Galaxy evolution at low redshift? -- I. Optical counts

Research paper by Emmanuel Bertin, Michel Dennefeld

Indexed on: 13 May '96Published on: 13 May '96Published in: Astrophysics


We present bright galaxy number counts in the blue (16<Bj<21) and red (15<R<19.5) passbands, performed over 145 sq. degrees, both in the northern and southern galactic hemispheres. The work was conducted on Schmidt plates digitized with the MAMA machine, and individually calibrated using an adequate number of CCD sequences. We find a relatively large density of bright galaxies implying a ``high'' normalization of the local luminosity function. Our counts and colour distributions exhibit no large departure from what standard no-evolution models predict to magnitudes Bj<21, removing the need for evolution of the non-dwarf galaxy population in the optical, out to z # 0.2. This result disagrees with that of Maddox et al. (1990) on the APM catalog. We show that the APM and similar catalogs may be affected by a systematic magnitude scale error which would explain this discrepancy.