bluuebunny/crossref_metadata_2025_split huggingface dataset:
ALMA Observations of Giant Molecular Clouds in M33. II. Triggered High-mass Star Formation by Multiple Gas Colliding Events at the NGC 604 Complex
Authors: Muraoka Kazuyuki , Kondo Hiroshi , Tokuda Kazuki , Nishimura Atsushi , Miura Rie E. , Onodera Sachiko , Kuno Nario , Zahorecz Sarolta , Tsuge Kisetsu , Sano Hidetoshi , Fujita Shinji , Onishi Toshikazu , Saigo Kazuya , Tachihara Kengo , Fukui Yasuo , Kawamura Akiko 
Published: November 2020

Abstract
We present the results of ALMA observations in 12CO(J = 2 − 1), 13CO(J = 2 − 1), and C18O(J = 2 − 1) lines and 1.3 mm continuum emission toward a massive (∼106
M
⊙) giant molecular cloud associated with the giant H ii region NGC 604 in one of the nearest spiral galaxies, M33, at an angular resolution of 0.″44 × 0.″27 (1.8 pc × 1.1 pc). The 12CO and 13CO images show highly complicated molecular structures composed of a lot of filaments and shells whose lengths are 5–20 pc. We found three 1.3 mm continuum sources to be dense clumps at the edges of two shells and also at the intersection of several filaments. We examined the velocity structures of the 12CO(J = 2 − 1) emission in the shells and filaments containing dense clumps, and concluded that expansion of the H ii regions cannot explain the formation of such dense cores. Alternatively, we suggest that cloud–cloud collisions induced by an external H i gas flow and the galaxy’s rotation compressed the molecular material into dense filaments/shells which are ongoing high-mass star formation sites. We propose that multiple gas converging/colliding events with a velocity of a few tens of kilometers per second are necessary to build up NGC 604, the most significant cluster-forming complex in the Local Group of galaxies.
Binary Fraction Estimation of Main-sequence Stars in 12 Open Clusters: Based on the Homogeneous Data of LAMOST Survey and Gaia DR2
Authors: Niu Hubiao , Wang Jiaxin , Fu Jianning 
Published: November 2020

Abstract
Based on the homogeneous low-resolution spectra data observed by Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and the Gaia Data Release 2 (Gaia DR2) photometric data, we chose 12 open clusters (OCs) to study their fundamental parameters and binary fractions (BFs). For each OC, more than 20 cluster members were observed by LAMOST, and some of them were observed multiple times. We used these data to derive precise metallicities of OCs. Combining the metallicities and the Gaia DR2 photometric data, we used the isochrone fitting method to obtain fundamental parameters of these OCs. By fixing metallicity during the fitting, we avoided the effect of degeneracy between the metallicity and reddening. Based on the fundamental parameters, we utilized the synthetic color–magnitude diagram (CMD) method to derive the BFs of main-sequence (MS) stars, the mass functions (MFs) with correction of binaries, and the companion mass ratio distributions. The BFs of observed MS stars in OCs in this paper vary from 29% to 55%. Extrapolating the synthetic CMD to the hydrogen-burning limit, the BFs vary from 13% to 47%. Combining MFs published by previous literature with our results, we found that MFs with correction of binaries were steeper than those without correction by Δα = 0.6 ± 0.16 in the mass range of m ∈ [1M
⊙, 2.67M
⊙]. We found that the companion mass ratio distribution in OCs of our sample was flat. We also found a significant positive correlation between the BF and density.
An Analysis of Soft X-Ray Structures at Kiloparsec Distances from the Active Nucleus of Centaurus A Galaxy
Authors: Król Dominika Ł. , Marchenko Volodymyr , Ostrowski Michał , Stawarz Łukasz 
Published: November 2020

