Weak Gravitational Lensing by a Sample of X-ray Luminous Clusters of Galaxies -- III. Serendipitous Weak Lensing Detections of Dark and Luminous Mass Concentrations

摘要

In the course of a weak gravitational lensing survey of 39 clusters ofgalaxies,covering a total sky area of ~1 square degree, we have serendipitouslydiscovered mass concentrations in the fields of A1705 and A1722 which are mostprobably not associated with the main cluster target. By combining weak lensinginformation with two-color galaxy photometry in fields centered on our sampleclusters, we identify a new cluster candidate at z~0.5 in the field of A1705.This cluster candidate also displays strong lensing in the form of a giantluminous arc. The new mass concentration in the field of A1722 also seems to beassociated with an optically luminous cluster of galaxies at z~0.5, but in thiscase there is some evidence for additional structures along the line of sightthat may contribute to the lensing signal. A third cluster, A959, has a darksub-clump which shows interesting morphological evidence in the mass map forbeing associated with the main cluster. This is the first case where there isany significant evidence for a physical association between a dark sub-clump(discovered from weak lensing) and a normal cluster. Analysis of archival X-raydata shows that the three new mass concentrations are not firmly detected inX-rays and that they are X-ray underluminous.