The broad Hα, [O III] line wings in stellar supercluster A of NGC 2363 and the turbulent mixing layer hypothesis
The broad Hα, [O III] line wings in stellar supercluster A of NGC 2363 and the turbulent mixing layer hypothesis
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NGC 2363 恒星超星系团 A 中宽阔的 Hα、[O III] 线翼和湍流混合层假说
DOI：
10.1051/0004-6361/200811132
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发表时间：
2009
影响因子：
6.5
通讯作者：
Y. Krongold
中科院分区：
文献类型：
--
作者：
L. Binette;L. Drissen;L. Úbeda;A. Raga;C. Robert;Y. Krongold
上下文。银河系外H II区NGC 2363的超星系团A因其高超音速气体而引人注目，它被视为微弱的延伸的宽发射线，其全宽零强度为7000 km s -1。目标。我们探索了观察到的宽剖面是高速星系风与密集光离团块相互作用的结果的可能性。方法。所考虑的几何结构是近静态光电离冷凝的几何结构，其表面由于与热风的相互作用而产生湍流混合层。采用Canto & Raga的混合长度法对湍流进行了近似处理。使用mapsic代码推导了描述流动的平均量，并计算了湍流层内的线发射率。对线源的三维速度投影进行了解析求解。结果。似乎需要高达约4300km / s -1的快速夹带风才能重现宽广的Hα和[O III]轮廓的微弱翅膀。然而，3500公里/秒-1的慢风仍然可以重现大部分的宽分量，并且确实提供了比临时高斯剖面更好的拟合。结论。发射气体的三维径向加速度（远离超星系团A）提供了一个合理的一阶拟合宽线分量。正如所观察到的那样，对[N II]和[S II]谱线没有广泛的预测成分。所需的风速高得令人不舒服，因此可能必须考虑将排放气体加速到每秒4000公里的替代方法。
Context. Supercluster A in the extragalactic H II region NGC 2363 is remarkable for the hypersonic gas seen as faint extended broad emission lines with a full-width zero intensity of 7000 km s -1 . Aims. We explore the possibility that the observed broad profiles are the result of the interaction of a high-velocity cluster wind with dense photoionized clumps. Methods. The geometry considered is that of near static photoionized condensations at the surface of which turbulent mixing layers arise as a result of the interaction with the hot wind. The approximative treatment of turbulence was carried out using the mixing length approach of Canto & Raga. The code MAPPINGS Ic was used to derive the mean quantities describing the flow and to compute the line emissivities within the turbulent layers. The velocity projection in three dimensions of the line sources was carried out analytically. Results. A fast entraining wind of up to ≈4300km s -1 appears to be required to reproduce the faint wings of the broad Hα and [O III] profiles. A slower wind of 3500 km s -1 , however, can still reproduce the bulk of the broad component and does provide a better fit than an ad hoc Gaussian profile. Conclusions. Radial acceleration in 3D (away from supercluster A) of the emission gas provides a reasonable first-order fit to the broad line component. No broad component is predicted for the [N II ] and [S II] lines, as observed. The wind velocity required is uncomfortably high and alternative processes that would provide comparable constant acceleration of the emission gas up to 4000 km s -1 might have to be considered.