Angular Clustering with Photometric Redshifts in the SDSS: Bimodality in the Clustering Properties of Galaxies

Abstract

Understanding the clustering of galaxies has long been a goal of modern observational cosmology. Redshift surveys have been used to measure the correlation length as a function of luminosity and color. However, when subdividing the catalogs into multiple subsets, the errors increase rapidly.

Utilizing our photometric redshift technique a volume limited sample (0.1<z<0.3) containing more than 2 million galaxies is constructed from the SDSS galaxy catalog. In the largest such analysis to date, we study the angular clustering as a function of luminosity and spectral type. Using Limber’s equation we calculate the clustering length for the full data set as r ₀=5.77±0.10h ⁻¹ Mpc. We find that r ₀ increases with luminosity by a factor of 1.6 over the sampled luminosity range, in agreement with previous redshift surveys. We also find that both the clustering length and the slope of the correlation function depend on the galaxy type. In particular, by splitting the galaxies in four groups by their rest-frame type we find a bimodal behavior in their clustering properties.

Talk presented by Alexander S. Szalay