Mass versus velocity dispersion. Left: galaxies; right: haloes (red) and subhaloes (blue). The solid black line is the median of the baryonic (stellar plus gas) mass of galaxies (panel a)) and dark matter mass of haloes and subhaloes (panel b)) and the errorbars are the 15th and 85th percentiles. The dashed black line in the right panel shows the expected slope m ∝ σ³, and on the right panel, the lines show the slopes m ∝ σ³ and m ∝ σ².