On the Migration of the Galilean Satellites

Abstract

The migration of the Galilean satellites during formation due to interactions with the circumjovian disk is studied. In the gas-starved disk model proposed by Canup & Ward (2002, 2006), the Galilean satellites are the last generation of satellites formed in the circumjovian disk, and their migration and accretion depend on disk viscosity, opacity and material inflow rate. Relaxing the migration to non-isothermal type I regime (e.g. Paardekooper et al. 2010) allows the satellites to migrate outwards in optically-thick disk regions, and there is a position where the disk torque is zero. This contrasts with 278the results in the isothermal type I regime in which the satellites always migrate inwards. Including the effect of temperature dependence of disk opacity can produce multiple zero-torque positions in the circumjovian disk. As the disk depletes, these zero-torque positions shift towards Jupiter. Under this setting, a satellite at a range of initial locations will eventually converge to near one of these zero-torque positions, but stays at a fixed distance away (with the distance depending on satellite mass), so that it is moving inwards with the zero-torque position. However, if the satellite starts at a large-enough distance from Jupiter, it may move in a trajectory that does not converge to any of these zero-torque positions and survives to the end. The effect of satellite growth and variation of disk parameters on satellite migration will be discussed. The migration in multiple satellite system, and how these settings can possibly result in the Laplace resonance among the Galilean satellites, will be also investigated. This work is supported in part by Hong Kong RGC grant HKU 7030/11P