Two close large quasar groups of size ∼ 350 Mpc at

Abstract

The Clowes & Campusano large quasar group (LQG) atz = 1.28 has been re-examined using the quasar data from the DR7QSO catalogue 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 DR7QSO data, the western, northern and southern boundaries of the LQG remain essentially the same, but an extension eastwards of ∼2 • is indicated. In the DR7QSO data, the LQG has 34 members, withz = 1.28. A new group of 38 members is indicated atz = 1.11 and within ∼2. • 0 of the Clowes & Campusano LQG. The characteristic sizes of these two LQGs, ∼350-400 Mpc, appear to be only marginally consistent with the scale of homogeneity in the concordance cosmology. In addition to their intrinsic interest, these two LQGs provide locations in which to investigate early large-scale structure in galaxies and to identify high-z clusters. A method is presented for assessing the statistical significance and overdensity of groups found by linkage of points.

A giant ring-like structure at 0.78 < z < 0.86 displayed by GRBs

“…Haines, Campusano & Clowes (2004) reported the finding of two large-scale structures of galaxies in a 40 × 35 arcmin 2 field embedded in a 25 •2 area containing two 100 Mpcscale structures of quasars. As the identified scales of quasar clusters became larger, Clowes et al (2012) found two relatively close LQGs at z ∼ 1.2. The characteristic sizes of these two LQGs, ≈ 350 − 400 Mpc, and appear to be only marginally consistent with the scale of homogeneity in the concordance cosmology.…”

“…Until recently, this was the largest known structure in the Universe. Using a friend of friend (FoF) algorithm Einasto et al (2014) found that the linking length l = 70 h −1 M pc three systems from their QSR catalogue coincide with the LQGs from Clowes et al (2012Clowes et al ( , 2013. Horváth, Hakkila & Bagoly (2013); Horváth, Hakkila & Bagoly (2014) announced the discovery of a larger Universal structure than the Huge-LQG by analyzing the spatial distribution of gamma-ray bursts (GRBs).…”

Tracing a high redshift cosmic web with quasar systems

“…From this catalogue, we select a subsample of quasars in the redshift interval 1.0 ≤ z ≤ 1.8 and apply an i-magnitude limit i = 19.1. The full quasar catalogue by Schneider et al (2010) is not homogeneous; Vanden Berk et al (2005) and Richards et al (2006) (see also Clowes et al 2012) gave a detailed analysis of the completeness of the sample and suggested to use these selection limits for statistical studies. To reduce the edge effects of our analysis, we limit the data in the area of SDSS sky coordinate limits −55 ≤ λ ≤ 55 degrees and −33 ≤ η ≤ 35 degrees.…”

“…We choose this redshift range as we are interested in the study of the cosmic web at high redshifts. This redshift range was also used by Clowes et al (2012Clowes et al ( , 2013; with this choice, we can compare LQGs found in these studies and our systems. We shall use the Schneider et al (2010) catalogue of quasars based on the Sloan Digital Sky Survey Data Release 7 (SDSS DR7).…”

“…The studies of the quasar environment in the cosmic web helps us to understand the relation between the galaxy and quasar evolution and to test the evolutionary schemes of different type of objects. A&A 568, A46 (2014) Already decades ago, several studies described large systems in quasar distribution (Webster 1982;Clowes & Campusano 1991;Komberg et al 1996;Williger et al 2002;Clowes et al 2012Clowes et al , 2013, and references therein), which are known as large quasar groups (LQGs). Miller et al (2004) found significant 200 h −1 Mpc size over-and underdensities in the density field determined by quasars from the 2dF QSO Redshift survey.…”