The mass-L_x relation for moderate luminosity X-ray clusters

TL;DR

This study measures the masses of 25 moderate luminosity X-ray galaxy clusters using weak lensing, establishing a tight correlation between lensing mass and cluster richness, and refining the mass-luminosity scaling relation.

Contribution

It provides an empirical correction for charge transfer inefficiency effects and presents new measurements of the mass-luminosity relation for galaxy clusters.

Findings

Lensing signal detected around most clusters.

Mass correlates tightly with cluster richness.

Best-fit power law slope is 0.68 with a normalization of 1.2×10^14 M_sun.

Abstract

We present measurements of the masses of a sample of 25 moderate X-ray luminosity clusters of galaxies from the 160 square degree ROSAT survey. The masses were obtained from a weak lensing analysis of deep F814W images obtained using the Advanced Camera for Surveys (ACS). We present an accurate empirical correction for the effect of charge transfer (in)efficiency on the shapes of faint galaxies. A significant lensing signal is detected around most of the clusters. The lensing mass correlates tightly with the cluster richness. We measured the intrinsic scatter in the scaling relation between M_2500 and L_X and find the best fit power law slope and normalisation to be alpha=0.68+-0.07 and M_X=(1.2+-0.12)10^14M_sun (for L_X=2x10^44 erg/s). These results agree well with a number of recent studies, but the normalisation is lower compared to the study of Rykoff et al. (2008b). One explanation for this difference may be the fact that (sub)structures projected along the line-of-sight boost both the galaxy counts and the lensing mass. Such superpositions lead to an increased mass at a given L_X when clusters are binned by richness.