cEs in isolated environments are bona fide low-mass early-type galaxies (i.e., a nature origin).

Keywords: Galaxy formation, Black holes, Compact galaxies, Active galactic nuclei, Galaxy evolution, Elliptical galaxies
Protoplanetary Disk Birth in Massive Star-forming Clumps: The Essential Role of the Magnetic Field. Protoplanetary disks form through angular momentum conservation in collapsing dense cores. In this work, we perform the first simulations with a maximal resolution down to the astronomical unit (au) of protoplanetary disk formation, through the collapse of 1000 M⊙ clumps, treating self-consistently both non-ideal magnetohydrodynamics with ambipolar diffusion as well as radiative transfer in the flux-limited diffusion approximation including stellar feedback. Using the adaptive mesh-refinement code RAMSES, we investigate the influence of the magnetic field on the disks properties with three models. We show that, without magnetic fields, a population dominated by large disks is formed that is not consistent with Class 0 disk properties as estimated from observations. The inclusion of magnetic field leads, through magnetic braking, to a very different evolution. When it is included, small &lt;50 au disks represent about half the population. In addition, about 70% of the stars have no disk in this case, which suggests that our resolution is still insufficient to preserve the smaller disks. With ambipolar diffusion, the proportion of small disks is also prominent and we report a flat mass distribution around 0.01-0.1M⊙ and a typical disk-to-star mass ratios of ~10-2-10-1. This work shows that the magnetic field and its evolution plays a prominent role in setting the initial properties of disk populations.

Keywords: Magnetohydrodynamics, Molecular clouds, Star formation, Protoplanetary disks, Interstellar medium, Radiative transfer, Protostars
Dynamical Formation Channels for Fast Radio Bursts in Globular Clusters. The repeating fast radio burst (FRB) localized to a globular cluster (GC) in M81 challenges our understanding of FRB models. In this Letter, we explore dynamical formation scenarios for objects in old GCs that may plausibly power FRBs. Using N-body simulations, we demonstrate that young neutron stars (NSs) may form in GCs at a rate of up to ~50 Gpc-3 yr-1 through a combination of binary white dwarf (WD) mergers, WD-NS mergers, binary NS mergers, and accretion-induced collapse of massive WDs in binary systems. We consider two FRB emission mechanisms: First, we show that a magnetically powered source (e.g., a magnetar with field strength ≳1014 G) is viable for radio emission efficiencies ≳10-4. This would require magnetic activity lifetimes longer than the associated spin-down timescales and longer than empirically constrained lifetimes of Galactic magnetars. Alternatively, if these dynamical formation channels produce young rotation-powered NSs with spin periods of ~10 ms and magnetic fields of ~1011 G (corresponding to spin-down lifetimes of ≳105 yr), the inferred event rate and energetics can be reasonably reproduced for order unity duty cycles. Additionally, we show that recycled millisecond pulsars or low-mass X-ray binaries similar to those well-observed in Galactic GCs may also be plausible channels, but only if their duty cycle for producing bursts similar to the M81 FRB is small.

Keywords: Globular star clusters, Neutron stars, Magnetars, N-body simulations, Radio transient sources
Spacetime Hall-MHD Turbulence at Sub-ion Scales: Structures or Waves?. Spatiotemporal properties of two-dimensional (2D) Hall-magnetohydrodynamic (MHD) turbulence at intermediate plasma β = 2 are studied by means of Fast Iterative Filtering (FIF), a new technique for the decomposition of nonstationary nonlinear signals. Results show that the magnetic energy at sub-ion scales is concentrated in perturbations with frequencies smaller than the ion-cyclotron (IC) frequency and with polarization properties that are incompatible with both kinetic Alfvén waves (KAWs) and IC waves. At higher frequencies, we clearly identify signatures of both whistler waves and KAWs; however, their energetic contribution to the magnetic power spectrum is negligible. We conclude that the dynamics of 2D Hall-MHD turbulence at sub-ion scales is mainly driven by localized intermittent structures, with no significant contribution of wavelike fluctuations.

Keywords: Interplanetary turbulence, Space plasmas, Solar wind, Plasma astrophysics
XMM-Newton Observes the Intrabinary Shock of PSR J1959+2048. In a multi-orbit (100 ks) XMM-Newton exposure of the original black widow pulsar, PSR J1959+2048, we measure the strong orbital modulation caused by intrabinary shock (IBS) emission. The IBS light curve peak appears asymmetric, which we attribute to sweep-back effects in the companion wind. We also see evidence for an X-ray eclipse by the companion and its wind. Together with the IBS fit, this supports an edge-on i ~ 90° view of the system and a modest ~1.8 M☉ mass for the recycled pulsar. Our IBS fit parameters imply a wind flux that, if persistent, would evaporate the companion within a few Gyr.

