The formation and stability of a cold disc made out of stellar winds in the Galactic centre

IF 5.4 2区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS
Diego Calderón, Jorge Cuadra, Christopher M. P. Russell, Andreas Burkert, Stephan Rosswog, Mayura Balakrishnan
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Abstract

Context. The reported discovery of a cold (~104 K) disc-like structure within the central 5 × 10−3 pc around the super-massive black hole at the centre of the Milk Way, Sagittarius A* (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 indeed be a product of the multiple stellar wind interactions of the mass-losing stars in the region.Aims. The aims of this study are 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.Methods. 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.Results. The simulations show that the chemical composition of the plasma affects the radiative cooling to a sufficient degree 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.Conclusions. 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.
银河系中心由恒星风形成的冷盘的形成和稳定性
上下文。据报道,在银河系中心的超大质量黑洞人马座a * (Sgr a *)周围的5 × 10−3 pc中心发现了一个冷(~104 K)的盘状结构,这挑战了我们对其附近等离子体的气体动力学和热力学状态的理解。目前最先进的模拟并不认同这样的圆盘是否真的是该区域内失去质量的恒星之间多重恒星风相互作用的产物。本研究的目的是约束冷盘作为围绕Sgr a *运行的质量损失恒星系统的自然结果形成的条件,研究冷盘是短暂的还是持久的结构,并通过与观测结果的直接比较来评估模型的有效性。利用有限体积自适应网格细化代码Ramses,对观测到的WR恒星喂养Sgr a *进行了流体动力学模拟。我们首次关注了从WR恒星发出的等离子体化学成分的影响。模拟结果表明,等离子体的化学成分对辐射冷却的影响程度足以影响介质的特性,如密度和温度,以及物质流入Sgr a *的速率。我们证明,在某些化学成分与当前观测条件一致的情况下,恒星风形成冷盘是可能的。然而,即使在这种情况下,也不可能重现所报道的观察到的盘状结构的性质,即其倾角和氢复合线的通量。我们的结论是,从观测推断,仅靠恒星风不足以形成人马座A*周围的冷盘。要么是模型中仍然缺少相关成分,要么是对观测数据的解释需要修正。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Astronomy & Astrophysics
Astronomy & Astrophysics 地学天文-天文与天体物理
CiteScore
10.20
自引率
27.70%
发文量
2105
审稿时长
1-2 weeks
期刊介绍: Astronomy & Astrophysics is an international Journal that publishes papers on all aspects of astronomy and astrophysics (theoretical, observational, and instrumental) independently of the techniques used to obtain the results.
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