Abstract
Here we reanalyze the archival Chandra data for the central parts of the Centaurus A radio galaxy, aiming for a systematic investigation of the X-ray emission associated with the inner radio lobes in the system, and their immediate surroundings. In particular, we focus on four distinct features characterized by the soft excess with respect to the adjacent fields. Those include the two regions located at kiloparsec distances from the nucleus to the west and east, the extended bow-shock structure to the south, and a fragment of a thin arc north of the center. The selected north, west, and south features coincide with the edges of the radio lobes, while the east structure is seemingly displaced from the radio-emitting plasma. Our X-ray spectral analysis reveals (i) a power-law emission component with photon index Γ ∼ 2 in the north, east, and south regions, and (ii) a dense (number density ∼0.3 cm−3) and relatively cold (temperature ∼ 0.2 keV) gas in the east and west regions. The power-law emission is consistent with the synchrotron continuum generated at the edges of the radio structure, and implies that the efficiency of the electron acceleration at the terminal bow shock does not vary dramatically over the inner lobes’ extension. The presence of gaseous condensations, on the other hand, could possibly be understood in terms of a massive outflow from the central regions of the galaxy.
Full-sky Cosmic Microwave Background Foreground Cleaning Using Machine Learning
Authors: Petroff Matthew A. , Addison Graeme E. , Bennett Charles L. , Weiland Janet L. 
Published: November 2020

Abstract
In order to extract cosmological information from observations of the millimeter and submillimeter sky, foreground components must first be removed to produce an estimate of the cosmic microwave background (CMB). We developed a machine-learning approach for doing so for full-sky temperature maps of the millimeter and submillimeter sky. We constructed a Bayesian spherical convolutional neural network architecture to produce a model that captures both spectral and morphological aspects of the foregrounds. Additionally, the model outputs a per-pixel error estimate that incorporates both statistical and model uncertainties. The model was then trained using simulations that incorporated knowledge of these foreground components that was available at the time of the launch of the Planck satellite. On simulated maps, the CMB is recovered with a mean absolute difference of <4 μK over the full sky after masking map pixels with a predicted standard error of >50 μK; the angular power spectrum is also accurately recovered. Once validated with the simulations, this model was applied to Planck temperature observations from its 70 GHz through 857 GHz channels to produce a foreground-cleaned CMB map at a Healpix map resolution of nside = 512. Furthermore, we demonstrate the utility of the technique for evaluating how well different simulations match observations, particularly in regard to the modeling of thermal dust.
Ram Pressure Stripping of HI-rich Galaxies Infalling into Massive Clusters
Authors: Wang Jing , Xu Weiwei , Lee Bumhyun , Du Min , Overzier Roderik , Shao Li 
Published: November 2020

Abstract
We estimate the strength of ram pressure stripping (RPS) for Hi-rich galaxies in X-ray detected clusters. We find that galaxies under stronger RPS tend to show more significantly reduced total Hi mass and enhanced central SFR when compared to control galaxies in the field that have similar stellar mass, stellar surface density and integral star formation rate. Galaxies under strong or weak RPS account for ∼40% of the Hi-rich population at R
200, and even beyond R
200 in the most massive clusters. Our results imply the important role of RPS as a channel of environmental processing far before the galaxies reach the core region of clusters.
Transport, Destruction, and Growth of Pebbles in the Gas Envelope of a Protoplanet
Authors: Johansen Anders , Nordlund Åke 
Published: November 2020

Abstract
We analyze the size evolution of pebbles accreted into the gaseous envelope of a protoplanet growing in a protoplanetary disk, taking into account collisions driven by the relative sedimentation speed as well as the convective gas motion. Using a simple estimate of the convective gas speed based on the pebble accretion luminosity, we find that the speed of the convective gas is higher than the sedimentation speed for all particles smaller than 1 mm. This implies that both pebbles and pebble fragments are strongly affected by the convective gas motion and will be transported by large-scale convection cells both toward and away from the protoplanet’s surface. We present a simple scheme for evolving the characteristic size of the pebbles, taking into account the effects of erosion, mass transfer, and fragmentation. Including the downwards motion of convective cells for the transport of pebbles with an initial radius of 1 mm, we find pebble sizes between 100 μm and 1 mm near the surface of the protoplanet. These sizes are generally amenable to accretion at the base of the convection flow. Small protoplanets far from the star (>30 au) nevertheless erode their pebbles to sizes below 10 μm; future hydrodynamical simulations will be needed to determine whether such small fragments can detach from the convection flow and become accreted by the protoplanet.
A Model of Rotating Convection in Stellar and Planetary Interiors. II. Gravito-inertial Wave Generation
Authors: Augustson K. C. , Mathis S. , Astoul A. 
Published: November 2020

