υ_broad,Gaia vs υ sin i_GES (2D histogram). The green dashed line is the 1-to-1 relation. The pink thick line is the linear regression (see text for the parametrisation). The cyan thick dashed line is a non-parametric LOWESS model (locally weighted linear regression) implemented using the Python module StatsModels. The inset shows the distribution of Δυ_broad = υ_broad,Gaia − υ sin i_GES. The red dashed line in the inset indicates the location of the mean difference.