Restriction masks obtained with different methods.Top: restriction mask obtained by estimating the noise on the velocity-integrated Dame et al. (2001) CO data and keeping the lines where the integrated intensity is above the threshold (0.84K km s⁻¹). Middle: mask obtained after de-noising the CO signal with ROHSA, then keeping all the lines that have a position-position-velocity of at least above the threshold used for Fellwalker, namely 0.20 K. Bottom: mask obtained by applying the Fellwalker algorithm to the post-ROHSA data. This is the mask we used in our search for velocity assignment.