Sazuna/UAT_keywords huggingface dataset:
Detectability of Life Using Oxygen on Pelagic Planets and Water Worlds. The search for life on exoplanets is one of the grand scientific challenges of our time. The strategy to date has been to find (e.g., through transit surveys like Kepler) earthlike exoplanets in their stars' habitable zone, then use transmission spectroscopy to measure biosignature gases, especially oxygen, in the planets' atmospheres (e.g., using James Webb Space Telescope (JWST)). Already there are more such planets than can be observed by JWST, and missions like the Transiting Exoplanet Survey Satellite and others will find more. A better understanding of the geochemical cycles relevant to biosignature gases is needed, to prioritize targets for costly follow-up observations and to help design future missions. We define a Detectability Index to quantify the likelihood that a biosignature gas could be assigned a biological versus nonbiological origin. We apply this index to the case of oxygen gas, O2, on earthlike planets with varying water contents. We demonstrate that on earthlike exoplanets with 0.2 weight percent (wt%) water (I.e., no exposed continents) a reduced flux of bioessential phosphorus limits the export of photosynthetically produced atmospheric O2 to levels indistinguishable from geophysical production by photolysis of water plus hydrogen escape. Higher water contents &gt;1 wt% that lead to high-pressure ice mantles further slow phosphorus cycling. Paradoxically, the maximum water content allowing use of O2 as a biosignature, 0.2 wt%, is consistent with no water based on mass and radius. Thus, the utility of an O2 biosignature likely requires the direct detection of both water and land on a planet.

Keywords: Ocean planets, Exoplanets, Astrobiology, Biosignatures, Habitable planets
Doppler Imaging and Differential Rotation of σ<SUP>2</SUP> Coronae Borealis Using SONG. We present new Doppler images of both components of the double-lined binary σ2 CrB, based on the high-resolution spectroscopic data collected during 11 nights in 2015 March-April. The observed spectra form two independent data sets with sufficient phase coverage. We apply the least-squares deconvolution to all observed spectra to obtain high signal-to-noise mean profiles, from which we derive the Doppler images of both components of σ2 CrB simultaneously. The surfaces of both F9 and G0 components are dominated by pronounced polar spots. The F9 component exhibits a weak spot at latitude 30° and its mid-to-low latitudes are relatively featureless. The G0 star shows an extended spot structure at latitude 30°, and its surface spot coverage is larger than that of the F9 star, which suggests a higher level of magnetic activity. With the cross-correlation method, we derive a solar-like surface differential rotation on the G0 star of σ2 CrB for the first time, and the surface shear rate is ΔΩ = 0.180 ± 0.004 rad days-1 and α = ΔΩ/Ωeq = 0.032 ± 0.001. We do not obtain a clear surface shear law for the F9 star due to the lack of mid-to-low latitude features, but detect a systematic longitude shift of high-latitude spots, which indicates a slower rotation with respect to the corotating frame.

Keywords: Close binary stars, Starspots, Doppler imaging, Stellar activity
The Role of Quasar Radiative Feedback on Galaxy Formation during Cosmic Reionization. Recent observations have found that many z ∼ 6 quasar fields lack galaxies. This unexpected lack of galaxies may potentially be explained by quasar radiation feedback. In this paper, I present a suite of 3D radiative transfer cosmological simulations of quasar fields. I find that quasar radiation suppresses star formation in low-mass galaxies, mainly by photodissociating their molecular hydrogen. Photo-heating also plays a role, but only after ∼100 Myr. However, galaxies that already have stellar mass above 105M⊙ when the quasar turns on will not be suppressed significantly. Quasar radiative feedback suppresses the faint end of the galaxy luminosity function (LF) within 1 pMpc, but to a far lesser degree than the field-to-field variation of the LF. My study also suggests that by using the number of bright galaxies ( ${M}_{1500}$ &lt; -16) around quasars, we can potentially recover the underlying mass overdensity, which allows us to put reliable constraints on quasar environments.

