Sazuna/UAT_keywords huggingface dataset:
Cascade Model for Planetesimal Formation by Turbulent Clustering. We use a newly developed cascade model of turbulent concentration of particles in protoplanetary nebulae to calculate several properties of interest to the formation of primitive planetesimals and to the meteorite record. The model follows, and corrects, calculations of the primary initial mass function (IMF) of planetesimals by Cuzzi et al., in which an incorrect cascade model was used. Here we use the model of Hartlep et al., which has been validated against several published numerical simulations of particle concentration in turbulence. We find that, for a range of nebula and particle properties, planetesimals may be "born big," formed as sandpiles with diameters in the range 10-100 km, directly from freely floating particles. The IMFs have a modal nature, with a well-defined peak rather than a power-law size dependence. Predictions for the inner and outer parts of the nebula behave similarly in this regard, and observations of primitive bodies in the inner and outer nebula support such modal IMFs. Also, we present predictions of local particle concentrations on several lengthscales in which particles "commonly" find themselves, which have significance for meteoritical observations of the redox state and isotopic fractionation in regions of chondrule formation. An important difference between these results and those of Cuzzi et al. is that particle growth by sticking must proceed to a radius range of at least one to a few centimeters for the IMF and meteoritical properties to be most plausibly satisfied. That is, as far as the inner nebula goes, the predominant "particles" must be aggregates of chondrules (or chondrule-size precursors) rather than individual chondrules themselves.

Keywords: Protoplanetary nebulae, Chondrules, Planetary system formation, Protoplanetary disks, Planetesimals
Constraints on the Physical Properties of SNe Ia from Photometry. We present a photometric study of 17 SNe Ia based on multi-color (Johnson-Cousins-Bessell BVRI) data taken at Piszkéstet&amp;odblac mountain station of Konkoly Observatory, Hungary between 2016 and 2018. We analyze the light curves (LCs) using the publicly available LC-fitter SNooPy2 to derive distance and reddening information. The bolometric LCs are fit with a radiation-diffusion Arnett model to get constraints on the physical parameters of the ejecta: the optical opacity, the ejected mass and the initial nickel mass in particular. We also study the pre-maximum, dereddened (B-V)0 color evolution by comparing our data with standard delayed detonation and pulsational delayed detonation models, and show that the 56Ni masses of the models that fit the (B-V)0 colors are consistent with those derived from the bolometric LC fitting. We find similar correlations between the ejecta parameters (e.g., ejecta mass, or 56Ni mass versus decline rate) as published recently by Scalzo et al. (2019).

Keywords: Ejecta, Type Ia supernovae, Johnson photometry
A Novel Survey for Young Substellar Objects with the W-band Filter. II. The Coolest and Lowest Mass Members of the Serpens-South Star-forming Region. Given its relative proximity (∼430 pc), compact size (&lt;20'), young age (∼0.5 Myr), and rich number of young stellar objects, the Serpens-South star-forming region is a promising site for studying young substellar objects, yet the low-mass members of this region remain largely undiscovered. In this article we report on a deep photometric survey using a custom 1.45 μm filter (W band), as well as standard J and H near-IR filters, in order to identify candidate low-mass young brown dwarfs in the Serpens-South region. We constructed a reddening-insensitive index (Q) by combining J, H and W-band photometry for survey objects, in order to identify candidate low-mass members of Serpens based on the strength of the water-absorption feature at 1.45 μm in the atmospheres of mid-M and later objects. We then conducted spectroscopic follow-up to confirm youth and spectral type for our candidates. This is the first survey to identify the very low-mass and coolest members of Serpens-South. We identify four low-mass candidate Serpens members, which all display IR excess emission, indicating the likely presence of circumstellar disks around them. One of the four candidate low-mass members in our list, SERP182918-020245, exhibits Paβ and Brγ emission features, confirming its youth and ongoing magnetospheric accretion. Our new candidate members have spectral types &gt;M4 and are the coolest and lowest mass candidate members yet identified in Serpens-South.

