Dead Zones and the Origin of Planetary Masses

Protoplanets accrete material from their natal protostellar disks until theyare sufficiently massive to open a gap in the face of the disk's viscosity thatarises from the magneto-rotational instability (MRI). By computing theionization structure within observationally well-constrained disk models, wedemonstrate that poorly ionized, low viscosity "dead zones" stretch out to 12AU within typical disks. We find that planets of terrestrial mass robustly formwithin the dead zones while massive Jovian planets form beyond. Dead zones willalso halt the rapid migration of planets into their central stars. Finally, weargue that the gravitational scattering of low mass planets formed in the deadzone, to larger radii by a rapidly accreting Jupiter beyond, can explain thedistribution of planetary masses in our solar system.