A multiwavelength study of the young star clusters and interstellar mediumin the antennae galaxies

We report on a multiwavelength study of the relationship between young star clusters in the Antennae galaxies (NGC 4038/9) and their interstellar envi ronment, with the goal of understanding the formation and feedback effects of star clusters in merging galaxies. This is possible for the first time b ecause various new observations (from X-rays to radio wavelengths) have bec ome available in the past several years. Quantitative comparisons are made between the positions of the star clusters (broken into three age groups) a nd the properties of the interstellar medium by calculating the two-point c orrelation functions. We find that young star clusters are distributed in a clustered fashion, demonstrated by power-law angular autocorrelation funct ions with slopes in the range -0.8 to -1.0. The young embedded clusters (ag es similar to5 Myr) are found to be more associated with long-wavelength ra diation (mid-infrared and longer), while clusters with ages similar to 10 M yr or older are more associated with short-wavelength radiation (e.g., far- UV and X-ray). The youngest star clusters are associated with molecular clo ud complexes with characteristic radii of about 1 kpc. In addition, there i s a weak tendency for them to be found in regions with higher H I velocity dispersions. There is some evidence that both cloud-cloud collisions and sh ocks from recent star formation can trigger star cluster formation, but no dominant triggering mechanism is identified for the majority of the cluster s in the Antennae. Feedback from young bright cluster complexes reveals its elf in the form of large Ha bubbles and Ha velocity gradients in shells aro und the complexes. We estimate the current star formation rate to be approx imate to 20 M-circle dot yr(-1) and the gas consumption timescale to be sim ilar to 700 Myr. The latter is comparable to the merging timescale and indi cates that star formation has been enhanced by the merger event. Finally, w e find that the Schmidt law, with index N approximate to -1.4, is also a go od description of the cluster formation triggered by merging in the Antenna e. There is some evidence that feedback effects may modify the Schmidt law at scales below 1 kpc.