Koji Wada¹, Hidekazu Tanaka², Satoshi Okuzumi³, Hiroshi Kobayashi⁴, Toru Suyama⁵, Hiroshi Kimura⁶ and Tetsuo Yamamoto⁷

¹Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, 275-0016 Chiba Japan
²Institute of Low Temperature Science, Hokkaido University, 060-0819 Sapporo, Japan
³Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro-ku, 152-8511 Tokyo, Japan
⁴Department of Physics, Nagoya University, Nagoya, 464-8602 Aichi, Japan
⁵Nagano City Museum, Hachimanpara Historical Park Ojimada-machi, 381-2212 Nagano, Japan
⁶Graduate School of Science, Kobe University, c/o CPS (Center for Planetary Science), Chuo-ku Minatojima Minamimachi 7-1-48, 650-0047 Kobe, Japan
⁷CPS (Center for Planetary Science), Kobe University, Chuo-ku Minatojima Minamimachi 7-1-48, 650-0047 Kobe, Japan

Context. Collisional growth of dust aggregates is an essential process in forming planetesimals in protoplanetary disks, but disruption through high-velocity collisions (disruption barrier) could prohibit the dust growth. Mass transfer through very different-sized collisions has been suggested as a way to circumvent the disruption barrier.
Aims. We examine how the collisional growth efficiency of dust aggregates with different impact parameters depends on the size and the mass ratio of colliding aggregates.
Methods. We used an N-body code to numerically simulate the collisions of different-sized aggregates.
Results. Our results show that high values for the impact parameter are important and that 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 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 that icy dust can grow through high-velocity offset collisions at several tens of m s^-1, the maximum collision velocity experienced in protoplanetary disks, whereas it is still difficult for silicate dust to grow in protoplanetary disks.

Reference
Wada K, Tanaka H, Okuzumi S, Kobayashi H, Suyama T, Kimura H and Yamamoto T (2013) Growth efficiency of dust aggregates through collisions with high mass ratios. Astronomy & Astrophysics 559:A62.
[doi:10.1051/0004-6361/201322259]
Reproduced with permission © ESO

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