Star Formation in NGC 4038/4039 as Seen in the NIR

Abstract

We obtained various sets of near infrared observations of the prototypical merger, NGC 4038/4039 (‘the Antennae’). Integral field spectroscopy and broad- and narrow band imaging aimed at obtaining age and extinction estimates of the young star clusters seen in large numbers distributed throughout the disks of the interacting galaxies. High resolution spectroscopy led to estimates of the dynamical masses of the clusters. The clusters have ages ranging from 3.7 to ≈ 20 Myrs. Those in the ‘overlap region’ are very young (below 8 Myrs), while in the nothwestern loop ages are above that limit, and the nuclear starbursts are much older (100 Myrs). Some photometric cluster masses lie above 10⁶ M_⊙. The stellar velocity dispersions determined from the medium- to high resolution spectra yielded virial cluster masses again up to a few 10⁶ M_⊙. Large differences in the estimated photometric and virial masses suggest a variation of the IMF between the clusters. At least some of the clusters have masses, concentrations and IMFs that could allow them to evolve into globular clusters.