Abstract
Gravito-inertial waves are excited at the interface of convective and radiative regions and by the Reynolds stresses in the bulk of the convection zones of rotating stars and planets. Such waves have notable asteroseismic signatures in the frequency spectra of rotating stars, particularly among rapidly rotating early-type stars, which provides a means of probing their internal structure and dynamics. They can also transport angular momentum, chemical species, and energy from the excitation region to where they dissipate in radiative regions. To estimate the excitation and convective parameter dependence of the amplitude of those waves, a monomodal model for stellar and planetary convection as described in Paper I is employed, which provides the magnitude of the rms convective velocity as a function of rotation rate. With this convection model, two channels for wave driving are considered: excitation at a boundary between convectively stable and unstable regions and excitation due to Reynolds stresses. Parameter regimes are found where the sub-inertial waves may carry a significant energy flux, depending upon the convective Rossby number, the interface stiffness, and the wave frequency. The super-inertial waves can also be enhanced, but only for convective Rossby numbers near unity. Interfacially excited waves have a peak energy flux near the lower cutoff frequency when the convective Rossby number of the flows that excite them are below a critical Rossby number that depends upon the stiffness of the interface, whereas that flux decreases when the convective Rossby number is larger than this critical Rossby number.
Galactopause Formation and Gas Precipitation during Strong Galactic Outflows
Authors: Shull J. Michael , Moss Jacob A. 
Published: November 2020

Abstract
Using X-ray constrained β-models for the radial distribution of gas in the outskirts of galaxies, we analyze the termination of galactic winds and the formation and evolution of halo clouds by thermal instability. At low mass-loss rates (

) galactic winds are trapped within the halo, but they burst into the intergalactic medium during intermittent strong outflows with

. We develop analytic models of halo clouds as they cool radiatively over condensation timescales

for hydrogen number densities

, gas temperatures T ≈ (106 K)T
6, and metallicities (Z/Z
⊙). Halo gas can form kiloparsec-scale clouds out to galactocentric distances r ≈ 30–65 kpc, where efficient radiative cooling from 106 K down to T ≈ 104–5 K occurs at Z ≥ 0.3 Z
⊙ on timescales less than 1 Gyr. After condensing to column densities N
H ≥ 4 × 1016 cm−2, these clouds lose hydrostatic pressure support and fall inward on dynamical timescales of ∼200 Myr. Our baseline analysis will be followed by numerical calculations to understand the governing principles of halo cloud formation and transport of gas to the galactic disk.
Blue Large-amplitude Pulsators: The Possible Surviving Companions of Type Ia Supernovae
Authors: Meng Xiang-Cun , Han Zhan-Wen , Podsiadlowski Philipp , Li Jiao 
Published: November 2020

Abstract
The single degenerate (SD) model, one of the leading models for the progenitors of Type Ia supernovae (SNe Ia), predicts that there should be binary companions that survive the supernova explosion, which, in principle, should be detectable in the Galaxy. The discovery of such surviving companions could therefore provide conclusive support for the SD model. Several years ago, a new type of mysterious variable was discovered, the so-called blue large-amplitude pulsators (BLAPs). Here we show that all the properties of BLAPs can be reasonably well reproduced if they are indeed such surviving companions, in contrast to other proposed channels. This suggests that BLAPs could potentially be the long-sought surviving companions of SNe Ia. Our model also predicts a new channel for forming single hot subdwarf stars, consistent with a small group in the present sample of hot subdwarf stars.
Prediction and Understanding of Soft-proton Contamination in XMM-Newton: A Machine Learning Approach
Authors: Kronberg Elena A. , Gastaldello Fabio , Haaland Stein , Smirnov Artem , Berrendorf Max , Ghizzardi Simona , Kuntz K. D. , Sivadas Nithin , Allen Robert C. , Tiengo Andrea , Ilie Raluca , Huang Yu , Kistler Lynn 
Published: November 2020

