Mass-loading factor versus outflow velocity for our sample (circles and square symbols) and the PHANGS-ALMA sample (stars). The lightblue line is the best linear bisector fit to the data and the shaded areas indicates the 1σ uncertainty on the fit with and without including the intrinsic scatter term (lighter and darker colour, respectively). The blue dashed line shows the predictions for a energy-driven outflow (α = −2) and the red dotted-dashed line for a momentum-driven outflow (α = −1).