Volume 578, June 2015
|Number of page(s)||11|
|Section||Galactic structure, stellar clusters and populations|
|Published online||29 May 2015|
The Gaia-ESO Survey: N-body modelling of the Gamma Velorum cluster
INAF–Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122
2 Astrophysics Group, Keele University, Keele, Staffordshire ST5 5BG, UK
3 Institute for Computational Science, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
4 INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Florence, Italy
5 Institute for Astronomy, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland
6 Instituto de Astrofísica de Andalucía-CSIC, Apdo. 3004, 18080 Granada, Spain
7 INAF–Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
8 INAF–Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
9 Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Università di Catania, via S. Sofia 78, 95123 Catania, Italy
10 INAF–Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
11 ASI Science Data Center, via del Politecnico SNC, 00133 Roma, Italy
12 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
13 Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK
Accepted: 9 April 2015
The Gaia-ESO Survey has recently unveiled the complex kinematic signature of the Gamma Velorum cluster: this cluster is composed of two kinematically distinct populations (hereafter, population A and B), showing two different velocity dispersions and a relative ~ 2 km s-1 radial velocity (RV) shift. In this paper, we propose that the two populations of the Gamma Velorum cluster originate from two different sub-clusters, born from the same parent molecular cloud. We investigate this possibility by means of direct-summation N-body simulations. Our scenario is able to reproduce not only the RV shift and the different velocity dispersions, but also the different centroid (~0.5 pc), the different spatial concentration and the different line-of-sight distance (~5 pc) of the two populations. The observed 1−2 Myr age difference between the two populations is also naturally explained by our scenario, in which the two sub-clusters formed in two slightly different star formation episodes. Our simulations suggest that population B is strongly supervirial, while population A is close to virial equilibrium. We discuss the implications of our models for the formation of young star clusters and OB associations in the Milky Way.
Key words: methods: numerical / open clusters and associations: individual: Gamma Velorum cluster / stars: formation / stars: kinematics and dynamics
© ESO, 2015
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