X‐Ray Galaxy Clusters in NoSOCS: Substructure and the Correlation of Optical and X‐Ray Properties

We present a comparison of optical and X-ray properties of galaxy clusters inthe northern sky. We determine the recovery rate of X-ray detected clusters inthe optical as a function of richness, redshift and X-ray luminosity, showingthat the missed clusters are typically low contrast systems when observedoptically. We employ four different statistical tests to test for the presenceof substructure using optical two-dimensional data, finding that approximately35% of the clusters show strong signs of substructure. However, the results aretest-dependent, with variations also due to the magnitude range and radiusutilized.We have also performed a comparison of X-ray luminosity andtemperature with optical galaxy counts (richness). We find that the slope andscatter of the relations between richness and the X-ray properties are heavilydependent on the density contrast of the clusters. The selection ofsubstructure-free systems does not improve the correlation between X-rayluminosity and richness, but this comparison also shows much larger scatterthan one obtained using the X-ray temperature. In the latter case, the sampleis significantly reduced because temperature measurements are available onlyfor the most massive (and thus high contrast) systems. However, the comparisonbetween temperature and richness is very sensitive to the exclusion of clustersshowing signs of substructure. The correlation of X-ray luminosity and richnessis based on the largest sample to date ($\sim$ 750 clusters), while testsinvolving temperature use a similar number of objects as previous works($\lsim$100). The results presented here are in good agreement with existingliterature.Comment: 32 pages, 18 figures, ApJ in press, including minor changes following the ApJ's editio