Abstract
One of the major and unfortunately unforeseen sources of background for the current generation of X-ray telescopes are few tens to hundreds of keV (soft) protons concentrated by the mirrors. One such telescope is the European Space Agency’s (ESA) X-ray Multi-Mirror Mission (XMM-Newton). Its observing time lost due to background contamination is about 40%. This loss of observing time affects all the major broad science goals of this observatory, ranging from cosmology to astrophysics of neutron stars and black holes. The soft-proton background could dramatically impact future large X-ray missions such as the ESA planned Athena mission (http://www.the-athena-x-ray-observatory.eu/). Physical processes that trigger this background are still poorly understood. We use a machine learning (ML) approach to delineate related important parameters and to develop a model to predict the background contamination using 12 yr of XMM-Newton observations. As predictors we use the location of the satellite and solar and geomagnetic activity parameters. We revealed that the contamination is most strongly related to the distance in the southern direction, Z (XMM-Newton observations were in the southern hemisphere), the solar wind radial velocity, and the location on the magnetospheric magnetic field lines. We derived simple empirical models for the first two individual predictors and an ML model that utilizes an ensemble of the predictors (Extra-Trees Regressor) and gives better performance. Based on our analysis, future missions should minimize observations during times associated with high solar wind speed and avoid closed magnetic field lines, especially at the dusk flank region in the southern hemisphere.
Stellar Spins in the Open Cluster NGC 2516
Authors: Healy Brian F. , McCullough P. R. 
Published: November 2020

Abstract
Measuring the distribution of stellar spin axis orientations in a coeval group of stars probes the physical processes underlying the stars’ formation. In this paper, we use spectrophotometric observations of the open cluster NGC 2516 to determine the degree of spin alignment among its stars. We combine TESS light curves, ground-based spectroscopy from the Gaia-ESO and GALAH surveys, broadband stellar magnitudes from several surveys, and Gaia astrometry to measure 33 stellar inclinations and quantify overall cluster rotation. Our measurements suggest that stellar spins in this cluster are isotropically oriented, while allowing for the possibility that they are moderately aligned. An isotropic distribution of NGC 2516 spins would imply a star-forming environment in which turbulence dominated ordered motion, while a moderately aligned distribution would suggest a more substantial contribution from rotation. We also perform a three-dimensional analysis of the cluster’s internal kinematics, finding no significant signatures of overall rotation. Stemming from this analysis, we identify evidence of cluster contraction, suggesting possible ongoing mass segregation in NGC 2516.
Delivery of Pebbles from the Protoplanetary Disk into Circumplanetary Disks
Authors: Homma Toru , Ohtsuki Keiji , Maeda Natsuho , Suetsugu Ryo , Machida Masahiro N. , Tanigawa Takayuki 
Published: November 2020

Abstract
Small bodies likely existed in the late stage of planet formation either as remnants of the planetesimal formation stage or as fragments of larger planetesimals. Recent studies suggest that they may have played an important role in the formation of regular satellites of giant planets, but their delivery process into the circumplanetary disk has been poorly understood. Using orbital integration that incorporates the gas flow around the planet obtained by hydrodynamic simulation, we examine delivery of small bodies in the protoplanetary disk into circumplanetary disks. We find that large bodies can be captured when they experience strong gas drag near the midplane of the circumplanetary disk, while particles with Stokes number near unity tend to settle toward the midplane of the protoplanetary disk and can be captured near the outer edge of the circumplanetary disk. On the other hand, small particles coupled to the gas can be delivered into the circumplanetary disk with the vertically accreting gas and are captured near the surface of the circumplanetary disk over a wide radial region, if they are sufficiently stirred off the midplane of the protoplanetary disk. However, if the turbulence in the protoplanetary disk is not sufficiently strong, delivery of small particles by such a mechanism would not be efficient. Also, gas depletion in the vicinity of the planet’s orbit reduces the efficiency of the delivery. In these cases, larger bodies directly captured by gas drag from the circumplanetary disk would be the major building blocks of regular satellites.
Cosmological Insights into the Early Accretion of r-process-enhanced Stars. I. A Comprehensive Chemodynamical Analysis of LAMOST J1109+0754
Authors: Mardini Mohammad K. , Placco Vinicius M. , Meiron Yohai , Ishchenko Marina , Avramov Branislav , Mazzarini Matteo , Berczik Peter , Sedda Manuel Arca , Beers Timothy C. , Frebel Anna , Taani Ali , Donnari Martina , Al-Wardat Mashhoor A. , Zhao Gang 
Published: November 2020

