Sazuna/UAT_keywords huggingface dataset:
HSC-XD 52: An X-Ray Detected AGN in a Low-mass Galaxy at z ∼ 0.56. The properties of low-mass galaxies hosting central black holes provide clues about the formation and evolution of the progenitors of supermassive black holes. In this Letter, we present HSC-XD 52, a spectroscopically confirmed low-mass active galactic nucleus (AGN) at an intermediate redshift of z ∼ 0.56. We detect this object as a very luminous X-ray source coincident with a galaxy observed by the Hyper Suprime-Cam (HSC) as part of a broader search for low-mass AGN. We constrain its stellar mass through spectral energy distribution modeling to be LMC-like at M ⋆ ≈ 3 × 109 M ☉, placing it in the dwarf regime. We estimate a central black hole mass of M BH ∼ 106 M ☉. With an average X-ray luminosity of {L}{{X}}≈ 3.5× {10}43 {erg} {{{s}}}-1, HSC-XD 52 is among the most luminous X-ray selected AGN in dwarf galaxies. The spectroscopic and photometric properties of HSC-XD 52 indicate that it is an intermediate-redshift counterpart to local low-mass AGN.

Keywords: Supermassive black holes, Dwarf galaxies, X-ray active galactic nuclei
Varstrometry for Off-nucleus and Dual Sub-Kpc AGN (VODKA): How Well Centered Are Low-z AGN?. Off-nucleus active galactic nuclei (AGN) can be signposts of inspiraling supermassive black holes (SMBHs) on galactic scales, or accreting SMBHs recoiling after the coalescence of an SMBH binary or slingshot from three-body interactions. Because of the stochastic variability of AGN, the measured photocenter of an unresolved AGN-host system will display astrometric jitter that depends on the off-nucleus distance of the AGN, the total photometric variability of the system, and the AGN-host contrast. Here we use the precision astrometry from Gaia DR2 to constrain the off-nucleus population of a low-redshift (0.3 &lt; z &lt; 0.8) sample of unobscured broad-line AGN drawn from the Sloan Digital Sky Survey with significant host contribution and photometric variability. We find that Gaia DR2 already provides strong constraints on the projected off-nucleus distance in the sub-kiloparsec regime at these redshifts: 99%, 90%, and 40% of AGN must be well centered to &lt;1 kpc, &lt;500 pc, and &lt;100 pc, respectively. Limiting the sample to the most variable subset constrains &gt;99% of AGN to be well centered below 500 pc. These results suggest that genuine off-nucleus AGN (offset by &gt; a few hundred parsecs) must be rare at low redshift. Future Gaia releases of time series of photocenter and flux measurements, improved treatments for extended sources, and longer baselines will further tighten these constraints, and enable a systematic full-sky search for rare off-nucleus AGN on ∼10-1000 pc scales.

Keywords: Surveys, Black hole physics, Active galaxies, Quasars
Ion Cyclotron Waves in Field-aligned Solar Wind Turbulence. The nature of the solar wind parallel fluctuations is investigated in this Letter by using magnetic helicity to characterize their polarization state at proton scales. Our aim is to assess the role of the proton cyclotron instability as a mechanism for generating ion cyclotron waves (ICWs) in solar wind turbulence. The wave polarization is found to depend strongly on the proton temperature anisotropy and on the power level of magnetic fluctuations at fluid scales. The results indicate a clear link between fluid and kinetic scales in the solar wind turbulence, allowing for a picture in which the resonant dissipation of high-frequency Alfvén waves heats protons in a direction perpendicular to the magnetic field, increasing their temperature anisotropy. The velocity distribution thus becomes unstable to the proton cyclotron instability, which then drives the local generation of ICWs in the solar wind.

