The VLT-FLAMES Tarantula Survey^⋆

VI. Evidence for rotation of the young massive cluster R136

¹ Scottish Universities Physics Alliance (SUPA), Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ, UK
e-mail: vhb@roe.ac.uk
² Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
³ UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ, UK
⁴ Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Postbus 94249, 1090 GE, Amsterdam, The Netherlands
⁵ Excellence Cluster Universe, Technische Universität München, Boltzmannstr. 2, 85748 Garching, Germany
⁶ Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
⁷ Institute of Astronomy with NAO, Bulgarian Academy of Sciences, PO Box 136, 4700 Smoljan, Bulgaria
⁸ School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
⁹ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 87548 Garching bei München, Germany
¹⁰ Harvard-Smithsonian CfA, 60 Garden Street, Cambridge, MA 02138, USA
¹¹ Astrophysics Group, Lennard-Jones Laboratories, Keele University, Staffordshire ST5 5BG, UK

Received: 24 April 2012
Accepted: 31 July 2012

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.