The Color and Stellar Mass Dependence of Small-scale Galaxy Clustering in SDSS-III BOSS

Abstract

We measure the color and stellar mass dependence of clustering in spectroscopic galaxies at $0.6 < z < 0.65$ using data from the Baryon Oscillation Spectroscopic Survey component of the Sloan Digital Sky Survey. We greatly increase the statistical precision of our clustering measurements by using the cross-correlation of 66,657 spectroscopic galaxies to a sample of 6.6 million fainter photometric galaxies. The clustering amplitude $w(R)$ is measured as the ratio of the mean excess number of photometric galaxies found within a specified radius annulus around a spectroscopic galaxy to that from a random photometric galaxy distribution. We recover many of the familiar trends at high signal-to-noise ratio. We find the ratio of the clustering amplitudes of red and blue massive galaxies to be $w_\text{red}/w_\text{blue} = 1.92 \pm 0.11$ in our smallest annulus of 75-125 kpc. At our largest radii (2-4 Mpc), we find $w_\text{red}/w_\text{blue} = 1.24 \pm 0.05$. Red galaxies therefore have denser environments than their blue counterparts at $z \sim 0.625$, and this effect increases with decreasing radius. Irrespective of color, we find that $w(R)$ does not obey a simple power-law relation with radius, showing a dip around 1 Mpc. Holding stellar mass fixed, we find a clear differentiation between clustering in red and blue galaxies, showing that clustering is not solely determined by stellar mass. Holding color fixed, we find that clustering increases with stellar mass, especially for red galaxies at small scales (more than a factor of 2 effect over 0.75 dex in stellar mass).