Fundamental limitations of high contrast imaging set by small sample statistics

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DOIResolve DOI: http://doi.org/10.1088/0004-637X/792/2/97
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TypeArticle
Journal titleThe Astrophysical Journal
ISSN0004-637X
Volume792
Issue2
Article number97
Subjectmethods: statistical; techniques: high angular resolution
AbstractIn this paper, we review the impact of small sample statistics on detection thresholds and corresponding confidence levels (CLs) in high-contrast imaging at small angles. When looking close to the star, the number of resolution elements decreases rapidly toward small angles. This reduction of the number of degrees of freedom dramatically affects CLs and false alarm probabilities. Naively using the same ideal hypothesis and methods as for larger separations, which are well understood and commonly assume Gaussian noise, can yield up to one order of magnitude error in contrast estimations at fixed CL. The statistical penalty exponentially increases toward very small inner working angles. Even at 5-10 resolution elements from the star, false alarm probabilities can be significantly higher than expected. Here we present a rigorous statistical analysis that ensures robustness of the CL, but also imposes a substantial limitation on corresponding achievable detection limits (thus contrast) at small angles. This unavoidable fundamental statistical effect has a significant impact on current coronagraphic and future high-contrast imagers. Finally, the paper concludes with practical recommendations to account for small number statistics when computing the sensitivity to companions at small angles and when exploiting the results of direct imaging planet surveys.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); National Science Infrastructure
Peer reviewedYes
NPARC number21272997
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Record identifierc3818d46-3c49-4429-bd2e-779e271c2e39
Record created2014-12-04
Record modified2016-07-18
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