Sonic Mach number, calculated using a single-component fit. The solid black contour shows the boundary of the subsonic region in this map, which is similar to the previously determined boundary of the coherent dense core. The dashed black contour shows the boundary of the extended subsonic region that can only be detected using multicomponent analysis as described in this work. The dotted red and dotted blue contours show the extents of the narrow-red and narrow-blue components, respectively. The beam and scale bar are shown in the bottom left and the bottom right corners, respectively.