2016A&A...592A...4L

Context. The XXL Survey is the largest survey carried out by XMM-Newton. Covering an area of 50deg², the survey contains ∼450 galaxy clusters out to a redshift ∼2 and to an X-ray flux limit of ∼5x10^–15erg/s/cm². This paper is part of the first release of XXL results focussed on the bright cluster sample.
Aims. We investigate the scaling relation between weak-lensing mass and X-ray temperature for the brightest clusters in XXL. The scaling relation discussed in this article is used to estimate the mass of all 100 clusters in XXL-100-GC.
Methods. Based on a subsample of 38 objects that lie within the intersection of the northern XXL field and the publicly available CFHTLenS shear catalog, we derive the weak-lensing mass of each system with careful considerations of the systematics. The clusters lie at 0.1<z<0.6 and span a temperature range of T~=1-5keV. We combine our sample with an additional 58 clusters from the literature, increasing the range to T~=1-10keV. To date, this is the largest sample of clusters with weak-lensing mass measurements that has been used to study the mass-temperature relation.
Results. The mass-temperature relation fit (M∝T^b) to the XXL clusters returns a slope b=1.78^+0.37_–0.32 and intrinsic scatter σ_lnM|T~=0.53; the scatter is dominated by disturbed clusters. The fit to the combined sample of 96 clusters is in tension with self-similarity, b=1.67±0.12 and σ_lnM|T~=0.41.
Conclusions. Overall our results demonstrate the feasibility of ground-based weak-lensing scaling relation studies down to cool systems of ∼1 keV temperature and highlight that the current data and samples are a limit to our statistical precision. As such we are unable to determine whether the validity of hydrostatic equilibrium is a function of halo mass. An enlarged sample of cool systems, deeper weak-lensing data, and robust modelling of the selection function will help to explore these issues further.