Sazuna/UAT_keywords huggingface dataset:
Magnetic Field Intermittency in the Solar Wind: Parker Solar Probe and SolO Observations Ranging from the Alfvén Region up to 1 AU. Parker Solar Probe (PSP) and SolO data are utilized to investigate magnetic field intermittency in the solar wind (SW). Small-scale intermittency (20-100 d  i ) is observed to radially strengthen when methods relying on higher-order moments are considered (SF q ; SDK), but no clear trend is observed at larger scales. However, lower-order moment-based methods (e.g., partial variance of increments; PVI) are deemed more appropriate for examining the evolution of the bulk of coherent structures (CSs), PVI ≥ 3. Using PVI, we observe a scale-dependent evolution in the fraction of the data set occupied by CSs, f PVI≥3. Specifically, regardless of the SW speed, a subtle increase is found in f PVI≥3 for ℓ = 20 d  i , in contrast to a more pronounced radial increase in CSs observed at larger scales. Intermittency is investigated in relation to plasma parameters. Though, slower SW speed intervals exhibit higher f PVI≥6 and higher kurtosis maxima, no statistical differences are observed for f PVI≥3. Highly Alfvénic intervals display lower levels of intermittency. The anisotropy with respect to the angle between the magnetic field and SW flow, ΘVB is investigated. Intermittency is weaker at ΘVB ≈ 0° and is strengthened at larger angles. Considering the evolution at a constant alignment angle, a weakening of intermittency is observed with increasing advection time of the SW. Our results indicate that the strengthening of intermittency in the inner heliosphere is driven by the increase in comparatively highly intermittent perpendicular intervals sampled by the probes with increasing distance, an effect related directly to the evolution of the Parker spiral.

Keywords: Space plasmas, Magnetohydrodynamics, Interplanetary turbulence, Solar wind, Plasma astrophysics, Solar physics
The ALMA REBELS Survey: Average [C II] 158 μm Sizes of Star-forming Galaxies from z   7 to z   4. We present the average [C II] 158 μm emission line sizes of UV-bright star-forming galaxies at z ~ 7. Our results are derived from a stacking analysis of [C II] 158 μm emission lines and dust continua observed by the Atacama Large Millimeter/submillimeter Array (ALMA), taking advantage of the large program Reionization Era Bright Emission Line Survey. We find that the average [C II] emission at z ~ 7 has an effective radius r  e  of 2.2 ± 0.2 kpc. It is ≳2× larger than the dust continuum and the rest-frame UV emission, in agreement with recently reported measurements for z ≲ 6 galaxies. Additionally, we compared the average [C II] size with 4 &lt; z &lt; 6 galaxies observed by the ALMA Large Program to INvestigate [C II] at Early times (ALPINE). By analyzing [C II] sizes of 4 &lt; z &lt; 6 galaxies in two redshift bins, we find an average [C II] size of r e = 2.2 ± 0.2 kpc and r e = 2.5 ± 0.2 kpc for z ~ 5.5 and z ~ 4.5 galaxies, respectively. These measurements show that star-forming galaxies, on average, show no evolution in the size of the [C II] 158 μm emitting regions at redshift between z ~ 7 and z ~ 4. This finding suggests that the star-forming galaxies could be morphologically dominated by gas over a wide redshift range.

Keywords: Submillimeter astronomy, High-redshift galaxies, Interstellar medium
Resolving the Inner Parsec of the Blazar J1924─2914 with the Event Horizon Telescope. The blazar J1924─2914 is a primary Event Horizon Telescope (EHT) calibrator for the Galactic center's black hole Sagittarius A*. Here we present the first total and linearly polarized intensity images of this source obtained with the unprecedented 20 μas resolution of the EHT. J1924─2914 is a very compact flat-spectrum radio source with strong optical variability and polarization. In April 2017 the source was observed quasi-simultaneously with the EHT (April 5─11), the Global Millimeter VLBI Array (April 3), and the Very Long Baseline Array (April 28), giving a novel view of the source at four observing frequencies, 230, 86, 8.7, and 2.3 GHz. These observations probe jet properties from the subparsec to 100 pc scales. We combine the multifrequency images of J1924─2914 to study the source morphology. We find that the jet exhibits a characteristic bending, with a gradual clockwise rotation of the jet projected position angle of about 90° between 2.3 and 230 GHz. Linearly polarized intensity images of J1924─2914 with the extremely fine resolution of the EHT provide evidence for ordered toroidal magnetic fields in the blazar compact core.

