Stokes I, Q, and U maps (5″ × 3″) of the afterglow of GRB 171205A taken on 2018 December 10 (5.187 days after the burst). The ALMA beam size is shown with the open cyan circles. The map created using the entire ALMA Band 3 data set with a representative frequency of 97.5 GHz (a), and four individual spectral windows (SPW) with a representative frequency of 90.5 GHz (b), 92.5 GHz (c), 102.5 GHz (d), and 104.5 GHz (e). The units of color bars are mJy for Stokes I and μJy for Stokes Q and U maps.