The LX--M relation of Clusters of Galaxies
Abstract
We present a new measurement of the scaling relation between X-ray luminosity and total mass for 17,000 galaxy clusters in the maxBCG cluster sample. Stacking sub-samples within fixed ranges of optical richness, N200, we measure the mean 0.1-2.4 keV X-ray luminosity, <LX>, from the ROSAT All-Sky Survey. The mean mass, <M200>, is measured from weak gravitational lensing of SDSS background galaxies (Johnston et al. 2007). For 9 <= N200 < 200, the data are well fit by a power-law, <LX>/1042 h-2 erg/s = (12.6+1.4-1.3 (stat) +/- 1.6 (sys)) (<M200>/1014 h-1 Msun)1.65+/-0.13. The slope agrees to within 10% with previous estimates based on X-ray selected catalogs, implying that the covariance in LX and N200 at fixed halo mass is not large. The luminosity intercent is 30%, or 2σ, lower than determined from the X-ray flux-limited sample of Reiprich & Bohringer (2002), assuming hydrostatic equilibrium. This difference could arise from a combination of Malmquist bias and/or systematic error in hydrostatic mass estimates, both of which are expected. The intercept agrees with that derived by Stanek et al. (2006) using a model for the statistical correspondence between clusters and halos in a WMAP3 cosmology with power spectrum normalization sigma8 = 0.85. Similar exercises applied to future data sets will allow constraints on the covariance among optical and hot gas properties of clusters at fixed mass.