Keywords: Jets, High energy astrophysics, Blazars, Very long baseline interferometry, Active galaxies, Active galactic nuclei, Radio interferometry
Predictions of Astrometric Jitter for Sun-like Stars. III. Fast Rotators. A breakthrough in exoplanet detections is foreseen with the unprecedented astrometric measurement capabilities offered by instrumentation aboard the Gaia space observatory. Besides, astrometric discoveries of exoplanets are expected from the planned space mission, Small-JASMINE. In this setting, the present series of papers focuses on estimating the effect of the magnetic activity of G2V-type host stars on the astrometric signal. This effect interferes with the astrometric detections of Earth-mass planets. While the first two papers considered stars rotating at the solar rotation rate, this paper focuses on stars having solar effective temperature and metallicity but rotating faster than the Sun, and consequently more active. By simulating the distribution of active regions on such stars using the Flux Emergence And Transport model, we show that the contribution of magnetic activity to the astrometric measurements becomes increasingly significant with increasing rotation rates. We further show that the jitter for the most variable periodic Kepler stars is high enough to be detected by Gaia. Furthermore, due to a decrease in the facula-to-spot area ratio for more active stars, the magnetic jitter is found to be spot dominated for rapid rotators. Our simulations of the astrometric jitter have the potential to aid the interpretation of data from Gaia and upcoming space astrometry missions.

Keywords: Stellar rotation, Astrometric exoplanet detection, Stellar activity
First High-resolution Observations of Interstellar Pickup Ion Mediated Shocks in the Outer Heliosphere. This study reports the first high-time-resolution observations of interstellar pickup ions (PUIs) in the outer heliosphere, including the first high-resolution observations of PUIs mediating shocks collected anywhere. These new data were enabled by a clever flight software reprogramming of the Solar Wind Around Pluto (SWAP) instrument on New Horizons to provide ~30 minutes resolution as compared to the previous ~24 hr time resolution. This time resolution is sufficient to resolve the shock structures and quantify the particle heating across these shocks. In the ~10 months of initial data, we observed seven relatively small shocks, including one reverse shock. We find that the PUIs are preferentially compressed and heated across the shocks, indicating compression ratios from ~1.2-1.8, with little heating for values less than ~1.5 and progressively more PUI heating for larger compression ratios. In contrast, core solar wind properties did not show consistent changes across the shocks, indicating that these particles (1) participate little in the large-scale fluid-like interactions of the outer heliosphere's combined solar wind and PUI plasma and (2) cannot be used to characterize PUI-mediated shocks as prior studies sought to do. All six forward shock crossings showed gradual increases in PUI pressure over shock widths of ~0.05-0.13 au, which is roughly three decades larger than characteristic particle scales such as the PUI gyroradii. The new high-resolution observations and results described here are important for understanding shocks in the outer heliosphere, the termination shock, and more broadly for PUI-mediated shocks across many astrophysical systems.

Keywords: Space plasmas, Interplanetary shocks, Heliosphere, Plasma physics, Solar wind, Pickup ions, Interplanetary particle acceleration
Testing White Dwarf Age Estimates Using Wide Double White Dwarf Binaries from Gaia EDR3. White dwarf (WD) stars evolve simply and predictably, making them reliable age indicators. However, self-consistent validation of the methods for determining WD total ages has yet to be widely performed. This work uses 1565 wide (&gt;100 au) WD+WD binaries and 24 new triples containing at least two WDs to test the accuracy and validity of WD total age determinations. For these 1589 wide double WD binaries and triples, we derive the total age of each WD using photometric data from all-sky surveys, in conjunction with Gaia parallaxes and current hydrogen atmosphere WD models. Ignoring the initial-to-final mass relation and considering only WD cooling ages, we find that roughly 21%-36% of the more massive WDs in a system have a shorter cooling age. Since more massive WDs should be born as more massive main-sequence stars, we interpret this unphysical disagreement as evidence of prior mergers or the presence of an unresolved companion, suggesting that roughly 21%-36% of wide WD+WD binaries were once triples. Among the 423 wide WD+WD pairs that pass high-fidelity cuts, we find that 25% total age uncertainties are generally appropriate for WDs with masses &gt;0.63 M ⊙ and temperatures &lt;12,000 K and provide suggested inflation factors for age uncertainties for higher-mass WDs. Overall, WDs return reliable stellar ages, but we detail cases where the total ages are least reliable, especially for WDs &lt;0.63 M ⊙.

