Galaxy cluster centering is one of the key issues for precision cosmology studies using galaxy surveys. The red-sequence Matched-filter Probabilistic Percolation (redMaPPer) estimates the centering probability of member galaxies from photometric information; however, the centering algorithm has not previously been well-tested. We test the centering probabilities of redMaPPer cluster catalog using the projected cross correlation between redMaPPer clusters with photometric red galaxies and galaxy-galaxy lensing. We focus on the subsample of redMaPPer clusters in which the redMaPPer central galaxies (RMCGs) are not the brightest member galaxies (BMEM) and both of them have spectroscopic redshift. This subsample represents nearly 10% of the whole cluster sample. We also make a “High Pcen” sample where the central probability of RMCGs is larger than 99% to be used as a reference sample of central galaxies. We find a clear difference in the cross-correlation measurements between RMCGs and BMEMs, and the estimated centering probability is 74$\pm$10% for RMCGs and 13$\pm$4% for BMEMs in the sample. These values are in agreement with the central probability values reported by redMaPPer (75% for RMCG and 10% for BMEMs) within 1$\sigma$. Our analysis provides a strong consistency test of the redMaPPer centering probabilities. Our results suggest that redMaPPer centering probabilities are reliably estimated, and that the brightest galaxy in the cluster is not always the central galaxy.
C. Hikage, R. Mandelbaum, A. Leauthaud, et. al.
Wed, 1 Mar 17
Comments: 8 pages, 3 figures, 2 tables