Proto-clusters in the Lambda CDM Universe

Abstract

We compare the highly clustered populations of very high redshift galaxies with proto-clusters identified numerically in a standard $\Lambda$CDM universe (${\Omega }_0=0.3,{\lambda }_0=0.7$) simulation. We evolve 256^3 dark matter particles in a comoving box of side 150h^{-1}Mpc. By the present day there are 63 cluster sized objects of mass in excess of 10^{14}h^{-1}Mo in this box. We trace these clusters back to higher redshift finding that their progenitors at z=4--5 are extended regions of typically 20--40 Mpc (comoving) in size, with dark halos of mass in excess of 10^{12}h^{-1}Mo and are overdense by typically 1.3--13 times the cosmological mean density. Comparison with the observation of Lyman alpha emitting (LAEs) galaxies at z=4.86 and at z=4.1 indicates that the observed excess clustering is consistent with that expected for a proto-cluster region if LAEs typically correspond to massive dark halos of more than 10^{12}h^{-1}Mo. We give a brief discussion on the relation between high redshift concentration of massive dark halos and present day rich clusters of galaxies.

4 pages, 5 figures, Accepted for publication in ApJ Letters

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• LCDM predictions for galaxy protoclusters I: the relation between galaxies, protoclusters and quasars at z~6
• Surveying Galaxy Proto-clusters in Emission: A Large-scale Structure at z=2.44 and the Outlook for HETDEX
• Characterising and Identifying Galaxy Protoclusters
• Emergence of an Ultra-Red Ultra-Massive Galaxy Cluster Core at $z=4$
• Assembly of Massive Galaxies in a High-z Protocluster
• Probing the existence of a rich galaxy overdensity at z=5.2
• [OIII] emitters in the field of the MRC 0316-257 protocluster
• A search for galaxies in and around an HI overdense region at z=5