Density map obtained with the matched filter technique from the IN6 sample. The symbols are the same as in Fig. 11. A higher level of smoothing has been adopted. The H i column density contours obtained from LITTLE THINGS data (with a beam of 28.2″ × 16.9″) were superimposed. The associated density is 0.5, 1.0, 3.0, 5.0, 7.0, 9.0 × 10²⁰ cm^-2, from the outermost to the innermost contour.