Sazuna/UAT_keywords huggingface dataset:
Kinematics of the M87 Jet in the Collimation Zone: Gradual Acceleration and Velocity Stratification. We study the kinematics of the M87 jet using the first-year data of the KVN and VERA Array (KaVA) large program, which has densely monitored the jet at 22 and 43 GHz since 2016. We find that the apparent jet speeds generally increase from ≈0.3c at ≈0.5 mas from the jet base to ≈2.7c at ≈20 mas, indicating that the jet is accelerated from subluminal to superluminal speeds on these scales. We perform a complementary jet kinematic analysis by using archival Very Long Baseline Array monitoring data observed in 2005-2009 at 1.7 GHz and find that the jet is moving at relativistic speeds up to ≈5.8c at distances of 200-410 mas. We combine the two kinematic results and find that the jet is gradually accelerated over a broad distance range that coincides with the jet collimation zone, implying that conversion of Poynting flux to kinetic energy flux takes place. If the jet emission consists of a single streamline, the observed trend of jet acceleration (Γ ∝ z 0.16±0.01) is relatively slow compared to models of a highly magnetized jet. This indicates that Poynting flux conversion through the differential collimation of poloidal magnetic fields may be less efficient than expected. However, we find a nonnegligible dispersion in the observed speeds for a given jet distance, making it difficult to describe the jet velocity field with a single power-law acceleration function. We discuss the possibility that the jet emission consists of multiple streamlines following different acceleration profiles, resulting in jet velocity stratification.

Keywords: Jets, Active galactic nuclei, High energy astrophysics, Interferometry
The Canada-France Imaging Survey: Reconstructing the Milky Way Star Formation History from Its White Dwarf Population. As the remnants of stars with initial masses ≲8 M ⊙, white dwarfs contain valuable information on the formation histories of stellar populations. In this paper, we use deep, high-quality, u-band photometry from the Canada-France Imaging Survey, griz photometry from Pan-STARRS1, as well as proper motions from Gaia DR2, to select 25,156 white dwarf candidates over ∼4500 deg2 using a reduced proper motion diagram. We develop a new white dwarf population synthesis code that returns mock observations of the Galactic field white dwarf population for a given star formation history, while simultaneously taking into account the geometry of the Milky Way (MW), survey parameters, and selection effects. We use this model to derive the star formation histories of the thin disk, thick disk, and stellar halo. Our results show that the MW disk began forming stars (11.3 ± 0.5) Gyr ago, with a peak rate of (8.8 ± 1.4) M ⊙ yr -1 at (9.8 ± 0.4) Gyr, before a slow decline to a constant rate until the present day—consistent with recent results suggesting a merging event with a satellite galaxy. Studying the residuals between the data and best-fit model shows evidence for a slight increase in star formation over the past 3 Gyr. We fit the local fraction of helium-atmosphere white dwarfs to be (21 ± 3)%. Incorporating this methodology with data from future wide-field surveys such as the Large Synoptic Survey Telescope, Euclid, The Cosmological Advanced Survey Telescope for Optical and ultraviolet Research, and the Wide Field Infrared Survey Telescope should provide an unprecedented view into the formation of the MW at its earliest epoch through its white dwarfs.

Keywords: White dwarf stars, Milky Way rotation, Milky Way evolution
Origins of Molecular Clouds in Early-type Galaxies. We analyze Chandra observations of the hot atmospheres of 40 early spiral and elliptical galaxies. Using new temperature, density, cooling time, and mass profiles, we explore relationships between their hot atmospheres and cold molecular gas. Molecular gas mass correlates with atmospheric gas mass and density over four decades from central galaxies in clusters to normal giant ellipticals and early spirals. The mass and density relations follow power laws: {M}mol}\propto {M}{{X}}1.4+/- 0.1 and {M}mol}\propto {n}{{e}}1.8+/- 0.3, respectively, at 10 kpc. The ratio of molecular gas to atmospheric gas within a 10 kpc radius lies between 3% and 10% for early-type galaxies and between 3% and 50% for central galaxies in clusters. Early-type galaxies have detectable levels of molecular gas when their atmospheric cooling times fall below ∼1 Gyr at a radius of 10 kpc. A similar trend is found in central cluster galaxies. We find no relationship between the ratio of the cooling time to free-fall time, t c/t ff, and the presence or absence of molecular clouds in early-type galaxies. The data are consistent with much of the molecular gas in early-type galaxies having condensed from their hot atmospheres.

