Spectral indices. Color images of the spectral indices between 3.1 and 1.3 mm of the Stokes I (left top panel) and of the polarized intensity (left bottom panel). The associated uncertainties images are shown in the right panels. The scale is the same for the two images (shown in the wedge at the top of the panels). The contours in both panels show the Stokes I emission at 3.1 mm. Contours are 1, 3, 6, 12, 24, 48 and 96% of the peak intensity, 12 mJy beam⁻¹. The images presented here were obtained using a common uv-range for the 3.1 and 1.3 mm data (see text).