Discovery of X‐Ray Emission from the Distant Lensing Cluster of Galaxies Cl 2236−04 atz= 0.552

Abstract

X-ray emission from the distant lensing cluster Cl 2236-04 at z = 0.552 was discovered by ASCA and ROSAT/HRI observations. If the spherical symmetric mass distribution model of the cluster is assumed, the lensing estimate of the cluster mass is a factor of 2 higher than that obtained from X-ray observations as reported for many distant clusters. However, the elliptical and clumpy lens model proposed by Kneib and coworkers is surprisingly consistent with the X-ray observations, assuming that the X-ray-emitting hot gas is isothermal and in a hydrostatic equilibrium state. The existence of the cooling flow in the central region of the cluster is indicated by the short central cooling time and the excess flux detected by ROSAT/HRI compared to the ASCA flux. However, it is shown that, even if the Cl 2236-04 has a cooling flow in the central region, the temperature measured by ASCA, which is the mean emission-weighted cluster temperature in this case, should not be different from the virial temperature of the cluster. Therefore, we conclude that the effects of the clumpiness and nonzero ellipticity in the mass distribution of the cluster are essential to explain the observed feature of the giant luminous arc, and in this cluster there is no discrepancy between strong lensing and X-ray estimation of the cluster mass.