Keywords: Space plasmas, Magnetohydrodynamics, Interplanetary turbulence, Solar wind, Alfven waves
The Influence of Gas-phase Chemistry on Organic Haze Formation. Although photochemically produced organic hazes are common in planetary atmospheres, there have been few experimental investigations of the gas-phase chemistry leading to organic haze formation. We report a laboratory study of the gas-phase compounds formed by far-ultraviolet irradiation of a CH4/N2 mixture. Using high-resolution chemical ionization mass spectrometry (CIMS) we made in situ measurements of gas-phase products up to m/z 400. Organic nitrogen species dominate the mass spectra with smaller contributions from unsaturated hydrocarbons. Using a structural group method to estimate vapor pressures, we calculate that for compounds detected at m/z &gt; 320, ≥50% of the total compound loading (gas + condensed phase) would be present in the condensed (aerosol) phase at 300 K. Using approximations for changes in vapor pressure with temperature, we estimate that ≥50% of the total loading for species with m/z &gt; 110 would be in the aerosol-phase at 150 K, suggesting that the measured compounds may be important for aerosol composition for a range of temperatures. Finally, we leverage the sensitivity and fast time response of the CIMS measurements to investigate how the gas-phase chemistry evolved over the course of the experiment. This analysis shows that hydrocarbons were the initial products followed by the formation of unsaturated organic nitrogen compounds. Higher molecular weight species and alkylamines appear late in the experiment. Comparison of our measurements to chemical mechanisms used to model planetary haze formation suggests that larger molecular weight compounds need to be considered in haze formation chemistry.

Keywords: Mass spectrometry, Astrobiology, Planetary atmospheres, Atmospheric science
The First Detection of a Low-frequency Turnover in Nonthermal Emission from the Jet of a Young Star. Radio emission in jets from young stellar objects (YSOs) in the form of nonthermal emission has been seen toward several YSOs. Thought to be synchrotron emission from strong shocks in the jet, it could provide valuable information about the magnetic field in the jet. Here we report on the detection of synchrotron emission in two emission knots in the jet of the low-mass YSO DG Tau A at 152 MHz using the Low-Frequency Array, the first time nonthermal emission has been observed in a YSO jet at such low frequencies. In one of the knots, a low-frequency turnover in its spectrum is clearly seen compared to higher frequencies. This is the first time that such a turnover has been seen in nonthermal emission in a YSO jet. We consider several possible mechanisms for the turnover and fit models for each of these to the spectrum. Based on the physical parameters predicted by each model, the Razin effect appears to be the most likely explanation for the turnover. From the Razin effect fit, we can obtain an estimate for the magnetic field strength within the emission knot of ∼20 μG. If the Razin effect is the correct mechanism, this is the first time that the magnetic field strength along a YSO jet has been measured based on a low-frequency turnover in nonthermal emission.

Keywords: Stellar jets, Stellar magnetic fields, Classical T Tauri stars, Star formation, Non-thermal radiation sources
Comparing the Quenching Times of Faint M31 and Milky Way Satellite Galaxies. We present the star formation histories (SFHs) of 20 faint M31 satellites (-12 ≲ M  V  ≲ -6) that were measured by modeling sub-horizontal branch depth color-magnitude diagrams constructed from Hubble Space Telescope (HST) imaging. Reinforcing previous results, we find that virtually all galaxies quenched between 3 and 9 Gyr ago, independent of luminosity, with a notable concentration 3-6 Gyr ago. This is in contrast to the Milky Way (MW) satellites, which are generally either faint with ancient quenching times or luminous with recent (&lt;3 Gyr) quenching times. We suggest that systematic differences in the quenching times of M31 and MW satellites may be a reflection of the varying accretion histories of M31 and the MW. This result implies that the formation histories of low-mass satellites may not be broadly representative of low-mass galaxies in general. Among the M31 satellite population we identify two distinct groups based on their SFHs: one with exponentially declining SFHs (τ ∼ 2 Gyr) and one with rising SFHs with abrupt quenching. We speculate how these two groups could be related to scenarios for a recent major merger involving M31. The Cycle 27 HST Treasury survey of M31 satellites will provide well-constrained ancient SFHs to go along with the quenching times we measure here. The discovery and characterization of M31 satellites with M  V  ≳ -6 would help quantify the relative contributions of reionization and environment to quenching of the lowest-mass satellites.

