Journal Article

The evolution of the surface brightness of a star cluster as a result of residual star-forming gas expulsion

F. Lüghausen, G. Parmentier, J. Pflamm-Altenburg and P. Kroupa

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 423, issue 3, pages 1985-1991
Published in print July 2012 | ISSN: 0035-8711
Published online June 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.20302.x
The evolution of the surface brightness of a star cluster as a result of residual star-forming gas expulsion

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Direct N-body calculations are presented of the early evolution of exposed clusters to quantify the influence of gas expulsion on the time-varying surface brightness. By assuming that the embedded OB stars drive out most of the gas after a given time delay, the change of the surface brightness of expanding star clusters is studied.

The influence of stellar dynamics and stellar evolution is discussed. The growth of the core radii of such models shows a remarkable core re-virialization. The decrease of the surface mass density during gas expulsion is large and is only truncated by this re-virialization process. However, the surface brightness within a certain radius does not increase noticeably. Thus, an embedded star cluster cannot reappear in observational surveys after re-virialization. This finding has a bearing on the observed infant mortality fraction.

Keywords: methods: miscellaneous; open clusters and associations: general

Journal Article.  3226 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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