Channel maps of CN hyperfine components towards DM Tau. From top to bottom, the velocity scales are referred to 226.874745 GHz (3 blended components), 226.679382 GHz, 226.663703 GHz, and 226.659575 GHz. Note the better spectral resolution in the top panel. The spatial resolution is 1.7 × 1.2″ at PA 120°, contour spacing is 53 mJy/beam, or 0.61 K, corresponding to 2.0σ in the upper panel, and 2.3σ in the lower ones.

As Fig. A.1, but towards LkCa15. All panels use the same spectral resolution. Note the repeated channels in the two bottom panels, as the velocity spacing between these components is 5 km s^-1, i.e. 12 channels. The spatial resolution is 1.7 × 1.0″ at PA 44°, contour spacing is 60 mJy/beam, or 0.81 K and 2.1σ.

As Fig. A.2, but towards MWC 480. The spatial resolution is 2.2 × 1.35″ at PA 60°, contour spacing is 55 mJy/beam, or 0.45 K and 2σ. The high rotation velocity result in an overlap of emission between the two hyperfine components in the bottom panels.

Channel maps of HCN hyperfine components towards DM Tau. The spatial resolution is 3.7 × 2.4″ at PA 39°, and contour spacing is 12 mJy/beam, or 0.21 K, 2.0σ.

Channel maps of HCN hyperfine components towards LkCa15. The spatial resolution is 4.1 × 2.9″ at PA 51°, contour spacing is 16 mJy/beam, or 0.21 K and 2.0σ.

Channel maps of HCN hyperfine components towards MWC 480. The spatial resolution is 4.5 × 3.6″ at PA 66°, contour spacing is 16 mJy/beam, or 0.15 K and 1.8σ.

Value of Σ₃₀₀ and p from our chemistry modeling for the three sources, with our “standard” chemistry. o: density and temperature from theoretical models, p: temperature increased by 30%, m: temperature decreased by 30%, f: density multiplied by a factor 3 and d: density divided by a factor 3. In many models the blue and green markers overlap, as do the red and black ones.

H, H₂, C⁺, C, CO, CN, HCN abundance and CN/HCN ratio as a function of opacity from atmosphere (A_v = 0) to midplane at R = 304 AU for DM Tau with CR = 10^-17 s^-1.