Keywords: Local Group, Stellar populations, Andromeda Galaxy, Dwarf spheroidal galaxies
Detection of CN Gas in Interstellar Object 2I/Borisov. The detection of interstellar objects passing through the solar system offers the promise of constraining the physical and chemical processes involved in planetary formation in other extrasolar systems. While the effect of outgassing by 1I/2017 U1 (’Oumuamua) was dynamically observed, no direct detection of the ejected material was made. The discovery of the active interstellar comet 2I/Borisov means spectroscopic investigations of the sublimated ices is possible for this object. We report the first detection of gas emitted by an interstellar comet via the near-UV emission of CN from 2I/Borisov at a heliocentric distance of r = 2.7 au on 2019 September 20. The production rate was found to be Q(CN) = (3.7 ± 0.4) × 1024 s-1, using a simple Haser model with an outflow velocity of 0.5 km s-1. No other emission was detected, with an upper limit to the production rate of C2 of 4 × 1024 s-1. The spectral reflectance slope of the dust coma over 3900 Å &lt; λ &lt; 6000 Å is steeper than at longer wavelengths, as found for other comets. Broadband R  c  photometry on 2019 September 19 gave a dust production rate of Afρ = 143 ± 10 cm. Modeling of the observed gas and dust production rates constrains the nuclear radius to 0.7-3.3 km assuming reasonable nuclear properties. Overall, we find the gas, dust, and nuclear properties for the first active interstellar object are similar to normal solar system comets.

Keywords: Comets, Planetary system formation
Detection of Pulses from the Vela Pulsar at Millimeter Wavelengths with Phased ALMA. We report on the first detection of pulsed radio emission from a radio pulsar with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope. The detection was made in the Band-3 frequency range (85-101 GHz) using ALMA in the phased-array mode developed for VLBI observations. A software pipeline has been implemented to enable a regular pulsar observing mode in the future. We describe the pipeline and demonstrate the capability of ALMA to perform pulsar timing and searching. We also measure the flux density and polarization properties of the Vela pulsar (PSR J0835-4510) at millimeter wavelengths, providing the first polarimetric study of any ordinary pulsar at frequencies above 32 GHz. Finally, we discuss the lessons learned from the Vela observations for future pulsar studies with ALMA, particularly for searches near the supermassive black hole in the Galactic center, and the potential of using pulsars for polarization calibration of ALMA.

Keywords: Millimeter astronomy, Pulsars, Interferometry
Round-trip Slipping Motion of the Circular Flare Ribbon Evidenced in a Fan-spine Jet. A solar jet that occurred on 2014 July 31, which was accompanied by a GOES C1.3 flare and a mini-filament eruption at the jet base, was studied by using observations taken by the New Vacuum Solar Telescope and the Solar Dynamic Observatory. Magnetic field extrapolation revealed that the jet was confined in a fan-spine magnetic system that hosts a null point at the height of about 9 Mm from the solar surface. An inner flare ribbon surrounded by an outer circular ribbon and a remote ribbon were observed to be associated with the eruption, in which the inner and remote ribbons, respectively located at the footprints of the inner and outer spines, while the circular one manifested the footprint of the fan structure. It is worth noting that the west part of the circular ribbon exhibited an interesting round-trip slipping motion, while the inner ribbon and the circular ribbon’s east part displayed a northward slipping motion. Our analysis results indicate that the slipping motions of the inner and the circular flare ribbons reflected the slipping magnetic reconnection process in the fan’s quasi-separatrix layer, while the remote ribbon was associated with the magnetic reconnection at the null point. In addition, the filament eruption was probably triggered by the magnetic cancellation around its south end, which further drove the slipping reconnection in the fan quasi-separatrix layer and the reconnection at the null point.