Keywords: Brown dwarfs, M subdwarf stars, Infrared excess, Young stellar objects, Pre-main sequence stars, Low mass stars
Constraints on the Intergalactic Magnetic Field from Bow Ties in the Gamma-Ray Sky. Pair creation on the cosmic infrared background and subsequent inverse-Compton scattering on the cosmic microwave background potentially reprocesses the TeV emission of blazars into faint GeV halos with structures sensitive to intergalactic magnetic fields (IGMF). Previous work has shown that these halos are then highly anisotropic and extended. If the coherence length of the IGMF is greater than the inverse-Compton cooling length of the pairs, then the orientation of the gamma-ray halo will be correlated with the direction of the magnetic field which is unknown and expected to change for each source. In order to constructively add each source we then use angular power spectra which are insensitive to the jet orientation. By looking at known GeV blazars detected by Fermi, we exclude the existence of an IGMF with coherence lengths &gt;100 Mpc at greater than 3.9σ with current-day strengths in the range 10-16 to 10-15 G, and at 2σ from 10-17 to 10-14 G. This provides a direct measurement of the nonexistence of gamma-ray halos, providing an important check on previous results.

Keywords: BL Lacertae objects, Gamma-rays, High energy astrophysics
Unified Simulations of Planetary Formation and Atmospheric Evolution: Effects of Pebble Accretion, Giant Impacts, and Stellar Irradiation on Super-Earth Formation. A substantial number of super-Earths have been discovered, and atmospheres of transiting super-Earths have also been observed by transmission spectroscopy. Several lines of observational evidence indicate that most super-Earths do not possess massive H2/He atmospheres. However, accretion and retention of less massive atmospheres on super-Earths challenge planet formation theory. We consider the following three mechanisms: (I) envelope heating by pebble accretion, (II) mass loss during giant impacts, and (III) atmospheric loss by stellar X-ray and EUV photoevaporation. We investigate whether these mechanisms influence the amount of the atmospheres that form around super-Earths. We develop a code combining an N-body simulation of pebble-driven planetary formation and an atmospheric evolution simulation. We demonstrate that the observed orbital properties of super-Earths are well reproduced by the results of our simulations. However, (I) heating by pebble accretion ceases prior to disk dispersal, (II) the frequency of giant impact events is too low to sculpt massive atmospheres, and (III) many super-Earths having H2/He atmospheres of ≳10 wt% survive against stellar irradiation for 1 Gyr. Therefore, it is likely that other mechanisms, such as suppression of gas accretion, are required to explain less massive atmospheres (≲10 wt%) of super-Earths.

Keywords: Exoplanet dynamics, Exoplanet formation, Exoplanet atmospheres
Simulating JWST/NIRCam Color Selection of High-redshift Galaxies. The Near Infrared Camera (NIRCam) instrument on the upcoming James Webb Space Telescope will offer an unprecedented view of the most distant galaxies. In preparation for future deep NIRCam extragalactic surveys, it is crucial to understand the color selection of high-redshift galaxies using the Lyman dropout technique. To that end, we have used the JAdes extraGalactic Ultradeep Artificial Realizations mock catalog to simulate a series of extragalactic surveys with realistic noise estimates. This enables us to explore different color selections and their impact on the number density of recovered high-redshift galaxies and lower-redshift interlopers. We explore how survey depth, detection signal-to-noise ratio, color selection method, detection filter choice, and the presence of the Lyα emission line affects the resulting dropout selected samples. We find that redder selection colors reduce the number of recovered high-redshift galaxies, but the overall accuracy of the final sample is higher. In addition, we find that methods that utilize two or three color cuts have higher accuracy because of their ability to select against low-redshift quiescent and faint dusty interloper galaxies. We also explore the near-IR colors of brown dwarfs and demonstrate that, while they are predicted to have low on-sky densities, they are most likely to be recovered in F090W dropout selection, but there are color cuts that help to mitigate this contamination. Overall, our results provide NIRCam selection methods to aid in the creation of large, pure samples of ultra-high-redshift galaxies from photometry alone.

