Mosaic of CO spectra obtained when mapping the M 63 disk along its major axis from the center of the galaxy out to the isophotal radius, r₂₅. The CO(2–1) spectra (red thin line) are overplotted on the CO(1–0) spectra (black thick line). While CO(1–0) is clearly detected up to the optical radius, CO(2–1) appears to be confined to r_gal ≲ 0.68 r₂₅. The bottom right hand panel shows the CO(1–0) and CO(2–1) spectra obtained when summing all scans at the ten outermost pointings from r_gal = 1.06 r₂₅ to 1.6 r₂₅ and smoothed to a resolution of 9.7 km s^-1 and 10.4 km s^-1, respectively. No CO emission is detected at these outermost pointings.