The candidate cluster and protocluster catalog (CCPC) of spectroscopically identified structures spanning $2.74 < z < 3.71$

TL;DR

This paper introduces the CCPC, a catalog of galaxy protoclusters at redshifts 2.74 to 3.71, identified through a new search methodology applied to 14,000 galaxies, revealing significant overdensities and potential challenges to cosmological models.

Contribution

The paper presents a novel search method for high-redshift protoclusters and provides the first comprehensive catalog of such structures in the specified redshift range.

Findings

12 highly significant overdensity clusters identified

31 candidate protoclusters of lower overdensity found

Some systems have virial mass estimates exceeding 10^15 solar masses

Abstract

We have developed a search methodology to identify galaxy protoclusters at $z>2.74$, and implemented it on a sample of $\sim$14,000 galaxies with previously measured redshifts. The results of this search are recorded in the Candidate Cluster and Protocluster Catalog (CCPC). The catalog contains 12 clusters that are highly significant overdensities ($\delta_{gal}>7$), 6 of which are previously known. We also identify another 31 candidate protoclusters (including 4 previously identified structures) of lower overdensity. CCPC systems vary over a wide range of physical sizes and shapes, from small, compact groups to large, extended, and filamentary collections of galaxies. This variety persists over the range from $z=3.71$ to $z=2.74$. These structures exist as galaxy overdensities ($\delta_{gal}$) with a mean value of 2, similar to the values found for other protoclusters in the literature. The median number of galaxies for CCPC systems is 11. Virial mass estimates are large for these redshifts, with thirteen cases apparently having $M > 10^{15}\, M_{\odot}$. If these systems are virialized, such masses would pose a challenge to $\Lambda$CDM.