The role of star clusters in the evolution of the Galactic disk

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Our basic aim is understanding the role of star clusters in the evolution of the Galactic disk. This involves a study of young (embedded) clusters, their survival or decay, as well as a study of the fate of classical open clusters. We want to determine the stellar input to the disk at every stage of cluster evolution. Our observational basis will be the new deep sky survey, PPM-S (Positions and Proper Motions - Survey, Röser and Demleitner 2009), of some 800 million stars (and galaxies) down to about R = 20 mag. We will cover 4 major topics:a) Using PPM-S, we will study the youngest, possibly embedded generation of open clusters. These play an important role in our understanding of star formation and the evolution of the Galactic disk as a whole. However, most of them are still lacking even basic parameters like distance and age. We will determine these parameters using PPM-S.b) We will carry out a search for unknown clusters of all ages (looking for spatial and proper motion clusterings in PPM-S having consistent photometry). This results in an unbiased census within a distance of at least 3 kpc from the Sun and down to a well-defined magnitude limit.c) We will compare cluster formation rates of embedded and classical open clusters and construct the initial luminosity function of clusters (CILF).d) We will study the (about 15) open clusters in our immediate neighbourhood (d < 250pc) down to low-mass (0.2M⊙) members. In addition, we will construct a full stellar census of the Scorpius-Centaurus association. For both purposes, PPM-S is ideally suited.Although this is a stand-alone (autonomous) project, it is complementary to the subproject B2 “Open Star Clusters in the Milky Way” of the proposed SFB “The Milky Way System” from Heidelberg. Should both be approved we see synergetic effects: transfer of know-how to the younger colleagues of the SFB especially from the experience of our Russian partners, and developing tools for the future exploitation of the GAIA observations.