Keywords: Galaxy formation, Quasars, Reionization, High-redshift galaxies, Galaxies
Necroplanetology: Simulating the Tidal Disruption of Differentiated Planetary Material Orbiting WD 1145+017. The WD 1145+017 system shows irregular transit features that are consistent with the tidal disruption of differentiated asteroids with bulk densities $\lt 4\,{\rm{g}}\,{\mathrm{cm}}^{-3}$ and bulk masses $\lesssim {10}^{21}\,\mathrm{kg}$ . We use the open-source N-body code REBOUND to simulate this disruption with different internal structures: varying the core volume fraction, mantle/core density ratio, and the presence/absence of a thin low-density crust. We allow the rubble pile to partially disrupt and capture lightcurves at a specific point during the disruption at cadences comparable to those from ground-based photometry. As a proof-of-concept we show that varying these structural parameters have observationally distinguishable effects on the transit lightcurve as the asteroid is disrupted and compare the simulation-generated lightcurves to data from Gary et al. With the caveat that our simulations do not model the sublimation in detail or account for its effects on orbital evolution, we find that a low core fraction and low mantle/core density ratio asteroid is most consistent with the stable transit feature present for multiple weeks circa 2016 April (referred to as G6121 in Gary et al. and A1 in Hallakoun et al.). Connecting tidal disruption simulations to photometry suggests characteristics for the interior structure and composition of an exoplanetary body, information that is only possible because we are observing the death of the planetary system in action. All-sky survey missions such as TESS and LSST will be able to detect other systems like WD 1145+017, creating a sample of subjects for a new subfield of planetary science: necroplanetology.

Keywords: Exoplanet dynamics, Asteroids, White dwarf stars, Exoplanet evolution, Computational methods
Relativistic Oblique Shock: A Geometric Object. A geometric perspective for the relativistic oblique shock structure is proposed. The proposed oblique shock geometry in angle-phase space may be helpful to better understand the physical structure of an interstellar shock.

Keywords: Shocks, Astrophysical fluid dynamics, Relativistic fluid dynamics
H<SUB>2</SUB>O<SUB>2</SUB>-induced Greenhouse Warming on Oxidized Early Mars. The existence of liquid water within an oxidized environment on early Mars has been inferred by the Mn-rich rocks found during recent explorations on Mars. The oxidized atmosphere implied by the Mn-rich rocks would basically be comprised of CO2 and H2O without any reduced greenhouse gases such as H2 and CH4. So far, however, it has been thought that early Mars could not have been warm enough to sustain water in liquid form without the presence of reduced greenhouse gases. Here, we propose that H2O2 could have been the gas responsible for warming the surface of the oxidized early Mars. Our one-dimensional atmospheric model shows that only 1 ppm of H2O2 is enough to warm the planetary surface because of its strong absorption at far-infrared wavelengths, in which the surface temperature could have reached over 273 K for a CO2 atmosphere with a pressure of 3 bar. A wet and oxidized atmosphere is expected to maintain sufficient quantities of H2O2 gas in its upper atmosphere due to its rapid photochemical production in slow condensation conditions. Our results demonstrate that a warm and wet environment could have been maintained on an oxidized early Mars, thereby suggesting that there may be connections between its ancient atmospheric redox state and possible aqueous environment.

Keywords: Mars, Planetary atmospheres, Solar system terrestrial planets
The Kepler Peas in a Pod Pattern is Astrophysical. Kepler planets around a given star have similar sizes to each other and regular orbital spacing, like "peas in a pod." Several studies have tested whether detection bias could produce this apparent pattern by resampling planet radii at random and applying a sensitivity function analogous to that of the Kepler spacecraft. However, Zhu argues that this pattern is not astrophysical but an artifact of Kepler's discovery efficiency at the detection threshold. To support this claim, their new analysis samples the transit signal-to-noise ratio (S/N) to derive a synthetic population of bootstrapped planet radii. Here, we examine the procedure of sampling transit S/N and demonstrate it is not applicable. Sampling transit S/N does not set up random, independent planet radii, and so it is unsuitable for corroborating (or falsifying) detection bias as the origin of apparent patterns in planet radius. By sampling the planet radii directly and using a simple model for Kepler's sensitivity, we rule out detection bias as the source of the peas-in-a-pod pattern with &gt;10σ confidence.

