Reduction of ringing effects by an improved deconvolution algorithm^*

Application to A370 CFHT image of gravitational arcs

¹ UMR 6525 Astrophysique, Université de Nice Sophia Antipolis, Parc Valrose, 06108 Nice Cedex 2, France
² Institut Fresnel, UMR 6133, École Nationale Supérieure de Physique de Marseille, Domaine Universitaire de Saint Jérôme, 13397 Marseille Cedex 20, France e-mail: muriel.roche@fresnel.fr
³ Institut Astrophysique de Paris, UMR 7095, 98bis boulevard Arago, 75014 Paris, France
⁴ Observatoire de Paris, LERMA, UMR 8112, 61 avenue de l'Observatoire, 75014 Paris, France

Corresponding author: M. Roche, muriel.roche@fresnel.fr

Received: 4 February 2003
Accepted: 17 June 2003

Abstract

We develop a self-consistent automatic procedure to restore information from astronomical observations. It relies on both a new deconvolution algorithm called LBCA (Lower Bound Constraint Algorithm) and the use of the Wiener filter. In order to explore its scientific potential for strong and weak gravitational lensing, we process a CFHT image of the galaxy cluster Abell 370 which exhibits spectacular strong gravitational lensing effects. A high quality restoration is here of particular interest to map the dark matter within the cluster. We show that the LBCA is especially efficient to reduce ringing effects introduced by classical deconvolution algorithms in images with a high background. The method allows us to make a blind detection of the radial arc and to recover morphological properties similar to those observed from HST data. We also show that the Wiener filter is suitable to stop the iterative process before noise amplification, using only the unrestored data.