Near‐Infrared Properties of Moderate‐Redshift Galaxy Clusters. II. Halo Occupation Number, Mass‐to‐Light Ratios, and Ωm

Using K-band imaging for 15 of the Canadian Network for Observational Cosmology (CNOC1) clusters we examine the near-infrared properties of moderate-redshift (0.19 < z < 0.55) galaxy clusters. We find that the number of K-band selected cluster galaxies within R₅₀₀ (the Halo Occupation Number, HON) is well-correlated with the the cluster dynamical mass (M₅₀₀) and X-ray Temperature (Tₓ); however, the intrinsic scatter in these scaling relations is 37% and 46% respectively. Comparison with clusters in the local universe shows that the HON-M₅₀₀ relation does not evolve significantly between z = 0 and z ~ 0.3. This suggests that if dark matter halos are disrupted or undergo significant tidal-stripping in high-density regions as seen in numerical simulations, the stellar mass within the halos is tightly bound, and not removed during the process. The total K-band cluster light (L200,K) and K-band selected richness (parameterized by Bgc,K) are also correlated with both the cluster Tₓ and M₂₀₀. The total (intrinsic) scatter in the L200,K-M₂₀₀ and Bgc,K-M₂₀₀ relations are 43%(31%) and 35%(18%) respectively and indicates that for massive clusters both L200,K and Bgc,K can predict M₂₀₀ with similar accuracy as Tₓ, Lₓ or optical richness (Bgc). Examination of the mass-to-light ratios of the clusters shows that similar to local clusters, the K-band mass-to-light ratio is an increasing function of halo mass. Using the K-band mass-to-light ratios of the clusters, we apply the Oort technique and find Omegam,0 = 0.22 pm 0.02, which agrees well with recent combined concordance cosmology parameters, but, similar to previous cluster studies, is on the low-density end of preferred values.