The galaxy correlation function as a constraint on galaxy formation physics

TL;DR

This paper presents a new method combining galaxy clustering and luminosity functions to better constrain galaxy formation physics and cosmological parameters using semi-analytic models and MCMC techniques.

Contribution

It introduces a novel approach to estimate galaxy correlation functions efficiently and use them with abundance data for joint constraints on galaxy formation and cosmology.

Findings

Achieved ~10% accuracy in correlation function estimation from small subsamples.

Constrained semi-analytic model parameters with improved precision.

Demonstrated potential for multi-epoch clustering and abundance data to inform galaxy formation and cosmology.

Abstract

We introduce methods which allow observed galaxy clustering to be used together with observed luminosity or stellar mass functions to constrain the physics of galaxy formation. We show how the projected two-point correlation function of galaxies in a large semi-analytic simulation can be estimated to better than ~10% using only a very small subsample of the subhalo merger trees. This allows measured correlations to be used as constraints in a Monte Carlo Markov Chain exploration of the astrophysical and cosmological parameter space. An important part of our scheme is an analytic profile which captures the simulated satellite distribution extremely well out to several halo virial radii. This is essential to reproduce the correlation properties of the full simulation at intermediate separations. As a first application, we use low-redshift clustering and abundance measurements to constrain a recent version of the Munich semi-analytic model. The preferred values of most parameters are consistent with those found previously, with significantly improved constraints and somewhat shifted "best" values for parameters that primarily affect spatial distributions. Our methods allow multi-epoch data on galaxy clustering and abundance to be used as joint constraints on galaxy formation. This may lead to significant constraints on cosmological parameters even after marginalising over galaxy formation physics.