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 1 Mpc, modelled as M-WL proportional to L-K(b), obtaining a power-law slope of b = 0.83(-0.24)(+0.27) and an intrinsic scatter of sigma ln M-WL- L-K = 10(-5)(+8) per cent. Intrinsic scatter of similar to 10 per cent 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 ln M-WL- L-K = 10(-5)(+7) per cent 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 r500 (typically 1 Mpc 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.