A multiscale approach to environment

TL;DR

This paper introduces a multiscale parameterization of galaxy environment to analyze how galaxy properties, like color distribution, depend on environment across different scales, supporting the halo model and galaxy evolution theories.

Contribution

It presents a new multiscale approach to quantify galaxy environment, enabling detailed analysis independent of the halo model and supporting existing theories.

Findings

Galaxy color distribution depends on multiscale density.

Environment influences galaxy properties in a way consistent with the halo model.

Supports the existence of virialized haloes in galaxy evolution.

Abstract

Physical processes influencing the properties of galaxies can be traced by the dependence and evolution of galaxy properties on their environment. A detailed understanding of this dependence can only be gained through comparison of observations with models, with an appropriate quantification of the rich parameter space describing the environment of the galaxy. We present a new, multiscale parameterization of galaxy environment which retains an observationally motivated simplicity whilst utilizing the information present on different scales. We examine how the distribution of galaxy (u-r) colours in the Sloan Digital Sky Survey (SDSS), parameterized using a double gaussian (red plus blue peak) fit, depends upon multiscale density. This allows us to probe the detailed dependence of galaxy properties on environment in a way which is independent of the halo model. Nonetheless, cross-correlation with the group catalogue constructed by Yang et al, 2007 shows that galaxy properties trace environment on different scales in a way which mimics that expected within the halo model. This provides independent support for the existence of virialized haloes, and important additional clues to the role played by environment in the evolution of the galaxy population. This work is described in full by Wilman et al., 2010, MNRAS, accepted