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Description
Collisional growth of dust aggregates is an essential process to form planetesimals in protoplanetary disks, but disruption through high-velocity collisions (disruption barrier) could prohibit the dust growth. Mass transfer through highly different-sized collisions has been suggested to be a way to circumvent the disruption barrier. We examine how the collisional growth efficiency of dust aggregates at different impact parameters depends on the size and the mass-ratio of colliding aggregates. We use an N-body code to numerically simulate the collisions of different-sized aggregates. Our results show that large values of the impact parameter are important and the growth efficiency averaged over the impact parameter does not depend on the aggregate size although the growth efficiency for nearly head-on collisions increases with size. We also find that the averaged growth efficiency tends to increase with increasing the mass-ratio of colliding aggregates. However, the critical collision velocity, above which the growth efficiency becomes negative, does not strongly depend on the mass-ratio. These results indicate icy dust can grow through high-velocity offset collisions at several tens of m/s, the maximum collision velocity experienced in protoplanetary disks, whereas it is still difficult for silicate dust to grow in protoplanetary disks.
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