Colour related properties of galaxies on deep Schmidt plates

Broadband J-R colours have been obtained from COSMOS measurements of UKST plates, for a large sample of (approximately 20 000) galaxies, complete to limiting magnitude J = 21.5. The distribution of colours found is consistent with other studies. The modelling of this distribution shows that galaxies, in particular the later types, have bluer colours than are predicted by current models of galaxy K-corrections and luminosity evolution. Galaxy colours combined with other image parameters may be a practical method of automatically differentiating between ellipticals and spirals at faint limits. The spatial distributions of 'colour subsamples' of data are examined using correlation function techniques. (author)