标题： 银河系中心由恒星风形成的冷盘的形成与稳定性 显示英文标题

标题： The formation and stability of a cold disc made out of stellar winds in the Galactic Centre

摘要： 在银河系中心超大质量黑洞人马座A*（Sgr A*）周围约0.005秒差距内的冷（~10$^4$ K）盘状结构的发现挑战了我们对人马座A*附近等离子体气体动力学和热力学状态的理解。最先进的模拟尚未就这种盘是否可以作为该区域质量损失恒星多重星风相互作用的结果达成一致。 本研究旨在限制质量损失恒星环绕人马座A*系统的冷盘形成的条件，调查该盘是瞬时还是持久结构，并通过直接与观测结果对比来评估模型的有效性。我们使用有限体积自适应网格细化代码Ramses进行了针对人马座A*吸积的观测到的沃尔夫-拉叶（WR）星的一组流体动力学模拟。我们首次关注从WR星发出的等离子体化学成分的影响。模拟表明，等离子体的化学成分足以影响辐射冷却，从而影响介质的性质，如密度和温度，进而影响物质流入人马座A*的速度。我们证明，对于某些与当前观测约束一致的化学组成，从恒星风形成冷盘是可能的。然而，即使在这种情况下，也无法重现观测到的盘状结构的报告特性，即其倾角和氢复合线的流量。我们得出结论，恒星风本身不足以形成从观测推断出的人马座A*周围的冷盘。要么模型中仍然缺少相关成分，要么需要重新解释观测数据。 显示英文摘要

摘要： The reported discovery of a cold (~10$^4$ K) disc-like structure within 0.005 pc around the super-massive black hole at the centre of the Milky Way, Sgr A*, has challenged our understanding of the gas dynamics and thermodynamic state of the plasma in its immediate vicinity. State-of-the-art simulations do not agree on whether or not such a disc can be a product of the multiple stellar wind interactions of the mass-losing stars in the region. This study aims to constrain the conditions for the formation of a cold disc as a natural outcome of the system of the mass-losing stars orbiting around Sgr A*, to investigate whether the disc is a transient or long-lasting structure, and to assess the validity of the model through direct comparisons with observations. We performed a set of hydrodynamic simulations of the observed Wolf-Rayet (WR) stars feeding Sgr A* using the finite-volume adaptive mesh refinement code Ramses. We focus, for the first time, on the impact of the chemical composition of the plasma emanating from the WR stars. The simulations show that the chemical composition of the plasma affects the radiative cooling enough to impact the properties of the medium, such as density and temperature, and, as a consequence, the rate at which the material inflows onto Sgr A*. We demonstrate that the formation of a cold disc from the stellar winds is possible for certain chemical compositions that are consistent with the current observational constraints. However, even in such cases, it is not possible to reproduce the reported properties of the observed disc-like structure, namely its inclination and the fluxes of its hydrogen recombination lines. We conclude that the stellar winds alone are not sufficient to form the cold disc around Sgr A* inferred from observations. Either relevant ingredients are still missing in the model, or the interpretation of the observed data needs to be revised.