ESA Science & Technology - A weak lensing study of X-ray groups in the COSMOS survey: form and evolution of the Mass-Luminosity relation

Publication date: 20 January 2010

Authors: Leauthaud, A., et al.,

Journal: Astrophysical Journal
Year: 2010

Copyright: Institute of Physics and IOP Publishing Limited

Measurements of X-ray scaling laws are critical for improving cosmological constraints derived with the halo mass function and for understanding the physical processes that govern the heating and cooling of the intracluster medium. In this paper, we use a sample of 206 X-ray selected galaxy groups to investigate the scaling relation between X-ray luminosity (L_X) and halo mass (M₂₀₀) where M₂₀₀ is derived via stacked weak gravitational lensing. This work draws upon a broad array of multiwavelength COSMOS observations including 1.64 degrees² of contiguous imaging with the Advanced Camera for Surveys (ACS) to a limiting magnitude of I_F814W = 26.5 and deep XMM-Newton/Chandra imaging to a limiting flux of 1.0 x 10^-15 erg cm^-2 s^-1 in the 0.5-2 keV band. The combined depth of these two data-sets allows us to probe the lensing signals of X-ray detected structures at both higher redshifts and lower masses than previously explored. Weak lensing profiles and halo masses are derived for nine sub-samples, narrowly binned in luminosity and redshift. The COSMOS data alone are well fit by a power law with a slope of alpha = 0.66 +/- 0.14. These results significantly extend the dynamic range for which the halo masses of X-ray selected structures have been measured with weak gravitational lensing. As a result, tight constraints are obtained for the slope of the M-L_X relation. The combination of our group data with previously published cluster data demonstrates that the M-L_X relation is well described by a single power law, alpha = 0.64 +/- 0.03, over two decades in mass. These results are inconsistent at the 3.7 sigma level with the self-similar prediction of alpha = 0.75. We examine the redshift dependence of the M - L_X relation and find little evidence for evolution beyond the rate predicted by self-similarity from z ~0.25 to z ~0.8.