Left: map of fractional linear polarization of dust emission from Planck at 353 GHz at a resolution of 80′ (GNILC). Right: background image showing a map of E(B − V) from Planck Collaboration Int. XLVIII (2016; PG). The map has a pixel size of 1.7′. For stars with a significant detection of p̂_R, we show segments that form an angle θ with the Galactic reference frame (according to the IAU convention). The length of each segment is proportional to the p̂_R of the star (measured in the R band) and a line of p = 1% is shown on the bottom left for scale. In both panels the dashed circle marks the region in which we have measured stellar polarization. The locations of stars in the observed sample are shown with black dots.