Evolution and Color Dependence of the Galaxy Angular Correlation Function: 350,000 Galaxies in 5 Square Degrees

Abstract

When applied to deep photometric catalogs, the two-point angular correlation function, ω(θ), is a sensitive probe of the evolution of galaxy clustering properties. Here we present measurements of ω(θ) as a function of IAB magnitude and (R-I) color to a depth of IAB=24 on scales θ=7''-3', using a sample of ~350,000 galaxies covering 5 deg2 in total over five separate fields. Using redshifts of 2954 galaxies in early DEEP2 Galaxy Redshift Survey data, we construct robust galaxy redshift distributions as a function of IAB magnitude and (R-I) color for galaxies in the range 0 =1 to z=0. A model in which the comoving scale length, x0, evolves linearly with redshift, x0(z)=x0(0)(1-Bz), fits the data better than the ɛ model proposed by Groth & Peebles. The clustering properties depend strongly on observed (R-I) color, with both the reddest and bluest galaxies exhibiting large clustering amplitudes and steeper slopes. Different observed (R-I) color ranges are sensitive to very disparate redshift regimes. Red galaxies with (R-I)~1.5 lie in a narrow redshift range centered at z~0.85 and have a comoving scale length of clustering at z=0.85 of x0=5.0+/-0.3 h-1 Mpc. These galaxies have early-type spectra and are likely progenitors of massive local ellipticals. The bluest galaxies with (R-I)~0 appear to be a mix of star-forming galaxies, both relatively local (z~0.3-0.6) dwarfs and bright z>1.4 galaxies, as well as broad-line active galactic nuclei. We find that local blue dwarfs are relatively unclustered, with x0=1.6+/-0.2 h-1 Mpc. The z>1.4 blue galaxies have a larger clustering scale length, x0>~5 h-1 Mpc.