Keywords: Wide binary stars, White dwarf stars, Stellar ages
Idealized 2D Cloud-resolving Simulations for Tidally Locked Habitable Planets. Cloud is critical for planetary climate and habitability, but it is also one of the most challenging aspects of studying planets in and beyond the solar system. Here we use a cloud-resolving model (CRM) with high resolution (2 km) in a 2D configuration to simulate the clouds and circulation on tidally locked aquaplanets. We find that the substellar area is covered by deep convective clouds, the nightside is dominated by low-level clouds, and the two are linked by a global-scale Walker circulation. We further find that uniform surface warming causes the substellar cloud width to decrease, but a reduction in the day-night surface temperature contrast or an increase in the longwave radiative cooling rate causes the substellar cloud width to increase. These relationships can be roughly interpreted in accordance with simple thermodynamic theories. Comparing the results between the CRM and the global 3D general circulation model (GCM), we find that they are qualitatively consistent, including the Walker circulation, the substellar clouds, and the responses of the substellar ascending area and strength to changes in the surface temperature or in its zonal contrast. But large quantitative differences exist, such as the magnitude of the cloud water path, the cloud width, and their responses to external forcings. These results increase our confidence in using GCMs to model exoplanetary climates, although large quantitative uncertainties are always likely to exist. Future work is required to use 3D CRMs with realistic radiative transfer and the Coriolis force to examine the clouds and climates of tidally locked planets.

Keywords: Atmospheric clouds, Atmospheric circulation, Exoplanets, Planetary atmospheres, Habitable planets, Exoplanet atmospheres
The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XXIII. Proper-motion Catalogs and Internal Kinematics. A number of studies based on the data collected by the Hubble Space Telescope (HST) GO-13297 program "HST Legacy Survey of Galactic Globular Clusters: Shedding UV Light on Their Populations and Formation" have investigated the photometric properties of a large sample of Galactic globular clusters and revolutionized our understanding of their stellar populations. In this paper, we expand upon previous studies by focusing our attention on the stellar clusters' internal kinematics. We computed proper motions for stars in 56 globular clusters and one open cluster by combining the GO-13297 images with archival HST data. The astrophotometric catalogs released with this paper represent the most complete and homogeneous collection of proper motions of stars in the cores of stellar clusters to date, and expand the information provided by the current (and future) Gaia data releases to much fainter stars and into the crowded central regions. We also census the general kinematic properties of stellar clusters by computing the velocity dispersion and anisotropy radial profiles of their bright members. We study the dependence on concentration and relaxation time, and derive dynamical distances. Finally, we present an in-depth kinematic analysis of the globular cluster NGC 5904.

