LoCuSS: A COMPARISON OF CLUSTER MASS MEASUREMENTS FROMXMM-NEWTONAND SUBARU—TESTING DEVIATION FROM HYDROSTATIC EQUILIBRIUM AND NON-THERMAL PRESSURE SUPPORT

Abstract

We compare X-ray hydrostatic and weak-lensing mass estimates for a sample of 12 clusters that have been observed with both XMM-Newton and Subaru. At an over-density of ∆ = 500, we obtain 1 − M X /M WL = 0.01 ± 0.07 for the whole sample. We also divided the sample into undisturbed and disturbed sub-samples based on quantitative X-ray morphologies using asymmetry and fluctuation parameters, obtaining 1 − M X /M WL = 0.09 ± 0.06 and −0.06 ± 0.12 for the undisturbed and disturbed clusters, respectively. In addition to non-thermal pressure support, there may be a competing effect associated with adiabatic compression and/or shock heating which leads to overestimate of X-ray hydrostatic masses for disturbed clusters, for example, in the famous merging cluster A1914. Despite the modest statistical significance of the mass discrepancy, on average, in the undisturbed clusters, we detect a clear trend of improving agreement between M X and M WL as a function of increasing overdensity, M X /M WL = (0.908 ± 0.004) + (0.187 ± 0.010) · log 10 (∆/500). We also examine the gas mass fractions, f gas = M gas /M WL , finding that they are an increasing function of cluster radius, with no dependence on dynamical state, in agreement with predictions from numerical simulations. Overall, our results demonstrate that XMM-Newton and Subaru are a powerful combination for calibrating systematic uncertainties in cluster mass measurements.

Planckintermediate results

“…For the clusters we have in common, the ratio of X-ray masses measured at R 500 is M HE Zhang,500 /M HE 500 = 0.83 ± 0.13. This offset is similar to the offset we find between the X-ray and weak lensing masses discussed above, as expected since Zhang et al (2010) found M WL 500 ∼ M HE 500 . However for relaxed systems (four in total), we find good agreement between hydrostatic mass estimates, with a ratio of M HE Zhang,500 /M HE 500 = 1.00 ± 0.09.…”

“…Such systems also show a clear tendency to have smaller weak lensing to X-ray mass ratios as a function of offset between the X-ray peak and the BCG position. On the other hand there is a mass normalisation offset for relaxed systems, but it is not significant, as found by previous studies (e.g., Vikhlinin et al 2009;Zhang et al 2010).…”

“…agreement between the different mass measures [M WL 500 = (1.01 ± 0.07) M HE 500 ]. As part of their X-ray-weak lensing study, Zhang et al (2010) analysed the same XMM-Newton data for ten of the clusters presented here. For the clusters we have in common, the ratio of X-ray masses measured at R 500 is M HE Zhang,500 /M HE 500 = 0.83 ± 0.13.…”

“…5, this in turn typically explains the trend for the weak lensing masses to be lower than the X-ray masses at R 500 . Recent simulations (and some observations) have found that the X-ray "hydrostatic mass bias" is radially dependent (e.g., Mahdavi et al 2008;Meneghetti et al 2010;Zhang et al 2010;Rasia et al 2012), presumably due to the ICM becoming progressively less virialised the further one pushes into the cluster outskirts. The difference in concentration that we find here cannot be solved by appealing to such a radially dependent X-ray "hydrostatic mass bias".…”

“…The systematic 5-10 percent underestimate of the true mass in the simulations of Becker & Kravtsov (2011) is apparently due to the use of a Navarro-Frenk-White (NFW) model that does not describe the data correctly at large radii. Notwithstanding, the most recent observational results from small samples of clusters for which both X-ray and weak lensing data are available indicate either that there is good agreement between X-ray and weak lensing masses (Zhang et al 2010;Vikhlinin et al 2009), or that the X-ray mass is systematically lower than the weak lensing mass by up to 20 percent, with the underestimate being more important at larger radii (e.g., Mahdavi et al 2008).…”