JWST High-Contrast Imaging

High-contrast imaging (HCI) with JWST will allow observers to obtain images of faint sources located near bright point sources

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See also: High-Contrast Imaging RoadmapHigh-Contrast Imaging Proposal PlanningHigh-Contrast Imaging Supporting Technical Information


High-contrast imaging (HCI) is used to obtain images of faint sources ("companions") located near bright point sources ("hosts"). Typical hosts are stars and quasars. Companions include exoplanets, circumstellar structures of gas and dust, and luminous feeding zones around supermassive black holes. In normal imaging, a faint companion could be swamped and lost in the noise of diffracted light in one of the wings of the host. HCI strategies—comprising special optics, observing procedures, and post-processing—are designed to reduce the impact of host light at the position of the companion, in order to make the companion detectable against the residual noise.In HCI, the reduction of wing light from the host occurs in 2 steps: optical cancellation and image subtraction. Optical cancellation is achieved by special optics, using pairs of masks located on the focal and pupil planes. Image subtraction is performed in post-observation processing by differencing a scaled PSF reference image and a science image.

JWST offers 3 HCI designs for optical cancellation: 2 types of coronagraph and one interferometer (see HCI Optics). Subsets of these designs are implemented in NIRCam, MIRI, and NIRISS: 

  • Lyot coronagraph (LYOT; 5 implementations in NIRCam, one in MIRI)
  • 4-quadrant phase mask coronagraph (4QPMC; 3 implementations in MIRI)
  • aperture masking interferometer (AMI; one implementation in NIRISS) 

The instrument-specific modes for HCI, including allowed mask-filter combinations, are described in: 

NIRCam Coronagraphic Imaging

MIRI Coronagraphic Imaging

NIRISS Aperture Masking Interferometry

There are 2 primary performance metrics for HCI: (1) the inner working angle (IWA) and (2) the limiting contrastClimit(s), which is a function of apparent separation (s).

For more detailed information about JWST HCI options, see the references listed below.



Resources for high-contrast imaging

Additional HCI articles

Observing modes

MIRI Coronagraphic Imaging

NIRCam Coronagraphic Imaging

NIRISS Aperture Masking Interferometry

Instrument

MIRI Coronagraphs

NIRCam Coronagraphic Occulting Masks and Lyot Stops
NIRCam Filters for Coronagraphy

NIRISS Non-Redundant Mask

Detector

Understanding Exposure Times

MIRI Detector Readout Overview
MIRI Detector Subarrays

NIRCam Detector Readout Patterns
NIRCam Detector Subarrays

NIRISS Detector Readout Patterns
NIRISS Detector Subarrays

Operations

MIRI Coronagraphic Imaging Target Acquisition

NIRCam Coronagraphic Imaging Target Acquisition
NIRCam Coronagraphic PSF Estimation
NIRCam Coronagraph Astrometric Confirmation
NIRCam Small Grid Dithers

NIRISS Target Acquisition
NIRISS AMI Dithers

Performance

MIRI Bright Source Limits
MIRI Sensitivity
HCI MIRI Limiting Contrast

NIRCam Point Spread Functions
NIRCam Bright Source Limits
HCI NIRCam Limiting Contrast
NIRCam Sensitivity

NIRISS Bright Limits
NIRISS Sensitivity
HCI NIRISS Limiting Contrast

Recommended strategies

MIRI Observing Strategies

NIRCam Coronagraphic Imaging Recommended Strategies

NIRISS AMI Recommended Strategies

Science use cases

MIRI and NIRCam Coronagraphy of the Beta Pictoris Debris Disk

MIRI and NIRCam Coronagraphy of HR8799 b

NIRISS AMI Observations of Extrasolar Planets Around a Host Star

Astronomer's Proposal Tool

JWST Astronomers Proposal Tool Overview

HCI APT Instructions

HCI APT Coronagraphic Sequence Examples 

MIRI Coronagraphic Imaging APT Template

NIRCam Coronagraphic Imaging APT Template

NIRISS Aperture Masking Interferometry APT Template

APT Target Acquisition

APT Special Requirements

Exposure Time Calculator

JWST Exposure Time Calculator Overview

HCI ETC Instructions

JWST ETC Coronagraphy Strategy

JWST ETC Target Acquisition

JWST ETC to APT Interface Support Information

Proposing tools

JWST Coronagraphic Visibility Tool Help



References

Beichman, C. A., et al. 2020, PASP, 132:1007
Imaging Young Giant Planets from Ground and Space

Beichman, C. A., et al. 2010, PASP, 122:162
Imaging Young Giant Planets from Ground and Space

Boccaletti, A. et al. 2015, PASP, 127, 633
The Mid-Infrared Instrument for the James Webb Space Telescope, V: Predicted Performance of the MIRI Coronagraphs

Girard, J. et al. 2018, SPIE, 106983V 
Making good use of JWST's coronagraphs: tools and strategies from a user's perspective

Greenbaum, A.Z., Pueyo, L., Sivaramakrishnan, A. et al. 2015, ApJ, 798, 68
An Image-Plane Algorithm for JWST's Non-Redundant Aperture Mask Data




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