The Effects of Metallicity and Grain Size on Gravitational Instabilities in Protoplanetary Disks

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  • 3 November 2005
Abstract
Observational studies show that the probability of finding gas giant planets around a star increases with the star's metallicity. Our latest simulations of disks undergoing gravitational instabilities (GI's) with realistic radiative cooling indicate that protoplanetary disks with lower metallicity generally cool faster and thus show stronger overall GI-activity. Moreover, the global cooling times in our simulations appear to be too long for disk fragmentation to occur, and, so far, we find no evidence for formation of persistent dense protoplanetary clumps. Our results run counter to the observed metallicity trend for any scenario where gas giant planet formation requires strong GI's and suggest that direct gas giant planet formation via disk instabilities is unlikely to be the mechanism that produced most observed planets. Nevertheless, GI's may still play an important role in a hybrid scenario, compatible with the observed metallicity trend, where structure created by GI's accelerates planet formation by core accretion.

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