采用改进的辐射冷却模型重新研究原恒星盘中的引力不稳定性
Revisiting gravitational instability in protostellar discs with improved radiative cooling models
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中文总结 AI 辅助
本研究采用改进的辐射冷却模型进行流体动力学模拟，发现原恒星盘的碎裂参数与早期模拟不同，GI驱动的行星形成不局限于最延展的盘，大尺度螺旋臂并非GI的典型结果。
中文摘要 AI 辅助
年轻原恒星盘的质量预计会显著大于年龄超过1百万年的观测盘，而行星形成很可能正是在这一最早阶段开始的。这类大质量盘可能易受引力不稳定性（GI）影响，因此我们需要确定使GI活跃的盘和恒星属性，以理解其在早期盘演化和行星形成中的作用。以往研究受限于模型假设和原恒星盘热力学复杂性质带来的不准确性，因此我们采用流体动力学模拟中近似辐射冷却的改进方法重新研究该问题。我们探索了0.1至1倍太阳质量的年轻原恒星盘的宽参数空间，并纳入了宿主恒星的辐照。结果发现，盘形成螺旋结构和碎裂的参数与早期模拟得到的参数存在差异。半径为50天文单位的盘的外区可能易发生碎裂，这意味着GI驱动的行星形成并不局限于最延展的盘。恒星辐照带来的额外热支撑提高了抵抗GI保持稳定的盘质量：盘可达到不碎裂的大于0.4倍恒星质量，为行星形成提供了大量物质。仅当恒星质量小于0.3倍太阳质量时才会形成大尺度螺旋臂，最致密盘除外。此外，形成的长寿命螺旋结构倾向于絮状且致密，表明大尺度螺旋臂不应被视为GI的典型结果。
英文摘要
Young discs are expected to be significantly more massive than those observed at $>1$ Myr and it is at this earliest stage that planet formation likely begins. Such massive discs may be susceptible to the gravitational instability (GI), therefore we need to determine the disc and stellar properties for which the GI is active to understand its role in early disc evolution and planet formation. Prior work has been limited by model assumptions and inaccuracies due to the complex nature of the thermodynamics of protostellar discs so we now revisit this question using an improved method to approximate radiative cooling within hydrodynamics simulations. We have explored a wide parameter space, representative of young protostellar discs of 0.1 to 1 M$_{\odot}$ and include irradiation from the host star. The parameters for which discs form spirals and fragment were found to differ to those obtained from earlier simulations. The outer regions of discs with radii of 50 au may be susceptible to fragmentation, meaning that GI-driven planet formation is not restricted to only the most extended discs. The additional thermal support due to stellar irradiation increases the disc mass that remains stable against GI: discs may reach up to $\gtrsim 0.4$ M$_*$ without fragmenting, providing a considerable quantity of material for building planets. Large scale spiral arms only developed for $M_*\lesssim$ 0.3 M$_{\odot}$, except in the most compact discs. Furthermore, the long-lived spiral structures that form tend to be flocculent and compact, indicating that large-scale spiral arms should not be considered a typical outcome of GI.
