Tracing high redshift cosmic web with quasar systems

TL;DR

This study maps the high-redshift cosmic web using quasar data, applying a friend-of-friend algorithm to identify systems and analyze their properties, revealing similarities to local superclusters and providing a valuable database for future research.

Contribution

It introduces a novel application of the friend-of-friend algorithm to high-redshift quasars, characterizing the cosmic web at z~1-2 and creating a publicly accessible quasar system catalog.

Findings

Quasar systems at small linking lengths are smaller and more numerous than random expectations.

Richest quasar systems have up to four members, comparable to poor galaxy superclusters.

Quasar system sizes at large linking lengths resemble local supercluster structures.

Abstract

We trace the cosmic web at redshifts 1.0 <= z <= 1.8 using the quasar data from the SDSS DR7 QSO catalogue (Schneider et al. 2010). We apply a friend-of-friend (FoF) algorithm to the quasar and random catalogues to determine systems at a series of linking lengths, and analyse richness and sizes of these systems. At the linking lengths l <= 30 Mpc/h the number of quasar systems is larger than the number of systems detected in random catalogues, and systems themselves have smaller diameters than random systems. The diameters of quasar systems are comparable to the sizes of poor galaxy superclusters in the local Universe, the richest quasar systems have four members. The mean space density of quasar systems is close to the mean space density of local rich superclusters. At intermediate linking lengths (40 <= l <= 70 Mpc/h) the richness and length of quasar systems are similar to those derived from random catalogues. Quasar system diameters are similar to the sizes of rich superclusters and supercluster chains in the local Universe. At the linking length 70 Mpc/h the richest systems of quasars have diameters exceeding 500 Mpc/h. The percolating system which penetrate the whole sample volume appears in quasar sample at smaller linking length than in random samples (85 Mpc/h). Quasar luminosities in systems are not correlated with the system richness. Quasar system catalogues at our web pages http://www.aai.ee/~maret/QSOsystems.html serve as a database to search for superclusters of galaxies and to trace the cosmic web at high redshifts.