Keywords: Exoplanets, Exoplanet systems, Exoplanet astronomy, Planetary system formation, Exoplanet detection methods, Exoplanet formation, Planet formation
Magnetic Connectivity between the Light Bridge and Penumbra in a Sunspot. A light bridge is a prominent structure commonly observed within a sunspot. Its presence usually triggers a wealth of dynamics in a sunspot and has a lasting impact on sunspot evolution. However, the fundamental structure of light bridges is still not well understood. In this study, we used the high-resolution spectropolarimetry data obtained by the Solar Optical Telescope on board the Hinode satellite to analyze the magnetic and thermal structure of a light bridge at AR 12838. We also combined the high-cadence $1700\,\mathring{\rm A} $ channel data provided by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory to study the dynamics on this bridge. We found a pair of blue and red Doppler shift patches at two ends of this bridge; this pattern appears to be the convective motion directed by the horizontal component of the magnetic field aligned with the spine of the bridge. Paired upward and downward motions imply that the light bridge could have a two-legged or undulating magnetic field. Significant 4 minute oscillations in the emission intensity of the $1700\,\mathring{\rm A} $ bandpass were detected at two ends, which overlapped the paired blue- and redshift patches. The oscillatory signals at the light bridge and the penumbra were highly correlated with each other. Although they are separated in space at the photosphere, the periodicity seems to have a common origin from underneath the sunspot. Therefore, we infer that the light bridge and penumbra could share a common magnetic source and become fragmented at the photosphere by magnetoconvection.

Keywords: Magnetohydrodynamics, Sunspot flow, Solar magnetic reconnection, Sunspots, Solar coronal waves, Solar magnetic fields
Observing the Effects of Galaxy Interactions on the Circumgalactic Medium. We continue our empirical study of the emission line flux originating in the cool (T ∼ 104 K) gas that populates the halos of galaxies and their environments. Specifically, we present results obtained for a sample of galaxy pairs with a range of projected separations, $10\lt {S}_{p}/\mathrm{kpc}\lt 200$ , and mass ratios &lt;1:5, intersected by 5443 Sloan Digital Sky Survey lines of sight at projected radii of 10-50 kpc from either or both of the two galaxies. We find significant enhancement in Hα emission and a moderate enhancement in [N II]6583 emission for low-mass pairs (mean stellar mass per galaxy, ${\overline{M}}_{* },\lt {10}^{10.4}{M}_{\odot }$ ) relative to the results from a control sample. This enhanced Hα emission comes almost entirely from sight lines located between the galaxies, consistent with a short-term, interaction-driven origin for the enhancement. We find no enhancement in Hα emission, but significant enhancement in [N II]6583 emission for high-mass ( ${\overline{M}}_{* }\gt {10}^{10.4}{M}_{\odot }$ ) pairs. Furthermore, we find a dependence of the emission line properties on the galaxy pair mass ratio such that those with a mass ratio below 1:2.5 have enhanced [N II]6583 and those with a mass ratio between 1:2.5 and 1:5 do not. In all cases, departures from the control sample are only detected for close pairs (Sp &lt; 100 kpc). Attributing an elevated [N II]6583/Hα ratio to shocks, we infer that shocks play a role in determining the circumgalactic medium properties for close pairs that are among the more massive and have mass ratios closer to 1:1.

Keywords: Interacting galaxies, Galaxy pairs, Circumgalactic medium
Searching for Exotic Cores with Binary Neutron Star Inspirals. We study the feasibility of detecting exotic cores in merging neutron stars with ground-based gravitational-wave detectors. We focus on models with a sharp nuclear/exotic matter interface, and assume a uniform distribution of neutron stars in the mass range [1, 2] M⊙. We find that the existence of exotic cores can be confirmed at the 70% confidence level with as few as several tens of detections. Likewise, with such a sample, we find that some models of exotic cores can be excluded with high confidence.

