The Evolution of Field Galaxies

During the late 1980’s, successively deeper redshift surveys carried out with multi-object spectrographs on 4-m class telescopes produced growing evidence for evolution in the galaxy population. While some evolution had been expected from analysis of the galaxy number counts, the surprise indication from the first deep redshift surveys was that this appeare involve moderate luminosity galaxies lying at moderate redshifts (hurst et al. 1988, Colless et al. 1990, Cowie et al. 1991). However, results were suggestive, these early surveys suffered a number of problems that hampered their interpretation: (a) the samples were small, especially at the faintest levels, weight was limited and analysis was based on crude of the data such as the median redshift of sample (b) the typical redshifts were small (z ≪0.5), so t could only be seen against “local” populations quite different — indeed the local luminosity fi poorly defined (Loveday et al. 1992, Marzke (c) the samples were selected in the observed B-band, so that comparison with local samples was based on the poorly constrained ultraviolet properties and relative numbers of galaxies of different types.