Integral field spectroscopy in the K-band ( 1.9-2.4 \mu m ) was performed on four IR-bright star clusters and the two nuclei in NGC 4038/4039 ( “ The Antennae ” ) .
Two of the clusters are located in the overlap region of the two galaxies , and together comprise \approx 25 % of the total 15 \mu m and \approx 10 % of the total 4.8 GHz emission from this pair of merging galaxies .
The other two clusters , each of them spatially resolved into two components , are located in the northern galaxy , one in the western and one in the eastern loop of blue clusters .
Comparing our analysis of Br \gamma , CO band-heads , He I \lambda 2.058 \mu m , H \alpha ( from archival HST data ) , and V - K colors with stellar population synthesis models indicates that the clusters are extincted ( A _ { V } \approx 0.7 - 4.3 mags ) and young , displaying a significant age spread ( 4-13 Myrs ) .
The starbursts in the nuclei are much older ( 65 Myrs ) , with the nucleus of NGC 4038 displaying a region of recent star formation northward of its K-band peak .
Using our derived age estimates and assuming the parameters of the IMF ( Salpeter slope , upper mass cut-off of 100 M _ { \sun } , Miller-Scalo between 1 M _ { \sun } and 0.1 M _ { \sun } ) , we find that the clusters have masses between 0.5 and 5 \times 10 ^ { 6 } M _ { \sun } .