Angular correlations in decontaminated Abell catalogs
Scot S. Olivier, Joel R. Primack, George R. Blumenthal, Avishai Dekel, David Stanhill · The Astrophysical Journal · 1990
We study the effect of projection contamination on the angular autocorrelation function w_cc_(θ) in the Abell northern and Abell- Corwin-Olowin southern catalogs of rich clusters of galaxies. We do this by constructing a "decontaminated" catalog of richness R >= 1, distance D = 5, 6 clusters, using a robust model in which the galaxy number density is a superposition of a uniform field plus spherical halos centered on each cluster. The halo profile functions are derived from observed cluster- galaxy correlation functions, ξ_cg_(r). This procedure eliminates 9%-14% of the 2004 clusters in the two catalogs, depending on the ξ_cg_ used. At small angles, θ 3^deg^, the effect of decontamination is negligible. On these scales the north and the south differ significantly; while in the south w_cc_ is consistent with zero at the 2 σ level, it stays significantly positive in the north out to 40^deg^. This inconsistency and other problems with the northern sample argue against drawing any conclusions from the results beyond 3^deg^. The w_cc_(θ) of the decontaminated D = 5, 6 sample for θ < 3^deg^ is consistent with our previous results on the ξ_cc_(r) of the decontaminated D <= 4 redshift sample to within 2 σ, roughly consistent with the expected scaling with depth. The data in the 1^deg^- 3^deg^ zone is in significant conflict with the predictions of the "standard" cold dark matter model; the discrepancy is ~ 5 σ with Poisson errors, and ~ 3.5 σ when the error bars are corrected to include clustering. In this zone, w_cc_ is consistent with other models such as the hybrid model of CDM and baryons in an open universe, while the "explosion scenario" somewhat overestimates the cluster correlations.