DOLPHOT JWST/NIRISS Module
Note: this module is still in the beta testing phase and is not yet demonstrated to be suitable for science.
- Comparison of the model PSFs (from WebbPSF) to images in NIRISS F090W and F150W indicate the model PSFs are much too sharp. It is unlikely that DOLPHOT can produce reliable photometry until this has been resolved.
- Photometry calibrations were updated with CRDS context file jwst_0895.pmap. For data obtained before that context file was added to the pipeline, manual adjustments (different for every chip and filter combination) must be applied. Check the CRDS_CTX header keyword to confirm what version was used for your data. Additionally, the photometry reference file (R_PHOTOM) should be jwst_niriss_photom_0035.fits or higher.
- Stage 2 Data Quality (DQ) arrays have not been thoroughly tested for reliability. In the current release, (a) pixels flagged as saturated by the pipeline (DQ array value of 2) are considered saturated, (b) other pixels masked out by the pipeline (Science array value is exactly zero) are considered bad pixels, and (c) all other pixels are assumed good.
- DOLPHOT currently uses the file data in the FITS headers, rather than what is provided in the ASDF extension.
- DOLPHOT does not yet support NIRISS subarray observing modes.
Possible Limitations (Testing in Progress)
- Limited testing to date has been performed only on data obtained by program JWST-ERS-01334
- Comparison of observational CMDs to isochrones and/or synthetic CMDs (e.g., as a check on zero points and calibrations) not yet performed
- Impacts from time variability of the PSFs not yet assessed
Longer Term Enhancements
- Identification of optimal DOLPHOT parameters for both short and long modes
- Incorporation and testing of additional empirical PSF libraries
- Testing combined photometry with NIRISS and other instruments
Please provide feedback if you use this code, as it will be greatly appreciated whether or not there were issues.
If you make use of the JWST NIRISS module in your work, please cite Weisz et al. in prep in addition to the DOLPHOT references (Dolphin 2000 and Dolphin 2016). For more information on the JWST ERS program that is developing this module (as well as a companion NIRISS module), please see https://ers-stars.github.io.
DOLPHOT 2.0 NIRISS module sources (updated 6 Apr 2023)
DOLPHOT 2.0 NIRISS module manual (also included in sources)