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The Super Eight Galaxies: Properties of a Sample of Very Bright Galaxies at 7 < z < 8
Holwerda, Benne W.; Illingworth, Garth D.; Bouwens, Rychard J. +12 more
We present the Super Eight galaxies—a set of very luminous, high-redshift (7.1 < z < 8.0) galaxy candidates found in the Brightest of Reionizing Galaxies (BoRG) Survey fields. The original sample includes eight galaxies that are Y-band dropout objects with H-band magnitudes of m H < 25.5. Four of these objects were originally…
Can an Unobserved Concentration of Magnetic Flux Above the Poles of the Sun Resolve the Open Flux Problem?
Downs, Cooper; Riley, Pete; Linker, Jon A. +3 more
Global models of the extended solar corona, driven by observed photospheric magnetic fields, generally cannot reproduce the amplitude of the measured interplanetary magnetic field at 1 au (or elsewhere in the heliosphere), often underestimating it by a factor of two or more. Some modelers have attempted to resolve this “open flux” problem by adjus…
Nine tiny star clusters in Gaia DR1, PS1, and DES
Belokurov, V.; Koposov, S. E.; Torrealba, G.
We present the results of a systematic Milky Way satellite search performed across an array of publicly available wide-area photometric surveys. Our aim is to complement previous searches by widening the parameter space covered. Specifically, we focus on objects smaller than 1 arcmin and include old, young, metal-poor, and metal-rich stellar popul…
Nature versus nurture: what regulates star formation in satellite galaxies?
Hirschmann, Michaela; De Lucia, Gabriella; Fontanot, Fabio
We use our state-of-the-art Galaxy Evolution and Assembly (GAEA) semi-analytic model to study how and on which time-scales star formation is suppressed in satellite galaxies. Our fiducial stellar feedback model, implementing strong stellar driven outflows, reproduces relatively well the variations of passive fractions as a function of galaxy stell…
The EBLM Project. V. Physical properties of ten fully convective, very-low-mass stars
Smalley, Barry; Hellier, Coel; Triaud, Amaury H. M. J. +28 more
Measurements of the physical properties of stars at the lower end of the main sequence are scarce. In this context we report masses, radii and surface gravities of ten very-low-mass stars in eclipsing binary systems, with orbital periods of the order of several days. The objects probe the stellar mass-radius relation in the fully convective regime…
Surveys of Clumps, Cores, and Condensations in Cygnus X. I. A New Catalog of ∼0.1 pc Massive Dense Cores
Qiu, Keping; Liu, Junhao; Cao, Yue +3 more
Using infrared to (sub)millimeter data from Spitzer, Herschel, the James Clerk Maxwell Telescope, and the IRAM 30 m telescope, we conducted an unbiased survey of the massive dense cores (MDCs) in the Cygnus X molecular cloud complex, aimed at characterizing the physical conditions of high-mass star formation (HMSF) at ∼0.1 pc scales. We created 5°…
The velocity anisotropy of the Milky Way satellite system
Grand, Robert J. J.; Gómez, Facundo A.; Fattahi, Azadeh +9 more
We analyse the orbital kinematics of the Milky Way (MW) satellite system utilizing the latest systemic proper motions for 38 satellites based on data from Gaia Data Release 2. Combining these data with distance and line-of-sight velocity measurements from the literature, we use a likelihood method to model the velocity anisotropy, β, as a function…
Machine Learning Applied to Star-Galaxy-QSO Classification and Stellar Effective Temperature Regression
Bai, Yu; Wang, Song; Yang, Fan +1 more
In modern astrophysics, machine learning has increasingly gained popularity with its incredibly powerful ability to make predictions or calculated suggestions for large amounts of data. We describe an application of the supervised machine-learning algorithm, random forests (RF), to the star/galaxy/QSO classification and the stellar effective tempe…
Galactic rotation from Cepheids with Gaia DR2 and effects of non-axisymmetry
Bovy, Jo; Matsunaga, Noriyuki; Kawata, Daisuke +1 more
We apply a simple axisymmetric disc model to 218 Galactic Cepheids whose accurate measurements of the distance and velocities are obtained by cross-matching an existing Cepheids catalogue with the Gaia DR2 data. Our model fit determines the `local centrifugal speed', Vc - defined as the rotation speed required to balance the local radia…
Particle-in-cell Simulations of Firehose Instability Driven by Bi-Kappa Electrons
Lazar, M.; Poedts, S.; Viñas, A. F. +4 more
We report the first results from particle-in-cell simulations of the fast-growing aperiodic electron firehose instability driven by the anisotropic bi-Kappa distributed electrons. Such electrons characterize space plasmas, e.g., solar wind and planetary magnetospheres. Predictions made by the linear theory for full wave-frequency and wave-vector s…