Keywords: Galaxy colors, High-redshift galaxies
Evidence for Asteroid Scattering and Distal Solar System Solids From Meteorite Paleomagnetism. Asteroid-sized bodies are predicted to have been scattered throughout the solar system following gravitational interactions with the giant planets. This process could have delivered water-rich small bodies to the inner solar system. However, evidence from the meteorite record supporting this scattering is limited due to difficulties in recovering the formation distance of meteorite parent bodies from laboratory measurements. Moreover, ancient millimeter-sized solids that formed in the inner solar system (calcium-aluminum-rich inclusions (CAIs) and chondrules) have also been proposed to have migrated throughout the solar system, which could have been key to their survival. Our understanding of the driving mechanisms, distances, and timings involved in this motion is also restricted for the same reasons. Here, we address these limitations by recovering the formation distance of the parent asteroid of the Tagish Lake meteorite from measurements of its natural remanent magnetization. We find that this meteorite experienced an ancient field intensity &lt;0.15 μT. Accounting for the average effect of a tilted parent body rotation axis and possible uncertainties associated with the remanence acquisition mechanism, this result argues that the Tagish Lake parent body formed at &gt;8-13 au, suggesting this body originates from the distal solar system. Tagish Lake came to Earth from the asteroid belt which, combined with our recovered formation distance, suggests that some small bodies traveled large distances throughout the solar system. Moreover, Tagish Lake contains CAIs and chondrules, indicating that these solids were capable of traveling to the distal solar system within just a few million years.

Keywords: Chondrites, Asteroids, Primordial magnetic fields, Kuiper belt, Carbonaceous chondrites, Chondrules, Protoplanetary disks, Meteorites, Asteroid belt, Magnetic fields
When is Chemical Disequilibrium in Earth-like Planetary Atmospheres a Biosignature versus an Anti-biosignature? Disequilibria from Dead to Living Worlds. Chemical disequilibrium in exoplanetary atmospheres (detectable with remote spectroscopy) can indicate life. The modern Earth's atmosphere-ocean system has a much larger chemical disequilibrium than other solar system planets with atmospheres because of oxygenic photosynthesis. However, no analysis exists comparing disequilibrium on lifeless, prebiotic planets to disequilibrium on worlds with primitive chemotrophic biospheres that live off chemicals and not light. Here, we use a photochemical-microbial ecosystem model to calculate the atmosphere-ocean disequilibria of Earth with no life and with a chemotrophic biosphere. We show that the prebiotic Earth likely had a relatively large atmosphere-ocean disequilibrium due to the coexistence of water vapor and volcanic H2, CO2, and CO. Subsequent chemotrophic life probably destroyed nearly all of the prebiotic disequilibrium through its metabolism, leaving a likely smaller disequilibrium between N2, CO2, CH4, and liquid water. So, disequilibrium fell with the rise of chemotrophic life then later rose with atmospheric oxygenation due to oxygenic photosynthesis. We conclude that big prebiotic disequilibrium between H2 and CO2 or CO and water is an anti-biosignature because these easily metabolized species can be eaten due to redox reactions with low activation energy barriers. However, a large chemical disequilibrium can also be a biosignature when the disequilibrium arises from a chemical mixture with biologically insurmountable activation energy barriers and clearly identifiable biogenic gases. Earth's modern disequilibrium between O2, N2, and liquid water along with minor CH4 is such a case. Thus, the interpretation of disequilibrium requires context. With context, disequilibrium can be used to infer dead or living worlds.

Keywords: Biosignatures, Astrobiology, Planetary atmospheres, Earth atmosphere
Distortion of Magnetic Fields in BHR 71. The magnetic field structure of a star-forming Bok globule BHR 71 was determined based on near-infrared polarimetric observations of background stars. The magnetic field in BHR 71 was mapped from 25 stars. By using a simple 2D parabolic function, the plane-of-sky magnetic axis of the core was found to be θmag = 125° ± 11°. The plane-of-sky mean magnetic field strength of BHR 71 was found to be Bpos = 8.8-15.0 μG, indicating that the BHR 71 core is magnetically supercritical with λ = 1.44-2.43. Taking into account the effect of thermal/turbulent pressure and the plane-of-sky magnetic field component, the critical mass of BHR 71 was Mcr = 14.5-18.7 M⊙, which is consistent with the observed core mass of Mcore ≈ 14.7 M⊙. We conclude that BHR 71 is in a condition close to a kinematically critical state, and the magnetic field direction lies close to the plane of sky. Since BHR 71 is a star-forming core, a significantly subcritical condition (I.e., the magnetic field direction deviating from the plane of sky) is unlikely, and collapsed from a condition close to a kinematically critical state. There are two possible scenarios to explain the curved magnetic fields of BHR 71, one is an hourglass-like field structure due to mass accumulation and the other is the Inoue &amp; Fukui mechanism, which proposes the interaction of the core with a shock wave to create curved magnetic fields wrapping around the core.

