The Candidate Cluster and Protocluster Catalog (CCPC) is a list of objects at redshifts z > 2 composed of galaxies with spectroscopically confirmed redshifts that are coincident on the sky and in redshift. These protoclusters are identified by searching for groups in volumes corresponding to the expected size of the most massive protoclusters at these redshifts. In CCPC1 we identified 43 candidate protoclusters among 14,000 galaxies between 2.74 < z < 3.71. Here we expand our search to more than 40,000 galaxies with spectroscopic redshifts z > 2.00, resulting in an additional 173 candidate structures. The most significant of these are 36 protoclusters with overdensities δ gal > 7. We also identify three large proto-supercluster candidates containing multiple protoclusters at z = 2.3, 3.5 and z = 6.56. Eight candidates with N ≥ 10 galaxies are found at redshifts z > 4.0. The last system in the catalog is the most distant spectroscopic protocluster candidate known to date at z = 6.56.

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.

A multi-epoch Hα survey of the late-type spiral galaxy NGC 2403 has been completed in order to determine its nova rate. A total of nine nova candidates were discovered in 48 nights of observation with two different telescopes over the period from 2001 February to 2012 April. After making corrections for temporal coverage and spatial completeness, a nova rate of 2.0 +0.5 −0.3 yr −1 was determined. This rate corresponds to a luminosity-specific nova rate of 2.5 ± 0.7 novae per year per 10 10 L ⊙,K . This value is consistent with that of the similar Hubble type galaxy, M33, and is typical of those of other galaxies with measured nova rates, which range from 1 − 3 novae per year per 10 10 L ⊙,K .

The Candidate Cluster and Protocluster Catalog (CCPC) contains 218 galaxy overdensities composed of more than 2000 galaxies with spectroscopic redshifts spanning the first few Gyrs after the Big Bang (2.0 ≤ z < 6.6). We use Spitzer archival data to track the underlying stellar mass of these overdense regions in various temporal cross sections by building rest-frame near-infrared luminosity functions across the span of redshifts.This exercise maps the stellar growth of protocluster galaxies, as halos in the densest environments should be the most massive from hierarchical accretion. The characteristic apparent magnitude, m * (z), is relatively flat from 2.0 ≤ z < 6.6, consistent with a passive evolution of an old stellar population. This trend maps smoothly to lower redshift results of cluster galaxies from other works. We find no difference in the luminosity functions of galaxies in the field versus protoclusters at a given redshift, apart from their density.

We present near-infrared observations of the environments around three radio-loud sources (MG1 J0442+0202, 3C 068.2, and MS 1426.9+1052) at redshifts z = 1.10, 1.57, and 1.83 (respectively), that are surrounded by near-infrared galaxy overdensities. Overdensities with respect to field counts were found to be significant up to 19σ, with twelve times the expected number of galaxies within the inner regions of the densest proto-cluster. Color-magnitude relations are constructed in K s , J − K s , with each candidate cluster exhibiting a feature consistent with the beginnings of a red sequence. Galaxy models based on the redshift of the radio source are used to compare expected color-magnitude relations for a given formation epoch with the observed red sequence of each candidate, and are found to be consistent with an old (z f > 5) formation epoch for a few bright, red galaxies on the red sequence.