Keywords: Pulsars
Toward the Gravitational Redshift Detection in NGC 4258 and the Estimation of Its Black Hole Mass-to-distance Ratio. We construct from first principles a general relativistic approach to study Schwarzschild black hole (BH) rotation curves and estimate the mass-to-distance ratio of the active galactic nucleus of NGC 4258 in terms of astrophysical observable quantities. The presented method allows one to clearly distinguish and quantify the general and special relativistic contributions to the total redshift expression. The total relativistic redshift/blueshift comprises three components: the gravitational redshift due to the spacetime curvature generated by the mass of the BH in its vicinity, the kinematic shift, originated by the photons' local Doppler effect, and the redshift due to a special relativistic boost that describes the motion of a galaxy from a distant observer. We apply our method to the largest data set of highly redshifted water megamaser measurements on the accretion disk of the NGC 4258 active galaxy and use this general relativistic method to estimate its BH mass-to-distance ratio: M/D = (0.5326 ± 0.00022) × 107 M⊙ Mpc-1.

Keywords: Supermassive black holes, Galaxy accretion disks, Megamasers, Schwarzschild metric
Dark Matter Deficient Galaxies and Their Member Star Clusters Form Simultaneously during High-velocity Galaxy Collisions in 1.25 pc Resolution Simulations. How diffuse dwarf galaxies that are deficient in dark matter-such as NGC1052-DF2 and NGC1052-DF4-formed remains a mystery. Along with their luminous member globular clusters (GCs), the so-called dark matter deficient galaxies (DMDGs) have challenged observers and theorists alike. Here we report a suite of galaxy collision simulations using the adaptive mesh refinement code ENZO with 1.25 pc resolution, which demonstrates that high-velocity galaxy collisions induce the formation of DMDGs and their star clusters (SCs) simultaneously. With a numerical resolution that is significantly better than our previous study, we resolve the dynamical structure of the produced DMDGs and the detailed formation history of their SCs, which are possible progenitors of the DMDG's member GCs. In particular, we show that a galaxy collision with a high relative velocity of ~300 km s-1, invoking severe shock compression, spawns multiple massive SCs $\left({M}_{\star }\gtrsim {10}^{6}\,{M}_{\odot }\right)$ in &lt;150 Myr after the collision. At the end of the ~800 Myr evolution in our fiducial run, the resulting DMDG of M⋆ ≃ 3.5 × 108 M⊙ hosts 10 luminous MV ≲ -8.5 mag, gravitationally bound SCs with a line-of-sight velocity dispersion 11.2 km s-1. Our study suggests that DMDGs and their luminous member SCs could form simultaneously in high-velocity galaxy collisions while being in line with the key observed properties of NGC1052-DF2 and NGC1052-DF4.

Keywords: Cosmology, Globular star clusters, Galaxy formation, Hydrodynamical simulations, Star formation, Galaxy evolution, Star clusters
Modeling the Observed Distortion of Multiple (Ghost) CME Fronts in STEREO Heliospheric Imagers. In this work we have, for the first time, applied the interpretation of multiple "ghost-fronts" to two synthetic coronal mass ejections (CMEs) propagating within a structured solar wind using the Heliospheric Upwind eXtrapolation time (HUXt) solar wind model. The two CMEs occurred on 2012 June 13-14 showing multiple fronts in images from Solar Terrestrial Relations Observatory Heliospheric Imagers (HIs). The HUXt model is used to simulate the evolution of these CMEs across the inner heliosphere as they interacted with structured ambient solar wind. The simulations reveal that the evolution of CME shape is consistent with observations across a wide range of solar latitudes and that the manifestation of multiple "ghost-fronts" within HIs' field of view is consistent with the positions of the nose and flank of the same CME structure. This provides further confirmation that the angular separation of these features provides information on the longitudinal extent of a CME. For one of the CMEs considered in this study, both simulations and observations show that a concave shape develops within the outer CME front. We conclude that this distortion results from a latitudinal structure in the ambient solar wind speed. The work emphasizes that the shape of the CME cannot be assumed to remain a coherent geometrical shape during its propagation in the heliosphere. Our analysis demonstrates that the presence of "ghost" CME fronts can be used to infer the distortion of CMEs by ambient solar wind structure as a function of both latitude and longitude. This information has the potential to improve the forecasting of space weather events at Earth.

Keywords: Space weather, Solar coronal mass ejections, Heliosphere
An Ancient Massive Quiescent Galaxy Found in a Gas-rich z   3 Group. Deep Atacama Large Millimeter/submillimeter Array and Hubble Space Telescope observations reveal the presence of a quenched massive galaxy within the z = 2.91 galaxy group RO-1001. With a mass-weighted stellar age of 1.6 ± 0.4 Gyr this galaxy is one of the oldest known at z ~ 3, implying that most of its 1011 M⊙ of stars were rapidly formed at z &gt; 6-8. This is a unique example of the predominantly passive evolution of a galaxy over at least 3 &lt; z &lt; 6 following its high-redshift quenching and a smoking-gun event pointing to the early imprint of an age-environment relation. At the same time, being in a dense group environment with extensive cold gas reservoirs as betrayed by a giant Lyα halo, the existence of this galaxy demonstrates that gas accretion shutdown is not necessary for quenching and its maintenance.

