自引力原行星盘辐射流体力学 II：引力不稳定碎块的吸积、迁移、自旋与内部结构
Radiation Hydrodynamics of Self-gravitating Protoplanetary Disks II. Accretion, Migration, Spin, and Internal Structure of GI Fragments
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中文总结 AI 辅助
通过三维辐射流体力学模拟跟踪原行星盘引力不稳定碎块的演化，发现其质量增长受希尔极限标度调控、迁移双向、自旋由吸积主导且内部准绝热，最终可形成气态巨行星、褐矮星乃至自由漂浮行星。
中文摘要 AI 辅助
在本系列的第一篇论文中，我们展示了原行星盘中的引力不稳定性（GI）可以产生行星质量而非褐矮星质量的碎块，但这些碎块随后的演化和最终命运仍是一个悬而未决的问题。在此，我们跟踪了一个围绕 $1\\,M_\odot$ 恒星、质量为 $0.196\\,M_\odot$ 的碎裂盘的三维辐射流体力学全局模拟中的每一个束缚天体：七个存活的碎块、一个被瓦解的团块和一个合并的团块，共跟踪了 $1.2$ 千年。这些碎块形成时的质量为 $1.4$--$3.0\\,M_\mathrm{J}$，与论文 I 的归一化初始质量分布一致。质量增长遵循单一的希尔极限标度关系 $\propto \Sigma \Omega R_\mathrm{H}^2$，受气体输运至排水供给区的调控，而最新形成的碎块则经历供给匮乏。迁移是双向的，受与盘和邻近团块的引力相互作用共同支配。吸积提供了碎块的大部分自旋，其自旋方向与轨道对齐，并提供约十分之一的支持力以抵抗引力。碎块内部呈熵分层，大部分区域对流稳定，且质量累积速度远快于辐射冷却速度：压缩为准绝热过程，中心熵接近每重子 $12\\,k_\mathrm{B}$，这有利于演化成气态巨行星的碎块采用热启动初始条件。将测得的增长律与测得的气体预算相结合，我们预测该盘会产生气态巨行星、褐矮星以及可能的低质量恒星伴星，而一个被散射的碎块可能成为自由漂浮行星：盘碎裂的结果不仅取决于诞生时的条件，还取决于后续的质量供给和动力学过程。
英文摘要
In the first paper of this series, we showed that gravitational instability (GI) in protoplanetary disks can produce fragments of planetary rather than brown-dwarf mass, leaving the subsequent evolution and ultimate fates of such fragments an open question. Here, we follow every bound object in a global three-dimensional radiation hydrodynamic simulation of a fragmenting $0.196\,M_\odot$ disk around a $1\,M_\odot$ star: seven surviving fragments, one disrupted clump, and one merged clump, followed for $1.2$\,kyr. The fragments form at $1.4$--$3.0\,M_\mathrm{J}$, consistent with the normalized initial-mass distribution of Paper~I. Mass growth follows a single Hill-limited scaling $\propto ΣΩR_\mathrm{H}^2$, regulated by the delivery of gas into draining feeding zones, while the latest-forming fragments experience supply starvation. Migration is bidirectional and governed by gravitational interactions with both the disk and neighboring clumps. Accretion supplies most of the fragments' spin, which aligns with their orbits and provides roughly a tenth of the support against gravity. The interiors are entropy-stratified, largely convectively stable, and accumulate mass far faster than they can radiatively cool: compression is quasi-adiabatic, and central entropies near $12\,k_\mathrm{B}$ per baryon favor hot-start initial conditions for fragments that evolve into gas giants. Integrating the measured growth law against the measured gas budget, we predict that the disk produces gas giants, brown dwarfs, and a possible low-mass stellar companion, while one scattered fragment may become a free-floating planet: the outcome of disk fragmentation is determined not merely at birth, but by the subsequent mass supply and dynamics.
发表机构
- Institute for Advanced Study, Tsinghua University（清华大学高等研究院）
- Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）
- Department of Astronomy, Tsinghua University（清华大学天文系）
机构由 AI 辅助整理，请以论文原文为准。
