Abstract
It is widely accepted that terrestrial planets are formed in2 stages. First step is the coagulation of km-sized planetesimals,which results in the formation of Mars-sized protoplanets.These protoplanets are orbitally stabilized by eccentricity dampingdue to tidal interaction with a gas disk until significant fraction of disk gas is depleted.In the next stage, planets are formed through the accretion of protoplanets. When the planets are just formed, their eccentricities are still large. Kominami \& Ida (2002) shows that the eccentricities can be diminished by including the effect of gravitational gas drag by a remnant gas disk, and succeeded to form Earth-like planets.This gravitational drag force becomes effective when the mass of the bodyis larger than that of the Moon.However, simulations including this gravitational drag effect on the stage from planetesimal to protoplanets have not done yet.Since the protoplanet's mass is larger than the mass of the Moon,this effect may change the outcome distribution of the protoplanets.We would like to do the N-body simulations on formation of protoplanetsincluding the effect of gravitational gas drag from the disk, and seehow the drag effects the formation of protoplanets.
