Cosmology with Galaxy Correlations

TL;DR

This review discusses how galaxy correlation measurements, like BAO and large-scale structure, constrain cosmological parameters and support a Lambda-dominated, flat universe, with recent data from SDSS and 2dFGRS providing key evidence.

Contribution

It synthesizes recent observational results from galaxy surveys and their implications for cosmological models, emphasizing the role of galaxy correlations in constraining dark matter, dark energy, and gravity theories.

Findings

Galaxy correlations constrain Omega_m h^2 to less than 0.3.

BAO and power spectrum measurements support a flat, Lambda-dominated universe.

Detection of the ISW effect out to redshift z>1 provides evidence for dark energy and tests of gravity.

Abstract

In this review, I outline the use of galaxy correlations to constrain cosmological parameters. As with the Cosmic Microwave Background (CMB), the density of dark and baryonic matter imprints important scales on the fluctuations of matter and thus the clustering of galaxies, e.g., the particle horizon at matter--radiation equality and the sound horizon at recombination. Precision measurements of these scales from the Baryon Acoustic Oscillations (BAO) and the large scale shape of the power spectrum of galaxy clustering provide constraints on Omega_m h^2. Recent measurements from the Sloan Digital Sky Survey (SDSS) and 2dF Galaxy Redshift Survey (2dFGRS) strongly suggest that Omega_m < 0.3. This forms the basic evidence for a flat Universe dominated by a Cosmological Constant (Lambda) today (when combined with results from the CMB and supernova surveys). Further evidence for this cosmological model is provided by the late-time Integrated Sachs-Wolfe (ISW) effect, which has now been detected using a variety of tracers of the large scale structure in the Universe out to redshifts of z>1. The ISW effect also provides an opportunity to discriminate between Lambda, dynamical dark energy models and the modification of gravity on large scales.