The Gaia-ESO Survey: Discovery of a spatially extended low-mass population in the Vela OB2 association

TL;DR

The study reveals a widespread, young, low-mass stellar population in the Vela OB2 association, indicating complex formation history and spatial distribution of stars in this nearby young region.

Contribution

It identifies a kinematically distinct, young low-mass population in Vela OB2, expanding understanding of star formation and cluster dispersal in this region.

Findings

Discovery of a young, low-mass population spread over several square degrees.

The secondary population shares properties with stars near γ² Velorum.

Implication of cluster expansion or dispersed formation in Vela OB2.

Abstract

The nearby (distance~350-400 pc), rich Vela OB2 association, includes $\gamma^2$ 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 $\gamma^2$ Velorum. Here we analyse the results of Gaia-ESO survey observations of NGC 2547, a 35 Myr cluster located two degrees south of $\gamma^2$ 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 $\gamma^2$ 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 $\gamma^2$ Velorum that expanded after gas expulsion or formed in a less dense environment that is spread over the whole Vela OB2 region.