We present results from a suite of N-body simulations that follow the
accretion history of the terrestrial planets using a new parallel treecode that
we have developed. We initially place 2000 equal size planetesimals between
0.5--4.0 AU and the collisional growth is followed until the completion of
planetary accretion (> 100 Myr). All the important effect of gas in laminar
disks are taken into account: the aerodynamic gas drag, the disk-planet
interaction including Type I migration, and the global disk potential which
causes inward migration of secular resonances as the gas dissipates. We vary
the initial total mass and spatial distribution of the planetesimals, the time
scale of dissipation of nebular gas, and orbits of Jupiter and Saturn. We end
up with one to five planets in the terrestrial region. In order to maintain
sufficient mass in this region in the presence of Type I migration, the time
scale of gas dissipation needs to be 1-2 Myr. The final configurations and
collisional histories strongly depend on the orbital eccentricity of Jupiter.
If today's eccentricity of Jupiter is used, then most of bodies in the
asteroidal region are swept up within the terrestrial region owing to the
inward migration of the secular resonance, and giant impacts between
protoplanets occur most commonly around 10 Myr. If the orbital eccentricity of
Jupiter is close to zero, as suggested in the Nice model, the effect of the
secular resonance is negligible and a large amount of mass stays for a long
period of time in the asteroidal region. With a circular orbit for Jupiter,
giant impacts usually occur around 100 Myr, consistent with the accretion time
scale indicated from isotope records. However, we inevitably have an Earth size
planet at around 2 AU in this case. It is very difficult to obtain spatially
concentrated terrestrial planets together with very late giant impacts.Comment: 51 pages, 19 figures, 2 tables, published in Icaru