@article{WolfWisotzkiBorchetal.2003,
  author    = {Wolf, C. and Wisotzki, Lutz and Borch, Andrea and Dye, S. and Kleinheinrich, M. and Meisenheimer, Klaus},
  title     = {The evolution of faint AGN between z similar or equal to 1 and z similar or equal to 5 from the COMBO-17 survey},
  year      = {2003},
  abstract  = {We present a determination of the optical/UV AGN luminosity function and its evolution, based on a large sample of faint (R < 24) QSOs identified in the COMBO-17 survey. Using multi-band photometry in 17 filters within 350 nm <~ lambdaobs <~ 930 nm, we could simultaneously determine photometric redshifts with an accuracy of sigmaz <0.03 and obtain spectral energy distributions. The redshift range covered by the sample is 1.2 < z < 4.8, which implies that even at z =~ 3, the sample reaches below luminosities corresponding to MB = -23, conventionally employed to distinguish between Seyfert galaxies and quasars. We clearly detect a broad plateau-like maximum of quasar activity around z =~ 2 and map out the smooth turnover between z =~ 1 and z =~ 4. The shape of the LF is characterised by some mild curvature, but no sharp ``break'' is present within the range of luminosities covered. Using only the COMBO-17 data, the evolving LF can be adequately described by either a pure density evolution (PDE) or a pure luminosity evolution (PLE) model. However, the absence of a strong L*-like feature in the shape of the LF inhibits a robust distinction between these modes. We present a robust estimate for the integrated UV luminosity generation by AGN as a function of redshift. We find that the LF continues to rise even at the lowest luminosities probed by our survey, but that the slope is sufficiently shallow that the contribution of low-luminosity AGN to the UV luminosity density is negligible. Although our sample reaches much fainter flux levels than previous data sets, our results on space densities and LF slopes are completely consistent with extrapolations from recent major surveys such as SDSS and 2QZ.},
  language  = {en}
}
@article{WolfDyeKleinheinrichetal.2001,
  author    = {Wolf, C. and Dye, S. and Kleinheinrich, M. and Meisenheimer, Klaus and Rix, Hans-Walter and Wisotzki, Lutz},
  title     = {Deep BVR photometry of the Chandra Deep Field South from the COMBO-17 survey},
  year      = {2001},
  abstract  = {We report on deep multi-color imaging (R5sigma = 26) of the Chandra Deep Field South, obtained with the Wide Field Imager (WFI) at the MPG/ESO 2.2 m telescope on La Silla as part of the multi-color survey COMBO-17. As a result we present a catalogue of 63 501 objects in a field measuring 31farcm5 x 30arcmin with astrometry and BVR photometry. A sample of 37 variable objects is selected from two-epoch photometry. We try to give interpretations based on color and variation amplitude.},
  language  = {en}
}