  We present the results of the first multi-scale N-Body+SPH simulations of
merging galaxies containing central supermassive black holes (SMBHs) and having
a spatial resolution of only a few parsecs. Strong gas inflows associated with
equal-mass mergers produce non-axisymmetric nuclear disks with masses of order
$10^9 M_{\odot}$, resolved by about $10^6$ SPH particles. Such disks have sizes
of several hundred parsecs but most of their mass is concentrated within less
than $50$ pc. We find that a close SMBH pair forms after the merger. The
separation of the two SMBHs then shrinks further owing to dynamical friction
against the predominantly gaseous background. The orbits of the SMBHs decay
down to the minimum resolvable scale in a few million years for an ambient gas
temperature and density typical of a region undergoing a starburst. These
results suggest the initial conditions necessary for the eventual coalescence
of the two holes arise naturally from the merging of two equal-mass galaxies
whose structure and orbits are consistent with the predictions of the
$\Lambda$CDM model. Our findings have important implications for planned
gravitational wave detection experiments such as {\it LISA}.