Keywords: High-redshift galaxies, Galaxy evolution, Galaxy groups
A Corotating Group of Dwarf Galaxies around NGC 2750 as a Centaurus A Analog. We study a low-mass spiral galaxy NGC 2750 (~5 times less massive than the Milky Way), located ~40 Mpc away in a sparse region that hosts seven satellite galaxies within a projected distance of 150 Kpc. Among them six are star-forming dwarfs with stellar masses of &gt;≈107 M⊙ and one is an early-type dwarf with a stellar mass of 2.6 × 106 M⊙. The star-forming dwarfs are gas rich, with gas mass fractions as high as Log(MH I/M*) = 1.2 and their star formation rates vary between 0.03 and 0.35 M⊙ yr-1. The projected distances and measured radial velocities of the six star-forming satellites provide a high probability that they are members of the group. The radial velocity distribution of the six satellites exhibits evidence of a systematic corotation. We devise a method to quantify such a corotation signal by calculating the correlation coefficient between satellites' relative line-of-sight velocities (ΔVr) and their sky-projected distances from the host (Rp). For the NGC 2750 system, we show a clear correlation between ΔVr and Rp, with a Pearson's R correlation coefficient c = 0.90 and p-value = 0.005. We compare the NGC 2750 system with the Centaurus A (NGC 5128) system, a previously known corotating group, and conclude that the former could be a small version of the latter but is located in an isolated field, away from the influence of the large-scale structure. The results open up opportunities to explore the galactic anisotropy phenomenon on a low-mass scale and in a rarified environment.

Keywords: Galaxy evolution, Dwarf galaxies, Galaxy groups, Galaxy interactions
On the Evidence for a Common-spectrum Process in the Search for the Nanohertz Gravitational-wave Background with the Parkes Pulsar Timing Array. A nanohertz-frequency stochastic gravitational-wave background can potentially be detected through the precise timing of an array of millisecond pulsars. This background produces low-frequency noise in the pulse arrival times that would have a characteristic spectrum common to all pulsars and a well-defined spatial correlation. Recently the North American Nanohertz Observatory for Gravitational Waves collaboration (NANOGrav) found evidence for the common-spectrum component in their 12.5 yr data set. Here we report on a search for the background using the second data release of the Parkes Pulsar Timing Array. If we are forced to choose between the two NANOGrav models-one with a common-spectrum process and one without-we find strong support for the common-spectrum process. However, in this paper, we consider the possibility that the analysis suffers from model misspecification. In particular, we present simulated data sets that contain noise with distinctive spectra but show strong evidence for a common-spectrum process under the standard assumptions. The Parkes data show no significant evidence for, or against, the spatially correlated Hellings-Downs signature of the gravitational-wave background. Assuming we did observe the process underlying the spatially uncorrelated component of the background, we infer its amplitude to be $A={2.2}_{-0.3}^{+0.4}\times {10}^{-15}$ in units of gravitational-wave strain at a frequency of 1 yr-1. Extensions and combinations of existing and new data sets will improve the prospects of identifying spatial correlations that are necessary to claim a detection of the gravitational-wave background.

Keywords: Bayesian statistics, Pulsar timing method, Millisecond pulsars, Gravitational wave astronomy, Gravitational waves
Magnetic Field Draping of the Heliopause and Its Consequences for Radio Emission in the Very Local Interstellar Medium. We discuss the observations and simulations related to the interaction of the solar wind (SW) and local interstellar medium (LISM), and the interstellar magnetic field draping around the heliopause (HP). This Letter sheds light on some processes that are not directly seen in the Voyager data. Special attention is paid to the magnetic field behavior at the HP crossing, penetration of shocks, and compression waves across the HP, and their merging in the LISM surrounding it. Modeling identifies forward and reverse shocks propagating through the heliosheath. Voyager data shows that the magnetic field strength experiences a jump at the HP, while the elevation and azimuthal angles are continuous across it. We show that our prior numerical results are in agreement with the Voyager data, if the heliospheric magnetic field is not assumed unipolar. The simulations confirm the importance of taking into account time dependencies of the SW flow, including the presence of transient structures and magnetohydrodynamic instabilities. For the first time, we provide the heliospheric community with the Alfvén speed distribution observed by Voyagers, which shows that it is unexpectedly small and decreases with distance from the HP. This is of critical importance for the identification of physical mechanisms responsible for the Langmuir wave and radio emission generation behind the HP. The data shows that outward-propagating, subcritical shocks traversing the LISM have a rather wide dissipation structure, which raises questions about their ability to reflect electrons as collisionless shocks can do.

Keywords: Heliopause, Heliosphere, Interstellar magnetic fields, Interstellar medium, Heliosheath