Sazuna/UAT_keywords huggingface dataset:
A Tip of the Red Giant Branch Distance to the Dark Matter Deficient Galaxy NGC 1052-DF4 from Deep Hubble Space Telescope Data. Previous studies have shown that the large, diffuse galaxies NGC 1052-DF2 and NGC 1052-DF4 both have populations of unusually luminous globular clusters as well as a very low dark matter content. Here we present newly obtained deep Hubble Space Telescope Advanced Camera for Surveys imaging of one of these galaxies, NGC 1052-DF4. We use these data to measure the distance of the galaxy from the location of the tip of the red giant branch (TRGB). We find a rapid increase in the number of detected stars fainter than mF814W ∼ 27.3, which we identify as the onset of the red giant branch. Using a forward modeling approach that takes the photometric uncertainties into account, we find a TRGB magnitude of ${m}_{{\rm{F}}814{\rm{W}},\mathrm{TRGB}}=27.47\pm 0.16$ . The inferred distance, including the uncertainty in the absolute calibration, is DTRGB = 20.0 ± 1.6 Mpc. The TRGB distance of NGC 1052-DF4 is consistent with the previously determined surface brightness fluctuation distance of DSBF = 18.7 ± 1.7 Mpc to NGC 1052-DF2 and is consistent with the distance of the bright elliptical galaxy NGC 1052. We conclude that the unusual properties of these galaxies cannot be explained by distance errors.

Keywords: Globular star clusters, Galaxy dark matter halos, Red giant tip, Distance measure, Dwarf galaxies, HST photometry, Low surface brightness galaxies
High-velocity Type Ia Supernova Has a Unique Host Environment. Ejecta velocity of Type Ia supernovae (SNe Ia) is one powerful tool to differentiate between progenitor scenarios and explosion mechanisms. Here we revisit the relation between photospheric Si II λ6355 velocities (VSi II) and host-galaxy properties with ∼280 SNe Ia. A more stringent criterion on the phase of SN spectra is adopted to classify SNe Ia in terms of their photospheric velocities. We find a significant trend that SNe Ia with faster Si II λ6355 (high-VSi II SNe Ia) tend to explode in massive environments, whereas their slower counterparts can be found in both lower-mass and massive environments. This trend is further supported by the direct measurements on host gas-phase metallicities. We suggest this relation is likely caused by at least two populations of SNe Ia. Since stars of higher metallicity (at a given mass) generally form less massive white dwarfs, our results support some theoretical models that high-VSi II SNe Ia may originate from sub-Chandrasekhar class of explosions. Previous observations also showed some evidence that high-VSi II SNe Ia could be related to the single degenerate systems. However, we find high-VSi II SNe Ia do not come from particularly young populations. We conclude metallicity is likely the dominant factor in forming high-VSi II SNe Ia. This also implies their potential evolution with redshift and impact on the precision of SN Ia cosmology.

Keywords: Type Ia supernovae, Galaxy environments
A Fast Radio Burst Discovered in FAST Drift Scan Survey. We report the discovery of a highly dispersed fast radio burst (FRB), FRB 181123, from an analysis of ∼1500 hr of drift scan survey data taken using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The pulse has three distinct emission components, which vary with frequency across our 1.0-1.5 GHz observing band. We measure the peak flux density to be &gt;0.065 Jy and the corresponding fluence &gt;0.2 Jy ms. Based on the observed dispersion measure of 1812 cm-3 pc, we infer a redshift of ∼1.9. From this, we estimate the peak luminosity and isotropic energy to be ≲2 × 1043 erg s-1 and ≲2 × 1040 erg, respectively. With only one FRB from the survey detected so far, our constraints on the event rate are limited. We derive a 95% confidence lower limit for the event rate of 900 FRBs per day for FRBs with fluences &gt;0.025 Jy ms. We performed follow-up observations of the source with FAST for four hours and have not found a repeated burst. We discuss the implications of this discovery for our understanding of the physical mechanisms of FRBs.

