MERGERS AND CLUSTERING EVOLUTION

Merging of close pairs of galaxies diminishes the amplitude of cluster ing on both small and large scales. The power spectrum of the postmerg er population at long waves is approximately the initial P(k) multipli ed by (1 - f(mg))2 (1 - k2R(mg)2), valid for small kR(mg), where R(mg) is set by the characteristic initial separation of crossing orbits. T he quantity f(mg) is the fraction of galaxies merged, which can be est imated from a variety of observations. On small scales, less than appr oximately 2 h-1 Mpc, the clustering of the merged population is sensit ive to the details of the merger process, although continuing infall a nd orbital mixing will maintain density gradients of the galaxy popula tion on small scales. Prior to merging, galaxy populations form in abu ndance at peak heights, nu greater than or similar to 1, and are more correlated than the dark matter on both large and small scales. Mergin g greatly reduces small scale clustering (possibly into a mild antibia sing on small scales) but can leave statistically upward biased large- scale galaxy clustering substantially in place. Applying the merger fi lter gives a galaxy spectrum which, for normalizations sigma8 greater than or similar to 0.7 and merged fractions of around 20%, have large- scale galaxy tracer power comparable to a linear sigma8 = 1.2 model. A second application is that the strength of the observed clustering of faint blue galaxies, m(B) congruent-to 22-24, sets an upper limit on the fraction that can have merged away to the present epoch, about 1/3 to 1/2, arguing that the other 1/2 to 2/3 of their faded remnants sho uld still be present.