Keywords: Globular star clusters, Open star clusters, Proper motions, Stellar kinematics
Solar Wind Electron Pressure Gradients, Suprathermal Spectral Hardness, and Strahl Localization Organized by Single-point Measurements of 0.1 nV m<SUP>-1</SUP> Ambipolar E <SUB>∥</SUB>. A new, fast technique to measure the solar wind's ambipolar E ∥ routinely with 10% precision and accuracy is demonstrated using 4 yr of 1 au electron data from the Wind 3DP experiment. The 3DP electron instrument duty cycle determines E ∥ ≃ 0.1 nV m-1 from a single spectrum over much shorter time intervals than those requiring radial transits for pressure profiles. The measured weak electric field is invariably strong (in the dimensionless sense of Dreicer), with a modal value of ${{\mathbb{E}}}_{\parallel }=0.8$ , and positively correlated with solar wind speed, while E ∥ decreases with increasing wind speed. These observations establish across all solar wind conditions the nearly equal accelerations provided by E ∥ and coulomb drags on thermal electrons, a central hypothesis of the Steady Electron Runaway Model (SERM) for the solar wind. Filtered E ∥ observations successfully recover previously reported 1 au bulk speed dependence of electron temperature gradients. The filter screens for unstructured spherically symmetric solar wind (USSSW) conditions of solar wind theory. Outside USSSW conditions much shorter scaled pressure gradients (of both signs) and stronger ∣E ∥∣ are observed predominantly in corotating regimes. Consistent with modeling by Dreicer and SERM, the observed spectral hardness of electrons at suprathermal energies is positively correlated with increasing local values of ${{\mathbb{E}}}_{\parallel }$ across the 4 yr data set. Virtually all strahl electrons, crucial to the electron heat flux, are shown to be confined within the local closed coulomb separatrix of each spectrum as determined using the locally measured value of ${{\mathbb{E}}}_{\parallel }$ .

Keywords: Space plasmas, Solar wind, Plasma astrophysics, Collision physics, Interplanetary particle acceleration
Patches of Magnetic Switchbacks and Their Origins. Parker Solar Probe (PSP) has shown that the solar wind in the inner heliosphere is characterized by the quasi omnipresence of magnetic switchbacks ("switchback" hereinafter), local backward bends of magnetic field lines. Switchbacks also tend to come in patches, with a large-scale modulation that appears to have a spatial scale size comparable to supergranulation on the Sun. Here we inspect data from the first 10 encounters of PSP focusing on different time intervals when clear switchback patches were observed by PSP. We show that the switchbacks modulation, on a timescale of several hours, seems to be independent of whether PSP is near perihelion, when it rapidly traverses large swaths of longitude remaining at the same heliocentric distance, or near the radial-scan part of its orbit, when PSP hovers over the same longitude on the Sun while rapidly moving radially inwards or outwards. This implies that switchback patches must also have an intrinsically temporal modulation most probably originating at the Sun. Between two consecutive patches, the magnetic field is usually very quiescent with weak fluctuations. We compare various parameters between the quiescent intervals and the switchback intervals. The results show that the quiescent intervals are typically less Alfvénic than switchback intervals, and the magnetic power spectrum is usually shallower in quiescent intervals. We propose that the temporal modulation of switchback patches may be related to the "breathing" of emerging flux that appears in images as the formation of "bubbles" below prominences in the Hinode/SOT observations.

Keywords: Interplanetary turbulence, Solar wind, Solar prominences, Solar corona
New Detections of Phosphorus Molecules toward Solar-type Protostars. Phosphorus is a necessary element for life on Earth, but at present, we have limited constraints on its chemistry in star- and planet-forming regions; to date, phosphorus carriers have only been detected toward a few low-mass protostars. Motivated by an apparent association between phosphorus molecule emission and outflow shocking, we used the IRAM 30 m telescope to target PN and PO lines toward seven solar-type protostars with well-characterized outflows and firmly detected phosphorus molecules in three new sources. This sample, combined with archival observations of three additional sources, enables the first exploration of the demographics of phosphorus chemistry in low-mass protostars. The sources with PN detections show evidence for strong outflow shocks based on their H2O 110-101 fluxes. On the other hand, no protostellar properties or bulk outflow mechanical properties are found to correlate with the detection of PN. This implies that gas-phase phosphorus is specifically linked to shocked gas within the outflows. Still, the PN and PO line kinematics suggest an emission origin in postshocked gas rather than directly shocked material. Despite sampling a wide range of protostellar properties and outflow characteristics, we find a fairly narrow range of source-averaged PO/PN ratios (0.6-2.2) and volatile P abundances as traced by (PN+PO)/CH3OH (~1%-3%). Spatially resolved observations are needed to further constrain the emission origins and environmental drivers of the phosphorus chemistry in these sources.

