Stellar Systems Group

Sacco, G. G.; Jeffries, R. D.; Randich, S.; Franciosini, E.; Jackson, R. J.; Cottaar, M.; Spina, L.; Palla, F.; Mapelli, M.; Alfaro, E. J.; Bonito, R.; Damiani, F.; Frasca, A.; Klutsch, A.; Lanzafame, A.; Bayo, A.; Barrado, D.; Jimenez-Esteban, F.; Gilmore, G.; Micela, G.; Vallenari, A.; Allende Prieto, C.; Flaccomio, E.; Carraro, G.; Costado, M. T.; Jofre, P.; Lardo, C.; Magrini, L.; Morbidelli, L.; Prisinzano, L.; Sbordone, L.
Astronomy & Astrophysics, Volume 574, id.L7, 5 pp. (2015).
02/2015

ABSTRACT

The nearby (distance ~ 350-400 pc), rich Vela OB2 association, includes γ² Velorum, one of the most massive binaries in the solar neighbourhood and an excellent laboratory for investigating the formation and early evolution of young clusters. Recent Gaia-ESO survey observations have led to the discovery of two kinematically distinct populations in the young (10-15 Myr) cluster immediately surrounding γ² Velorum. Here we analyse the results of Gaia-ESO survey observations of NGC 2547, a 35 Myr cluster located two degrees south of γ² Velorum. The radial velocity distribution of lithium-rich pre-main sequence stars shows a secondary population that is kinematically distinct from and younger than NGC 2547. The radial velocities, lithium absorption lines, and the positions in a colour-magnitude diagram of this secondary population are consistent with those of one of the components discovered around γ² Velorum. This result shows that there is a young, low-mass stellar population spread over at least several square degrees in the Vela OB2 association. This population could have originally been part of a cluster around γ² Velorum that expanded after gas expulsion or formed in a less dense environment that is spread over the whole Vela OB2 region.

Based on observations made with the ESO/VLT, at Paranal Observatory, under program 188.B-3002 (The Gaia-ESO Public Spectroscopic Survey).Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/574/L7