Keywords: Galaxy dynamics, Galaxy kinematics
Numerical Simulation on the Propagation and Deflection of Fast Coronal Mass Ejections (CMEs) Interacting with a Corotating Interaction Region in Interplanetary Space. Previous research has shown that the deflection of coronal mass ejections (CMEs) in interplanetary space, especially fast CMEs, is a common phenomenon. The deflection caused by the interaction with background solar wind is an important factor to determine whether CMEs could hit Earth or not. As the Sun rotates, there will be interactions between solar wind flows with different speeds. When faster solar wind runs into slower solar wind ahead, it will form a compressive area corotating with the Sun, which is called a corotating interaction region (CIR). These compression regions always have a higher density than the common background solar wind. When interacting with CME, will this make a difference in the deflection process of CME? In this research, first, a three-dimensional (3D) flux-rope CME initialization model is established based on the graduated cylindrical shell (GCS) model. Then this CME model is introduced into the background solar wind, which is obtained using a 3D IN (INterplanetary) -TVD-MHD model. The Carrington Rotation (CR) 2154 is selected as an example to simulate the propagation and deflection of fast CME when it interacts with background solar wind, especially with the CIR structure. The simulation results show that: (1) the fast CME will deflect eastward when it propagates into the background solar wind without the CIR; (2) when the fast CME hits the CIR on its west side, it will also deflect eastward, and the deflection angle will increase compared with the situation without CIR.

Keywords: Solar wind, Corotating streams, Solar coronal mass ejections, Magnetohydrodynamical simulations
Camouflage of the Phase Transition to Quark Matter in Neutron Stars. It has been known for some time that compact stars containing quark matter can masquerade as neutron stars in the range of measured mass and radius, making it difficult to draw firm conclusions on the phases of matter present inside the star. Using the vector-enhanced Bag model (vBag), we examine mass-radius and mass-compactness relations with Maxwell and Gibbs construction for hybrid stars with transitions from nuclear matter to two- or three-flavor quark matter, including sequential transitions. Not only can stable hybrid stars with either two- or three-flavor quark matter mimic neutron stars (the traditional masquerade), it also appears difficult to distinguish two-flavor from three-flavor quark matter, even in cases where a phase transition can be said to have occurred, such as in the presence of a distinct kink in the mass-radius relation. Furthermore, allowing for sequential flavor transitions, we find that the transition into an unstable branch can be caused by either a transition from nuclear to unstable quark matter or the sequential transition from nuclear to stable but “masquerading” two-flavor to unstable three-flavor quark matter. Addressing chiral restoration as well as quark deconfinement in a model of the phase transition, as the vBag does, adds further flexibility to the high-density equation of state, motivating caution in using even high-precision M-R data to draw firm conclusions on the nature of phases and phase transitions in neutron stars.

Keywords: Nuclear astrophysics, Neutron star cores, Compact objects
Circumplanetary Disk Dynamics in the Isothermal and Adiabatic Limits. Circumplanetary disks (CPDs) may be essential to the formation of planets, regulating their spin and accretion evolution. We perform a series of 3D hydrodynamics simulations in both the isothermal and adiabatic limits to systematically measure the rotation rates, sizes, and masses of CPDs as functions of {q}thermal}, the ratio of the planet mass to the disk thermal mass. Our {q}thermal} ranges from 0.1 to 4; for our various disk temperatures, this corresponds to planet masses between one Earth mass and four Jupiter masses. Within this parameter space, we find that isothermal CPDs are disky and bound within ∼10% of the planet’s Bondi radius {r}{{B}}, with the innermost ∼ 0.05 {r}{{B}} in full rotational support. Adiabatic CPDs are spherical (and therefore not actually “disks”), bound within ∼ 0.2 {r}{{B}}, and mainly pressure-supported, with rotation rates scaling linearly with {q}thermal}; extrapolation suggests full rotational support of adiabatic envelopes at ∼ 10 {q}thermal}. Fast rotation and 3D supersonic flow render isothermal CPDs significantly different in structure from—and orders of magnitude less massive than—their 1D isothermal hydrostatic counterparts. Inside a minimum-mass solar nebula, even a maximally cooled, isothermal CPD around a 10 Earth-mass core may have less than one Earth mass, suggesting that gas giant formation may hinge on angular momentum transport processes in CPDs. Our CPD sizes and masses appear consistent with the regular satellites orbiting solar system giants.

