Formation of Massive Star Clusters and Cluster Complexes in Galaxies

It has been found that most (maybe all) stars form in groups. These groups of stars are called 'star clusters'. These groups can contain between a few to a few million stars. But when we look into the universe today we see that less than 1% of all stars are in star clusters now. What happened? The answer to this mystery probably lies in the way the star clusters form and how they change as they grow older. To investigate this problem, we are going to study star clusters just after they form. The project is based on a recent finding that star clusters themselves form in groups. These groups are called 'cluster complexes' and contain 5 to a few hundred star clusters. We want to study why these complexes form (why do they form in one place and not another) and what will become of them. Will the complexes collapse to form one huge star cluster, will it grow larger (kind of like a slow explosion) or will it remain unchanged? Another question that we hope to answer is do all of the clusters within a single complex form at the same time or does the formation of one cluster cause the formation of another cluster? To answer these questions we will use some of the world's largest telescopes (the Very Large Telescope, the Gemini Telescope, the William Herschel Telescope, and the Hubble Space Telescope) to examine many of the star clusters within these complexes at the same time. Star clusters of different ages give off different kinds of light, which means we can 'see' the ages of the star clusters with careful measurements. Additionally, precise measurements allow for the determination of the speed of which the individual clusters are moving within the complexes. Once the current positions and speeds of all the clusters are known, we can use the laws of gravity to predict the fate of the complexes. The ability to carry out this research project has only recently become possible with the new generation of instruments on 8-metre class telescopes (e.g. the European Southern Observatory's Very Large Telescope; VLT). Of particular excitement, are the new generation of Integral Field Units, which combine the benefits of imaging and spectroscopy in one. Europe is leading the world in this type of instrument (e.g. VIMOS, SINFONI, and ARGUS on the VLT), providing unprecedented tools for European astronomers.