LoCuSS: The Near-Infrared Luminosity and Weak-Lensing Mass Scaling Relation of Galaxy Clusters

TL;DR

This study establishes a near-infrared luminosity to weak-lensing mass scaling relation for galaxy clusters, demonstrating that near-infrared light is a low-scatter, cost-effective proxy for cluster mass, useful for cosmology.

Contribution

First to empirically derive a scaling relation between near-infrared luminosity and weak-lensing mass for galaxy clusters, with detailed analysis of scatter and measurement methods.

Findings

Intrinsic scatter of ~10% in the mass-luminosity relation.

Near-infrared luminosity within 1 Mpc is a low-scatter mass proxy.

The relation's slope varies with measurement approach but remains consistent in low scatter.

Abstract

We present the first scaling relation between weak-lensing galaxy cluster mass, $M_{WL}$, and near-infrared luminosity, $L_K$. Our results are based on 17 clusters observed with wide-field instruments on Subaru, the United Kingdom Infrared Telescope, the Mayall Telescope, and the MMT. We concentrate on the relation between projected 2D weak-lensing mass and spectroscopically confirmed luminosity within 1Mpc, modelled as $M_{WL} \propto L_{K}^b$, obtaining a power law slope of $b=0.83^{+0.27}_{-0.24}$ and an intrinsic scatter of $\sigma_{lnM_{WL}|L_{K}}=10^{+8}_{-5}\%$. Intrinsic scatter of ~10% is a consistent feature of our results regardless of how we modify our approach to measuring the relationship between mass and light. For example, deprojecting the mass and measuring both quantities within $r_{500}$, that is itself obtained from the lensing analysis, yields $\sigma_{lnM_{WL}|L_{K}}=10^{+7}_{-5}\%$ and $b=0.97^{+0.17}_{-0.17}$. We also find that selecting members based on their (J-K) colours instead of spectroscopic redshifts neither increases the scatter nor modifies the slope. Overall our results indicate that near-infrared luminosity measured on scales comparable with $r_{500}$ (typically 1Mpc for our sample) is a low scatter and relatively inexpensive proxy for weak-lensing mass. Near-infrared luminosity may therefore be a useful mass proxy for cluster cosmology experiments.