Astronomy & Astrophysics

Free access article

Issue		A&A Volume 455, Number 2, August IV 2006
Page(s)		L17 - L20
Section		Letters
DOI		10.1051/0004-6361:20065567

A&A 455, L17-L20 (2006)
DOI: 10.1051/0004-6361:20065567

Letter

Clusters in the solar neighbourhood: how are they destroyed?

H. J. G. L. M. Lamers^{1, 2} and M. Gieles¹

¹ Astronomical Institute, Utrecht University, Princetonplein 5, 3584CC Utrecht, The Netherlands
e-mail: [lamers;gieles]@astro.uu.nl
² SRON Laboratory for Space Research, Sorbonnelaan 2, 3584CC, Utrecht, The Netherlands

(Received 8 May 2006 / Accepted 26 June 2006)

Abstract
We predict the survival time of initially bound star clusters in the solar neighbourhood taking into account: (1) stellar evolution, (2) tidal stripping, (3) shocking by spiral arms and (4) encounters with giant molecular clouds. We find that the predicted dissolution time is $\mbox{$t_{\rm dis}$ }= 1.7 (\mbox{$M_i$ }/10^4~\mbox{$M_{\odot}$ })^$ Gyr for clusters in the mass range of $10^2 < \mbox{$M_i$ }< 10^5~\mbox{$M_{\odot}$ }$ . The resulting predicted shape of the logarithmic age distribution agrees very well with the empirical one, derived from a complete sample of clusters in the solar neighbourhood within 600 pc. The required scaling factor implies a star formation rate of 4 $\times$ 10² $M_{\odot}$ Myr^-1 within 600 pc from the Sun or a surface formation rate of 3.5 $\times$ 10^-10 $M_{\odot}$ yr^-1 pc^-2 for stars in bound clusters with an initial mass in the range of 10² to 3 $\times$ 10⁴ $M_{\odot}$ .

Key words: Galaxy: open clusters and associations: general -- Galaxy: solar neighbourhood -- Galaxy: disk -- Galaxy: general -- Galaxies: star clusters -- Galaxy: kinematics and dynamics

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