Probability density functions of ages (panel a) and initial masses (panel b) of all stars in our sample. The contributions of slash and WNh, WR, O, B and A stars are shown. The blue shaded areas are bootstrapped ±1σ estimates (Sect. 2.2) and the numbers along the curves indicate the cumulative number of stars up to certain ages and masses to judge which features of the distributions are populated by how many stars. The age distribution beyond 10 Myr keeps dropping and is essentially zero after ≈40 Myr. In panel b, a power-law mass-function, ζ(M) = dp/dM ∝ M^−α, is fitted to the mass distribution and the inferred high-mass IMF slope γ_>15 after correcting for those stars that already ended their nuclear burning lifetime is also provided (see Sect. 3.4). For reference, a Salpeter IMF has a power-law slope of γ = 2.35 (Salpeter 1955).