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The ACS and NICMOS have been used to obtain new HST images of NGC 4038/4039("The Antennae"). These new observations allow us to better differentiatecompact star clusters from individual stars, based on both size and color. Weuse this ability to extend the cluster luminosity function by approximately twomagnitudes over our previous WFPC2 results, and find that it continues as asingle power law, dN/dL propto L^alpha with alpha=-2.13+/-0.07, down to theobservational limit of Mv~-7. Similarly, the mass function is a single powerlaw dN/dM propto M^beta with beta=-2.10+/-0.20 for clusters with ages t<3x10^8yr, corresponding to lower mass limits that range from 10^4 to 10^5 Msun,depending on the age range of the subsample. Hence the power law indices forthe luminosity and mass functions are essentially the same. The luminosityfunction for intermediate-age clusters (i.e., ~100-300 Myr old objects found inthe loops, tails, and outer areas) shows no bend or turnover down to Mv~-6,consistent with relaxation-driven cluster disruption models which predict theturnover should not be observed until Mv~-4. An analysis of individual ~0.5-kpcsized areas over diverse environments shows good agreement between values ofalpha and beta, similar to the results for the total population of clusters inthe system. Several of the areas studied show evidence for age gradients, withsomewhat older clusters appearing to have triggered the formation of youngerclusters. The area around Knot B is a particularly interesting example, with an~10-50 Myr old cluster of estimated mass ~10^6 Msun having apparently triggeredthe formation of several younger, more massive (up to 5x10^6 Msun) clustersalong a dust lane.

The Antennae Galaxies (NGC 4038/4039) Revisited: ACS and NICMOS Observations of a Prototypical Merger