Comparison between closure phase and phase referenced interferometric image reconstructions Nuno Gomes a, b, c , Paulo J. V. Garcia c, d , Eric Thi´ ebaut e , St´ ephanie Renard d , Mercedes Filho f a European Organisation for Astronomical Research in the Southern Hemisphere (ESO), Karl-Schwarzschild-Straße 2, Garching bei M¨ unchen, D-85748 M¨ unchen, Germany; b Faculdade de Ciˆ encias da Universidade do Porto (FCUP), Rua do Campo Alegre, s/n, 4169-007 Porto, Portugal; c Laborat´orio de Sistemas, Instrumenta¸ c˜aoeModela¸c˜ ao em Ciˆ encias e Tecnologias do Ambiente e do Espa¸ co (SIM)/Faculdade de Engenharia da Universidade do Porto (FEUP), Rua Dr. Roberto Frias, s/n, 4200-465 Porto, Portugal; d Laboratoire d’Astrophysique, Observatoire de Grenoble (LAOG), 414, Rue de la Piscine, Saint-Martin d’H´ eres, France; e Centre de Recherche Astrophysique de Lyon (CRAL)/Observatoire de Lyon, 9, Avenue Charles Andr´ e, 69561 Saint-Genis Laval C´ edex, France; f Centro de Astrof´ ısica da Universidade do Porto (CAUP), Rua das Estrelas, 4150-762 Porto, Portugal; 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. Keywords: Interferometry, PRIMA, power-spectrum, visibility phase, phase referencing, closure phase, imaging, MiRA 1. INTRODUCTION Image reconstruction is a key problem in optical interferometry. Data is obtained in a sparse coverage of the Fourier plane (UV plane), not in the form of an image. By means of visibility and closure phase information and supported by physical models, modern optical interferometers allow one to yield reconstructed images of real objects. 3, 4 The Phase-Referenced Imaging and Micro-arcsecond Astrometry (PRIMA) dual-feed facility, recently installed at the Very Large Telescope Interferometer (VLTI), will offer a phase referenced imaging mode, where data consisting on spectrally dispersed visibilities and phases can be used to generate images. 5, 6 The second generation instrument General Relativity Analysis via VLT InterferometrY (GRAVITY), 7 to be implemented in the VLTI during this decade, will use four telescopes simultaneously in order to achieve an accuracy of 10 μas in astrometry on six baselines and to offer phase referencing on faint targets (K ≥ 15). 8 Therefore, two scenarios for interferometric image reconstruction arise from current facilities: power-spectrum + closure phase Further author information: send correspondence to Nuno Gomes. E-mail: ngomes@eso.org. Optical and Infrared Interferometry II, edited by William C. Danchi, Françoise Delplancke, Jayadev K. Rajagopal, Proc. of SPIE Vol. 7734, 773438 · © 2010 SPIE · CCC code: 0277-786X/10/$18 · doi: 10.1117/12.857146 Proc. of SPIE Vol. 7734 773438-1 Downloaded from SPIE Digital Library on 25 Feb 2011 to 134.171.37.57. Terms of Use: http://spiedl.org/terms