Position–velocity diagram of ¹²CO (1–0) (panel a), ¹³CO (1–0) (panel b), and the model (panel c) and velocity (panel d) offsets between ¹² CO (1–0) and ¹³CO (1–0) observations and model. The assumed parameters for the accretion model are summarized in Table 1. The cut line of the PV diagrams is indicated in Fig 1. In panels a–c, black squares indicate the peak velocity positions at each offset. In panels a and b, black crosses are the peak velocity positions at each offset in the model. In panel d, lines indicate the velocity offset (black) between ¹² CO (1–0) and the model and (red) between ¹³CO (1–0) and the model. In panels a–d, black and gray vertical lines indicate offset = 0′ and |offset| < R_out.