Towards a new galaxy template library for multi-colour classification

The COMBO-17 survey cite(Wolf et al., 2002) contains ≈ 40000 galaxies down to R=24 mag on an area of one square degree, obtained with the wide field imager at the 2.2 m telescope at La Silla. A multi-colour classification on the basis of 5 broadband and 12 medium band filters (=17 bands) yields accurate redshifts (σz ≤ 0.01 at the bright end up to σz ≈ 0.1 at the faint end) and spectral energy distribution types (SEDs) when using observed galaxy templates from (Kinney et al.,1996). However, there is an obvious weakness in this classification scheme: The relation between star formation history and SED remains unclear. It is therefore impossible to draw firm conclusions about the age of the underlying stellar population and the expected aging between z ≈ 1 and z ≈ 0 can not be quantified. We will present first results of our attempt to replace the observed templates with model spectra from the PEGASE code (Fioc and Rocca-Volmerange, 1997), in order to get a better handle on the star formation history.