A&A Supplement series, Vol. 129, May I 1998, 637-645

Received May 23; accepted October 06, 1997

Deconvolution of interferometric observations by MIM

J. Pfleiderer - G. Köb

Institut für Astronomie der Leopold-Franzens-Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria

Abstract:

We derive deconvolution equations - dirty map and dirty beam - without use of Fourier transforms. We thus avoid interpolation of observed complex visibilities (CVs) as well as aliasing effects. MIM (= minimum information method) implies the modification of the dirty beam such that a straightforward deconvolution without constraints gives a smoothed result. Smoothing can be diminished at edges and point sources by modification of the dirty map near these features. We give test examples in which we discuss in detail the Gibbs phenomenon encountered in any smoothed deconvolution of sharp features. Finally, we deconvolve old VLBI observations of
3C 309.1.

keywords: methods: data analysis -- techniques: image processing, interferometric -- quasars: individual: 3C 309.1

• 1. Introduction
• 2. Deconvolution equations
• 3. Method of solution
• 4. Edge detection
• 5. Tests
• 6. Example: 3C 309.1
• References