Three-dimensional initial data for the collision of two black holes. II. Quasicircular orbits for equal-mass black holes

The construction of initial-data sets representing binary black-hole configurations in quasicircular orbits is studied in the context of the conformal-imaging formalism. An effective-potential approach for locating quasicircular orbits is outlined for the general case of two holes of arbitrary size and with arbitrary spins. Such orbits are explicitly determined for the case of two equal-sized nonrotating holes, and the innermost stable quasicircular orbit is located. The characteristics of this innermost orbit are compared to previous estimates for it, and the entire sequence of quasicircular orbits is compared to results from the post-Newtonian approximation. Some aspects of the numerical evolution of such data sets are explored.