Speckle Statistics in Adaptively Corrected Images

Fitzgerald, Michael P.; Graham, James R.

doi:10.1086/498339

Cited by 78 publications

(85 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Following the work of Goodman (1968), Soummer & Aime (2004), and Fitzgerald & Graham (2006), the speckle intensity PDF for one location in the image plane and random temporal phase errors can be shown to be a modified Rician function. At a specific location in the image plane, the MR PDF p MR (I ) is a function of the local time-averaged static point-spread function (PSF) intensity I c and random speckle noise intensities I s :…”

Section: Speckle Noise Statisticsmentioning

confidence: 94%

“…The atmosphere ( Roddier 1981;Racine et al 1999;Macintosh et al 2005), telescopes, and instruments optics ( Marois et al 2003Hinkley et al 2007) produce speckles with a range of timescales that limit the direct detection of faint companions. From previous theoretical analyses, it is known that the speckle intensity temporal distribution is a modified Rician ( MR;Goodman 1968;Soummer & Aime 2004;Fitzgerald & Graham 2006). If a large number of uncorrelated speckle realizations are co-added, we know from the central limit theorem that the final residual speckle noise will follow a Gaussian intensity distribution.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Confidence Level and Sensitivity Limits in High‐Contrast Imaging

Marois

Lafrenière

Macintosh

et al. 2008

ApJ

115

124

View full text Add to dashboard Cite

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 analyses have shown that the time intensity variations of a single speckle follow 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 fixed separation from the point-spread function center; this fact is demonstrated using numerical simulations for coronagraphic and noncoronagraphic 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 (CL). In this paper, a technique is described to obtain the pixel intensity distribution of an image and its corresponding CL as a function of the detection threshold. Using numerical simulations, it is shown that in the presence of speckle noise, a detection threshold up to 3 times higher is required to obtain a CL equivalent to that at 5 for Gaussian noise. The technique is then tested on data acquired by simultaneous spectral differential imaging with TRIDENT and by angular differential imaging with NIRI. It is found that the angular differential imaging technique produces quasi-Gaussian residuals, a remarkable result compared to classical adaptive optic imaging. Finally, a power law is derived to predict the 1 À 3 ; 10 À7 CL detection threshold when averaging a partially correlated non-Gaussian noise.

show abstract

Section: Speckle Noise Statisticsmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Confidence Level and Sensitivity Limits in High‐Contrast Imaging

Marois

Lafrenière

Macintosh

et al. 2008

ApJ

115

124

View full text Add to dashboard Cite

show abstract

“…Statistical descriptions of stellar speckles have been proposed by many authors (Racine et al 1999;Fitzgerald & Graham 2006), who showed that speckle noise is not negligible. The distribution of speckle statistics in AO were also studied by Canales & Cagigal (1999).…”

Section: Analysis Methodsmentioning

confidence: 99%

Spatially extended emission around the Cepheid RS Puppis in near-infrared hydrogen lines

Gallenne

Mérand

Kervella

et al. 2011

A&A

View full text Add to dashboard Cite

Context. It has been recently discovered that Cepheids harbor circumstellar envelopes (CSEs). RS Pup is the Cepheid that presents the most prominent circumstellar envelope known, the origin of which is not yet understood. Aims. Our purpose is to estimate the flux contribution of the CSE around RS Pup at the one arcsecond scale (∼2000 AU) and to investigate its geometry, especially regarding asymmetries, to constrain its physical properties. Methods. We obtained near-infrared images in two narrow band filters centered on λ = 1.644 and 2.180 μm (NB_1.64 and IB_2.18, respectively) that comprise two recombination lines of hydrogen: the 12-4 and 7-4 (Brackett γ) transitions, respectively. We used NACO's cube mode observations in order to improve the angular resolution with the shift-and-add technique, and to qualitatively study the symmetry of the spatially extended emission from the CSE with a statistical study of the speckle noise. Results. We probably detect at a 2σ level an extended emission with a relative flux (compared with the star in the same filter) of 38 ± 17% in the NB_1.64 filter and 24 ± 11% in the IB_2.18 filter. This emission is centered on RS Pup and does not present any detectable asymmetry. We attribute the detected emission to the likely presence of an hydrogen envelope surrounding the star.

show abstract

“…It is known that speckle noise does not follow Gaussian statistics (Goodman 1968;Fitzgerald & Graham 2006). However, Marois et al (2008a) have performed a detailed analysis of NIRI data processed with ADI (Marois et al 2006) and demonstrated that the residual noise follows quasi-Gaussian statistics when a sufficient number of images (i.e.…”

Section: Detection Limitsmentioning

confidence: 99%

The International Deep Planet Survey

Vigan

Patience

Marois

et al. 2012

A&A

154

200

View full text Add to dashboard Cite

Breakthrough direct detections of planetary companions orbiting A-type stars confirm the existence of massive planets at relatively large separations, but dedicated surveys are required to estimate the frequency of similar planetary systems. To measure the first estimation of the giant exoplanetary systems frequency at large orbital separation around A-stars, we have conducted a deep-imaging survey of young (8−400 Myr), nearby (19−84 pc) A-and F-stars to search for substellar companions in the ∼10−300 AU range. The sample of 42 stars combines all A-stars observed in previous AO planet search surveys reported in the literature with new AO observations from VLT/NaCo and Gemini/NIRI. It represents an initial subset of the International Deep Planet Survey (IDPS) sample of stars covering M-to B-stars. The data were obtained with diffraction-limited observations in H-and K s -band combined with angular differential imaging to suppress the speckle noise of the central stars, resulting in typical 5σ detection limits in magnitude difference of 12 mag at 1 , 14 mag at 2 and 16 mag at 5 which is sufficient to detect massive planets. A detailed statistical analysis of the survey results is performed using Monte Carlo simulations. Considering the planet detections, we estimate the fraction of A-stars having at least one massive planet (3−14 M Jup ) in the range 5−320 AU to be inside 5.9−18.8% at 68% confidence, assuming a flat distribution for the mass of the planets. By comparison, the brown dwarf (15−75 M Jup ) frequency for the sample is 2.0−8.9% at 68% confidence in the range 5−320 AU. Assuming power law distributions for the mass and semimajor axis of the planet population, the AO data are consistent with a declining number of massive planets with increasing orbital radius which is distinct from the rising slope inferred from radial velocity (RV) surveys around evolved A-stars and suggests that the peak of the massive planet population around A-stars may occur at separations between the ranges probed by existing RV and AO observations. Finally, we report the discovery of three new close M-star companions to HIP 104365 and HIP 42334.

show abstract

Speckle Statistics in Adaptively Corrected Images

Cited by 78 publications

References 37 publications

Confidence Level and Sensitivity Limits in High‐Contrast Imaging

Confidence Level and Sensitivity Limits in High‐Contrast Imaging

Spatially extended emission around the Cepheid RS Puppis in near-infrared hydrogen lines

The International Deep Planet Survey

Contact Info

Product

Resources

About