JWST/HST Alignment Tool (JHAT)

The WCS alignment of JWST and HST faces some unique challenges, since reference catalogs have significantly larger centroid uncertainties and/or might be sparse with respect to the small FOV of the instruments from these telescopes. We present JHAT, a new and flexible tool that provides robust WCS alignment of JWST and HST images using Gaia, PS1, DECam, or a custom catalog. JHAT mitigates several failure modes of classical HST/JWST image alignment, and can function inside of the JWST/HST pipeline analysis flow to ensure excellent absolute and relative alignment for the final data products (e.g., stacks).