Orbital Migration of Earth-Mass Planets in a Marginally Gravitationally Unstable Disk

The core accretion mechanism for gas giant planet formation requires multiple-Earthmass protoplanets to form in the presence of the disk gas, i.e., prior to the dispersal of the protoplanetary disk. Such protoplanets are subject to rapid orbital migration through their gravitational interactions with the disk. Studies of the interactions of Earth-mass protoplanets with the disk gas generally assume a disk mass low enough that the disk’s self-gravity can be neglected. However, forming Earth-mass cores prior to dissipation of the gaseous disk may require a disk that is massive enough (~ 0.1 solar mass) to be marginally gravitationally unstable. In this case, the self-gravity of the disk must be taken into account when attempting to follow the orbital evolution of growing protoplanets.