Weak lensing study of dark matter filaments and application to the binary cluster A 222 and A 223

Abstract

We present a weak lensing analysis of the double cluster system Abell 222 and Abell 223. The lensing reconstruction shows evidence for a possible dark matter filament connecting both clusters. The case for a filamentary connection between A 222/223 is supported by an analysis of the galaxy density and X-ray emission between the clusters. Using the results of N-body simulations, we try to develop a criterion that separates this system into cluster and filament regions. The aim is to find a technique that allows the quantification of the significance of (weak lensing) filament candidates in close pairs of clusters. While this mostly fails, the aperture quadrupole statistics (Schneider & Bartelmann 1997) shows some promise in this area. The cluster masses determined from weak lensing in this system are considerably lower than those previously determined from spectroscopic and X-ray observations (Dietrich et al. 2002; Proust et al. 2000; Wang et al. 1999). Additionally, we report the serendipitous weak lensing detection of a previously unknown cluster in the field of this double cluster system.

20 pages, 22 figures, replaced with version accepted by A&A. New title, changes to Sect. 5, conclusions unchanged. Version with full resolution figures available at http://www.astro.uni-bonn.de/~dietrich/publications/1523.ps.gz