How High Metallicity Can Trigger Planet Formation

Details How High Metallicity Can Trigger Planet Formation How High Metallicity Can Trigger Planet Formation

Sep 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009dps....41.5202y&link_type=abstract

American Astronomical Society, DPS meeting #41, #52.02

Astronomy and Astrophysics

Astronomy

Scientific paper

Extrasolar planet detections increase markedly with host star metallicity. This suggests that the growth of planets and gas giant cores depends on the abundance of heavy elements in primordial circumstellar disks. We present numerical simulations of the coupled dynamics of gas and several centimeter scale rocks in a 3D, vertically-stratified Keplerian disk. The clumping of solids increases dramatically when the mass ratio of solids to gas increases above Z = 0.01, i.e. roughly Solar abundances. For Z = 0.02 and higher, overdense clumps form with particle densities greater than 1000 times the gas density. When the effects of self-gravity are included, the dense particle clumps in the high Z simulations collapse into bound protoplanetesimals with a mass equivalent to the largest modern asteroids. The clumping arises due to streaming instabilities driven by the two-way aerodynamic coupling of solids and gas. We compare the dynamical behavior in our simulations to previous studies of smaller grains subject to vertical shearing instabilities in the disk midplane. A particularly striking feature of our simulations is that the midplane layer is not uniformly thick. Rather the solids execute coherent oscillations about the midplane as they drift radially inward. This allows for high particle densities despite the energy injected by sub-Keplerian gas rotation. These findings support the core accretion theory of giant planet formation, while offering the possibility that initially low metallicity systems can still produce super-Earths as the gas disk is dispersed.

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