2011ApJ...734...11K

We re-examine the age distribution of star clusters in the Antennae in the context of N-body+hydrodynamical simulations of these interacting galaxies. All of the simulations that account for the observed morphology and other properties of the Antennae have star formation rates that vary relatively slowly with time, by factors of only 1.3-2.5 in the past 10⁸ yr. In contrast, the observed age distribution of the clusters declines approximately as a power law, dN/dτ∝τ^γ with γ = -1.0, for ages 10⁶ yr ≲ τ ≲ 10⁹ yr. These two facts can only be reconciled if the clusters are disrupted progressively for at least ∼10⁸ yr and possibly ∼10⁹ yr. When we combine the simulated formation rates with a power-law model, f_surv∝τ^δ, for the fraction of clusters that survive to each age τ, we match the observed age distribution with exponents in the range -0.9 ≲ δ ≲ -0.6 (with a slightly different δ for each simulation). The similarity between δ and γ indicates that dN/dτ is shaped mainly by the disruption of clusters rather than variations in their formation rate. Thus, the situation in the interacting Antennae resembles that in relatively quiescent galaxies such as the Milky Way and the Magellanic Clouds.