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P. F. Hopkins (Princeton University Astrophysical Sciences Department), S. Doeleman, C. J. Lonsdale (MIT Haystack Observatory)
The Low-Frequency Array (LOFAR) will conduct observations from 10 to 240 MHz, with arcsecond angular resolution. However, there are currently no models of the statistical distribution of source sizes and flux densities at these low frequencies and high resolutions. Such a model is needed for the refinement of LOFAR calibration algorithms and strategies, and for the development of calibration software. To build such a model, a wide-field image centered on the extragalactic radio source 3C249.1 was created at 328 MHz from VLA A-array observations of the source, with an approximate 3.5 degree field of view. A source catalog was compiled from the image with identification by eye and subsequent use of routines in the AIPS environment to extract source properties. The resolution and sensitivity of this image represents the current state-of-the-art, and such data are the closest available match to the relevant properties of the LOFAR calibrator source population. The data were fitted for various statistics, and empirical models, based partly on VLA 74 MHz images, were used to extrapolate those statistics to LOFAR frequencies. The information is used by a sky simulator, which takes output frequency, the distribution of spectral indices, and field of view size as independent variables, and generates random skies for analysis by LOFAR simulation software.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.