Processing math: 100%

Algorithms to merge single-dish and interferometer information

The measurement equations of a single-dish and an interferometer are quite different from each other. Indeed, the measurement equation of a single-dish antenna is Isdmeas=BsdIsource+N i.e. the measured intensity ( Isdmeas ) is the convolution of the source intensity distribution ( Isource ) by the single-dish beam ( Bsd ) plus some thermal noise, while the measurement equation of an interferometer can be rewritten as Iidmeas=Bdirty(Bprimary.Isource)+N, i.e. the measured intensity ( Iidmeas ) is the convolution of the source intensity distribution times the primary beam ( Bprimary.Isource ) by the dirty beam ( Bdirty ) plus some thermal noise. Bsd has very similar properties than Bprimary and very different properties than Bdirty . In radioastronomy, Bsd and Bprimary both have (approximately) Gaussian shapes. Moreover, the fact that we will use the single-dish information to produce the short-spacing information filtered out by the interferometer implies that Bsd and Bprimary have similar full width at half maximum. Now, Bdirty is quite far from a Gaussian shape with the current generation of interferometer (in particular, it has large sidelobes) and the primary side lobe of Bdirty has a full width at half maximum close to the interferometer resolution, i.e. much smaller than the FWHM of Bsd .

Merging both kinds of information obtained from such different measurement equations thus asks for a dedicated processing. There are mainly two families of short-spacing processing: the hybridization and the pseudo-visibility techniques.



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