Giant planet formation at inner and outer edges of dead zones

ZS. SÁNDOR; O. M. GUILERA

Cartajena de Indias

Congreso; XV Latin American Regional IAU Meeting; 2016

In the standard model of core accretion, the formation of giant planets occurs by two main processes: first, a massive core is formed by the accretion of solid material; then, when this core exceeds a critical value (typically greater than 10 Earth masses) a gaseous runaway growth is triggered and the planet accretes big quantities of gas in a short period of time until the planet achieves its final mass. Thus, the formation of a massive core has to occur when the nebular gas is still available in the disk. This is the key in the formation of giant planets in the standard model. This phenomenon imposes a strong time-scale constraint in giant planet formation due to the fact that the lifetimes of the observed protoplanetary disks are between ~1 Myr and ~10 Myr. The formation of massive cores before ~10 Myr by the accretion of big planetesimals (with radii > 10 km) in the oligarchic growth regime is only possible in massive disks. On the other hand, when a dead zone (a zone of lower viscosity) is present in the gaseous disk, it generates a maximum pressure in its inner and outer edge. This maximum pressure generates a maximum in the gas surface density near the edges of the dead zone. The direction of migration of the planetesimals due to the nebular drag depends on the local radial derivative of the density. So, it is expected that the presence of a dead zone modified the migration of the population of planetesimals, at least near the edges of the dead zone. In this talk we show that if planetesimal migration is considered, there is a significant accumulation of planetesimals in the locations of the maximum pressure which triggers a quickly formation of massive cores, even for big planetesimals in moderate mass disks.