Automatic Synthesis Imaging with Difmap

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Session 8 -- Radio Surveys and Techniques
Display presentation, Monday, 9, 1995, 9:20am - 6:30pm

[8.08] Automatic Synthesis Imaging with Difmap

T. J. Pearson, M. C. Shepherd, G. B. Taylor, and S. T. Myers (Caltech)

{\sc Difmap} is a new interactive program for synthesis imaging. It includes data display, data editing, self-calibration, imaging, deconvolution, and model-fitting. The program can handle continuum, spectral-line, and polarization data from connected-element and very-long-baseline interferometer arrays. The program is written in ANSI C and runs on UNIX workstations. We describe the operation of the program with example data sets from the Very Large Array, the global VLBI network, and the Owens Valley Millimeter Array. We have developed {\sc Difmap} scripts for automatic mapping and self-calibration of both VLA and VLBI data. We describe the strategies adopted for choosing the imaging, deconvolution, and self-calibration parameters, and show how these automatic scripts have made possible the rapid imaging of several hundred sources in the Caltech--Jodrell Bank VLBI surveys (CJ1 and CJ2) and several thousand sources in a VLA search for gravitational lenses (CLASS). Other images made with automatic mapping in {\sc Difmap} are presented at this meeting by Fassnacht et al., Myers et al., and Taylor et al.

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