Map from the ratio of flux values between the deconvolved 70 μm and 160 μm PACS images of R Aqr overplotted with contours from an EMMI observation at 653 nm [N ii]. The colour code represents the flux ratio between 70 and 160 μm. Both arms show gradients in the flux ratio, which is a signature of continuum dust emission. Furthermore, the highest flux ratio occurs at the ends of both arms.