Keywords: Radio bursts, Astronomical object identification, Radio astronomy, Radio transient sources
3D Numerical Simulation of Kink-driven Rayleigh-Taylor Instability Leading to Fast Magnetic Reconnection. Fast magnetic reconnection involving non-MHD microscale physics is believed to underlie both solar eruptions and laboratory plasma current disruptions. While there is extensive research on both the MHD macroscale physics and the non-MHD microscale physics, the process by which large-scale MHD couples to the microscale physics is not well understood. An MHD instability cascade from a kink to a secondary Rayleigh-Taylor instability in the Caltech astrophysical jet laboratory experiment provides new insights into this coupling and motivates a 3D numerical simulation of this transition from large to small scale. A critical finding from the simulation is that the axial magnetic field inside the current-carrying dense plasma must exceed the field outside. In addition, the simulation verifies a theoretical prediction and experimental observation that, depending on the strength of the effective gravity produced by the primary kink instability, the secondary instability can be Rayleigh-Taylor or mini-kink. Finally, it is shown that the kink-driven Rayleigh-Taylor instability generates a localized electric field sufficiently strong to accelerate electrons to very high energy.

Keywords: Magnetohydrodynamics, Laboratory astrophysics, Plasma astrophysics, Magnetohydrodynamical simulations
A Link between Ram Pressure Stripping and Active Galactic Nuclei. The dense environment of a galaxy cluster can radically transform the content of in-falling galaxies. Recent observations have found a significant population of active galactic nuclei (AGN) within "jellyfish galaxies," galaxies with trailing tails of gas and stars that indicate significant ram pressure stripping. The relationship between AGN and ram pressure stripping is not well understood. In this Letter, we investigate the connection between AGN activity and ram pressure in a fully cosmological setting for the first time using the ROMULUS C simulation, one of the highest resolution simulations of a galaxy cluster to date. For lower mass galaxies (with stellar masses M* ≲ 109.5 M⊙) both star formation and black hole accretion are suppressed by ram pressure before they reach pericenter, whereas for more massive galaxies accretion onto the black hole is enhanced during pericentric passage. Our analysis also indicates that as long as the galaxy retains gas, AGN with higher Eddington ratios are more likely to be found in galaxies experiencing higher ram pressure. We conclude that prior to quenching star formation, ram pressure triggers enhanced accretion onto the black hole, which in our model then produces heating and outflows due to AGN feedback. These simulations suggest that AGN feedback may in turn serve to aid in the quenching of star formation in tandem with ram pressure.

Keywords: AGN host galaxies, Supermassive black holes, Galaxy clusters, Active galactic nuclei, Galaxy quenching
A 700 pc Extended Coronal Gas Emission in the Circinus Galaxy. We report the first characterization of an extended outflow of high ionized gas in the Circinus Galaxy by means of the coronal line (CL) [Fe VII] λ6087. This emission is located within the ionization cone already detected in the [O III] λ5007 line and is found to extend up to a distance of ∼700 pc from the active galactic nucleus. The gas distribution appears clumpy, with several knots of emission. Its kinematics is complex, with split profiles and line centroids shifted from the systemic velocity. The physical conditions of the gas show that the extended coronal emission is likely the remnant of shells inflated by the passage of a radio jet. This scenario is supported by extended X-ray emission, which is spatially coincident with the morphology and extension of the [Fe VII] λ6087 gas in the NW side of the galaxy. The extension of the coronal gas in the Circinus galaxy is unique among active galaxies and demonstrates the usefulness of CLs for tracing the shock ionization component in these objects.

Keywords: Shocks, Active galactic nuclei, Radio jets, Line intensities
Observation of Energy Conversion Near the X-line in Asymmetric Guide-field Reconnection. With high-resolution data of the recently launched Magnetospheric Multiscale mission, the present study reports an asymmetric guide-field reconnection at the dayside magnetopause, which has a density asymmetry NMSP/NMSH ∼ 15 on the two sides of the current sheet and a guide field Bg ∼ 1.4BL, MSH in the out-of-plane direction, exhibiting all the two-fluid features including Alfvénic plasma jets and Hall field systems. Using the First Order Taylor Expansion method, we identify the X-line of this reconnection. Different from previous observations, the energy conversion dominantly occurs sunward of the X-line, while the local waves arise simultaneously. The qualitative analysis about the electron energization in this reconnection is proposed, suggesting that the guide field may play an important role in modifying the location where the energy conversion occurs together with the electric field near the X-line.

