Search Publications
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…
H0LiCOW - X. Spectroscopic/imaging survey and galaxy-group identification around the strong gravitational lens system WFI 2033-4723
Smith, M.; Annis, J.; Bertin, E. +65 more
Galaxies and galaxy groups located along the line of sight towards gravitationally lensed quasars produce high-order perturbations of the gravitational potential at the lens position. When these perturbation are too large, they can induce a systematic error on H0 of a few per cent if the lens system is used for cosmological inference an…
SPHERE view of the jet and the envelope of RY Tauri
Ménard, F.; Fantinel, D.; Podio, L. +40 more
Context. Jets are rarely associated with pre-main sequence intermediate-mass stars. This contrasts with the frequent detection of jets in lower mass or younger stars. Optical and near-IR observations of jet-driving sources are often hindered by the presence of a natal envelope.
Aims: Jets around partly embedded sources are a useful diagnostic…
The Orbits of 451 Wide Visual Double Stars
Izmailov, I. S.
Based on positional observations, we have determined the orbits of 130 visual double stars for the first time and improved the orbits of 321 stars. The histogram of eccentricities for all of the derived orbits corresponds to the relation f = 2e. The period distribution has two pronounced maxima at P ≈ 200 and ≈550 yr. The ephemeris relative positi…
Multiple nitrogen reservoirs in a protoplanetary disk at the epoch of comet and giant planet formation
Forveille, T.; Hily-Blant, P.; Magalhaes de Souza, V. +1 more
The isotopic ratio of nitrogen measured in primitive Solar System bodies shows a broad range of values, the origin of which remains unknown. One key question is whether these isotopic reservoirs of nitrogen predate the comet formation stage or are posterior to it. Another central question is elucidating the processes that can produce the observed …
Li Evolution and the Open Cluster NGC 6819: A Correlation between Li Depletion and Spindown in Dwarfs More Massive Than the F-Dwarf Li-Dip
Twarog, Bruce A.; Anthony-Twarog, Barbara J.; Deliyannis, Constantine P. +1 more
Spectroscopy of 333 NGC 6819 stars and Gaia astrometry are used to map Li evolution from the giant branch tip to 0.5 mag below the Li dip. Isochrone comparison with [Fe/H] = -0.04, based upon neural network spectroscopic analysis, produces an age of 2.25 (2.4) Gyr for E(B - V) = 0.16 (0.14) and (m - M) = 12.40 (12.29). Despite originating outside …