Astrometry and photometry in high contrast imaging
Raphael Galicher and Christian Marois
National Research Council Canada, Herzberg Institute of Astrophysics
The direct exoplanet imaging field will strongly benefit from the larger aperture and the higher angular resolution achieved by next generation 30+m telescopes. To fully take advantage of these new facilities, one of the biggest challenges that ground-based adaptive optics imaging must overcome is to be able to derive accurate astrometry and photometry with realistic estimate of residual errors. The planet photometry and its astrometry are used to compare with atmospheric models and to fit orbits. If erroneous numbers are found, or if errors are underestimated, spurious fits can lead to unphysical planet characteristics or wrong/unstable orbits. Overestimating the errors also needs to be avoided as it degrades the value of the data. In the high-contrast planet imaging context, we will present various photometry/astrometry biases induced by several noise sources (anisoplanatism, non-Gaussian noise, etc.) or processing techniques (ADI/SSDI/LOCI) that we have uncovered during our ongoing direct exoplanet imaging campaign at Gemini, VLT and Keck. We will describe the procedures that we have implemented to properly estimate those biases. These solutions will be implemented in the Gemini Planet Imager campaign data pipeline and we expect that they will also play a crucial role in any future 30+m survey.