Keywords: Space plasmas, Magnetohydrodynamics, Plasma physics, Planetary magnetospheres, Magnetic fields
The Chiral Puzzle of Life. Biological molecules chose one of two structurally chiral systems which are related by reflection in a mirror. It is proposed that this choice was made, causally, by cosmic rays, which are known to play a major role in mutagenesis. It is shown that magnetically polarized cosmic rays that dominate at ground level today can impose a small, but persistent, chiral bias in the rate at which they induce structural changes in simple, chiral monomers that are the building blocks of biopolymers. A much larger effect should be present with helical biopolymers, in particular, those that may have been the progenitors of ribonucleic acid and deoxyribonucleic acid. It is shown that the interaction can be both electrostatic, just involving the molecular electric field, and electromagnetic, also involving a magnetic field. It is argued that this bias can lead to the emergence of a single, chiral life form over an evolutionary timescale. If this mechanism dominates, then the handedness of living systems should be universal. Experiments are proposed to assess the efficacy of this process.

Keywords: Astrobiology, Cosmic rays
The Rotation Curve, Mass Distribution, and Dark Matter Content of the Milky Way from Classical Cepheids. With the increasing number of large stellar survey projects, the quality and quantity of excellent tracers for studying the Milky Way are rapidly growing, one of which is the classical Cepheids. Classical Cepheids are high-precision standard candles with very low typical uncertainties (&lt;3%) available via the mid-infrared period-luminosity relation. About 3500 classical Cepheids identified from the Optical Gravitational Lensing Experiment, All-Sky Automated Survey for Supernova, Gaia, Wide-field Infrared Survey Explorer, and Zwicky Transient Facility survey data have been analyzed in this work, and their spatial distributions show a clear signature of Galactic warp. Two kinematical methods are adopted to measure the Galactic rotation curve (RC) in the Galactocentric distance range of $4\lesssim {R}_{\mathrm{GC}}\lesssim 19\,\mathrm{kpc}$ . Gently declining RCs are derived by both the proper motion (PM) method and three-dimensional velocity vector (3DV) method. The largest sample of classical Cepheids with the most accurate 6D phase-space coordinates available to date are modeled in the 3DV method, and the resulting RC is found to decline at the relatively smaller gradient of (-1.33 ± 0.1) $\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{kpc}}^{-1}$ . Comparing to results from the PM method, a higher rotation velocity ((232.5 ± 0.83) $\mathrm{km}\,{{\rm{s}}}^{-1}$ ) is derived at the position of the Sun in the 3DV method. The virial mass and local dark matter density are estimated from the 3DV method, which is the more reliable method, ${M}_{\mathrm{vir}}=(0.822\pm 0.052)\times {10}^{12}\,{M}_{\odot }$ and ${\rho }_{\mathrm{DM},\odot }=0.33\pm 0.03$ GeV, respectively.

Keywords: Milky Way dark matter halo, Milky Way dynamics, Dark matter density, Galaxy mass distribution, Cepheid variable stars, Galaxy rotation curves, Dark matter
Coupling between the Magnetospheric Dipolarization Front and the Earth's Ionosphere by Ultralow-frequency Waves. Magnetosphere-ionosphere coupling is representative of a class of astrophysical problems involving the interaction between very different plasma regimes that are connected by magnetic fields. It is a major issue of the planet's (e.g., Earth, Jupiter, Saturn) system how the magnetospheric plasma is coupled to the planet's ionosphere/atmosphere. Due to their roles on energy transport and conversion in the terrestrial magnetosphere, dipolarization fronts (DFs) in the magnetotail have been intensively studied. While the energy may also be transported toward the ionosphere during the magnetosphere-ionosphere coupling, the coupling processes during DF events remain unclear. Using high-quality MMS and Swarm measurements, we present new conjugated observations of ultralow-frequency waves associated with the DF in the magnetotail and multiscale field-aligned currents (FACs) in the ionosphere. The tail large-amplitude low-frequency magnetic disturbances and associated FACs were found connected with a pair of ionospheric FACs near the magnetic footprints of MMS. The earthward field-aligned Poynting flux of low-frequency waves reveals the energy transport from the DF toward the ionosphere. Meanwhile, small-scale and highly temporal ionospheric FACs suggest that the magnetotail shear Alfvén waves may evolve into kinetic Alfvén waves during the coupling processes. This finding implies that a very localized dynamic process (e.g., DFs in the terrestrial magnetotail) in the magnetosphere could couple the ionosphere with Alfvén waves.

