Illustration of the cleaning pipeline: (1) the unaltered source image (OSIRIS level 3E); (2) the masked-out nucleus; (3) the estimated background level (a) and the corresponding RMS map of the background-subtracted image (b); (4) the background- and nucleus-subtracted image predominated by dust particles. All images show the same central region indicated in Fig. 2 and are brightness-inverted for better reading.