Schedule Jan 17, 2009
Star Clusters and Field Star Populations in the Spiral Galaxy NGC 4395
Esteban Silva-Villa (Univ. Utrect)

It is generally recognized that a large fraction of stars are initially born in clusters. However, due to stellar evolution and dynamical effects, clusters gradually lose mass and disrupt, so that most stars eventually end up belonging to the field. Understanding this process is of paramount importance if we wish to constrain the star formation histories of external galaxies by studying their cluster populations. Our aim is to understand the detailed relation between field stars and star clusters by simultaneously studying the two in a number of nearby galaxies. These galaxies are all close enough that we can easily identify star clusters as extended objects and obtain photometry for individual field stars. As a pilot study, we present results for the late-type spiral NGC 4395. A comparison between Padova group theoretical isochrones and observed field stars colour-magnitude diagrams allowed us to estimate the star formation history. Using single stellar population models fitting we calculated the mass and age for the cluster candidates. We observed a decreasing star formation history in our fields of view and a cluster population with low masses (Log(Mass/Mo) <= 4.5).

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