Keywords: Nuclear astrophysics, Gravitational waves
First Embedded Cluster Formation in California Molecular Cloud. We performed a multi-wavelength observation toward the LkHα 101 embedded cluster and its adjacent 85'×60' region. The LkHα 101 embedded cluster is the first and only significant cluster in the California molecular cloud (CMC). These observations have revealed that the LkHα 101 embedded cluster is located just at the projected intersectional region of two filaments. One filament is the highest-density section of the CMC, the other is a new identified filament with a low-density gas emission. Toward the projected intersection, we find the bridging features connecting the two filaments in velocity, and identify a V-shaped gas structure. These agree with the scenario that the two filaments are colliding with each other. Using the Five-hundred-meter Aperture Spherical radio Telescope, we measured the radio recombination line velocity of the LkHα 101 H II region to be 0.5 km s-1, which is related to the velocity component of the CMC filament. Moreover, there are some young stellar objects (YSOs) distributed outside the intersectional region. We suggest that the cloud-cloud collision, together with the fragmentation of the main filament, may play an important role in the YSOs' formation of the cluster.

Keywords: Star formation, Interstellar clouds, Dynamical evolution
Electromagnetic Precursors to Gravitational-wave Events: Numerical Simulations of Flaring in Pre-merger Binary Neutron Star Magnetospheres. The detection of gravitational waves from neutron star merger events has opened up a new field of multimessenger astronomy linking gravitational-wave events to short gamma-ray bursts and kilonova afterglows. A further - yet to be discovered - electromagnetic counterpart is a precursor emission produced by the nontrivial interaction of the magnetospheres of the two neutron stars prior to merger. By performing special-relativistic force-free simulations of orbiting neutron stars we discuss the effect of different magnetic field orientations and show how the emission can be significantly enhanced by differential motion present in the binary, either due to stellar spins or misaligned stellar magnetospheres. We find that the buildup of twist in the magnetic flux tube connecting the two stars can lead to the repeated emission of powerful flares for a variety of orbital configurations. We also discuss potential coherent radio emission mechanisms in the flaring process.

Keywords: Neutron stars, Magnetohydrodynamics, High energy astrophysics, Plasma astrophysics, Compact binary stars, Pulsars, Magnetars
First-principles Demonstration of Diffusive-advective Particle Acceleration in Kinetic Simulations of Relativistic Plasma Turbulence. Nonthermal relativistic plasmas are ubiquitous in astrophysical systems like pulsar wind nebulae and active galactic nuclei, as inferred from their emission spectra. The underlying nonthermal particle acceleration (NTPA) processes have traditionally been modeled with a Fokker-Planck (FP) diffusion-advection equation in momentum space. In this Letter, we directly test the FP framework in ab initio kinetic simulations of driven magnetized turbulence in relativistic pair plasma. By statistically analyzing the motion of tracked particles, we demonstrate the diffusive nature of NTPA and measure the FP energy diffusion (D) and advection (A) coefficients as functions of particle energy $\gamma {m}_{e}{c}^{2}$ . We find that $D(\gamma )$ scales as ${\gamma }^{2}$ in the high-energy nonthermal tail, in line with second-order Fermi acceleration theory, but has a much weaker scaling at lower energies. We also find that A is not negligible and reduces NTPA by tending to pull particles toward the peak of the particle energy distribution. This study provides strong support for the FP picture of turbulent NTPA, thereby enhancing our understanding of space and astrophysical plasmas.

Keywords: Non-thermal radiation sources, High energy astrophysics, Plasma astrophysics
The NANOGrav 11 yr Data Set: Constraints on Planetary Masses Around 45 Millisecond Pulsars. We search for extrasolar planets around millisecond pulsars using pulsar timing data and seek to determine the minimum detectable planetary masses as a function of orbital period. Using the 11 yr data set from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), we look for variations from our models of pulse arrival times due to the presence of exoplanets. No planets are detected around the millisecond pulsars in the NANOGrav 11 yr data set, but taking into consideration the noise levels of each pulsar and the sampling rate of our observations, we develop limits that show we are sensitive to planetary masses as low as that of the moon. We analyzed potential planet periods, P, in the range 7 days &lt; P &lt; 2000 days, with somewhat smaller ranges for some binary pulsars. The planetary-mass limit for our median-sensitivity pulsar within this period range is $1\,{M}_{\mathrm{moon}}{(P/100\mathrm{days})}^{-2/3}$ .