Keywords: Solar flares, Solar filaments, Solar magnetic fields, Solar activity, Solar chromosphere
Four Newborn Planets Transiting the Young Solar Analog V1298 Tau. Exoplanets orbiting pre-main-sequence stars are laboratories for studying planet evolution processes, including atmospheric loss, orbital migration, and radiative cooling. V1298 Tau, a young solar analog with an age of 23 ± 4 Myr, is one such laboratory. The star is already known to host a Jupiter-sized planet on a 24 day orbit. Here, we report the discovery of three additional planets—all between the sizes of Neptune and Saturn—based on our analysis of K2 Campaign 4 photometry. Planets c and d have sizes of 5.6 and 6.4 {R}\oplus , respectively, and with orbital periods of 8.25 and 12.40 days reside 0.25% outside of the nominal 3:2 mean-motion resonance. Planet e is 8.7 {R}\oplus  in size but only transited once in the K2 time series and thus has a period longer than 36 days, but likely shorter than 223 days. The V1298 Tau system may be a precursor to the compact multiplanet systems found to be common by the Kepler mission. However, the large planet sizes stand in sharp contrast to the vast majority of Kepler multiplanet systems, which have planets smaller than 3 {R}\oplus . Simple dynamical arguments suggest total masses of &lt;28 {M}\oplus  and &lt;120 {M}\oplus  for the c-d and d-b planet pairs, respectively. The implied low masses suggest that the planets may still be radiatively cooling and contracting, and perhaps losing atmosphere. The V1298 Tau system offers rich prospects for further follow-up including atmospheric characterization by transmission or eclipse spectroscopy, dynamical characterization through transit-timing variations, and measurements of planet masses and obliquities by radial velocities.

Keywords: Exoplanets, Young star clusters, Weak-line T Tauri stars, Exoplanet astronomy, Exoplanet evolution, Planetary system formation, Transit photometry
The Evolution of Baryonic Mass Function of Galaxies to z = 3. We combine the published stellar mass function (SMF) and gas scaling relations to explore the baryonic (stellar plus cold gas) mass function (BMF) of galaxies to redshift z = 3. We find evidence that at log(M baryon/M ⊙) &gt; 11.3, the BMF has evolved little since z ∼ 2.2. With the evolution of BMF and SMF, we investigate the baryon net accretion rate ({\dot{ρ }}baryon}) and stellar mass growth rate ({\dot{ρ }}star}) for the galaxy population of log(M star/M ⊙) &gt; 10. The ratio between these two quantities, {\dot{ρ }}baryon}/{\dot{ρ }}star}, decreases from {\dot{ρ }}baryon}/{\dot{ρ }}star}∼ 2 at z ∼ 2.5 to {\dot{ρ }}baryon}/{\dot{ρ }}star}&lt; 0.5 at z ∼ 0.5, suggesting that massive galaxies are transforming from the “accretion-dominated” phase to the “depletion-dominated” phase from high-z to low-z. The transition of these two phases occurs at z ∼ 1.5, which is consistent with the onset redshift of the decline of cosmic star formation rate density (CSFD). This provides evidence to support the idea that the decline of CSFD since z ∼ 1.5 mainly results from the decline of baryon net accretion rate and star formation quenching in galaxies.

Keywords: Galaxy quenching, Galaxy evolution
First Detection of Plasmoids from Breakout Reconnection on the Sun. Transient collimated plasma ejections (jets) occur frequently throughout the solar corona, in active regions, quiet Sun, and coronal holes. Although magnetic reconnection is generally agreed to be the mechanism of energy release in jets, the factors that dictate the location and rate of reconnection remain unclear. Our previous studies demonstrated that the magnetic breakout model explains the triggering and evolution of most jets over a wide range of scales, through detailed comparisons between our numerical simulations and high-resolution observations. An alternative explanation, the resistive-kink model, invokes breakout reconnection without forming and explosively expelling a flux rope. Here we report direct observations of breakout reconnection and plasmoid formation during two jets in the fan-spine topology of an embedded bipole. For the first time, we observed the formation and evolution of multiple small plasmoids with bidirectional flows associated with fast reconnection in 3D breakout current sheets (BCSs) in the solar corona. The first narrow jet was launched by reconnection at the BCS originating at the deformed 3D null, without significant flare reconnection or a filament eruption. In contrast, the second jet and release of cool filament plasma were triggered by explosive breakout reconnection when the leading edge of the rising flux rope formed by flare reconnection beneath the filament encountered the preexisting BCS. These observations solidly support both reconnection-driven jet models: the resistive kink for the first jet, and the breakout model for the second explosive jet with a filament eruption.

