Kennicutt-Schmidt relations that relate the SFR surface density to the gas surface density plotted for Σ_{H I} (top-left panel), Σ_H2 (top-right panel), and Σ_{H I + H2} (bottom panel). The blue squares correspond to the 17 pointings used to map CO along the M 63 major axis (the radial cut) out to the isophotal radius, r₂₅, and the red circles correspond to the 8 pointings with 24 μm emission detection used to map CO over the bright UV region at r_gal = 1.36 r₂₅. The K-S relation is best parametrized by a power law of the form Σ_SFR = A(Σ_gas)^N, which in log space translates into a linear relation. The best-fitting bisector linear K-S relations are derived separately for the radial cut (blue dashed-dotted lines) and for the UV region (red dashed lines). The corresponding coefficients log  A and slopes N can be found in the labels of each panel. The black dotted lines represent “isochrones” of constant star formation efficiencies, indicating the level of Σ_SFR needed to consume 100%, 10%, and 1% of the total amount of gas within 10⁸ years. The vertical dashed line in the top-left panel corresponds to the Σ_{H I} ~ 9 M_⊙ pc^-2 threshold at which the atomic gas saturates (Bigiel et al. 2008).