Keywords: Interstellar molecules, Protostars, Astrochemistry
Long-term Evolution of Tightly Packed Stellar Black Holes in AGN Disks: Formation of Merging Black Hole Binaries via Close Encounters. We study the long-term evolution of two or more stellar black holes (BHs) on initially separated but unstable circular orbits around a supermassive BH (SMBH). Such a close-packed orbital configuration can naturally arise from BH migrations in the AGN disk. Dynamical instability of the orbits leads to recurring close encounters between two BHs, during which the BH separation r p becomes less than the Hill radius R H. In rare very close encounters, a tight merging BH binary can form with the help of gravitational wave emission. We use N-body simulations to study the time evolution of close encounters of various degrees of closeness. For a typical "SMBH+2BH" system, the averaged cumulative number of close encounters (with r p ≲ R H) scales approximately as ∝ t 0.5. The minimum encounter separation r p follows a cumulative distribution P(&lt;r p) ∝ r p for r p ≪ R H. We obtain a semi-analytical expression for the averaged rate of binary captures that lead to BH mergers. Our results suggest that close-packed BHs in AGN disks may take a long time (≳107 orbits around the SMBH) to experience a sufficiently close encounter and form a bound binary. This time can be shorter if the initial BH orbits are highly aligned. The BH binary mergers produced in this scenario have high eccentricities when entering the LIGO band and broad distribution of orbital inclinations relative to the original AGN disk. We explore the effects of the gas disk and find that simple gas drags on the BHs do not necessarily lead to an enhanced BH binary capture rate.

Keywords: Black holes, Galaxy accretion disks, Gravitational wave sources, N-body simulations, Star clusters
Solar Magneto-seismology of a Magnetic Slab in an Asymmetric Magnetic Environment. Diagnosing the solar atmospheric plasma remains one of the major challenges in solar physics. In recent years, new methods have been developed to apply the powerful concept of solar magneto-seismology (SMS) to obtain information about plasma parameters in solar structures guiding magnetohydrodynamic (MHD) waves that would otherwise be difficult to measure. This paper uses the Cartesian model of a magnetic slab placed in an asymmetric magnetic environment to generalize recently discovered SMS techniques. Utilizing the fact that the asymmetric environment changes the character of the classical kink and sausage eigenmodes, we describe two spatial seismology methods built upon this mixed character of quasi-sausage and quasi-kink modes. First, we present the amplitude ratio technique, which compares the oscillation amplitudes measured at the two boundaries of the slab, and we provide expressions to estimate the internal Alfvén speed in the thin slab and in the incompressible plasma approximations. The second main technique relies on the changed distribution of wave power throughout the slab under the effect of waveguide asymmetry. This minimum perturbation shift technique is then also utilized to provide Alfvén speed estimates that depend on the plasma and magnetic parameters of the environment, as well as the measured slab width and oscillation frequency. Finally, we perform a brief investigation of how the amplitude ratio and the minimum perturbation shift depend on the different sources of waveguide asymmetry, and illustrate our findings with numerical results.

Keywords: Solar atmosphere, Magnetohydrodynamics, The Sun, Solar physics, Solar coronal waves, Solar coronal seismology
Testing a New Model of Embedded Protostellar Disks against Observations: The Majority of Orion Class 0/I Disks Are Likely Warm, Massive, and Gravitationally Unstable. We formulate a parameterized model of embedded protostellar disks and test its ability to estimate disk properties by fitting dust-continuum observations. The main physical assumptions of our model are motivated by a recent theoretical study of protostellar disk formation; these assumptions include that the disk should be marginally gravitationally unstable, and that the dominant dust heating mechanism is internal accretion heating instead of external protostellar irradiation. These assumptions allow our model to estimate reliably the disk mass even when the observed emission is optically thick and to determine self-consistent disk (dust) temperatures. Using our model to fit multiwavelength observations of 163 disks in the VANDAM Orion survey, we find that the majority (57%) of this sample can be fit well by our model. Using our model, we produce new estimates of Orion protostellar disk properties. We find that these disks are generally warm and massive, with a typical star-to-disk mass ratio   in Class 0/I. We also discuss why our estimates differ from those in previous studies and the implications of our results on disk evolution and fragmentation.

Keywords: Stellar accretion disks, Gravitational instability, Astronomy data modeling