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_⊙, 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.