Keywords: Accretion, Hydrodynamical simulations, Exoplanets, Natural satellite formation, Planet formation, Natural satellites (Solar system), Exoplanet evolution, Protoplanetary disks, Exoplanet structure, Exoplanet formation, Extrasolar gaseous giant planets, Exoplanet atmospheres
Revisiting Metastable Dark Energy and Tensions in the Estimation of Cosmological Parameters. We investigate constraints on some key cosmological parameters by confronting metastable dark energy (DE) models with different combinations of the most recent cosmological observations. Along with the standard ΛCDM model, two phenomenological metastable DE models are considered: (i) DE decays exponentially, (ii) DE decays into dark matter. We find that: (1) when considering the most recent supernovae and BAO data, and assuming a fiducial ΛCDM model, the inconsistency in the estimated value of the {{{Ω }}}{{m},0}{h}2 parameter obtained by either including or excluding Planck cosmic microwave background (CMB) data becomes very much substantial and points to a clear tension; (2) although the two metastable DE models that we study provide greater flexibility in fitting the data, and they indeed fit the supernovae (SNe) Ia+BAO data substantially better than ΛCDM, they are not able to alleviate this tension significantly when CMB data are included; (3) while local measurements of the Hubble constant are significantly higher relative to the estimated value of H 0 in our models (obtained by fitting to SNe Ia and BAO data), the situation seems to be rather complicated with hints of inconsistency among different observational data sets (CMB, SNe Ia+BAO, and local H 0 measurements). Our results indicate that we might not be able to remove the current tensions among different cosmological observations by considering simple modifications of the standard model or by introducing minimal DE models. A complicated form of expansion history, different systematics in different data and/or a nonconventional model of the early universe might be responsible for these tensions.

Keywords: Observational cosmology
Spectroscopic and Stereoscopic Observations of the Solar Jets. We present a comprehensive study of a series of recurrent jets that occurred at the periphery of the NOAA active region 12114 on 2014 July 7. These jets were found to share the same source region and exhibited rotational motions as they propagated outward. The multiwavelength imaging observations made by the AIA and IRIS telescopes reveal that some of the jets contain cool plasma only, while some others contain not only cool but also hot plasma. The Doppler velocities calculated from the IRIS spectra show a continuous evolution from blue- to redshifts as the jet motions change from upward to downward. Additionally, some jets exhibit opposite Doppler shifts on both their sides, indicative of rotating motions along their axes. The inclination angle and three-dimensional velocity of the largest jet were inferred from the imaging and spectroscopic observations, which show high consistency with those derived from the stereoscopic analysis using dual-perspective observations by SDO/AIA and STEREO-B/EUVI. By relating the jets to the local UV/EUV and full-disk GOES X-ray emission enhancements, we found that the previous five small-scale jets were triggered by five bright points while the last/largest one was triggered by a C1.6 solar flare. Together with a number of type III radio bursts generated during the jet eruptions as well as a weak CME that was observed in association with the last jet, our observations provide evidence in support of multiscale magnetic reconnection processes being responsible for the production of jet events.

