Angular Clustering with Photometric Redshifts in the Sloan Digital Sky Survey: Bimodality in the Clustering Properties of Galaxies

Understanding the clustering of galaxies has long been a goal of modernobservational cosmology. Utilizing our photometric redshift technique a volumelimited sample containing more than 2 million galaxies is constructed from theSDSS galaxy catalog. In the largest such analysis to date, we study the angularclustering as a function of luminosity and spectral type. Using Limber'sequation we calculate the clustering length for the full data set asr0=5.77+/-0.10 Mpc/h. We find that r0 increases with luminosity by a factor of1.6 over the sampled luminosity range, in agreement with previous redshiftsurveys. We also find that both the clustering length and the slope of thecorrelation function depend on the galaxy type. In particular, by splitting thegalaxies in four groups by their rest-frame type we find a bimodal behavior intheir clustering properties. Galaxies with spectral types similar to ellipticalgalaxies have a correlation length of 6.59 +/- 0.17 Mpc/h and a slope of theangular correlation function of 0.96 +/- 0.05 while blue galaxies have aclustering length of 4.51 +/- 0.19 Mpc/h and a slope of 0.68 +/- 0.09. The twointermediate color groups behave like their more extreme 'siblings', ratherthan showing a gradual transition in slope. We discuss these correlations inthe context of current cosmological models for structure formation.