Best-fit of the decomposition of the circular rotation curve traced by the [C II] line when allowing the black hole component to be free (left), fixed to 1.8 × 10⁹ M_⊙ (Feruglio et al. 2018; middle) and none (right). Black points with error bars are the circular velocities, these are the rotation velocities corrected for the asymmetric drift (caused by gas random motions). The solid yellow, green, brown and blue lines represent the black hole, stellar, gas and dark matter components, respectively. The dashed red lines are the sum of these four components. The blue diamonds with error bars are the circular velocities measured from the CO (9–8) line. These two lines trace the identical gravitational potential within the errors.