Keywords: Solar atmosphere, Solar ultraviolet emission, Solar radio emission, Spectroscopy, Solar chromosphere
GASP XXIII: A Jellyfish Galaxy as an Astrophysical Laboratory of the Baryonic Cycle. With MUSE, Chandra, VLA, ALMA, and UVIT data from the GASP program, we study the multiphase baryonic components in a jellyfish galaxy (JW100) with a stellar mass 3.2 × 1011 M ☉ hosting an active galactic nucleus (AGN). We present its spectacular extraplanar tails of ionized and molecular gas, UV stellar light, and X-ray and radio continuum emission. This galaxy represents an excellent laboratory to study the interplay between different gas phases and star formation and the influence of gas stripping, gas heating, and AGNs. We analyze the physical origin of the emission at different wavelengths in the tail, in particular in situ star formation (related to Hα, CO, and UV emission), synchrotron emission from relativistic electrons (producing the radio continuum), and heating of the stripped interstellar medium (ISM; responsible for the X-ray emission). We show the similarities and differences of the spatial distributions of ionized gas, molecular gas, and UV light and argue that the mismatch on small scales (1 kpc) is due to different stages of the star formation process. We present the relation Hα-X-ray surface brightness, which is steeper for star-forming regions than for diffuse ionized gas regions with a high [O I]/Hα ratio. We propose that ISM heating due to interaction with the intracluster medium (either for mixing, thermal conduction, or shocks) is responsible for the X-ray tail, observed [O I] excess, and lack of star formation in the northern part of the tail. We also report the tentative discovery in the tail of the most distant (and among the brightest) currently known ULX, a pointlike ultraluminous X-ray source commonly originating in a binary stellar system powered by either an intermediate-mass black hole or a magnetized neutron star.

Keywords: Galaxy clusters, Galaxy evolution, Galaxy processes
Spectral Evolution and Radial Dust Transport in the Prototype Young Eruptive System EX Lup. EX Lup is the prototype of a class of pre-main-sequence eruptive stars defined by their repetitive outbursts lasting several months. In 2008 January-September EX Lup underwent its historically largest outburst, brightening by about 4 mag in visual light. In previous studies we discovered ongoing silicate crystal formation in the inner disk during the outburst, but also noticed that the measured crystallinity fraction started decreasing after the source returned to the quiescent phase. Here we present new observations of the 10 μm silicate feature, obtained with the MIDI and VISIR instruments at Paranal Observatory. The observations demonstrate that within five years practically all crystalline forsterite disappeared from the surface of the inner disk. We reconstruct this process by presenting a series of parametric axisymmetric radiative transfer models of an expanding dust cloud that transports the crystals from the terrestrial zone to outer disk regions where comets are supposed to form. It is possible the early Sun also experienced similar flare-ups, and the forming planetesimals might have incorporated crystalline silicate material produced by such outbursts. Finally, we discuss how far the location of the dust cloud could be constrained by future James Webb Space Telescope observations. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 091.C-0668 and 097.C-0639.

Keywords: Pre-main sequence stars
The Exoplanet Population Observation Simulator. II. Population Synthesis in the Era of Kepler. The collection of planetary system properties derived from large surveys such as Kepler provides critical constraints on planet formation and evolution. These constraints can only be applied to planet formation models, however, if the observational biases and selection effects are properly accounted for. Here we show how epos, the Exoplanet Population Observation Simulator, can be used to constrain planet formation models by comparing the Bern planet population synthesis models to the Kepler exoplanetary systems. We compile a series of diagnostics, based on occurrence rates of different classes of planets and the architectures of multiplanet systems within 1 au, that can be used as benchmarks for future and current modeling efforts. Overall, we find that a model with 100-seed planetary cores per protoplanetary disk provides a reasonable match to most diagnostics. Based on these diagnostics we identify physical properties and processes that would result in the Bern model more closely matching the known planetary systems. These are as follows: moving the planet trap at the inner disk edge outward; increasing the formation efficiency of mini-Neptunes; and reducing the fraction of stars that form observable planets. We conclude with an outlook on the composition of planets in the habitable zone, and highlight that the majority of simulated planets smaller than 1.7 Earth radii in this zone are predicted to have substantial hydrogen atmospheres. The software used in this paper is available online for public scrutiny at https://github.com/GijsMulders/epos.

