SIMBAD references

Multi-frequency synthesis is the technique of using measurements at several observing frequencies when forming an image in radio interferometric aperture synthesis. The main advantage of this over the traditional single frequency approach is improved u-v coverage, allowing more rapid synthesis of the aperture. This paper considers several issues involved in a practical multi-frequency synthesis experiment. In particular, variation of source brightness distribution with frequency results in artifacts in the resultant images. A new, CLEAN-based, algorithm is presented which removes these artifacts during the deconvolution stage of image formation. As a demonstration of the technique we present an image of the double-lobed radio source PKSB1733-565.