JWST High-Contrast Imaging
High-contrast imaging (HCI) with JWST facilitates the direct imaging of faint companions and structures near bright sources.
On this page
See also: High-Contrast Imaging Roadmap, High-Contrast Imaging Proposal Planning, High-Contrast Imaging Supporting Technical Information
High-contrast imaging (HCI) is a technique used to detect and study faint sources, referred to as companions, located near much brighter hosts, such as stars or quasars. These companions can include exoplanets, circumstellar structures of gas and dust, or luminous accretion regions surrounding supermassive black holes. In conventional imaging, the light from a bright host can obscure a nearby faint source, burying it in the noise generated by diffraction and scattered light. JWST HCI employs a combination of specialized optics, optimized observing strategies, and post-processing techniques to suppress the host light at the companion's location, thereby improving the detectability of the companion against residual noise.
Light suppression
In JWST HCI, suppression of light from the host occurs in two stages:
- Optical suppression: This is accomplished using specialized optics, which employ a combination of masks located in the focal and pupil planes to attenuate the host star's light before it reaches the detector.
- Post-processing subtraction: Following observation, residual starlight is further reduced by subtracting a scaled reference point spread function (PSF) from the science images to improve contrast near the host.
Architectures and instruments
JWST offers three principal starlight suppression architectures: two types of coronagraphs and one interferometer (see HCI Optics). These designs are implemented across NIRCam, MIRI and NIRISS as follows:
- Lyot coronagraph (LYOT): Five implementations in NIRCam, one in MIRI.
- Four-quadrant phase mask coronagraph (4QPM): three implementations in MIRI.
- Aperture masking interferometer (AMI): one implementation in NIRISS.
For detailed descriptions of the instrument-specific HCI modes, including supported mask-filter combinations, consult the following resources:
Key performance metrics
HCI system performance is primarily characterized by two metrics:
- Inner working angle (IWA): The minimum angular separation from the central bright source at which a faint companion can be reliably detected or resolved.
- Limiting contrast, Climit(s): The achievable contrast ratio as a function of the apparent separation (s), quantifying the faintest detectable companion brightness relative to the host.
For comprehensive technical details and further information on JWST HCI capabilities and observing modes, please see the relevant documentation and references provided 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 Subtraction Operations
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
Astronomer's Proposal Tool
JWST Astronomer's 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