Abstract
Massive Black Holes (MBHs) are a key ingredient of the Universe, inhabiting the centers of most galaxies. Despite their abundance there is still much that is unknown about MBHs, but Gravitational Waves (GWs) offer the opportunity for new insight. MBH binary formation and coalescence follows the galactic mergers of their hosts, and these MBH mergers are responsible for the loudest GWs in the Universe. Observation of these events is possible through Pulsar Timing Array observatories, and their detection will offer a new insight into the histories of MBHs, providing information on the origin and growth of MBHs in the Universe.
Interpretations of the detected Gravitational Wave Background (GWB) signal will be aided by predictions of MBH merger statistics. In modelling individual mergers, numerical challenges arise as a high resolution is required for avoiding stochastic effects, but is difficult to achieve at the galaxy scales being modelled. First, I explore the utility of a multi-resolution scheme to preferentially increase the resolution at the centers of galaxies where MBH binaries reside. This is applied to isolated and merging models, for which I show the scheme is effective at increasing central resolution, reducing spurious relaxation and stochastic effect without adverse effects on the model stability. I continue by following each of the embedded MBH binaries to coalescence and obtaining merger timescales. I show the evolution of the orbital elements is sensitive to the resolution, improved by the use of the multi-resolution scheme at lower resolutions but still requiring high particle numbers to begin reaching convergence. Finally, I continue the analysis of the multi- resolution models with subsequent galaxy mergers, examining both new binary formation and triple interactions with an intruder MBH.
The tools developed and investigated in this thesis can be utilised in interpretation of GW detections, aiding in accurate assessments of MBH binary evolution and merger timescales.