Abstract
This study presents a comprehensive chemodynamical analysis of LAMOST J1109+0754, a bright (V = 12.8), extremely metal-poor ([Fe/H] = −3.17) star, with a strong r-process enhancement ([Eu/Fe] = +0.94 ± 0.12). Our results are based on the 7D measurements supplied by Gaia and the chemical composition derived from a high-resolution (R ∼ 110,000), high signal-to-noise ratio (

optical spectrum obtained by the 2.4 m Automated Planet Finder Telescope at Lick Observatory. We obtain chemical abundances of 31 elements (from lithium to thorium). The abundance ratios ([X/Fe]) of the light elements (Z ≤ 30) suggest a massive Population III progenitor in the 13.4–29.5 M
⊙ mass range. The heavy-element (30 < Z ≤ 90) abundance pattern of J1109+075 agrees extremely well with the scaled-solar r-process signature. We have developed a novel approach to trace the kinematic history and orbital evolution of J1109+0754 with a cOsmologically deRIved timE-varyiNg Galactic poTential (the ORIENT) constructed from snapshots of a simulated Milky Way analog taken from the Illustris-TNG simulation. The orbital evolution within this Milky Way–like galaxy, along with the chemical abundance pattern, implies that J1109+0754 likely originated in a low-mass dwarf galaxy located ∼60 kpc from the center of the Galaxy, which was accreted ∼6–7 Gyr ago, and that the star now belongs to the outer-halo population.
On the Presence of a Universal Acceleration Scale in Elliptical Galaxies
Authors: Chae Kyu-Hyun , Bernardi Mariangela , Sánchez Helena Domínguez , Sheth Ravi K. 
Published: November 2020

Abstract
Dark matter phenomena in rotationally supported galaxies exhibit a characteristic acceleration scale of g
† ≈ 1.2 × 10−10 m s−2. Whether this acceleration is a manifestation of a universal scale, or merely an emergent property with an intrinsic scatter, has been debated in the literature. Here we investigate whether a universal acceleration scale exists in dispersion-supported galaxies using two uniform sets of integral field spectroscopy (IFS) data from SDSS-IV MaNGA and ATLAS3D. We apply the spherical Jeans equation to 15 MaNGA and 4 ATLAS3D slow-rotator E0 (i.e., nearly spherical) galaxies. Velocity dispersion profiles for these galaxies are well determined with observational errors under control. Bayesian inference indicates that all 19 galaxies are consistent with a universal acceleration of

m s−2. Moreover, all 387 data points from the radial bins of the velocity dispersion profiles are consistent with a universal relation between the radial acceleration traced by dynamics and that predicted by the observed distribution of baryons. This universality remains if we include 12 additional non-E0 slow-rotator elliptical galaxies from ATLAS

. Finally, the universal acceleration from MaNGA and ATLAS3D is consistent with that for rotationally supported galaxies, so our results support the view that dark matter phenomenology in galaxies involves a universal acceleration scale.
ALMA Observations of Io Going into and Coming out of Eclipse
Authors: Pater Imke de , Luszcz-Cook Statia , Rojo Patricio , Redwing Erin , Kleer Katherine de , Moullet Arielle 
Published: November 2020

Abstract
We present 1 mm observations constructed from Atacama Large (sub)Millimeter Array (ALMA) data of SO2, SO, and KCl when Io went from sunlight into eclipse (2018 March 20) and vice versa (2018 September 2 and 11). There is clear evidence of volcanic plumes on March 20 and September 2. The plumes distort the line profiles, causing high-velocity (≳500 m s−1) wings and red-/blueshifted shoulders in the line profiles. During eclipse ingress, the SO2 flux density dropped exponentially, and the atmosphere re-formed in a linear fashion when reemerging in sunlight, with a “post-eclipse brightening” after ∼10 minutes. While both the in-eclipse decrease and in-sunlight increase in SO was more gradual than for SO2, the fact that SO decreased at all is evidence that self-reactions at the surface are important and fast, and that in-sunlight photolysis of SO2 is the dominant source of SO. Disk-integrated SO2 in-sunlight flux densities are ∼2–3 times higher than in eclipse, indicative of a roughly 30%–50% contribution from volcanic sources to the atmosphere. Typical column densities and temperatures are N ≈ (1.5 ± 0.3) × 1016 cm−2 and T ≈ 220–320 K both in sunlight and in eclipse, while the fractional coverage of the gas is two to three times lower in eclipse than in sunlight. The low-level SO2 emissions present during eclipse may be sourced by stealth volcanism or be evidence of a layer of noncondensible gases preventing complete collapse of the SO2 atmosphere. The melt in magma chambers at different volcanoes must differ in composition to explain the absence of SO and SO2, but simultaneous presence of KCl over Ulgen Patera.