THE CANDIDATE CLUSTER AND PROTOCLUSTER CATALOG (CCPC) OF SPECTROSCOPICALLY IDENTIFIED STRUCTURES SPANNING 2.74 < z < 3.71

Abstract

We developed a search methodology to identify galaxy protoclusters at z 2.74 > and implemented it on a sample of ∼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 ( 7 gal d > ), 6 of which were previously known. We also identify another 31 candidate protoclusters (including four previously identified structures) of lower overdensities. 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 in the range from z = 3.71 to z = 2.74. These structures exist as galaxy overdensities ( gal d ) 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 13 cases apparently having M M 10 15 >  . If these systems are virialized, such masses would pose a challenge to ΛCDM.

THE CANDIDATE CLUSTER AND PROTOCLUSTER CATALOG (CCPC). II. SPECTROSCOPICALLY IDENTIFIED STRUCTURES SPANNING 2 < z < 6.6

“…Catalogs of pure spectroscopically identified protoclusters in the high redshift universe, as in Venemans et al (2007), typically have fewer than 10 such candidates, however. Most of these previously identified structures are found within z ∼ 3 ± 1 (Venemans et al 2007;Wylezalek et al 2014;Franck & McGaugh 2016), with a few at z ∼ 6 (Utsumi et al 2010;Toshikawa et al 2014). These objects were identified with varying instruments, selection techniques, and fields-of-view (FOV) that rarely encompass the entire system.…”

“…CCPC-z22-001,CCPC-z23-001 and CCPC-z24-001 (all featured in CCPC2) have similar positions and redshifts to the overdensities reported by Salimbeni et al (2009), while CCPC-z25-004, CCPC-z25-005, CCPCz40-001, and CCPC-z42-001 may coincide with candidate structures in Kang & Im (2015). CCPC-z28-002, CCPC-z34-002, and CCPC-z37-001 in Franck & McGaugh (2016) are all overdensities originally found in the VIMOS GOODS-S spectroscopic survey by Balestra et al (2010).…”

“…Of these, 9 were identified in Franck & McGaugh (2016) (in the redshift range 2.74 < z < 3.71). It is the deepest, widest field from which we draw candidate spectroscopic galaxies to identify protoclusters.…”

“…In Franck & McGaugh (2016), we plotted the positions of field and CCPC1 protocluster galaxies within search radii of 20 cMpc to illustrate the distribution of members with respect to the survey widths in the Appendix. Surveys rarely extended beyond the probed search radius.…”

“…In CCPC1 (Franck & McGaugh 2016), we performed a number of tests on the algorithm in which candidate protoclusters were identified. In addition, the significance of the candidates were also evaluated.…”