Angular Differential Imaging: a Powerful High-Contrast Imaging Technique

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Angular differential imaging is a high-contrast imaging technique that reduces speckle noise from quasi-static optical aberrations and facilitates the detection of faint nearby companions. A sequence of images is acquired with an altitude/azimuth telescope, the instrument rotator being turned off. This keeps the instrument and telescope optics aligned, stabilizes the instrumental PSF and allows the field of view to rotate with respect to the instrument. For each image, a reference PSF obtained from other images of the sequence is subtracted. All residual images are then rotated to align the field and are median combined. Observed performances are reported for Gemini ... continued below

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Marois, C; Lafreniere, D; Doyon, R; Macintosh, B & Nadeau, D November 7, 2005.

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Angular differential imaging is a high-contrast imaging technique that reduces speckle noise from quasi-static optical aberrations and facilitates the detection of faint nearby companions. A sequence of images is acquired with an altitude/azimuth telescope, the instrument rotator being turned off. This keeps the instrument and telescope optics aligned, stabilizes the instrumental PSF and allows the field of view to rotate with respect to the instrument. For each image, a reference PSF obtained from other images of the sequence is subtracted. All residual images are then rotated to align the field and are median combined. Observed performances are reported for Gemini Altair/NIRI data. Inside the speckle dominated region of the PSF, it is shown that quasi-static PSF noise can be reduced by a factor {approx}5 for each image subtraction. The combination of all residuals then provides an additional gain of the order of the square root of the total number of images acquired. To our knowledge, this is the first time an acquisition strategy and reduction pipeline designed for speckle attenuation and high contrast imaging is demonstrated to significantly get better detection limits with longer integration times at all angular separations. A PSF noise attenuation of 100 was achieved from 2-hour long sequences of images of Vega, reaching a 5-sigma contrast of 20 magnitudes for separations greater than 7''. This technique can be used with currently available instruments to search for {approx} 1 M{sub Jup} exoplanets with orbits of radii between 50 and 300 AU around nearby young stars. The possibility of combining the technique with other high-contrast imaging methods is briefly discussed.

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PDF-file: 31 pages; size: 0 Kbytes

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  • Journal Name: Astrophysical Journal; Journal Volume: 641; Journal Issue: 1

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  • Report No.: UCRL-JRNL-216949
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 887287
  • Archival Resource Key: ark:/67531/metadc886399

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  • November 7, 2005

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  • Sept. 21, 2016, 2:29 a.m.

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  • Nov. 22, 2016, 6:31 p.m.

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Marois, C; Lafreniere, D; Doyon, R; Macintosh, B & Nadeau, D. Angular Differential Imaging: a Powerful High-Contrast Imaging Technique, article, November 7, 2005; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc886399/: accessed August 17, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.