Abstract
Abstract We identify 1901 galaxy clusters (N g ≥ 2) with the VoML+G algorithm (Paper I) on the Two-Degree Field Galaxy Redshift Survey. We present the 341 clusters with at least 10 galaxies that are within 0.009 < z < 0.14 (the Catalog), of which 254 (∼75%) have counterparts in the literature (NED), with the remainder (87) plausibly “new” because of incompleteness of previous searches or unusual galaxy contents. The 207 clusters within z = 0.04–0.09 are used to study the properties of the galaxy systems in the nearby universe, including their galaxy contents parameterized by the late-type galaxy fractions (f L ). For this nearly complete cluster subsample, we find the following: (i) 63% are dominated by early-type galaxies (i.e., the late-type-poor clusters, f L < 0.5) with corresponding mean multiplicity and logarithmic virial mass (in units of M ⊙) of 22 ± 1 and 12.91 ± 0.04, respectively; and (ii) 37% are dominated by late-type galaxies (i.e., the late-type-rich clusters, f L ≥ 0.5) with corresponding mean multiplicity and logarithmic virial mass (in units of M ⊙) of 15.7 ± 0.9 and 12.66 ± 0.07, respectively. The statistical analysis of the late-type fraction distribution supports, with a 3σ confidence level, the presence of two population components. It is suggested that the late-type-poor galaxy systems reflect and extend the class of Abell-APM-EDCC clusters and that the late-type-rich systems (∼one-third of the total) belong to a new, previously unappreciated class. The late-type-rich clusters, on average high mass-to-light ratio systems, appear to be more clustered on large scales than the late-type-poor clusters. A class of late-type-rich clusters is not predicted by current theory.
Highlights
Clusters of galaxies are the largest gravitationally bound systems known
This paper reports the detection of 1901 galaxy clusters resulting from the application of the VoML+G algorithm to the real 2dFGRS but focuses on the analyses of clusters with at least 10 galaxies that are open to mass estimates
We find that ∼90% (1706 out of 1901 clusters) of the VoML+G clusters have a correspondence in the 2PIGG catalog, a fraction that increases to 100% when only clusters with 10 or more member galaxies are taken into account
Summary
Clusters of galaxies are the largest gravitationally bound systems known They are detectable over a large fraction of the age of the universe, providing a testing ground for cosmology (Henry et al 2009; Vikhlinin et al 2009; Mantz et al 2010; Rozo et al 2010; Clerc et al 2012; Benson et al 2013), for the history of the agglomeration of matter (Jing et al 1998; Peacock & Smith 2000; Seljak 2000; Scoccimarro et al 2001; Berlind & Weinberg 2002; Zheng et al 2005, 2009), and for the description of galaxy evolution (e.g., Dressler 1980; Lewis et al 2002; Boselli & Gavazzi 2006; Haines et al 2015).
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