SCYON Abstract

Received on February 28 2006

Evidence for the Strong Effect of Gas Removal on the Internal Dynamics of Young Stellar Clusters

Authors	Nate Bastian(¹) and Simon Goodwin(²)
Affiliation	(¹) Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT (²) Department of Physics and Astronomy, The University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH
Accepted by	Monthly Notices of the Royal Astronomical Society
Contact	bastian@star.ucl.ac.uk
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Abstract

We present detailed luminosity profiles of the young massive clusters M82-F, NGC 1569-A, and NGC 1705-1 which show significant departures from equilibrium (King and EFF) profiles. We compare these profiles with those from N-body simulations of clusters which have undergone the rapid removal of a significant fraction of their mass due to gas expulsion. We show that the observations and simulations agree very well with each other suggesting that these young clusters are undergoing violent relaxation and are also losing a significant fraction of their stellar mass. That these clusters are not in equilibrium can explain the discrepant mass-to-light ratios observed in many young clusters with respect to simple stellar population models without resorting to non-standard initial stellar mass functions as claimed for M82-F and NGC 1705-A. We also discuss the effect of rapid gas removal on the complete disruption of a large fraction of young massive clusters ("infant mortality"). Finally we note that even bound clusters may lose >50% of their initial stellar mass due to rapid gas loss ("infant weight-loss").