O stars of the Galactic starburst NGC 3603

Here we build on the discovery by Mohr-Smith et al. of a large number of reddened O stars around this cluster. We construct a list of 288 candidate O stars with proper motions (PMs), in a region of sky spanning 1.5x1.5deg^2^ centred on NGC 3603, by cross-matching the Mohr-Smith et al. catalogue with Gaia DR2.

This provides the basis for a first comprehensive examination of the PMs of these massive stars in the halo of NGC 3603, relative to the much better studied central region. We identify up to 11 likely O star ejections - 8 of which would have been ejected between 0.60 and 0.95Myr ago (supporting the age of ~1Myr that has been attributed to the bright cluster centre). Seven candidate ejections are arranged in a partial ring to the south of the cluster core spanning radii of 9-18arcmin (18-36pc if the cluster is 7kpc away).