Protostars and Planets VI, Heidelberg, July 15-20, 2013
Photoevaporation of Externally Irradiated Protoplanetary Disks in Young Star Cluster
Takaya, Tamura (Kyoto University)
It has been suggested that most stars are formed in young star clusters. Therefore, for general understanding of planet formation process, it is important to study environmental effects in young star clusters. One of the most essential effects will be irradiation from nearby massive stars, which induces photoevaporation by heating the gas in the disks as in the case of proplyds in the Trapezium Cluster in the Orion Nebula. Photoevaporation and then gas dispersal process in the disks will control some fundamental processes of planet formation, such as gas giant formation and migration of planets.
In this work, we have studied evolution of disks irradiated by a nearby massive star in a young star cluster. The result of our model calculations of surface density evolution of externally irradiated disk shows that the gas in the outer region of the disk photoevaporates efficiently so that the edge of the disk shrinks to become several times ten AU in ~1Myr. This is consistent with the disk radii of proplyds observed in the Trapezium cluster. We also performed hydrodynamical simulations of photoevaporating flow and ionization fronts formed around the disks. As a result, we obtained a correlation between the radii of ionization fronts and the distances from the massive star, which also reproduces observations in the Trapezium cluster.
Our results suggest that the gas in proplyds is mainly dispersed with photoevaporation and the formation of planetary system in young star clusters can differ from that of isolated stars.
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