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

TL;DR

This study combines weak lensing and X-ray data for a large sample of galaxy clusters to refine scaling relations, revealing a steepening at low masses and the impact of system state and calibration on these relations.

Contribution

It provides bias-corrected scaling relations for low and high mass clusters, highlighting the steepening at low masses and the effects of system dynamics and calibration.

Findings

Tx has lower intrinsic scatter than Lx as a mass proxy.

Galaxy groups are more luminous and warmer for their mass than clusters.

Calibration differences affect the slope of scaling relations.

Abstract

We present weak lensing and X-ray analysis of 12 low mass clusters from the CFHTLenS and XMM-CFHTLS surveys. We combine these systems with high-mass systems from CCCP and low-mass systems from COSMOS to obtain a sample of 70 systems, spanning over two orders of magnitude in mass. We measure core-excised Lx-Tx, M-Lx and M-Tx scaling relations and include corrections for observational biases. By providing fully bias corrected relations, we give the current limitations for Lx and Tx as cluster mass proxies. We demonstrate that Tx benefits from a significantly lower intrinsic scatter at fixed mass than Lx. 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-Lx and M-Tx 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 Lx-Tx 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 Lx-Tx and M-Tx relations than XMM-Newton.