HCO⁺ column density and emission in a disk around a typical Herbig Ae star. Top panel: total HCO⁺ column densities. Middle and bottom panels: HCO⁺ J = 2− 1 radial emission profiles and H¹³CO⁺ J = 2− 1 radial emission profiles along the major axis predicted for chemical network NW (red) and chemical network W (light blue). The dotted lines refer to a model with very low dust opacities to lower the effects of continuum optical depth (see Sect. 3.2.1). The water snowline is indicated with the dashed black line. The radial emission profiles are convolved with a 0′′.05 beam.