Journal Article

The influence of gas expulsion and initial mass segregation on the stellar mass function of globular star clusters

Michael Marks, Pavel Kroupa and Holger Baumgardt

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 386, issue 4, pages 2047-2054
Published in print June 2008 | ISSN: 0035-8711
Published online April 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13165.x
The influence of gas expulsion and initial mass segregation on the stellar mass function of globular star clusters

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Recently, De Marchi, Paresce & Pulone studied a sample of 20 globular clusters and found that all clusters with high concentrations have steep stellar mass functions while clusters with low concentration have comparatively shallow mass functions. No globular clusters were found with a flat mass function and high concentration. This seems curious since more concentrated star clusters are believed to be dynamically more evolved and should have lost more low-mass stars via evaporation, which would result in a shallower mass function in the low-mass part.

We show that this effect can be explained by residual-gas expulsion from initially mass segregated star clusters, and is enhanced further through unresolved binaries. If gas expulsion is the correct mechanism to produce the observed trend in the c–α-plane, then observation of these parameters would allow to constrain cluster starting conditions such as star formation efficiency and the time-scale of gas expulsion.

Keywords: stellar dynamics; methods: N-body simulations; binaries: general; stars: luminosity function, mass function; globular clusters: general

Journal Article.  5669 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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