Flickering Faint Galaxies: Few and Far Between

Optical variability in galaxies at high redshift is a tracer of evolution in AGN activity, and should provide a useful constraint on models of galaxy evolution, AGN structure, and cosmology. We studied optical variability in multiple deep GCD and photographic surveys of blank fields for galaxies with B_j_ = 20-25 mag. Weakly variable objects are far more common than strongly variable ones. For objects near B_j_ = 22, 0.74% +/- 0.2% vary by 0.026 mag rms or more, over a decade. This is small compared with previous claims based on photographic surveys, and also small compared with the fraction of bright quasars (5% at B_j_= 20 mag) or Seyferts (~1% -2% for B_j_ < 18). The fraction of objects that vary increases slowly with magnitude. Detection probabilities and error rates were checked by simulations and statistical analysis of fluctuations of sample sky spots.