Comparison of the observed rotational velocity distribution (v_ϕ) for FGKM stars, shown as histograms, and a two-component model (dashed lines: individual components; solid line: their sum) given by Eq. (3) (using updated parameters discussed in text; the same Z-dependent model is shown in all four panels). The four panels show results for two |Z| bins (top row vs. bottom row) and towards North and South (|b|> 80°, left vs. right). The sample sizes are about 4000 stars for the nearer |Z| bin and about 900 stars for the more distant bin.