The low mass population of the Vela OB2 association from Gaia

TL;DR

This study uses Gaia data to identify and analyze the low-mass pre-main-sequence stars in the Vela OB2 association, revealing spatial distribution differences and potential new clusters, thus enhancing understanding of cluster formation.

Contribution

The paper introduces a new photometric selection method combining Gaia and 2MASS data to identify low-mass stars in Vela OB2 without relying on astrometry.

Findings

Identified known clusters around $\gamma^2$ Velorum and NGC-2547.

Discovered potential new stellar over-densities.

Found differences in spatial distributions of low- and high-mass stars.

Abstract

The first Gaia Data Release presents an opportunity to characterise the low-mass population of OB associations, providing larger statistical samples and better constraints on the formation and evolution of clusters and associations. Using previously known low mass members in a small region of Vela OB2 we have designed selection criteria that combine Gaia and 2MASS photometry, independently of any astrometric information, to identify low-mass pre-main-sequence (PMS) stars over the wider association area. Our method picks out the known clusters of young stars around $\gamma^2$ Velorum and NGC-2547, but also identifies other over-densities that may represent previously unknown clusters. There are clear differences in the spatial distributions of the low-mass and the high-mass OB populations, suggesting either that the structure and dynamics of these populations has evolved separately or that the initial mass function can vary considerably on small scales within a single association.