Two-Gaussian fit of the core rotation rate distributions in each bin of mixed mode density 𝒩. The grey histograms are the observed distributions of core rotation rates. The blue lines correspond to the first term on the right-hand side of Eq. (21), characterised by μ₁ and σ₁, which represent the over-density ridge. The blue horizontal lines and shaded areas illustrate the means and 1-σ regions of the over-density ridge in each bin. The red lines depict the second term on the right-hand side of Eq. (21), characterised by μ₂ and σ₂, representing the extended background. The black lines indicate the sum of the two Gaussian distributions, which provide a good reproduction of the observed histogram.