The original forward-fit algorithm (by Aschwanden) starts with the assumption that there are a very limited number of individual sources, usually only one or two. The parameters describing each source (e.g., the flux, location, size, and orientation of an elliptical Gaussian) are adjusted until the model-predicted count rates agree best with the measured count rates in a χ2 sense. The new visibility version of forward fit, VIS_FWDFIT or VF, adjusts the source parameters such that the model-predicted visibilities agree best with the measured visibilities. This approach offers fast determinations of these source parameters. However, as with any forward-fitting method, it is critical that the assumptions concerning the number of sources and their shapes match reality.

This page last updated: June 27, 2011