发表机构
Research School of Astronomy and Astrophysics, Australian National University; Lund Observatory, Division of Astrophysics, Department of Physics, Lund University（澳大利亚国立大学天文与天体物理研究学院; 隆德大学物理系天体物理学部隆德天文台）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出一种在自适应网格细化星系模拟中测量湍流驱动参数的新算法，发现大麦哲伦云类似体内部以螺线管驱动为主（b<0.4），外围转为压缩驱动（b>0.4），盘面中值b≈0.4，且该趋势在2 Gyr内稳定。
AI 中文摘要
湍流是控制星际介质（ISM）结构和恒星形成的关键因素，然而我们对其在星系中的驱动机制仍缺乏详细理解。以往的理想化湍流模拟采用随机强迫场来驱动湍流。该强迫场的几何特性——无论是主要呈螺线管型（无散）还是压缩型（有散）——是决定湍流如何塑造星际介质密度分布并调节恒星形成速率的关键参数。湍流驱动参数（$b$）量化了压缩驱动与螺线管驱动的相对贡献。因此，准确了解驱动参数对于理解和预测恒星形成，以及对于星际介质物理和恒星形成率的亚网格建模至关重要。在本工作中，我们提出了一种算法，用于在星系的自适应网格细化（AMR）模拟中测量湍流驱动参数。我们将分析重点放在一个合成的大麦哲伦云（LMC）现今类似体上，其总质量$M \approx 10^{11}\\,\mathrm{M}_\odot$。我们发现，在星系内部约$\sim4\\,\mathrm{kpc}$范围内，湍流主要由螺线管驱动（$b<0.4$），而在外围区域（$R\gtrsim4.5\\,\mathrm{kpc}$），湍流变得越来越具有压缩性，$b>0.4$。整个盘面的体积加权中值$b\simeq0.4$，与驱动模式的自然混合一致。我们进一步发现，$b$与剪切强度呈弱相关，即螺线管驱动往往与较高剪切区域相关，这符合星系中心区域的预期。这些趋势在星系约$\sim2\\,\mathrm{Gyr}$的演化过程中持续存在。
英文摘要
Turbulence is a key ingredient in controlling the structure of the interstellar medium (ISM) and star formation, yet we still lack a detailed understanding of its drivers in galaxies. Previous idealised simulations of turbulence employ a stochastic forcing field to drive turbulence. The geometry of this forcing field - whether it is predominantly solenoidal or compressive - is a key parameter governing how turbulence shapes the ISM density distribution and regulates the star formation rate. The turbulence driving parameter ($b$) quantifies the relative contribution of compressive versus solenoidal driving.. Therefore, accurate knowledge of the driving parameter is essential for understanding and predicting star formation, and for sub-grid modelling of ISM physics and the star formation rate. In this work, we introduce an algorithm to measure the turbulence driving parameter in adaptive mesh refinement (AMR) simulations of galaxies. We focus our analysis on a synthetic Large Magellanic Cloud (LMC), present-day analogue with a total mass $M \approx 10^{11}\,\mathrm{M}_\odot$. We find that turbulence is driven primarily solenoidally ($b<0.4$) within the inner $\sim4\,\mathrm{kpc}$ of the galaxy, and becomes increasingly compressive with $b>0.4$ towards the outskirts, $R\gtrsim4.5\,\mathrm{kpc}$. The volume-weighted median across the disc, $b\simeq0.4$, is consistent with the natural mixture of driving modes. We further find that $b$ is weakly correlated with the strength of shear, in that solenoidal driving tends to be associated with regions of higher shear, as expected for the more central parts of galaxies. These trends persist over $\sim\!2\,\mathrm{Gyr}$ of the galaxy's evolution.
Comments11 pages, 11 figures, submitted to MNRAS
