Astrometry and Photometry with HST WFC3. II. Improved Geometric-Distortion Corrections for 10 Filters of the UVIS Channel1

Abstract

We present an improved geometric-distortion solution for the Hubble Space Telescope UVIS channel of Wide Field Camera 3 for 10 broadband filters. The solution is made up of three parts: (1) a third-order polynomial to deal with the general optical distortion, (2) a table of residuals that accounts for both chip-related anomalies and fine-structure introduced by the filter, and (3) a linear transformation to put the two chips into a convenient master frame. The final correction is better than 0.008 pixel (∼0.3 mas) in each coordinate. We provide the solution in two different forms: a FORTRAN subroutine and a set of FITS files, one for each filter/chip/ coordinate.