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Title: Fundamental limitations of high contrast imaging set by small sample statistics

In 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.
Authors:
; ;  [1] ;  [2] ; ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9]
  1. European Southern Observatory, Alonso de Cordóva 3107, Vitacura, Santiago (Chile)
  2. LUTH, Observatoire de Paris, CNRS, UPMC and University Paris Diderot, 5 place Jules Janssen, F-92195 Meudon (France)
  3. Département d'Astrophysique, Géophysique et Océanographie, Université de Liège, 17 Allée du Six Août, B-4000 Liège (Belgium)
  4. LESIA, Observatoire de Paris, CNRS, UPMC and University Paris Diderot, 5 place Jules Janssen, F-92195 Meudon (France)
  5. European Southern Observatory Headquarters, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München (Germany)
  6. Leiden Observatory, Leiden University, P.O. Box 9513, 2300-RA Leiden (Netherlands)
  7. NRC, Herzberg Institute of Astrophysics, Victoria, BC V9E 2E7 (Canada)
  8. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)
  9. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
Publication Date:
OSTI Identifier:
22365129
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 792; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DEGREES OF FREEDOM; DETECTION; ERRORS; HYPOTHESIS; IMAGES; NOISE; PLANETS; PROBABILITY; RECOMMENDATIONS; REDUCTION; RESOLUTION; SENSITIVITY; STARS