Overlay of position-velocity diagrams of the (J, K) = (9, 9), (10, 10), (12, 12), (13, 13) lines observed with the JVLA B-array towards NGC 7538 IRS1. The cut is taken at the peak of the NH₃ core with a PA = 35°, except the (9, 9) line (taken at PA = 40°). The image shows the pv-diagram for (9, 9) line. The contours are −0.004, −0.012, −0.024 Jy beam^-1 for all transitions, except the (9, 9) transition that shows only the contour at −0.004 Jy beam^-1 and the (12, 12) transition that shows only the contours at −0.012 and −0.024 Jy beam^-1, respectively. The vertical dashed gray lines indicate the velocities of −59.3 and 56.4 km s^-1. The PA is measured from north to east.