Spectrum and radiative transfer models of CO J = 3−2 emission at ACA resolution (4.5 × 2.9′′) Left: spectrum of the emission around W Hya as observed with the ACA (project 2016.2.00025.S, Ramstedt et al. 2020) extracted in a single beam towards the star. The black line corresponds to the radiative transfer model from Khouri et al. (2014) shown for a small pencil beam in Fig. 4(left). The vertical lines correspond to the same lines in Fig. 2. Right: radiative transfer models of the CO emission including an enhanced IR radiation field with values of M = 2 and M = 3, compared to the baseline model with no IR enhancement M = 1.