The influence of binaries on the number statistics and population synthesis of large groups of stars.

Large telescopes make it possible to obtain high signal/ noise spectra of distant galaxies. The spectrum of a galaxy is obviously the combination of spectra of all stars in different evolutionary phases, single stars and close binaries. In order to make theoretical predictions and compare them to observation, up to date evolutionary libraries are needed for a wide range of stellar parameters (initial mass, chemical composition, binary period and binary mass ratio, ...). It is our purpose to update the binary evolutionary code and to extend our close binary evolutionary library. The results will then be combined with single star evolution libraries in order to study special features of galaxies assuming different kinds of star distributions (initial mass functions, binary frequencies, mass ratio distributions, period distributions,...). The project thus consists of three main parts: a) Continuous update of the library of the binary evolutionary code and the completion of an extended evolutionary library. b) High signal/noise spectra of distant galaxies and their interpretation. c) Using evolutionary libraries, predicting how the spectra of these galaxies should look like and detailed comparison with observations.