THE EVOLUTION OF BIAS

摘要

Bias in the galaxy distribution is often conceived as something applied at the present or as independent of time. In fact, a bias arising physically in the process of galaxy formation will evolve afterward, as galaxies move under the influence of gravity. I calculate the evolution of bias in a model in which galaxies are formed at a fixed time by a process that may depend nonlinearly on density but follow motions determined by the gravitational potential thereafter. The equation of continuity then determines the evolution. An initial bias decays with time, and in the long term, the galaxy distribution relaxes to that of the mass, but with galaxy formation occurring at a modest redshift, an appreciable bias may remain to the present. The evolution of bias changes somewhat the dependence of the bispectrum amplitude on configuration shape, but a weak dependence on configuration shape still corresponds to a large bias.