Rapid Formation of Gas-giant Planets via Collisional Coagulation from Dust Grains to Planetary Cores. II. Dependence on Pebble Bulk Density and Disk Temperature

Abstract

Thanks to “dust-to-planet” simulations (DTPSs), which treat the collisional evolution directly from dust to giant-planet cores in a protoplanetary disk, we showed that giant-planet cores are formed in ≲10 au in several 105 yr, because porous pebbles grow into planetesimals via collisions prior to drift in 10 au. However, such porous pebbles are unlikely to reproduce the polarized millimeter wavelength light observed from protoplanetary disks. We thus investigate gas-giant core formation with nonporous pebbles via DTPSs. Even nonporous bodies can grow into planetesimals and massive cores that are possible to be gas giants are also formed in several 105 yr. The rapid core formation is mainly via the accretion of planetesimals produced by collisional coagulation of pebbles drifting from the outer disk. The formation mechanism is similar to the case with porous pebbles, while core formation occurs in a wider region (5–10 au) than that with porous pebbles. Although pebble growth and core formation depend on the disk temperature, core formation is likely to occur with disk temperatures in typical optical thick disks around protostars.