 | |
Extended sources |
| | All formulae derived above are valid for point sources at the phase centre of the interferometer. The behaviour of extended sources is slightly different. |
| | For a point source, the quantity |
, which can be expressed in units Jansky per beamsize, is independent of the beam size. This means that also the signal-to-noise ratio will be independent of the beam size. | | The same is not true for extended sources! For an extended source (with constant surface brightness) that is larger than the synthesised beam, the flux density per beam varies as a function of beam size as |
| |  |
| | where |
is the flux density per beam area and 
is the imaging sensitivity of the interferometer.  | | RESOLUTION KILLS! |
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