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Roman Rafikov (Princeton University)
The formation of inhomogeneities in a planetesimal disk by a growing planetary embryo embedded in the disk is considered. Massive body stirs up planetesimal eccentricities and inclinations and also repels planetesimals away clearing a pronounced gap in their distribution of semimajor axes.
It is shown that there exists a single parameter characterizing formation of disk nonuniformities, which represents the competition between the gravitational influence of the embryo and planetesimal-planetesimal scattering. For realistic assumptions about the properties of the planetesimal disk and the planetary embryo, surface density of planetesimals could be strongly affected long before the embryo can accrete all the bodies within its region of influence. The implication of this result is that the embryo slows its growth considerably and, thus, large bodies formed during the coagulation stage should be less massive than is usually assumed. For conditions expected at 1 AU in the solar protoplanetary disk, gap formation is expected to occur around bodies of mass \la 1024 g. This limit is substantially smaller than the restriction based on isolation mass --- disk mass within planetary region of influence --- which is usually assumed to limit planetary accretion.
Financial support for this work was provided by NASA grants NAG5-7310 and NAG5-10456.