The VLT-FLAMES Tarantula Survey: VI. Evidence for rotation of the young massive cluster R136

Abstract

Although it has important ramifications for both the formation of star clusters and their subsequent dynamical evolution, rotation remains a largely unexplored characteristic of young star clusters (few Myr). Using multi-epoch spectroscopic data of the inner regions of 30 Doradus in the Large Magellanic Cloud obtained as part of the VLT-FLAMES Tarantula Survey, we search for rotation of the young massive cluster R136. From the radial velocities of 36 apparently single O-type stars within a projected radius of 10 pc from the centre of the cluster, we find evidence, at the 95% confidence level, for rotation of the cluster as a whole. We use a maximum likelihood method to fit simple rotation curves to our data and find a typical rotational velocity of ∼3 km s -1. When compared to the low velocity dispersion of R136, our result suggests that star clusters may form with at least ∼20% of the kinetic energy in rotation. © 2012 ESO.