Upper panel: mass function of Antennae clusters from this work (filled circles) and from Mengel et al. (2005) (open triangles). The former is based on an age-restricted subsample (τ = 1–10 Myr); the latter is based on a subsample limited in K _s -band luminosity but with no restriction on age. The vertical dashed line is the stated 50% completeness limit for the Mengel et al. sample ( K _s ≈ 18.4). Lower panel: mass function of Antennae clusters from this work (filled circles) and for a subsample with a luminosity limit similar to that of Mengel et al., based on K _s magnitudes predicted from stellar population models and the observed V magnitudes (open circles).