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

¹ Institut für Astrophysik und Extraterrestrische Forschung, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany e-mail: dietrich@astro.uni-bonn.de
² Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
³ Radioastronomisches Institut, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany

Received: 24 June 2004
Accepted: 19 May 2005

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, MNRAS, 286, 696) 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, A&A, 394, 395; Proust et al. 2000, A&A, 355, 443; David et al. 1999 ApJ, 519, 533). Additionally, we report the serendipitous weak lensing detection of a previously unknown cluster in the field of this double cluster system.