Searches for optical evidence of galaxy evolution

With improved photographic techniques and fast plate-measuring machines it is now possible to use deep photographic plates for statistical studies of faint galaxies. The evolutionary effects detectable with these samples are expected to be significant. Two such effects are currently being monitored by using P.D.S. and Cosmos scans of Schmidt and 4 m plates. First, number-magnitude counts are being used to constrain luminosity evolution, and secondly, correlation analyses of galaxy positions can be used to test physical models of galaxy clustering over large look-back times. The data can be reliably studied to magnitudes as faint as J approximately 24.5. Interpretation of the results is hampered by poor knowledge of the intrinsic properties of normal galaxies. (author)