GW190521 formation via three-body encounters in young massive star clusters

GW190521 is the most massive binary black hole (BBH) merger observed to date. This catastrophic event, which happened ~4.53 Gpc away from us, gave birth to a ~140 Msun black hole (BH) falling in the still unexplored intermediate-mass black hole (IMBH) regime. Nevertheless, the origin of GW190521 is still a matter of debate: several hints may favor a dense stellar environment as a birthplace. In this poster, I present the impact of three-body encounters on the formation of GW190521-like systems in young (<100 Myr) massive (10^3 - 3x10^4 Msun) star clusters. The poster shows the results of 2x10^5 dynamical interactions between a BBH and a massive BH simulated with post-Newtonian terms up to the 2.5 order, and a relativistic kick prescription for merger remnants. Overall, a total of 0.17% of the BBH mergers in our simulations match all the observed properties of GW190521. Our results imply that, if GW190521 was formed inside a young star cluster, it might have been either a second-generation binary or a first-generation BBH that experienced an exchange event. I discuss the implications of this result on the nature of GW190521 and, more specifically, how the spin of the BHs strongly constrain the formation of systems like GW190521 via three-body encounters. All the systems that match the properties of GW190521 have negligible eccentricity at the moment of the merger, with the exception of two second-generation BBHs that have e>0.3 in LISA band. Finally, I present the role of three-body interactions on the merger rate density of GW190521-like binaries, which in our simulations result as ~0.03 Gpc^-3 yr^-1.