Evolution of Galaxy and Quasar Clustering

We study the evolution of correlation function of dark matter halos in the CDM class of models. We show that the halo correlation function does not evolve in proportion with the correlation function of the underlying mass distribution. Earliest halos to collapse, which correspond to rare peaks in the density field, cluster very strongly. The amplitude of halo correlation function decreases from its initial, large, value. This decrease continues till the average peaks have collapsed, after which, the amplitude grows at a slow rate. This behaviour is shown to be generic and the epoch of minimum amplitude depends only on the rms fluctuations in mass at the relevant scale and, to a much smaller extent, on the slope of the power spectrum at that scale. We discuss the relevance of this result for interpretation of observations of galaxy and quasar clustering.