UV luminosities for overdensity significances about quasars. Panels (a), (b), and (c) show the relation between the i-band absolute magnitudes of quasars and the maximum overdensity significances centered on quasars with a radius of 1΄, 3΄, and 10΄, respectively. The FIRST-detected quasars are also shown with red points. The >4 σ overdense regions are to the right of the dashed line. The gray shaded region shows the complete limit, which corresponds to the BOSS limiting magnitude of r < 21.8. (Color online)