中心有黑洞的暗物质晕中的多方跨音速星系外流
Polytropic transonic galactic outflows in a dark matter halo with a central black hole
摘要：
研究了暗物质晕与超大质量黑洞引力势中球对称定常星系风的多方跨音速解。根据解的拓扑特征对解进行了分类，并且SMBH的引力势为DMH引力产生的跨音速解增加了一个新的分支。跨音速解的拓扑类型取决于DMH质量分布的质量分布、能量供应量、多变指数$γ$和斜率$α$。当$α$大于一个临界值$α_\mathrm{c}$时，跨音速解的类型发生了显著的变化。此外，我们的模型预测，即使在具有小$γ$的静止星系中，也有可能存在缓慢加速的外流。这种缓慢加速的外流不同于以前许多研究中所考虑的那些，这些研究集中在活跃的恒星形成星系中的超音速外流。此外，我们的模型表明，在活跃的恒星形成星系的外流只有一个跨音速点的内部区域（$\sim$ 0.01千秒差距）。该跨音速点的轨迹对$γ$的依赖性不强。我们应用多方模型，包括恒星组件提供的质量流量的草帽星系，并得出结论，它可以重现所观察到的气体密度和温度分布。该结果与等温模型显著不同，等温模型需要不切实际的大质量通量（Igarashi等人，2014）。因此，我们的结论是多方模型比等温模型更现实，草帽星系可以有一个缓慢加速流出。
英文摘要：
Polytropic transonic solutions of spherically symmetric and steady galactic winds in the gravitational potential of a dark matter halo (DMH) with a supermassive black hole (SMBH) are studied. The solutions are classified in terms of their topological features, and the gravitational potential of the SMBH adds a new branch to the transonic solutions generated by the gravity of the DMH. The topological types of the transonic solutions depend on the mass distribution, the amount of supplied energy, the polytropic index $γ$, and the slope $α$ of the DMH mass distribution. When $α$ becomes larger than a critical value $α_\mathrm{c}$, the transonic solution types change dramatically. Further, our model predicts that it is possible for a slowly accelerating outflow to exist, even in quiescent galaxies with small $γ$. This slowly accelerating outflow differs from those considered in many of the previous studies focusing on supersonic outflows in active star-forming galaxies. In addition, our model indicates that outflows in active star-forming galaxies have only one transonic point in the inner region ($\sim$ 0.01 kpc). The locus of this transonic point does not strongly depend on $γ$. We apply the polytropic model incorporating mass flux supplied by stellar components to the Sombrero Galaxy, and conclude that it can reproduce the observed gas density and the temperature distribution well. This result differs significantly from the isothermal model, which requires an unrealistically large mass flux (Igarashi et al. 2014). Thus, we conclude that the polytropic model is more realistic than the isothermal model, and that the Sombrero Galaxy can have a slowly accelerating outflow.
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