Definitive Identification of the Transition between Small- and Large-Scale Clustering for Lyman Break Galaxies

We present an angular correlation function (ACF) of z=4 LBGs with unprecedented statistical quality, based on measurements of 16,920 LBGs obtained in the 1 deg² sky of the Subaru/XMM-Newton Deep Field. The ACF significantly departs from a power law, and shows an excess on small scales. In particular, the ACFs of LBGs with i^'<27.5 show a clear break between the small- and large-scale regimes at an angular separation of ~=7", whose projected length corresponds to the virial radius of dark halos with a mass of 10¹¹-10¹² M_solar, indicating multiple LBGs residing in a single dark halo. At both small (2^''<θ<3^'') and large (40^''<θ<400^'') scales, clustering amplitudes increase monotonically with luminosity for the magnitude range of i^'=24.5-27.5 the small-scale clustering shows a stronger luminosity dependence than the large-scale clustering. The small-scale bias reaches b~=10-50, and the outskirts of small-scale excess extend to a larger angular separation for brighter LBGs. The ACF and number density of LBGs can be explained by the cold dark matter model.

Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.