Top panel: rotation curves for CH₃OH(10_2,9–9_3,9) in IRAS 18360. The projected distance is calculated as the distance from the velocity centroid point to the best-fitted line passing through the maximum flux position of this transition. Bottom panel: the left and right plots show the best fits to the rotation curves for the blueshifted lobe (below 103 km s⁻¹) and the redshifted lobe (above 104 km s⁻¹), respectively. The best-fit enclosed masses are 49.6 ± 1.1M_⊙ for the blue lobe and 162.4 ± 7.3 M_⊙ for the red lobe. The black lines represent the resulting fits for each lobe. The contours show the position–velocity diagram along the position angle of 127°. The contour levels begin at 3σ (60 mJy beam⁻¹) and increase to a maximum value of 2.33 Jy beam⁻¹ in 10 linearly spaced levels.