Keywords: Exoplanet dynamics, Open source software, Astrostatistics tools, Exoplanets, Surveys, Exoplanet systems, Astrostatistics, Planetary system formation, Protoplanetary disks, Exoplanet formation, Habitable planets, Planet formation
Jellyfish: Resolving the Kinematics of Extreme Ram-pressure Stripping at z ∼ 0.3. We present and discuss results from the first spatially resolved kinematic study of ram-pressure stripping of a massive late-type galaxy at intermediate redshifts. Our target, the spectacular “jellyfish” galaxy, A1758N_JFG1, was previously identified as a fast-moving member of the equal-mass merger A1758N (z = 0.28), with a star formation rate of 48 M ⊙ yr-1, far above the galaxy main sequence. Integral field unit (IFU) data obtained by us unambiguously confirm ram-pressure stripping as the physical mechanism driving the optical morphology and high star formation rate of this system by revealing extended [O II]λ3727 Å emission up to 40 kpc (in projection) downstream, as well as an ordered radial-velocity field generated by (a) conservation of angular momentum of the interstellar gas stripped from the edge of the galactic disk and (b) drag forces exerted by the intracluster medium on the “tentacles” of stripped material. We find no evidence of significant nuclear activity in A1758N_JFG1, although an AGN might, at this early stage of the stripping process, be obscured by high column densities of gas and dust near the galactic core. Finally, our exploration of possible trajectories of A1758N_JFG1 found solutions consistent with the notions (a) that the A1758N merger proceeds along an axis that is substantially inclined with respect to the plane of the sky and (b) that A1758N_JFG1 participated in the merger, rather than having been accreted independently from the field.

Keywords: Galaxy structure, Galaxy dynamics, Galaxy kinematics, Galaxy evolution, Star formation, Intracluster medium
An Imprint of the Galactic Magnetic Field in the Diffuse Unpolarized Dust Emission. It is well known that aligned, aspherical dust grains emit polarized radiation and that the degree of polarization depends on the angle ψ between the interstellar magnetic field and the line of sight (LOS). However, anisotropy of the dust absorption cross sections also modulates the total intensity of the radiation as the viewing geometry changes. We report a detection of this effect in the high Galactic latitude Planck data, finding that the 353 GHz dust intensity per N H I  is smaller when the Galactic magnetic field is mostly in the plane of the sky and larger when the field is mostly along the LOS. These variations are of opposite sign and roughly equal magnitude as the changes in polarized intensity per N H I  with ψ, as predicted. In principle, the variation in intensity can be used in conjunction with the dust polarization angle to constrain the full 3D orientation of the Galactic magnetic field.

Keywords: Interstellar dust, Interstellar magnetic fields, Dust continuum emission, H I line emission
No Evidence for Critical Balance in Field-aligned Alfvénic Solar Wind Turbulence. The properties of Alfvénic solar wind turbulence have been studied for decades using spacecraft measurements. In particular, the observation of spectral anisotropy of magnetic fluctuations has stimulated the development of several phenomenological models, one of the most popular being critical balance. However, the experimental validation of these models is intrinsically difficult because of the one-dimensional nature of the measurements provided by spacecraft instrumentation. In this work, a thorough search is performed in the Wind spacecraft database to extract samples of field-aligned fast solar wind, which allow the precise estimation of the parallel spectral properties of the magnetic fluctuations, and of their intermittency. Hilbert spectral analysis is used, in order to eliminate the possible role of nonstationarity and large-scale structures. Our results indicate that the spectral anisotropy predicted by the critical balance theory is not observed in the selected database, thus questioning the validity of the critical balance in the solar wind turbulence. A stochastic process characterized by a -5/3 spectral scaling, which is not necessarily attributed to usual turbulence, as indicated by the absence of intermittency, is indeed observed in the analyzed data samples.

Keywords: Interplanetary medium, Space plasmas, Magnetohydrodynamics, Interplanetary turbulence, Solar wind, Alfven waves