Keywords: Solar coronal transients, Solar magnetic reconnection, Solar corona, Solar magnetic fields, Solar magnetic bright points
Auroral Beads at Saturn and the Driving Mechanism: Cassini Proximal Orbits. During the Grand Finale Phase of Cassini, the Ultraviolet Imaging Spectrograph on board the spacecraft detected repeated detached small-scale auroral structures. We describe these structures as auroral beads, a term introduced in the terrestrial aurora. Those on DOY 232 2017 are observed to extend over a large range of local times, i.e., from 20 LT to 11 LT through midnight. We suggest that the auroral beads are related to plasma instabilities in the magnetosphere, which are often known to generate wavy auroral precipitations. Energetic neutral atom enhancements are observed simultaneously with auroral observations, which are indicative of a heated high pressure plasma region. During the same interval we observe conjugate periodic enhancements of energetic electrons, which are consistent with the hypothesis that a drifting interchange structure passed the spacecraft. Our study indicates that auroral bead structures are common phenomena at Earth and giant planets, which probably demonstrates the existence of similar fundamental magnetospheric processes at these planets.

Keywords: Space plasmas, Saturn, Ultraviolet transient sources
Lorentz Force Evolution Reveals the Energy Build-up Processes during Recurrent Eruptive Solar Flares. The energy release and build-up processes in the solar corona have significant implications in particular for the case of large recurrent flares, which pose challenging questions about the conditions that lead to the episodic energy release processes. It is not yet clear whether these events occur due to the continuous supply of free magnetic energy to the solar corona or because not all of the available free magnetic energy is released during a single major flaring event. In order to address this question, we report on the evolution of photospheric magnetic field and the associated net Lorentz force changes in ARs 11261 and 11283, each of which gave rise to recurrent eruptive M- and X-class flares. Our study reveals that after the abrupt downward changes during each flare, the net Lorentz force increases by (2-5) × 1022 dyne in between the successive flares. This distinct rebuild-up of net Lorentz forces is the first observational evidence found in the evolution of any nonpotential parameter of solar active regions (ARs), which suggests that new energy was supplied to the ARs in order to produce the recurrent large flares. The rebuild-up of magnetic free energy of the ARs is further confirmed by the observations of continuous shearing motion of moving magnetic features of opposite polarities near the polarity inversion line. The evolutionary pattern of the net Lorentz force changes reported in this study has significant implications, in particular, for the forecasting of recurrent large eruptive flares from the same AR and hence the chances of interaction between the associated CMEs.

Keywords: Solar active region magnetic fields, Solar flares, Solar coronal mass ejections
Collapse of the General Circulation in Shortwave-absorbing Atmospheres: An Idealized Model Study. The response of the general circulation in a dry atmosphere to various atmospheric shortwave absorptivities is investigated in a three-dimensional general circulation model with gray radiation. Shortwave absorption in the atmosphere reduces the incoming radiation reaching the surface but warms the upper atmosphere, significantly shifting the habitable zone toward the star. The strong stratification under high shortwave absorptivity suppresses the Hadley cell in a manner that matches previous Hadley cell scalings. General circulation changes may be observable through cloud coverage and superrotation. The equatorial superrotation in the upper atmosphere strengthens with the shortwave opacity, as predicted based on the gradient wind of the radiative-convective equilibrium profile. There is a sudden drop of equatorial superrotation at very low shortwave opacity. This is because the Hadley cell in those cases are strong enough to fill the entire troposphere with zero momentum air from the surface. A diurnal cycle (westward motion of substellar point relative to the planet) leads to acceleration of the equatorial westerlies in general, through the enhancement of the equatorward eddy momentum transport, but the response is not completely monotonic, perhaps due to the resonance of tropical waves and the diurnal forcing.

Keywords: Planetary atmospheres, Exoplanet atmospheres, Atmospheric circulation