CFHTLenS: weak lensing calibrated scaling relations for low-mass clusters of galaxies

We present weak lensing and X-ray analysis of 12 low-mass clusters from the Canada–France–Hawaii Telescope Lensing Survey and XMM-CFHTLS surveys. We combine these systems with high-mass systems from Canadian Cluster Comparison Project and low-mass systems from Cosmic Evolution Survey to obtain a sample of 70 systems, spanning over two orders of magnitude in mass. We measure core-excised L_X–T_X, M–L_X and M–T_X scaling relations and include corrections for observational biases. By providing fully bias-corrected relations, we give the current limitations for L_X and T_X as cluster mass proxies. We demonstrate that T_X benefits from a significantly lower intrinsic scatter at fixed mass than L_X. By studying the residuals of the bias-corrected relations, we show for the first time using weak lensing masses that galaxy groups seem more luminous and warmer for their mass than clusters. This implies a steepening of the M–L_X and M–T_X relations at low masses. We verify the inferred steepening using a different high-mass sample from the literature and show that variance between samples is the dominant effect leading to discrepant scaling relations. We divide our sample into subsamples of merging and relaxed systems, and find that mergers may have enhanced scatter in lensing measurements, most likely due to stronger triaxiality and more substructure. For the L_X–T_X relation, which is unaffected by lensing measurements, we find the opposite trend in scatter. We also explore the effects of X-ray cross-calibration and find that Chandra calibration leads to flatter L_X–T_X and M–T_X relations than XMM–Newton