红外尘埃Bubble:大质量恒星对其周围分子云环境反馈作用的相关研究

The UV radiation come from the massive star will ionize the neutral surrounding medium. Because of the higher pressure in the warm ionized gas than in the cold neutral surrounding medium, the HII region expands and a shock interacts with the surrounding medium. The input energy will cause a strong effect of the evolution of its parent molecular cloud and the star formation around it. Therefor, it is very significative to study the feekback of the massive star, which can help us to understand how the molecular cloud evolve and how the stucture and the YSOs (young stellar object) form. But in this topic there are still several questions remnant. Such as, till now thousands of HII regions with different morphology have been detected, whether their evolution follows any kind of sequence, are there any difference when they are evolving? In an evolutionary molecular cloud, which one is dominant between the ionizing radiation and the self-gravity? In order to answer the questions above, we will select 40 identified infrared dust Bubbles which, according to the morphology, will be classified into 4 types. And we will calculate their masses, temperatures, ages which are used to analyze their evolutionary state. For the star formation, we will find the YSOs around the HII region, and analyze their evolutionary state and their distribution. Then, we will use the SPH model upgraded by Dr. Miao to do some simulations with the selected Bubbles. Finally, analyzing and comparing with the result from observation and simulation, we will find the reasonable answers to the above questions.

大质量恒星的反馈作用将对其所在的母分子云环境产生强烈的影响，从而对恒星的形成产生重大的影响。因此研究大质量恒星的反馈作用，对理解分子云结构和演化以及恒星形成都有重要意义。 然而，相关的研究还存在许多疑问。比如：目前发现的大量结构形态各异的电离氢区，它们在演化上是否有先后顺序或其他不同的特征呢，在恒星形成效率和壳层年轻星的演化上有何差异吗？电离辐射和初始环境的自引力作用在分子云形态的演化过程中，到底哪个起主导作用？ 为了研究上述问题，我们将从已认证的红外Bubble中选取40个不同结构形态的源，并分为四类。对它们做多波段成图研究，计算它们的质量，温度，年龄，分析其演化状态，搜寻其壳层上年轻星的演化状态和分布情况。接着，我们将采用缪静琪博士改进后的SPH模型对这批源进行数值模拟。最后，对比分析，观测上和模拟上的结果，找出合理的解释回答上述问题。

恒星形成于分子云，而恒星形成(特别是大质量恒星的形成)会对其所在的母分子云环境产生强烈的影响。分子云环境的改变又反过来影响（触发或阻碍）恒星的形成。因此研究大质量恒星的反馈作用，对理解分子云的结构和演化以及恒星的形成都有重要意义。. 我们选取了50个具有不同形态和大小的红外尘泡，通过对多波段数据的研究，发现分子云环境对尘泡的演化起到关键的作用；同时我们还发现年轻星更倾向于分布在尘泡的壳层上，这说明大质量恒星的反馈作用对其周围的恒星形成有一定的促进作用；而且圆形尘泡周围的年轻星比双极尘泡的多，这在一定程度上说明双极尘泡更年轻。. 对双极尘泡的研究，我们发现双极尘泡的数量并没有我们想象中的少，它很可能是早期的圆形尘泡，只是角度的不同而已。从而我们倾向于认为，尘泡是二维的圆环结构而不是三维的球形结构。. 二维形态的尘泡，使我们更相信分子云应该为扁平的结构。而通过在数值模拟中加入磁场，确实会使分子云演化为扁平结构。这说明磁场在分子云的演化过程中，起到至关重要的引导作用。