Giant impacts between proto planets and late stage planetary accumulation

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Collisions between protoplanets are common events in the later stage of planetary formation process. Protoplanets grew into present planets through these collisional events. So it is necessary to obtain information about redistribution of mass and angular momentum between colliding two bodies in order to study the growth rates of planets and the origin of their spin. We have started a series of systematic studies on this theme and this is our first report. We concentrate on the impact between one proto planet, which has one Earth mass, and another protoplanet with 0.06 Earth mass. The motion of two bodies are pursued numerically by the SPH simulation method. We change the minimum distance between the two bodies as parameter to specify the orbital angular momentum of them. For each value of the parameter, we repeated the numerical simulations and obtain final states of bodies. Such various final states are examined by criteria developed to distinguish some clusters formed by many SPH particles. We determine instantaneous orbital elements for relative motion between central protoplanet and each cluster. From this information we forecast the destiny of each cluster, for examples to be merged into the target body or trapped. Then we determine initial conditions result to final characteristic states. The 5 states are merging state in which the impactor absorbed to the target, multiple impact state in which the impactor collide with the target again and again, disruption escaping state in which the impactor is tidally disrupted and a large part of the impactor escapes from the target, trapping state in which the impactor is trapped by the target, and passing state in which the impactor passes through as it is.