High-velocity collision of two black holes

We study nonaxisymmetric collision of two black holes (BHs) with a high velocity v=|dxi/dx0|=0.6c-0.9c at infinity, where xμ denotes four-dimensional coordinates. We prepare two boosted BHs for the initial condition which is different from that computed by a simple moving-puncture approach. By extrapolation of the numerical results, we find that the impact parameter has to be smaller than 2.5GM0/c2 for formation of a BH in the collision for v→c, where M0c2 is the initial total Arnowitt-Deser-Misner energy of the system. For the critical value of the impact parameter, 20%-30% of mass energy and 60%-70% of angular momentum are dissipated by gravitational radiation for v=0.6c-0.9c.