Keywords: Interstellar dust, Dense interstellar clouds, Interstellar magnetic fields, Infrared astronomy, Starlight polarization
Formation of Post-CME Blobs Observed by LASCO-C2 and K-Cor on 2017 September 10. Understanding the formation of post-CME blobs, we investigate 2 blobs in the outer corona observed by LASCO-C2 and 34 blobs in the inner corona by K-Cor on 2017 September 10 from 17:11 to 18:58 UT. By visual inspection of the structure of a post-CME current sheet (CS) and its associated blobs, we find that the CS is well identified in the K-Cor and its radial lengths are nine times longer than lateral widths, indicating the CS is unstable to the linear tearing mode. The inner corona blobs can be classified into two groups: 27 blobs generated in the middle of the CS (Group 1) and 7 blobs occurred above the tips of it (Group 2). Their lateral widths are &lt; 0.02 R⊙ &gt; and &lt; 0.05 R⊙&gt;, which is smaller than, or similar to, those (&lt; 0.06 R⊙ &gt;) of the CS. They have elongated shapes: ratios of lateral to radial widths are &lt; 0.53 &gt; and &lt; 0.40 &gt;, respectively. In the first group, only three blobs propagate above the tip of the CS while the others are located in the CS. In the second group, only two blobs have associations with those of outer corona in their temporal and spatial relationship and their initial heights are 1.81 and 1.95 R⊙, measured from the center of the Sun. The others cannot be identified in the outer corona. Our results first demonstrate that LASCO-C2 blobs could be generated by the tearing mode instability near the tips of post-CME CSs, similar to the magnetic reconnection process in the tail CS of Earth's magnetosphere.

Keywords: Solar corona, Solar coronal mass ejections, Solar magnetic reconnection
Intermediate-mass Black Holes' Effects on Compact Object Binaries. Although their existence is not yet confirmed observationally, intermediate-mass black holes (IMBHs) may play a key role in the dynamics of galactic nuclei. In this paper, we neglect the effect of the nuclear star cluster itself and investigate only how a small reservoir of IMBHs influences the secular dynamics of stellar-mass black hole binaries, using N-body simulations. We show that our simplifications are valid and that the IMBHs significantly enhance binary evaporation by pushing the binaries into the Hill-unstable region of parameter space, where they are separated by the supermassive black hole's tidal field. For binaries in the S-cluster region of the Milky Way, IMBHs drive the binaries to merge in up to 1%-6% of cases, assuming five IMBHs within 5 pc of mass 104 M⊙ each. Observations of binaries in the Galactic center may strongly constrain the population of IMBHs therein.

Keywords: Intermediate-mass black holes, Galactic center
Polarization Constraints on the Geometry of the Magnetic Field in the External Shock of Gamma-Ray Bursts. We study the ensemble of linear polarization measurements in the optical afterglows of long-duration gamma-ray bursts. We assume a non-sideways-expanding top-hat jet geometry and use the relatively large number of measurements under the assumption that they represent a statistically unbiased sample. This allows us to constrain the ratio between the maximum predicted polarization and the measured one, which is an indicator of the geometry of the magnetic field in the downstream region of the external shock. We find that the measured polarization is substantially suppressed with respect to the maximum possible for either a completely ordered magnetic field parallel to the shock normal or to a field that is entirely contained in the shock plane. The measured polarization is limited, on average, to between 25% and 30% of the maximum theoretically possible value. This reduction requires the perpendicular component of the magnetic field to be dominant in energy with respect to the component parallel to the shock front, as expected for a shock-generated and/or shock-compressed field. We find, however, that the data only marginally support the assumption of a simple top-hat jet, pointing toward a more complex geometry for the outflow.

