The Clowes-Campusano large quasar group survey. I.Galexselected sample of lyman Break Galaxies ATz∼ 1

Abstract

The Clowes & Campusano Large Quasar Group (LQG, MNRAS 1991, 249, 218) at z = 1.28 has been re-examined using the quasar data from the DR5QSO catalog of the Sloan Digital Sky Survey. In the 1991 discovery, the LQG impinged on the northern, southern and eastern limits of the survey. In the DR5QSO data, the western, northern and southern boundaries of the LQG remain essentially unchanged, but an extension eastwards of 2 deg. is indicated. In the DR5QSO data, the LQG has 31 members, with z = 1.27, and a characteristic size 250 Mpc. Its quasar density contrast is δρ/ρ 0.94, suggesting either that it is approaching the non-linear regime or that quasar formation is substantially enhanced in LQGs. A new LQG of 41 members is indicated at z = 1.11 and within 0.8 deg. of the Clowes & Campusano LQG. A further LQG, at z = 1.53 and within 1.5 deg. of the Clowes & Campusano LQG, was previously known but is found here with membership increased to 20. The characteristic sizes and quasar density contrasts of these two additional LQGs are (325 Mpc, 0.42) and (200 Mpc, 0.66) respectively. This concentration of three LQGs in the same cosmological neighborhood, with centroids that are almost co-linear, raises the possibility that large-scale structure can itself be associated on scales 350 Mpc.