Physical properties in the line emitting region of the ¹²CO J = 2−1 line forthe four fiducial models (see legend). Top row: gas and dust surface densities Σ (all models with gaps have the same dust surface density profile). The other panels show quantities averaged over the line emitting region (from top to bottom): shift in the height of the line emitting region ⟨δz⟩; dust to gas mass ratio ⟨d∕g⟩; total hydrogen number density ⟨n_⟨H⟩⟩; dust temperature ⟨T_d⟩; gas temperature ⟨T_g⟩; and the change in the rotational velocity ⟨δv_rot⟩ (see Eq. (3)). The vertical dotted lines indicate the locations of the dust gaps DG1, DG2, and DG2.