Keywords: Geomagnetic fields, Alfven waves, Earth (planet)
Stochastic Turbulent Acceleration in a Fractal Environment. We analyze the stochastic acceleration of particles inside a fully developed turbulent plasma. It is well known that large-amplitude magnetic fluctuations and coherent structures in such an environment obey a fractal scaling, and our specific aim is to study for the first time the effects of the fractality of these environments on stochastic acceleration. We have shown that an injected Maxwellian energy distribution is heated and forms a high-energy tail in a very short time. Using standard parameters for the low solar corona, the injected Maxwellian distribution of electrons gets heated from the initial 100 eV to 10 KeV, and the power-law index of the high-energy tail is about -2.3. The high-energy tail starts around 100 keV, and reaches 10 MeV. The index of the power-law tail depends on the system size, and it is in good agreement with observed values for realistic system sizes. The heating and acceleration process is very fast (∼2 s). The reason why the acceleration time is so short is that the particles are trapped within small-scale parts of the fractal environment, and their scattering mean free path reduces drastically. The presence of small-scale activity also easily pulls particles from the thermal pool, so there is no need for a seed population. The mean square displacement in space and energy is superdiffusive for the high-energy particles.

Keywords: Solar flares, Solar magnetic reconnection, Solar energetic particles, Plasma astrophysics, Solar magnetic fields, Particle astrophysics
Merging Black Holes in the Low-mass and High-mass Gaps from 2 + 2 Quadruple Systems. The origin of the black hole (BH) binary mergers observed by LIGO-Virgo is still uncertain, as are the boundaries of the stellar BH mass function. Stellar evolution models predict a dearth of BHs both at masses ≳50 ${M}_{\odot }$ and ≲5 ${M}_{\odot }$ , thus leaving low- and high-mass gaps in the BH mass function. A natural way to form BHs of these masses is through mergers of neutron stars (NSs; for the low-mass gap) or lower-mass BHs (for the high-mass gap); the low- or high-mass-gap BH produced as a merger product can then be detected by LIGO-Virgo if it merges again with a new companion. We show that the evolution of a 2 + 2 quadruple system can naturally lead to BH mergers with component masses in the low- or high-mass gaps. In our scenario, the BH in the mass gap originates from the merger of two NSs, or two BHs, in one of the two binaries and the merger product is imparted a recoil kick (from anisotropic gravitational wave emission), which triggers its interaction with the other binary component of the quadruple system. The outcome of this three-body interaction is usually a new eccentric compact binary containing the BH in the mass gap, which can then merge again. The merger rate is ∼10-7-10-2 Gpc-3 yr-1 and ∼10-3-10-2 Gpc-3 yr-1 for BHs in the low-mass and high-mass gap, respectively. As the sensitivity of gravitational wave detectors improves, tighter constraints will soon be placed on the stellar BH mass function.

Keywords: Neutron stars, Gravitational wave detectors, Stellar kinematics, Stellar mass black holes, Gravitational wave sources, Gravitational wave astronomy, Galaxy kinematics, Gravitational waves, Astrophysical black holes
Generation of High-resolution Solar Pseudo-magnetograms from Ca II K Images by Deep Learning. In this Letter, we generate realistic high-resolution (1024 × 1024 pixels) pseudo-magnetograms from Ca II K images using a deep learning model based on conditional generative adversarial networks. For this, we consider a model "pix2pixHD" that is specifically devised for high-resolution image translation tasks. We use Ca II K 393.3 nm images from the Precision Solar Photometric Telescope at the Rome Observatory and line-of-sight magnetograms from the Helioseismic and Magnetic Imager (HMI) at the Solar Dynamics Observatory from 2011 January to 2015 June. 2465 pairs of Ca II K and HMI are used for training except for January and July data. The remaining 436 pairs are used for an evaluation of the model. Our model shows that the mean correlation coefficient (CC) of total unsigned magnetic flux between AI-generated and real ones is 0.99 and the mean pixel-to-pixel CC after 8 × 8 binning over the full disk is 0.74. We find that the AI-generated absolute magnetic flux densities are highly consistent with real ones, even to the fine scale structures of quiet regions. On the other hand, the mean pixel-to-pixel correlations of magnetic flux densities strongly depend on a region of interest: 0.81 for active regions and 0.24 for quiet regions. Our results suggest a sufficient possibility that we can produce high-resolution solar magnetograms from historical Ca II data.

