The Luminosity Function of Field Galaxies in the CNOC1 Redshift Survey

Abstract

We have computed the luminosity function for a sample of 389 field galaxies from the Canadian Network for Observational Cosmology cluster redshift survey (CNOC1) over the redshift range z = 0.2-0.6. We find Schechter parameters M*r-5 log h = -20.8 ± 0.4 and α = -1.3 ± 0.2 in rest-frame Gunn r, and M*BAB- 5 log h = -19.6 ± 0.3 and α = -0.9 ± 0.2 in rest-frame BAB. We have also split our sample at the color of a redshifted but nonevolving Sbc galaxy and find distinctly different luminosity functions for red and blue galaxies. Red galaxies have a shallow slope α ≈ -0.4 and dominate the bright end of the luminosity function, while blue galaxies have a steep α ≈ -1.4 and prevail at the faint end. Comparisons of the CNOC1 results to analogous intermediate-redshift luminosity functions from the Canada-France (CFRS) and Autofib redshift surveys show broad agreement among these independent samples, but there are also significant differences which will require larger samples to resolve. Also, in CNOC1 the red galaxy luminosity density stays about the same over the range z = 0.2-0.6, while the blue galaxy luminosity density increases steadily with redshift. These results are consistent with the trend of the luminosity density versus redshift relations seen in the CFRS, although the normalizations of the luminosity densities appear to differ for blue galaxies. Comparison to the local luminosity function from the Las Campanas redshift survey (LCRS) shows that the luminosity density at z ≈ 0.1 is only about half that seen at z ≈ 0.4. A change in the luminosity function shape, particularly at the faint end, appears to be required to match the CNOC1 and LCRS luminosity functions, if galaxy evolution is the sole cause of the differences seen. However, it should be noted that the specific details of the construction of different surveys may complicate the comparison of results and so may need to be considered carefully.