2007A&A...468...25H

We quantitatively studied the X-ray cluster morphology, and then investigated the relationships between the cluster X-ray morphology and various cluster characteristics determined from the optical data. Using a sample of 101 clusters at redshift z∼0.05-1 taken from the Chandra archive, the X-ray morphology is characterized by a series of objectively-measured simple statistics of X-ray surface brightness, which are designed to be robust against variations of image quality caused by various exposure times and various cluster redshifts. The main conclusions from this work are: (1) X-ray morphologies of clusters show no significant correlation with optical richness, or related quantities. (2) X-ray morphologies of clusters are significantly correlated with the degree to which the brightest cluster member stands out against the cluster background. (3) X-ray morphologies of clusters are also correlated with optical concentration defined by galaxy distribution including fainter populations. (4) The ratio of the strong-lensing to X-ray mass measurements is correlated with the X-ray concentration, in that highly X-ray concentrated clusters show compatible strong-lensing and X-ray mass measurements, while those with low X-ray concentration show discrepancy between the two mass measurements.