Integrated intensities of CO 3 − 2 and isotopologues at the center of the gap (r = 28 AU) and in the outer disk (r = 100 AU). The ALMA detection limit for a 5σ detection after 1 h on-source observation with a 0.1′′ beam (see Sect. 6) is given by the vertical dashed black line. Upper panels: models with a dusty inner disk (δ_dust = 10^-5). Lower panels: models without inner disk (δ_dust = 10^-10).