<i>N</i>-BODY SIMULATIONS OF SATELLITE FORMATION AROUND GIANT PLANETS: ORIGIN OF ORBITAL CONFIGURATION OF THE GALILEAN MOONS

Abstract

As the number of discovered extrasolar planets has been increasing, diversity\nof planetary systems requires studies of new formation scenarios. It is\nimportant to study satellite formation in circumplanetary disks, which is often\nviewed as analogous to formation of rocky planets in protoplanetary disks. We\ninvestigated satellite formation from satellitesimals around giant planets\nthrough N-body simulations that include gravitational interactions with a\ncircumplanetary gas disk. Our main aim is to reproduce the observable\nproperties of the Galilean satellites around Jupiter through numerical\nsimulations, as previous N-body simulations have not explained the origin of\nthe resonant configuration. We performed accretion simulations based on the\nwork of Sasaki et al. (2010), in which an inner cavity is added to the model of\nCanup &amp; Ward (2002, 2006). We found that several satellites are formed and\ncaptured in mutual mean motion resonances outside the disk inner edge and are\nstable after rapid disk gas dissipation, which explains the characteristics of\nthe Galilean satellites. In addition, owing to the existence of the disk edge,\na radial compositional gradient of the Galilean satellites can also be\nreproduced. An additional objective of this study is to discuss orbital\nproperties of formed satellites for a wide range of conditions by considering\nlarge uncertainties in model parameters. Through numerical experiments and\nsemianalytical arguments, we determined that if the inner edge of a disk is\nintroduced, a Galilean-like configuration in which several satellites are\ncaptured into a 2:1 resonance outside the disk inner cavity is almost\nuniversal. In fact, such a configuration is produced even for a massive disk\nand rapid type I migration. This result implies the inevitability of a Galilean\nsatellite formation in addition to providing theoretical predictions for\nextrasolar satellites.\n