Abstract

The ringdown and coalescence of a black hole binary produce a strong gravitational wave signal. Asymmetries in this emission, caused by dissimilar black hole masses or spins, can produce beamed gravitational wave discharge, which carries away linear momentum. As a consequence, the remnant black hole recoils in the opposite direction with a velocity ranging from 100 < v < 4000 km/s. Large recoil velocities may have significant consequences in the co-evolution of galaxies and their central massive black holes (MBH). In cases where the recoil velocity is lower than the escape speed, the MBH will undergo damped oscillations and eventually return back to the center of the potential. We carry out simulations of recoiling massive black holes in high-resolution hosts and determine their possible orbits taking into consideration the effects of triaxiality of the dark matter component and gas drag. We discuss the long-term evolution of the MBH orbits under realistic conditions, and assess the detectability of MBHs as offset QSO / AGN. We review the implications of recoiling MBHs in the context of hierarchical structure formation.