MERGERS AND CLUSTERING EVOLUTION

Merging of close pairs of galaxies diminishes the amplitude of clustering on both small and large scales. The power spectrum of the postmerger population at long waves is approximately the initial P(k) multiplied 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. The quantity f(mg) is the fraction of galaxies merged, which can be estimated from a variety of observations. On small scales, less than approximately 2 h-1 Mpc, the clustering of the merged population is sensitive to the details of the merger process, although continuing infall and orbital mixing will maintain density gradients of the galaxy population on small scales. Prior to merging, galaxy populations form in abundance at peak heights, nu greater than or similar to 1, and are more correlated than the dark matter on both large and small scales. Merging greatly reduces small scale clustering (possibly into a mild antibiasing on small scales) but can leave statistically upward biased large-scale galaxy clustering substantially in place. Applying the merger filter 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 should still be present.