Reconciling Planck cluster counts and cosmology: Chandra/XMM instrumental calibration and hydrostatic mass bias

The temperature of X-ray emitting gas TX is often used to infer the total mass of galaxy clusters (under the assumption of hydrostatic equilibrium). Unfortunately, XMM-Newton and Chandra observatories measure inconsistent temperatures for the same gas, due to uncertain instrumental calibration. We translate the relative bias in temperature measurements of Schellenberger et al. (2014) into a bias on inferred mass for a sample of clusters with homogeneous weak lensing (WL) masses, in order to simultaneously examine the hydrostatic bias and instrument calibration. Israel et al. (2014) found consistent WL and Chandra hydrostatic X-ray masses for a sample of clusters at z∼0.5 and masses of a few 1014 M. Re-evaluating the latter, we find their XMM-Newton masses to be lower by bxcal = 15–20 % than their Chandra masses. At the massive end (&5 · 1014 M), the XMM-Newton masses are ∼35 % lower than the WL masses. Assuming that the true hydrostatic bias is 20 %, as indicated by simula-tions, our results for the massive end indicate that Chandra’s calibration of the energy dependence of the effective area is more accurate than XMM-Newton’s. However, th