The impact of chaotic dynamics and binary evolution on the formation of compact binary systems

Compact binary mergers stand out among the most energetic events in the Universe. These phenomena are driven by the emission of gravitational waves from two inspiraling compact objects, such as black holes (BHs) and neutron stars (NSs), which gradually draw closer and ultimately collide. The inspiraling dance of compact binary systems, observable through gravitational wave detectors like the LIGO, Virgo, and KAGRA, provides us with a unique window to probe the fundamental processes governing the evolution and interactions of these dense stellar remnants. Despite the observation of nearly 90 of these exotic systems to date, understanding their formation pathways still remains an ongoing challenge. In this thesis, I delved into the intricate interplay of diverse formation channels and their role in the production of compact binary mergers. This work is specifically centered on the two most important astrophysical processes that lead to the production of gravitational wave sources: chaotic dynamical interactions and binary stellar evolution. The former represents the fundamental building block of the dynamical formation channel in dense stellar environments. The latter drives the evolution of massive stars into compact binaries through the isolated formation channel. My research aims to analyze the physical properties of compact binary mergers and to establish connections to potential observables that can serve as evidence for reconstructing their formation history. In the first part of this work, I have focused on the gravitational wave event GW190521, which detains the record as the most massive binary black hole (BBH) merger observed to date. Here, I present a possible explanation for the formation of this peculiar BH merger event. This has been achieved through direct N-body simulations of three-body encounters between a binary and a single BH within young massive star clusters. My results indicate that the GW190521 origin may be attributed to a merger triggered by three-body encounters within young star clusters, compatible with a second-generation BBH merger. The substantial masses involved in this event, coupled with the significant precession of the spin parameter, support its dynamical formation. In the second part of this thesis, I have extended my study to other stellar environments, exploring the formation of eccentric BH mergers produced by chaotic dynamical encounters within young, globular, and nuclear star clusters. I discuss how dynamics might leave some major fingerprints in the physical properties of these dynamically assembled mergers, and how these can be used as a tool to disentangle their formation channel based on observations. My analysis suggests that three-body interactions can be a significant source of eccentric mergers detectable with gravitational wave signals. Eccentricity, combined with large masses and misaligned spins, can serve as compelling evidence for the dynamical origin of these gravitational wave sources. Finally, I conducted an innovative study using population-synthesis simulations to explore the effects of chemically homogeneous evolution (CHE) on the production of massive stars and the subsequent compact merger population. CHE quenches the formation of red supergiant stars in favour of the production of Wolf-Rayet stars (WRs). WRs produced by CHE are, on average, more numerous, more massive, and more luminous than their non-CHE counterparts. This promotes the creation of more massive BHs while concurrently halting the formation of NSs. If, on the one hand, with CHE the population of mergers becomes more massive, on the other, CHE strongly suppresses the formation of all types of compact binary mergers. My findings further show that accretion-induced CHE is a valid formation pathway to produce compact binary mergers with asymmetric mass ratio without involving any dynamical interaction.