A Multiwavelength Study of the Young Star Clusters and Interstellar Medium in the Antennae Galaxies

We report on a multi-wavelength study of the relationship between young starclusters in the Antennae galaxies (NGC 4038/9) and their interstellarenvironment, with the goal of understanding the formation and feedback effectsof star clusters in merging galaxies. This is possible for the first timebecause various new observations (from X-rays to radio wavelengths) have becomeavailable in the past several years. Quantitative comparisons are made betweenthe positions of the star clusters (broken into three age groups) and theproperties of the interstellar medium by calculating the two-point correlationfunctions. We find that young star clusters are distributed in a clusteredfashion. The youngest star clusters are associated with molecular cloudcomplexes with characteristic radii of about 1 kpc. In addition, there is aweak tendency for them to be found in regions with higher HI velocitydispersions. No dominant triggering mechanism is identified for the majority ofthe clusters in the Antennae. Feedback from young bright cluster complexes showlarge H_alpha bubbles and H_alpha velocity gradients in shells around thecomplexes. We estimate the current star formation rate to be 20 solar mass/yr,and the gas consumption timescale to be 700 Myr. The latter is comparable tothe merging time scale and indicates that star formation has been enchanced bythe merger event. Finally, we find that the Schmidt law, with index N=-1.4, isalso a good description of the cluster formation triggered by merging in theAntennae. There is some evidence that feedback effects may modify the Schmidtlaw at scales below 1 kpc.