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Proceedings Paper

Lucky imaging and speckle discrimination for the detection of faint companions with adaptive optics
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Paper Abstract

We have analyzed the application of frame selection ("lucky imaging") to adaptive optics (AO), short-exposure observations of faint companions. We have used the instantaneous Strehl ratio as an image quality metric. The probability density function (PDF) of this quantity can be used to determine the outcome of frame selection in terms of optimizing the Strehl ratio and the peak-signal-to-noise-ratio of the shift-and-add image. In the presence of static speckles, frame selection can lead to both: improvement in resolution--as quantified by the Strehl ratio, as well as faint signal detectability--given by the peak-signal-to-noise-ratio. This theoretical prediction is confirmed with real data from AO observations using Lick Observatory's 3m Shane telescope, and the Palomar Observatory's 5m Hale telescope. In addition, we propose a novel statistics-based technique for the detection of faint companions from a sequence of AO-corrected exposures. The algorithm, which we call stochastic speckle discrimination, utilizes the "statistical signature" of the centre of the point spread function (PSF) to discriminate between faint companions and static speckles. The technique yields excellent results even for signals invisible in the shift-and-add images.

Paper Details

Date Published: 10 July 2008
PDF: 12 pages
Proc. SPIE 7015, Adaptive Optics Systems, 70152H (10 July 2008); doi: 10.1117/12.788442
Show Author Affiliations
Szymon Gladysz, National Univ. of Ireland, Galway (Ireland)
Julian Christou, National Science Foundation (United States)
Nicholas Law, Caltech Optical Observatories, California Institute of Technology (United States)
Richard Dekany, Caltech Optical Observatories, California Institute of Technology (United States)
Michael Redfern, National Univ. of Ireland, Galway (Ireland)
Craig Mackay, Institute of Astronomy, Univ. of Cambridge (United Kingdom)

Published in SPIE Proceedings Vol. 7015:
Adaptive Optics Systems
Norbert Hubin; Claire E. Max; Peter L. Wizinowich, Editor(s)

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