Keywords: Exoplanet detection methods, Pulsar planets, Pulsar timing method, Millisecond pulsars
The Satellite Luminosity Function of M101 into the Ultra-faint Dwarf Galaxy Regime. We have obtained deep Hubble Space Telescope (HST) imaging of four faint and ultra-faint dwarf galaxy candidates in the vicinity of M101-Dw21, Dw22, Dw23 and Dw35, originally discovered by Bennet et al. Previous distance estimates using the surface brightness fluctuation technique have suggested that these four dwarf candidates are the only remaining viable M101 satellites identified in ground-based imaging out to the virial radius of M101 (D ≈ 250 kpc). Advanced Camera for Surveys imaging of all four dwarf candidates shows no associated resolved stellar populations, indicating that they are thus background galaxies. We confirm this by generating simulated HST color-magnitude diagrams of similar brightness dwarfs at the distance of M101. Our targets would have displayed clear, resolved red giant branches with dozens of stars if they had been associated with M101. With this information, we construct a satellite luminosity function for M101, which is 90% complete to MV = -7.7 mag and 50% complete to MV = -7.4 mag, that extends into the ultra-faint dwarf galaxy regime. The M101 system is remarkably poor in satellites in comparison to the Milky Way and M31, with only eight satellites down to an absolute magnitude of MV = -7.7 mag, compared to the 14 and 26 seen in the Milky Way and M31, respectively. Further observations of Milky Way analogs are needed to understand the halo-to-halo scatter in their faint satellite systems, and connect them with expectations from cosmological simulations.

Keywords: Luminosity function, Dwarf galaxies, HST photometry, Galaxy evolution, Galaxy groups
Electron-only Reconnection in Kinetic-Alfvén Turbulence. We study numerically small-scale reconnection events in kinetic, low-frequency, quasi-2D turbulence (termed kinetic-Alfvén turbulence). Using 2D particle-in-cell simulations, we demonstrate that such turbulence generates reconnection structures where the electron dynamics do not couple to the ions, similarly to the electron-only reconnection events recently detected in the Earth's magnetosheath by Phan et al. Electron-only reconnection is thus an inherent property of kinetic-Alfvén turbulence, where the electron current sheets have limited anisotropy and, as a result, their sizes are smaller than the ion inertial scale. The reconnection rate of such electron-only events is found to be close to 0.1.

Keywords: Alfven waves, Magnetic fields, Space plasmas
Multiple X-line Reconnection Observed in Mercury's Magnetotail Driven by an Interplanetary Coronal Mass Ejection. How magnetic reconnection drives Mercury's magnetospheric dynamics under extreme solar wind conditions is not well understood. Here we report MESSENGER observations of an active reconnection event in Mercury's magnetotail driven by an interplanetary coronal mass ejection on 2011 November 23. The primary Hall magnetic field, sequential passage of X-lines with Hall field perturbations, and flux ropes (FRs) provide unambiguous evidence of multiple X-line reconnection in an unstable ion diffusion region. In addition, large FRs consisting of multiple successive small-scale FRs are ejected tailward at quasi-periodic intervals of ∼1 minute, which is comparable to the Dungey cycle time. We propose that these large FRs are generated by the interaction and coalescence of multiple ion-scale FRs. This is distinct from the commonly accepted Earth-like substorm process where plasmoids are created by widely separated X-lines in the magnetotail. These observations suggest that during extreme solar wind conditions multiple X-line reconnection may dominate the tail reconnection process and control the global dynamics of Mercury's magnetosphere.

Keywords: Space plasmas, Solar magnetic reconnection, Solar-planetary interactions, Solar coronal mass ejections, Mercury (planet), Planetary magnetospheres
Dust Environment Model of the Interstellar Comet 2I/Borisov. 2I/Borisov is the first interstellar comet discovered on 2019 August 30, and it soon showed a coma and a dust tail. This study reports the results of images obtained at the Telescopio Nazionale Galileo telescope, on La Palma - Canary Islands, in 2019 November and December. The images have been obtained with the R filter in order to apply our dust tail model. The model has been applied to the comet 67P/Churyumov-Gerasimenko and compared to the Rosetta dust measurements showing a very good agreement. It has been applied to the comet 2I/Borisov, using almost the same parameters, obtaining a dust environment similar to that of 67P/Churyumov-Gerasimenko, suggesting that the activity may be very similar. The dust tail analysis provided a dust-loss rate Qd ≈ 35 kg s-1 in 2019 November and Qd ≈ 30 kg s-1 in 2019 December.

Keywords: Comets, Planetary science