Upper panel: considered ellipse geometry from the model in Corbelli & Schneider (1997) superposed on the HI velocity field at 21 cm of the M 33 galaxy (from Chemin et al. 2012). For each ellipse we also show the minor axis with respect to which the temperature asymmetry and HI velocity are calculated. Median panel: radial profile, in μK, for the temperature asymmetry in the 70 GHz Planck band (black curve) and for the 21 cm DRAO data relative to the M 33 HI velocity field (red profile). The points in the horizontal axis show the central value in degrees of the semi-major axes of two adjacent ellipses (i.e., (a_i + a_{i + 1}) / 2). Bottom panel: temperature and velocity radial profiles, but with the temperature and velocity asymmetry calculated shell by shell.