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Astrophysics Luncheon Seminar

Dust Evolution and Planet Traps: Effects on Planet Populations
Presented by Matthew Alessi
McMaster University, Canada

Monday, September 24, 2018
12:00 noon in 169-336

Abstract
The wealth of recently discovered exoplanets has revealed the existence of distinct planet populations on the mass-period diagram. Our work aims to understand the factors in planet formation processes that shape this distribution. We combine an evolving physical and chemical disk model and the core accretion model of planet formation in a population synthesis approach. A key feature of our model is the inclusion of planet traps that are barriers to rapid type-I migration. The traps we include are the water ice line, heat transition, and the dead zone outer edge. We find that low settings of accreting planets' envelope opacities (~0.001 cm2 g-1) are necessary to produce gas giants out to 3 AU. With higher envelope opacities and longer gas accretion timescales, prolonged planet migration results in hot Jupiters being the dominant gas giant population. With the assumption of a constant disk dust-to-gas ratio, our model produces many super Earths outside of 2 AU. We then consider a dust evolution model, including the effects of radial drift, on the distribution of disk solids and its affect on accretion rates. Within this framework, our model produces many more super Earths between 0.1-1 AU. However, the inclusion of dust evolution also produces too many gas giants near 1 AU due to efficient radial drift leading to an enhancement of solids at the ice line. This result is in agreement with observationally inferred disk spectral indices, suggesting that radial drift models need to be slowed to match observations.

JPL Contact: Yasuhiro Hasegawa (3-7253)


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