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Vega has been shown to host multiple dust populations, including both hotexo-zodiacal dust at sub-AU radii and a cold debris disk extending beyond 100AU. We use dynamical simulations to show how Vega's hot dust can be created bylong-range gravitational scattering of planetesimals from its cold outerregions. Planetesimals are scattered progressively inward by a system of 5-7planets from 30-60 AU to very close-in. In successful simulations the outermostplanets are typically Neptune-mass. The back-reaction of planetesimalscattering causes these planets to migrate outward and continually interactwith fresh planetesimals, replenishing the source of scattered bodies. The mostfavorable cases for producing Vega's exo-zodi have negative radial massgradients, with sub-Saturn- to Jupiter-mass inner planets at 5-10 AU and outerplanets of 2.5 to 20 Earth masses. The mechanism fails if a Jupiter-sizedplanet exists beyond ~15 AU because the planet preferentially ejectsplanetesimals before they can reach the inner system. Direct-imaging planetsearches can therefore directly test this mechanism.

Vega's hot dust from icy planetesimals scattered inward by an outward-migrating planetary system