Astronomical instrumentation

Abstract:

We performed near infrared integral field spectroscopy of several star clusters and the nuclei of the prototypical merger NGC 4038/39 ("The Antennae"). Near infrared (NIR) images covered both galaxies. The collision of the two gas-rich spiral galaxies has triggered a starburst obvious from a large number of young star clusters. ISO data suggest that the most active star formation occurs in the region where the two galaxy disks overlap. A significant fraction of the total bolometric luminosity of the system is produced there. Since this region is heavily extincted in the optical, the investigation was made in the NIR. Using Brgamma emission and CO absorption features as age indicators, we derive the ages and mass estimates of the star clusters from a comparison with stellar synthesis models. Extinction is calculated from the Brgamma/Halpha ratio. The young, bright star clusters have ages ranging from 4-12 Myrs, while the nuclear starbursts are much older (50-80 Myrs). The overlap region hosts most of the youngest star clusters below similar to8 Myrs, while the northwestern region is dominated by star clusters in the age range between 8 and 12 Myrs. Several regions, including the northern nucleus, show evidence for sequential star formation on small spatial scales (<100pc).