The different Clustering of red and blue galaxies: a robust signal from w(theta)

Abstract

A sample of ~20,000 galaxies covering 0.76 deg2 were observed with the CFHT-UH8K up to V<23.5 and I<22.5. The angular correlation analysis of the red selected sample (V-I>1.4) shows a stronger amplitude than the blue selected sample at all cutoff magnitudes. This effect could be explained either by luminosity selection effects or by a true color segregation in which red objects are preferably found in denser regions. If the latter is true, and assuming that red galaxies are dominated by an older population of stars, this measurement supports the idea that galaxies evolve faster in the harsh environment of dense clusters than in the field, at fiducial redshifts of z~0.5.