AI 中文总结
通过三维流体动力学模拟发现，冷却时间β增大时，间隙形成行星的气体吸积率呈幂律下降，需将热力学效应纳入年轻行星吸积率的观测解释中。
AI 中文摘要
原行星的气体吸积过程决定了巨行星的最终质量，并为正在进行的行星形成提供可观测的特征。该过程如何依赖于新吸积气体的冷却特性，目前仍缺乏严格约束。我们开展了长期的三维全球流体动力学模拟，以量化质量在1至3木星质量范围内、能打开间隙的行星的气体吸积情况。我们系统地改变冷却时间β，从近等温（β=10⁻²，以轨道时间为单位）到近绝热（β=10²），并追踪演化过程直至达到准稳态。模拟结果显示，气体吸积率随β增大呈单调下降，满足Ṁ_acc∝β⁻⁰·¹⁸关系；在β=10²时，吸积率约为局地等温假设预测值的十分之一，且该结果基本与行星质量无关。吸积率的降低可归因于行星周区域的热力学重构：低效冷却会削弱激波，缩窄为行星周盘供能的吸积带。我们的结果表明，在解释年轻行星的观测吸积率时，必须考虑热力学效应，而常用的局地等温假设可能会引入系统不确定性。
英文摘要
Gas accretion onto forming planets controls the final masses of giant planets and provides observable signatures of ongoing formation. How this process depends on the cooling properties of these newly attracted gas remains poorly constrained. We present long-term, three-dimensional global hydrodynamical simulations to quantify gas accretion onto gap-opening planets in the mass range between 1 and 3 Jupiter masses. We systematically vary the cooling time, $β$, from near-isothermal ($β=10^{-2}$ in units of orbital time) to near-adiabatic ($β=10^{2}$), and follow the evolution until a quasi-steady state is reached. Our simulations show that the gas accretion rate decreases monotonically with increasing $β$, as $\dot{M}_{\rm acc}\proptoβ^{-0.18}$, reaching values at $β=10^2$ that are approximately an order of magnitude lower than locally isothermal predictions, largely independent of planet mass. The reduction in accretion is traced to thermodynamic restructuring of the circumplanetary region: inefficient cooling weakens shocks, narrows the accretion bands feeding the circumplanetary disk. Our results imply that thermodynamic effects should be taken into account when interpreting observed accretion rates of young planets, and may introduce systematic uncertainties in commonly used locally isothermal assumptions.
CommentsAccepted for publication in Astronomy and Astrophysics (A&A)
