Top: RMS-weighted spectral stacking results for the disk of M82. The velocities of dense-gas tracers were corrected according to the line center of CO(3–2) before stacking. A scaling factor of 6 was applied to HCN(1–0) and HCO⁺(1–0). The velocities at the centers of the Gaussian fits for HCN(1–0), HCO⁺(1–0), HCN(4–3), and HCO⁺(4–3) are 14.3 ± 0.5, 13.6 ± 0.6, –0.6 ± 2.5, and –1.8 ± 1.9 km s⁻¹, respectively. Bottom: RMS-weighted spectral stacking results for the disk of M82 without velocity correction.