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 Roadmap, High-Contrast Imaging Proposal Planning, High-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:
NIRISS Aperture Masking Interferometry
There are 2 primary performance metrics for HCI: (1) the inner working angle (IWA) and (2) the limiting contrast, Climit(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
NIRISS Aperture Masking Interferometry
Instrument
NIRCam Coronagraphic Occulting Masks and Lyot Stops
NIRCam Filters for Coronagraphy
Detector
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 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
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 Coronagraphic Sequence Examples
MIRI Coronagraphic Imaging APT Template
NIRCam Coronagraphic Imaging APT Template
NIRISS Aperture Masking Interferometry APT Template
Exposure Time Calculator
JWST Exposure Time Calculator Overview
JWST ETC Coronagraphy Strategy
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