Transformation of HST WFC3/UVIS Filters to the Standard BVI System

Empirical transformations of selected broadband filters in the Hubble Space Telescope Wide Field Camera 3 (WFC3)/UVIS camera into the BVI system are derived. These conversions employ photometry of stars in a standard field in the globular cluster 47 Tucanae that has repeatedly been imaged with both the WFC3 and Advanced Camera for Surveys (ACS) cameras, enabling direct comparisons of photometry for large numbers of stars over a wide range of colors. The photometry of these stars on the ACS camera is used to define their BVI magnitudes, through the standard transformations from Sirianni et al. These BVI magnitudes are then used to define the conversions from the native WFC3 filter system. Results are presented for six WFC3 broadband filters: F438W, F475W, F475X, F555W, F606W, F814W. For these, convenient equations are given to transform (F438W, F475W, F475X) into standard B, (F555W, F606W) into V, and F814W into I. In a parallel study with the same database, a new transformation is presented for conversion of the ACS/WFC F475W filter into B.