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Abstract: Galaxy bias can be split into two components: a formation-bias based on thelocations of galaxy creation, and an evolution-bias that details theirsubsequent evolution. In this letter we consider evolution-bias in the peaksmodel. In this model, galaxy formation takes place at local maxima in thedensity field, and we analyse the subsequent peculiar motion of these galaxiesin a linear model of structure formation. The peak restriction yieldsdifferences in the velocity distribution and correlation between the galaxy andthe dark matter fields, which causes the evolution-bias component of the totalbias to evolve in a scale-dependent way. This mechanism naturally gives rise toa change in shape between galaxy and matter correlation functions that dependson the mean age of the galaxy population. This model predicts that oldergalaxies would be more strongly biased on large scales compared to youngergalaxies. Our arguments are supported by a Monte-Carlo simulation of galaxypairs propagated using the Zel-dovich-approximation for describing linearpeculiar galaxy motion.

Author: Will J. Percival, Bjoern M. Schaefer



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