The structural and scaling properties of nearby galaxy clusters

Abstract

Using a sample often nearby (z ≤ 0.15), relaxed galaxy clusters in the temperature range [2-9] keV, we have investigated the scaling relation between the mass at various density contrasts (6 = 2500, 1000, 500, 200) and the cluster temperature. The masses are derived from NFW-type model fits to mass profiles, obtained under the hydrostatic assumption using precise measurements, with XMM-Newton, at least down to 6 = 1000. The logarithmic slope of the M-T relation is well constrained and is the same at all 6, reflecting the self-similarity of the mass profiles. At 6 = 500, the slope of the relation for the sub-sample of hot clusters (kT > 3.5 keV) is consistent with the standard self-similar expectation: a = 1.49 ± 0.15. The relation steepens when the whole sample is considered: a = 1.71 ± 0.09. The normalisation of the relation is discrepant (by ∼30 per cent), at all density contrasts, with the prediction from purely gravitation based models. Models that take into account radiative cooling and galaxy feedback are generally in better agreement with our data. We argue that remaining discrepancies, in particular at low 6, are more likely due to problems with models of the ICM thermal structure rather than to an incorrect estimate of the mass from X-ray data.