Dense star clusters as nurseries of gravitational wave sources

Several  black  hole  binaries have been detected by the Advanced LIGO and Virgo interferometers, and a rich new catalog of gravitational wave sources is soon to be released.  While  the astrophysical  origin  of  these  sources is still unknown, one possibility is that they formed in dense star clusters through dynamical three-body interactions. I will discuss the results from a library of ~10 million globular cluster models that were obtained using our new fast code cBHBd. I will show that when uncertainties are properly taken into account, a scenario in which most of the detected sources are formed in globular clusters is consistent with current constraints. Finally, I will discuss the dynamical evolution of black holes in nuclear clusters, such as those observed at the centre of most nearby galaxies. In nuclear clusters, repeated mergers often lead to the formation of black holes with a mass much larger than predicted by stellar evolution alone and up to a few thousands of solar masses, providing an explanation to the recently discovered binary GW190521.