Predicting X-ray emission from wind-blown bubbles — limitations of fits to ROSAT spectra
Predicting X-ray emission from wind-blown bubbles — limitations of fits to ROSAT spectra
复制标题
预测风吹气泡的 X 射线发射 — ROSAT 光谱拟合的局限性
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
I. Stevens
中科院分区：
文献类型：
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作者：
D. Strickland;I. Stevens
风吹气泡，从大质量O星和沃尔夫-拉叶星周围的气泡到OB星协周围的超级气泡和星暴星系中的星系风，在确定星际介质（ISM）的结构方面起着主导作用。对这些气泡的X射线观测特别重要，因为它们的大部分体积都被热气体105 <$T（K）<$108所占据。 然而，很难比较这些X射线观测，通常分析单或双温度光谱模型拟合，与理论模型，因为真实的气泡没有这样简单的温度分布。光谱拟合以及由此推断的性质将以复杂的方式取决于真实的温度分布以及所使用的X射线天文台的特性和局限性。 在这一系列论文的介绍中，详细介绍了风吹气泡的可观测X射线特性，我们描述了我们打算解决这个问题的方法，分析了一个大质量星星周围的风吹气泡的模拟。 我们的模型是一个恒定的质量和能量注入率的风，吹成一个统一的ISM，从中我们计算X射线光谱，因为他们将看到的ROSAT PSPC。以与真实的观测相同的方式分析这些光谱，我们将从ROSAT数据推断出的气泡的性质与模拟中气泡的真实性质进行比较。 我们发现标准的光谱模型产生的推断的属性，显着偏离真实的属性，即使光谱拟合是统计上可以接受的，并没有给出任何迹象表明，他们不代表真实的光谱分布。例如，单温度光谱拟合给出的最佳拟合金属丰度仅为真实值的4%。一个凉爽的气泡具有比两倍热的气泡高得多的最佳温度。这些结果表明，在任何情况下，其中真正的源光谱不是来自一个简单的单或两个温度分布，“观察到的”属性不能天真地用来推断真正的属性。在这种情况下，为了将X射线观测与理论进行比较，有必要计算模型的可观测X射线性质。
Wind-blown bubbles, from those around massive O and Wolf–Rayet stars to superbubbles around OB associations and galactic winds in starburst galaxies, have a dominant role in determining the structure of the interstellar medium (ISM). X-ray observations of these bubbles are particularly important as most of their volume is taken up with hot gas, 105 ≲ T (K) ≲ 108. However, it is difficult to compare these X-ray observations, usually analysed in terms of single- or two-temperature spectral model fits, with theoretical models, as real bubbles do not have such simple temperature distributions. Spectral fits, and the properties inferred from them, will depend in a complex way on the true temperature distribution and the characteristics and limitations of the X-ray observatory used. In this introduction to a series of papers detailing the observable X-ray properties of wind-blown bubbles, we describe the method with which we intend to solve this problem, analysing a simulation of a wind-blown bubble around a massive star. Our model is of a wind of constant mass and energy injection rate, blowing into a uniform ISM, from which we calculate X-ray spectra as they would be seen by the ROSAT PSPC. Analysing these spectra in the same way as a real observation, we compare the properties of the bubble as would be inferred from the ROSAT data with the true properties of the bubble in the simulation. We find standard spectral models yield inferred properties that deviate significantly from the true properties, even though the spectral fits are statistically acceptable, and give no indication that they do not represent the true spectral distribution. For example, single-temperature spectral fits give best-fitting metal abundances that are only 4 per cent of the true value. A cool bubble has best-fitting temperatures significantly higher than a bubble twice as hot. These results suggest that in any case in which the true source spectrum does not come from a simple single- or two-temperature distribution, the ‘observed’ properties cannot naively be used to infer the true properties. In this situation, to compare X-ray observations with theory it is necessary to calculate the observable X-ray properties of the model.