Keywords: Non-thermal radiation sources, Gamma-ray bursts, Polarimetry
Spacetime Tomography Using the Event Horizon Telescope. We have now entered a new era of high-resolution imaging astronomy with the beginning of the Event Horizon Telescope (EHT). The EHT can resolve the dynamics of matter in the immediate vicinity around black holes at and below the horizon scale. One of the candidate black holes, Sagittarius A*, flares 1-4 times a day depending on the wavelength. A possible interpretation of these flares could be hotspots generated through magnetic-reconnection events in the accretion flow. In this paper, we construct a semi-analytical model for hotspots that includes the effects of shearing as a spot moves along the accretion flow. We then explore the ability of the EHT to recover these hotspots. Even including significant systematic uncertainties, such as thermal noise, diffractive scattering, and background emission due to an accretion disk, we were able to recover the hotspots and spacetime structure to sub-percent precision. Moreover, by observing multiple flaring events we show how the EHT could be used to tomographically map spacetime. This provides new avenues for testing relativistic fluid dynamics and general relativity near the event horizon of supermassive black holes.

Keywords: Accretion, Black hole physics, Galactic center, Gravitation, General relativity, Radiative transfer
TXS 2116-077: A Gamma-Ray Emitting Relativistic Jet Hosted in a Galaxy Merger. What triggers collimated relativistic outflows or jets from the centers of galaxies remains a fundamental question in astrophysics. The merging of two galaxies has been proposed to realize the conditions to successfully launch and drive such jets into the intergalactic medium. However, evidence for the operation of this mechanism is scarce. Here we report the first unambiguous detection of an ongoing merger of a narrow-line Seyfert 1 galaxy, TXS 2116-077, hosting a closely aligned, γ-ray emitting relativistic jet with a Seyfert 2 galaxy at a separation of ∼12 kpc, using the observations taken with the 8.2 m Subaru Telescope. Our subsequent follow-up observations with the 10.4 m Gran Telescopio Canarias, 4.2 m William Herschel Telescope, and Chandra X-ray observatory have provided what is likely to be the first glimpse of the merging environment hosting a closely aligned relativistic jet. Our finding that the jet is considerably younger than the merger demonstrates that jet activity can be triggered by galaxy mergers and that γ-ray detected narrow-line Seyfert 1 galaxies represent the beginning phase of that activity. These results also highlight the crucial role of mergers in shaping the fate of galaxies in their cosmological evolution and are consistent with recent studies focused on the host galaxy imaging of this enigmatic class of active galactic nuclei.

Keywords: AGN host galaxies, Blazars, Galaxy interactions, Relativistic jets, Galaxy jets
Is the High-Resolution Coronal Imager Resolving Coronal Strands? Results from AR 12712. Following the success of the first mission, the High-Resolution Coronal Imager (Hi-C) was launched for a third time (Hi-C 2.1) on 2018 May 29 from the White Sands Missile Range, NM, USA. On this occasion, 329 s of 17.2 nm data of target active region AR 12712 were captured with a cadence of ≈4 s, and a plate scale of 0.129 arcsec pixel-1. Using data captured by Hi-C 2.1 and co-aligned observations from SDO/AIA 17.1 nm, we investigate the widths of 49 coronal strands. We search for evidence of substructure within the strands that is not detected by AIA, and further consider whether these strands are fully resolved by Hi-C 2.1. With the aid of multi-scale Gaussian normalization, strands from a region of low emission that can only be visualized against the contrast of the darker, underlying moss are studied. A comparison is made between these low-emission strands and those from regions of higher emission within the target active region. It is found that Hi-C 2.1 can resolve individual strands as small as ≈202 km, though the more typical strand widths seen are ≈513 km. For coronal strands within the region of low emission, the most likely width is significantly narrower than the high-emission strands at ≈388 km. This places the low-emission coronal strands beneath the resolving capabilities of SDO/AIA, highlighting the need for a permanent solar observatory with the resolving power of Hi-C.

Keywords: Solar coronal loops, Solar active regions, Solar corona