A WEAK LENSING STUDY OF X-RAY GROUPS IN THE COSMOS SURVEY: FORM AND EVOLUTION OF THE MASS-LUMINOSITY RELATION

Abstract

Measurements of X-ray scaling laws are critical for improving cosmological\nconstraints derived with the halo mass function and for understanding the\nphysical processes that govern the heating and cooling of the intracluster\nmedium. In this paper, we use a sample of 206 X-ray selected galaxy groups to\ninvestigate the scaling relation between X-ray luminosity (Lx) and halo mass\n(M00) where M200 is derived via stacked weak gravitational lensing. This work\ndraws upon a broad array of multi-wavelength COSMOS observations including 1.64\nsquare degrees of contiguous imaging with the Advanced Camera for Surveys (ACS)\nand deep XMM-Newton/Chandra imaging. The combined depth of these two data-sets\nallows us to probe the lensing signals of X-ray detected structures at both\nhigher redshifts and lower masses than previously explored. Weak lensing\nprofiles and halo masses are derived for nine sub-samples, narrowly binned in\nluminosity and redshift. The COSMOS data alone are well fit by a power law,\nM200 ~ Lx^a, with a slope of a=0.66+-0.14. These results significantly extend\nthe dynamic range for which the halo masses of X-ray selected structures have\nbeen measured with weak gravitational lensing. As a result, tight constraints\nare obtained for the slope of the M-Lx relation. The combination of our group\ndata with previously published cluster data demonstrates that the M-Lx relation\nis well described by a single power law, a=0.64+-0.03, over two decades in\nmass, 10^13.5-10^15.5 h72^-1 Msun. These results are inconsistent at the 3.7\nlevel with the self-similar prediction of a=0.75. We examine the redshift\ndependence of the M-Lx relation and find little evidence for evolution beyond\nthe rate predicted by self-similarity from z ~ 0.25 to z ~ 0.8.\n