FUNDAMENTAL LIMITATIONS OF HIGH CONTRAST IMAGING SET BY SMALL SAMPLE STATISTICS

By D. Mawet, J. Milli, Z. Wahhaj, D. Pelat, O. Absil, C. Delacroix, Anthony Boccaletti, M. Kasper, M. Kenworthy, C. Marois and 2 more. 2014

208 citations recorded by the source corpus.

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.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/66ee5a3a53b7b4ca1d722e89916ebf3934892dd9

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In Astronomy and Astrophysics

1. B. Bowler
2. R. van Boekel
3. M. Benisty
4. R. Teague
5. Anthony Boccaletti
6. J. Beuzit
7. Th. Henning
8. M. Kasper

In Instrumentation

1. B. Bowler
2. R. van Boekel
3. Anthony Boccaletti
4. J. Beuzit
5. Th. Henning
6. L. Close
7. M. McClure
8. R. Gratton

Citations in the corpus

• Magellan Adaptive Optics Imaging of PDS 70: Measuring the Mass Accretion Rate of a Young Giant Planet within a Gapped Disk (2018, methodology): “We followed Equation 9 in Mawet et al. (2014) to estimate the SNR, taking into account the correction for small sample statistics at ∼3.5 beam widths from the star.”
• Discovery and spectroscopy of the young jovian planet 51 Eri b with the Gemini Planet Imager (2015, unknown): “No correction for small sample statistics was necessary because the object is at sufficiently wide separation (> 10 λ / D ) that this effect is negligible ( 77 ) .”
• Three Radial Gaps in the Disk of TW Hydrae Imaged with SPHERE (2016, methodology): “We applied a correction to the values following Mawet et al. (2014) to account for small sample statistics, relevant at small radial distances.”
• SPHERE: the exoplanet imager for the Very Large Telescope (2019, methodology): “Although recent work have showed the limitations of this approach (Mawet et al. 2014; Jensen-Clem et al. 2018), we quantify this capability using the 5-σ contrast level as a function of separation in the present work.”
• Imaging Extrasolar Giant Planets (2016, background): “…(Marois et al. 2010a; Amara & Quanz 2012; Pueyo et al. 2012; Meshkat et al. 2013a; Wahhaj et al. 2013a; Brandt et al. 2013; Fergus et al. 2014; Mawet et al. 2014; Marois et al. 2014; Currie et al. 2014c; Cantalloube et al. 2015; Rameau et al. 2015; Wahhaj et al. 2015; Savransky 2015; Dou et…”