Confidence Level and Sensitivity Limits in High Contrast Imaging

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In long adaptive optics corrected exposures, exoplanet detections are currently limited by speckle noise originating from the telescope and instrument optics, and it is expected that such noise will also limit future high-contrast imaging instruments for both ground and space-based telescopes. Previous theoretical analysis have shown that the time intensity variations of a single speckle follows a modified Rician. It is first demonstrated here that for a circular pupil this temporal intensity distribution also represents the speckle spatial intensity distribution at a fix separation from the point spread function center; this fact is demonstrated using numerical simulations for coronagraphic and ... continued below

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PDF-file: 31 pages; size: 0.4 Mbytes

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Marois, C November 7, 2007.

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In long adaptive optics corrected exposures, exoplanet detections are currently limited by speckle noise originating from the telescope and instrument optics, and it is expected that such noise will also limit future high-contrast imaging instruments for both ground and space-based telescopes. Previous theoretical analysis have shown that the time intensity variations of a single speckle follows a modified Rician. It is first demonstrated here that for a circular pupil this temporal intensity distribution also represents the speckle spatial intensity distribution at a fix separation from the point spread function center; this fact is demonstrated using numerical simulations for coronagraphic and non-coronagraphic data. The real statistical distribution of the noise needs to be taken into account explicitly when selecting a detection threshold appropriate for some desired confidence level. In this paper, a technique is described to obtain the pixel intensity distribution of an image and its corresponding confidence level as a function of the detection threshold. Using numerical simulations, it is shown that in the presence of speckles noise, a detection threshold up to three times higher is required to obtain a confidence level equivalent to that at 5{sigma} for Gaussian noise. The technique is then tested using TRIDENT CFHT and angular differential imaging NIRI Gemini adaptive optics data. It is found that the angular differential imaging technique produces quasi-Gaussian residuals, a remarkable result compared to classical adaptive optic imaging. A power-law is finally derived to predict the 1-3 x 10{sup -7} confidence level detection threshold when averaging a partially correlated non-Gaussian noise.

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PDF-file: 31 pages; size: 0.4 Mbytes

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  • Journal Name: The Astrophysical Journal, vol. 673, no. 1, January 1, 2008, pp. 647-656; Journal Volume: 673; Journal Issue: 1

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  • Report No.: UCRL-JRNL-236527
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 941394
  • Archival Resource Key: ark:/67531/metadc902136

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • November 7, 2007

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  • Sept. 27, 2016, 1:39 a.m.

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  • Nov. 23, 2016, 11:22 a.m.

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Marois, C. Confidence Level and Sensitivity Limits in High Contrast Imaging, article, November 7, 2007; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc902136/: accessed July 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.