Speckle noise and dynamic range in coronagraphic images

TL;DR

This paper analyzes the statistical properties of residual speckles and noise in high contrast coronagraphic images, providing insights into improving dynamic range for exoplanet detection.

Contribution

It generalizes a statistical model to include static, quasi-static, and atmospheric speckles, enhancing understanding of noise effects in coronagraphic imaging.

Findings

Residual speckles limit high contrast imaging.

The model helps evaluate wavefront control and speckle reduction techniques.

Insights are applicable to both ground-based and space telescopes.

Abstract

This paper is concerned with the theoretical properties of high contrast coronagraphic images in the context of exoplanet searches. We derive and analyze the statistical properties of the residual starlight in coronagraphic images, and describe the effect of a coronagraph on the speckle and photon noise. Current observations with coronagraphic instruments have shown that the main limitations to high contrast imaging are due to residual quasi-static speckles. We tackle this problem in this paper, and propose a generalization of our statistical model to include the description of static, quasi-static and fast residual atmospheric speckles. The results provide insight into the effects on the dynamic range of wavefront control, coronagraphy, active speckle reduction, and differential speckle calibration. The study is focused on ground-based imaging with extreme adaptive optics, but the approach is general enough to be applicable to space, with different parameters.