  As the number of discovered extrasolar planets has been increasing, diversity
of planetary systems requires studies of new formation scenarios. It is
important to study satellite formation in circumplanetary disks, which is often
viewed as analogous to formation of rocky planets in protoplanetary disks. We
investigated satellite formation from satellitesimals around giant planets
through N-body simulations that include gravitational interactions with a
circumplanetary gas disk. Our main aim is to reproduce the observable
properties of the Galilean satellites around Jupiter through numerical
simulations, as previous N-body simulations have not explained the origin of
the resonant configuration. We performed accretion simulations based on the
work of Sasaki et al. (2010), in which an inner cavity is added to the model of
Canup & Ward (2002, 2006). We found that several satellites are formed and
captured in mutual mean motion resonances outside the disk inner edge and are
stable after rapid disk gas dissipation, which explains the characteristics of
the Galilean satellites. In addition, owing to the existence of the disk edge,
a radial compositional gradient of the Galilean satellites can also be
reproduced. An additional objective of this study is to discuss orbital
properties of formed satellites for a wide range of conditions by considering
large uncertainties in model parameters. Through numerical experiments and
semianalytical arguments, we determined that if the inner edge of a disk is
introduced, a Galilean-like configuration in which several satellites are
captured into a 2:1 resonance outside the disk inner cavity is almost
universal. In fact, such a configuration is produced even for a massive disk
and rapid type I migration. This result implies the inevitability of a Galilean
satellite formation in addition to providing theoretical predictions for
extrasolar satellites.
