A primary beam simulation

Logged on 25/08/09 12:33:04

Let's use the five-source sky generated for SSSC21 and perform a primary beam simulation. The primary beam of an interferometer at its most benign will attenuate the brightness of sources away from the pointing centre. For an array consisting of equal dishes (e.g. WSRT, VLA) the primary beam of the interferometer closely resembles the of a single element. For a heterogeneous array (e.g. eMERLIN) the situation is a lot more complicated, and even more so for interferometers whose elements are phased arrays (e.g. LOFAR).

Furthermore the primary beam response, characterised by the so-called E-Jones matrix, generally exhibits time- and frequency-dependence and has different properties per polarization. Accurate understanding of it is essential if you want to achieve high dynamic range over a wide field. Fortunately the WSRT E-Jones is well behaved and well understood, so we're in at the shallow end here.

Please take a look at SSSC21 for to see what the sky in this simulation would look like without the primary beam effects. The note about intrinsic and apparent fluxes in SSSC20 might be worth reading, and in any case you should have a read about primary beams in a synthesis imaging text book if you're serious about them. This PURR log won't be an exhaustive introduction by any stretch of the imagination.

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