Title：Radiation Hydrodynamics of Self-gravitating Protoplanetary Disks: How GI Fragments Form and What They Become

报告人：倪阳 博士（清华大学）

Abstract：Gravitational instability (GI) is a natural route to giant planets at wide separations and around low-mass stars, where core accretion struggles. The long - standing objection is one of scale: disk fragmentation was generally expected to produce brown dwarfs rather than planets. We address this objection with global three-dimensional radiation hydrodynamic simulations using the meshless finite-mass method and M1 radiation transport. A suite of simulations spanning disk mass and opacity shows that fragmentation sets in where cooling becomes efficient, and that fragments are born at planetary masses, distributed log-normally about a scale set by local conditions in the fragmenting spiral arm. We then follow every bound object formed in one deep simulation through its first kiloyear, with per-object mass and angular-momentum budgets: growth obeys a single Hill-limited law, migration is bidirectional, driven by disk torques for most fragments but by fragment-fragment dynamics in the crowded late disk, and the interiors remain hot and entropy-stratified. Integrating the measured growth law against the measured gas budget, a fragmenting disk delivers gas giants, brown dwarfs, a possible low-mass stellar companion, and perhaps a free-floating planet. The outcome of disk fragmentation is set not only at birth but by the mass supply and dynamics that follow.

时间：2026年8月25日（周二）14:00 

地点：紫台仙林3-302会议室

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