Position-velocity plot along the direction with PA = 68° of the CH₃CN K, l = (6, 1) v₈ = 1 (12–11) line divided by the same plot of the CH₃¹³CN K = 2 line. The offsets are measured from the phase center, positive to the northeast. Contour levels range from 0.5 to 4 in steps of 0.5. The vertical solid red line indicates the position of the continuum peak, while the vertical dashed black lines show the positions of the two compact free-free continuum sources detected by Cesaroni et al. (2010). The horizontal dashed line indicates the systemic LSR velocity of 96.5 km s⁻¹.