Planck SZ vs. optical scaling relations

Many observables (e.g., Y_X, Y_SZ, N_200) are correlated with the halo mass. This enables obtaining mass function of halos at different redshifts, which is a sensitive probe of dark energy. However, different observables are biased differently. Thus it is necessary to cross-caliberate different observables. This paper

(http://arxiv.org/abs/1101.2027) shows that optical richness (which is calibrated against weak-lensing mass measurements) based prediction for Y_SZ is >~ twice larger than what is measured by Planck (Fig. 2). Y_SZ measurements are consistent with predictions of X-ray models applied to the same sample. Richness (number of elliptical galaxies > a cut-off luminosity within a fraction of virial radius) must have a large scatter for a fixed profile of the ICM. This is a puzzle that must be resolved if richness can be used for precision cosmology!