Spectral line profile of the Paβ line. Top panel: Observed Paβ line profile (black) from MIRI MRS channel 1, extracted within a 3-kpc radius. The red line corresponds to our best-fit model (red). The two individual Gaussian components are displayed on the bottom as green and magenta dashed lines (offset from zero by an arbitrary amount). We mask a noise spike (shown in grey) shortwards of the line. Middle panel: Continuum after multi-Gaussian line subtraction. Bottom panel: χ statistic corresponding to the residuals between the model and the observed spectral profile, divided by the rms error in the continuum.