Fourier Phase Analysis in Radio-Interferometry

Dr. F. Levrier

(Laboratoire de radioastronomie, Département de physique, École normale supérieure de Paris, France)

Dienstag/Tuesday, 2006-4-18 17:15, PN 114

Eugene-Paul-Wigner Gebäude (Physik-Neubau), Hardenbergstr. 36, 10623 Berlin

Abstract:

Most statistical tools used to characterize the complex structures of the interstellar medium can be related to the power spectrum, and therefore to the Fourier amplitudes of the observed fields. To tap into the vast amount of information contained in the Fourier phases, one may consider the probability distribution function (PDF) of phase increments, and the related concept of phase entropy. We use these ideas here with the purpose of assessing the ability of radio-interferometers to detect and recover the phase structure present in an extended source. By comparing current arrays such as the VLA and PdBI to the future ALMA instrument, we show that the latter is definitely needed to achieve significant detection of this phase structure. We also show that it may recover the actual "amount" of phase structure, if multiple configurations are used. However, the presence of atmospheric phase luctuations may completely wash out relevant phase information, which supports the proposition
that dedicated water vapor radiometers should be employed.