Constraints on the richness-mass relation and the optical-SZE positional offset distribution for SZE-selected clusters
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2015 The Author. We cross-match galaxy cluster candidates selected via their Sunyaev-Zel'dovich effect (SZE) signatures in 129.1 deg2 of the South Pole Telescope 2500d SPT-SZ survey with optically identified clusters selected from the Dark Energy Survey science verification data. We identify 25 clusters between 0.1 z 0.8 in the union of the SPT-SZ and redMaPPer (RM) samples. RM is an optical cluster finding algorithm that also returns a richness estimate for each cluster. We model the richness -mass relation with the following function ln|M500 BlnM500 + Cln E(z) and use SPT-SZ cluster masses and RM richnesses to constrain the parameters. We find B = 1.14-0.18+0.21 and C = 0.73-0.75+0.77. The associated scatter in mass at fixed richness is lnM| = 0.18-0.05+0.08 at a characteristic richness =70.We demonstrate that our model provides an adequate description of the matched sample, showing that the fraction of SPT-SZ-selected clusters with RM counterparts is consistent with expectations and that the fraction of RMselected clusters with SPT-SZ counterparts is in mild tension with expectation. We model the optical-SZE cluster positional offset distribution with the sum of two Gaussians, showing that it is consistent with a dominant, centrally peaked population and a subdominant population characterized by larger offsets. We also cross-match the RMcatalogue with SPT-SZ candidates below the official catalogue threshold significance = 4.5, using the RM catalogue to provide optical confirmation and redshifts for 15 additional clusters with [4, 4.5].