Observational results combining both NIR extinction (black) and both ¹³CO (red triangles) plus C¹⁸O (blue squares) (2−1) line measurements along the main axis of Musca. From top to bottom: (1) extinction profile obtained by Kainulainen et al. (2016); (2) CO main-beam brightness temperatures (T_mb); (3) centroid velocity (V_lsr); (4) non-thermal velocity dispersion along the line of sight (σ_NT); and (5) opacity corrected non-thermal velocity dispersion along the line of sight (σ_NT,corr) including upper limits for the ¹³CO emission (red arrows; see text for discussion). The velocity dispersion measurements are expressed in units of the sound speed c_s = 0.19 km s^-1 at 10 K. In these last plots the horizontal lines delimitate to the sonic (σ_NT/c_s ≤ 1; thick dashed line) and transonic (σ_NT/c_s ≤ 2; thin dotted line) regimes, respectively. Only those components with a S/N ≥ 3 are displayed in the plot. The position of the IRAS 12322-7023 source as well as a typical 3 km s^-1 pc^-1 velocity gradient are indicated in their corresponding panels. We note the presence of the double-peaked spectra at the positions L_fil ~ 0.4,4.2, and 5.8 pc in the middle panel. The two vertical lines delimitate the south, central, and north subregions identified by Kainulainen et al. (2016).