Comparison between closure phase and phase referenced interferometric image reconstructions

Abstract

We compare the quality of interferometric image reconstructions for two different sets of data: square of the visibility plus closure phase (e.g. AMBER like case) and square of the visibility plus visibility phase (e.g. PRIMA+AMBER or GRAVITY like cases). We used the Multi-aperture image Reconstruction Algorithm for reconstructions of test cases under different signal-to-noise ratios and noisy data (squared visibilities and phases). Our study takes into account noise models based on the statistics of visibility, phase and closure phase. We incorporate the works developed by Tatulli and Chelly (2005) on the noise of the power-spectrum and closure phase in the read-out and photon noise regimes,1 and by Colavita (1999) on the signal-to-noise ratio of the visibility phase.2 The final images were then compared to the original one by means of positions and fluxes, computing the astrometry and the photometry. For the astrometry, the precision was typically of tens of microarcseconds, while for the photometry, it was typically of a few percent. Although both cases are suitable for image restorations of real interferometric observations, the results indicate a better performance of phase referencing (V 2 + visibility phase) in a low signal-to-noise ratio scenario.