Left and center panels: Maps of instability parameters related to radial (Q) and azimuthal (S) perturbations, calculated from the minimum value of the corresponding component of the stellar velocity dispersion. Right panel: Distribution of instability wavelengths relative to azimuthal perturbations, λ_ϕ. The red contours on the left indicate isolines of Hα brightness, with values of logHα equal to −17.2 and −16.5 [erg/s/cm²]. Red and orange contours in the middle and right panels correspond to logHα = −17.2 [erg/s/cm²] and Σ_H2 = 30 M_⊙/pc².