Clusters in the solar neighbourhood: how are they destroyed?

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 t(dis) = 1.7(M-i/10(4) M-circle dot)(0.67) Gyr for clusters in the mass range of 10(2) < M-i < 10(5) M-circle dot. 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 x 10(2) M-circle dot Myr(-1) within 600 pc from the Sun or a surface formation rate of 3.5 x 10(-10) M-circle dot yr(-1) pc(-2) for stars in bound clusters with an initial mass in the range of 10(2) to 3 x 10(4) M-circle dot.