The early evolution of young massive clusters A Gaia study of OB runaways

Massive stars are predominantly born in stellar associations or clusters. Their radiation fields, stellar winds, and eventual supernovae have a strong impact on their local surroundings. A significant fraction of massive stars are observed to be so-called runaway stars, which travel through the galaxy at high speed. High-mass runaways can be created either by a supernova in a binary, or by dynamical interactions in a young and dense cluster. The Gaia space telescope now provides extremely accurate astrometry for nearly 2 billion sources. In this thesis, I investigate the young massive clusters in which massive stars are born, and the runaways originating in them. The first chapter introduces the aforementioned scientific context in more detail. In the next two chapters, I investigate two young massive clusters in our own Galaxy, NGC 6611 in the Eagle Nebula (M 16) and NGC 6618 in the Omega Nebula (M 17). In the next chapter, I study runaways coming from one of the most massive young dense clusters that we know of in our Galaxy, R136, in the Large Magellanic Cloud. In the final chapter, I study 15 young massive clusters in our Milky Way and find runaways coming from them. One of the key results is that the overall importance of dynamical runaways have been underestimated so far. The high-mass runaways can play a key role in shaping and heating the interstellar and galactic medium.