2:45 PM - 3:00 PM
[PPS07-10] Rocky Planetesimal Formation by Gravitational Instability of a Porous Dust Disk
Keywords:planetesimal formation, protoplanetary disk, gravitational instability, porous dust aggregate
We investigate the gravitational instability (GI) of the disk consisting of porous dust aggregates of nm-sized silicate monomers. We calculate the equilibrium random velocity of the dust aggregates considering gravitational scattering and collisions among them, gas drag, and turbulent stirring and scattering according to Michikoshi & Kokubo (2016) , and then evaluate Toomre’s stability parameter Q . The condition for the GI is defined as Q < 2 taking into account the non-axisymmetric mode .
We find that for the minimum mass solar nebula (MMSN) model at 1 au, the disk becomes gravitationally unstable as the dust aggregates evolve through gravitational compression if turbulent strength is α < 5×10-5. We also derive the critical disk mass and dust-to-gas ratio for the GI as a function of α.
References:  Arakawa, S., & Nakamoto, T. 2016, ApJL, 832, L19  Toriumi, M. 1989, Earth and Planetary Science Letters, 92, 265  Keller, L. P., & Messenger, S. 2011, GeoCoA, 75, 5336  Michikoshi, S., & Kokubo, E. 2016, ApJL, 825, L28  Toomre, A. 1964, ApJ, 139, 1217  Toomre, A. 1981, in Structure and Evolution of Normal Galaxies, ed. S. M. Fall & D. Lynden-Bell, 111–136
Figure 1. (left) Toomre’s Q in the md-ρint plane at 1 au for the MMSN disk with α = 10−5, where md is the mass and ρint is the mean internal density of the dust aggregates. The dash-dot, solid, and dash contours correspond to Q = 1, 2, and 4, respectively. The dot line shows the evolutional track of dust aggregates.
Figure 2. (right) Disk parameters for the GI at 1 au. The red triangle, blue circle, and black square shows α = 10-2, 10-3, and 10-4, respectively.