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Overview
WFC3 offers slitless spectroscopy with both the ultra-violet/optical (UVIS) and infrared (IR) channels. The table below gives a brief summary of the WFC3 grism capabilities. Grism calibration information is linked in the grism name column.
WFC3 Spectroscopic Capabilities
| Channel | Grism | Wavelength Range (nm) | Resolving Power | Dispersion† (nm/pixel) |
Recommended Direct Filters‡ |
|---|---|---|---|---|---|
| UVIS | G280 | 190-800 | 70 @ 300nm | 1.3 | F300X or F200LP |
| IR | G102 | 800-1150 | 210 @ 1000 nm | 2.45 | F105W or F098M |
| IR | G141 | 1075-1700 | 130 @ 1400 nm | 4.65 | F140W or F160W |
†For point sources. For extended sources, the extent of the target in the dispersion direction effectively determines the spectral resolution.
‡A direct image is required as part of all grism observations in order to set the wavelength zero-point. Note: these are only recommended filters. Other filters may be used if desired, but one must use the correct calibration files as indicated below.
Latest Developments
- ISR 2023-06: The WFC3/UVIS G280 Grism Sky
- ISR 2022-06: Improved Absolute Astrometry for ACS and WFC3 Data Products
- ISR 2020-09: Updated Calibration of the UVIS G280 Grism
- ISR 2020-04: The dispersed infrared background in WFC3 G102 and G141 observations
- ISR 2016-15: Trace and Wavelength Calibrations of the WFC3 G102 and G141 IR Grisms
Frequently Asked Questions
If you encounter any problems related to the WFC3 grisms, please consult our FAQ page. For further questions, contact our Help Desk.
Persistence
The WFC3 IR detector is susceptible to persistence which appears as afterglow in parts of the detector that experienced high fluence (total number of photo-electrons released) in earlier exposures. Persistence is not corrected for in calwf3 or aXe. Examples of persistence and suggestions on how to mitigate it are given in the WFC3 Data Handbook.
STScI provides a persistence model for each WFC3 IR dataset through a separate persistence search form which allows users to view and download the persistence model. Search for the dataset of interest and then follow the links under "Dataset" to view the model and the links under "Visit" to download the model. A full description of the data products is provided here. A detailed description of the current modeling algorithm can be found in ISR 2015-15.
Observers and archive users are encouraged to contact the help desk if the persistence subtraction substantially limits their ability to extract science from an image or set of images.
Additional Resources
2010 STScI Slitless Spectroscopy Workshop
The 2010 workshop highlighted scientific results of slitless spectroscopy and hosted tutorials on using and analyzing data from the WFC3 Grism; the archived webcast of workshops and talks is publically accessible.
PandExo
PandExo is a community tool and python package to generate instrument simulations of JWST (NIRSpec, NIRCam, and NIRISS) and HST/WFC3 for the purposes of transiting exoplanet science. It is publically hosted on Github.