Galaxy peculiar velocities and evolution-bias

TL;DR

This paper investigates how evolution-bias affects galaxy clustering and velocities, showing that older galaxies are more biased on large scales due to their formation at density peaks and subsequent motion.

Contribution

It introduces a scale-dependent evolution-bias model based on the peaks theory and supports it with Monte-Carlo simulations of galaxy motions.

Findings

Older galaxies exhibit stronger large-scale bias.

Galaxy and matter correlation functions differ in shape based on galaxy age.

Evolution-bias causes scale-dependent changes in galaxy clustering.

Abstract

Galaxy bias can be split into two components: a formation-bias based on the locations of galaxy creation, and an evolution-bias that details their subsequent evolution. In this letter we consider evolution-bias in the peaks model. In this model, galaxy formation takes place at local maxima in the density field, and we analyse the subsequent peculiar motion of these galaxies in a linear model of structure formation. The peak restriction yields differences in the velocity distribution and correlation between the galaxy and the dark matter fields, which causes the evolution-bias component of the total bias to evolve in a scale-dependent way. This mechanism naturally gives rise to a change in shape between galaxy and matter correlation functions that depends on the mean age of the galaxy population. This model predicts that older galaxies would be more strongly biased on large scales compared to younger galaxies. Our arguments are supported by a Monte-Carlo simulation of galaxy pairs propagated using the Zel'dovich-approximation for describing linear peculiar galaxy motion.