Measuring the mean and scatter of the X-ray luminosity -- optical richness relation for maxBCG galaxy clusters

Understand

Determining the scaling relations between galaxy cluster observables requires large samples of uniformly observed clusters.

• We measure the mean X-ray luminosity--optical richness (L_X--N_200) relation for an approximately volume-limited sample of more than 17,000 optically-selected clusters from the maxBCG catalog spanning the redshift range 0.1<z<0.3.
• By stacking the X-ray emission from many clusters using ROSAT All-Sky Survey data, we are able to measure mean X-ray luminosities to ~10% (including systematic errors) for clusters in nine independent optical richness bins.
• In addition, we are able to crudely measure individual X-ray emission from ~800 of the richest clusters.