Keywords: Solar atmosphere, The Sun, Astronomy data analysis, Solar physics, Solar magnetic fields
A Possible Transit of a Disintegrating Exoplanet in the Nearby Multiplanet System DMPP-1. We analyze TESS photometry of DMPP-1 (HD 38677; TIC 66560666), a nearby F8V star hosting hot super-Earth planets and a warm Neptune. Using the Transit Least Squares algorithm and other methods we find a transit signal at $P={3.2854}_{-0.0025}^{+0.0032}$ days with depth ${87}_{-30}^{+25}$ ppm and false alarm probability 1.6%. This is shallower than hitherto published TESS discoveries. The 3.285 day signal is recovered for several, but not all, methods for detrending stellar astrophysical variability. Further observations are needed to improve the significance of the detection. If this transit were due to an Earth-like rocky planet it would have been detected in the RV data, but it is not. The TESS data cover seven individual transits, one of which is consistent with zero depth. The insolation of the putative planet is 990 S⊕, typical of fluxes experienced by the three known catastrophically disintegrating exoplanets (CDEs). The transits can be self-consistently attributed to a CDE with a mass below the RV detection threshold. We searched for transits of the known RV planets, finding null results and detection thresholds of &lt;100 ppm, which we quantify for each. The DMPP-1 planetary system was discovered as a consequence of circumstellar gas attributed to ablation of hot planets. The RV planets may have been ablated to near-pure iron cores. We place limits on the orbital inclinations of the RV planets where the expected transit depth exceeds the detection threshold. If the 3.2854 day transit detection is confirmed, e.g., with CHEOPS photometry, DMPP-1 would be a first-rate target for James Webb Space Telescope spectroscopy.

Keywords: Circumstellar matter, Exoplanet systems
GW Ori: Interactions between a Triple-star System and Its Circumtriple Disk in Action. GW Ori is a hierarchical triple system with a rare circumtriple disk. We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of 1.3 mm dust continuum and 12CO J = 2 - 1 molecular gas emission of the disk. For the first time, we identify three dust rings in the GW Ori disk at ∼46, 188, and 338 au, with estimated dust mass of 74, 168, and 245 Earth masses, respectively. To our knowledge, its outermost ring is the largest dust ring ever found in protoplanetary disks. We use visibility modeling of dust continuum to show that the disk has misaligned parts, and the innermost dust ring is eccentric. The disk misalignment is also suggested by the CO kinematics. We interpret these substructures as evidence of ongoing dynamical interactions between the triple stars and the circumtriple disk.

Keywords: Circumstellar matter, Pre-main sequence stars, Protoplanetary disks, Planet formation
Ultra-impulsive Solar Flare Seismology. We examine a strong, coherent, highly impulsive acoustic transient radiated into the solar interior by the flare SOL20110730T02:04-M9.3. The acoustic spectrum of this transient extends out to 10 mHz. The fine diffraction limit of this high-frequency component of the flare acoustic transient allows us to discriminate different source components in operation during the flare. Acoustic-source power density maps of the 10 mHz component show sources that are compact to within the now 760 km diffraction limit of local helioseismic diagnostics for this frequency. One of the acoustic sources found is bifurcated across a sharp penumbral magnetic boundary, the component in the stronger magnetic field temporally lagging its partner. The facility to discriminate this level of acoustic-source detail could open the door to a long sought after understanding of the mechanics of transient emission from solar flares, still a mystery two decades after its discovery. It also suggests that helioseismic observations of higher cadence and spatial resolution could reveal coherent acoustic emission at even higher frequencies, with proportionately further potential benefits to solar seismology and its growing domain of applications.

Keywords: Helioseismology, Solar flares, Solar interior