AGN/galaxy separation in the ROSAT Bright Survey
  The X-ray luminosity function (XLF) of galaxies is dominated by AGN (classified by their optical spectra) above   Lx=10**42 erg/s, below this value by normal galaxies. The X-ray flux of AGN at low X-ray luminosity therefore contains contributions from stellar processes (winds, supernova explosions etc.). Until now it is not clear which fraction of the observed X-ray flux has to be associated to the underlying stellar emission. We started to investigate a complete luminosity-limited sample of AGN and galaxies with log Lx < 42.5 to discriminate between the nuclear and galaxy flux. Using the ROSAT HRI data we calculated the radial wobble-corrected profiles of the sources which were compared to a new HRI point spread function (PSF) template derived from 21 X-ray bright stars. The majority of the low-luminosiy AGN shows evidence for a significant fraction of extended X-ray emission. 
I. Lehmann, G. Hasinger, A.D. Schwope, Th. Boller