Bottom: spatial distribution of A_V in the Horsehead IFU footprint as estimated using Eq. (2) with R_V = 3.1. Top: estimates of A_V extracted from each region (points) along with a cut-through the spatial distribution map. Error bars on A_V for the region extractions are dominated by variation over the full region; “error” bars on the distance from the front are defined as the rough width of the region definition; see Fig. 1.