Towards a global understanding of high mass star formation

在过去的20年里，恒星形成领域取得了重大进展。我们已经确定，所有的恒星在出生时都深深嵌入其中，并随着时间的推移而出现，因为周围的物质要么吸积，要么分散。我们已经发现了红外暗云，这是在银河系平面产生的明亮的中红外背景下看到的冷密的气体和尘埃云的轮廓，并了解到它们很可能是年轻恒星的祖先，包括质量比太阳大的恒星。我们还了解到，恒星形成区气体的化学成分可能会对其物理演化产生影响。我们在恒星形成领域的很大一部分进展完全集中在低质量恒星的形成上，主要是因为这些天体形成时与附近的其他恒星隔离，减少了混乱。然而，现在人们已经认识到，大多数恒星，特别是质量比太阳大的恒星，并不是以孤立的方式形成的。相反，大约90%以上的恒星是在星团中形成的，这些星团也在形成大质量恒星的区域。我们在理解大质量恒星形成方面的类似进展受到了几个因素的阻碍：a)巨型分子云是大质量恒星的诞生地，距离更远，使得对单个天体的研究变得困难。B)大质量恒星的收缩时间要短得多，这意味着最早阶段的例子很少见。C)星团恒星形成的本质增加了混淆的可能性。因此，尽管大质量恒星是银河系能量生产和重元素丰度的关键驱动力，但它们的形成机制尚不清楚。在这项提案中，要求提供资金来解决大质量恒星形成领域中一些最紧迫的问题。它们的性质是什么(物理和速度结构、密度、温度、化学丰度等)大质量恒星形成区？它们与形成低质量恒星的区域有什么不同？产生大质量恒星的星云最初是如何形成的？

Over the past 20 years there have been significant advances in the field of star formation. We have determined that all stars are born deeply embedded and emerge over time as the surrounding material is either accreted or dispersed. We have discovered InfraRed Dark Clouds which are cold, dense clouds of gas and dust seen in silhouette against the bright mid-infrared background produced by the Galactic Plane and learned that they are likely the progenitors of young stars, including stars more massive than the Sun. We have also learned that the chemical composition of the gas in a star forming region can have an effect on its physical evolution. A large part of our progress in the field of star formation has focused solely on the formation of low-mass stars, predominantly because these objects form isolated from other nearby stars, reducing confusion. However, it has now been recognized that most stars, and especially stars more massive than the Sun, do not form in an isolated fashion. Instead, over approximately 90% of all stars form in clusters, in regions which are also forming massive stars. Similar progress in our understanding of the formation of massive stars has been hampered by several factors: a) The greater distances of the Giant Molecular Clouds that are the birth sites of massive stars makes studies of individual objects difficult. b) Contraction timescales for massive stars are much shorter meaning that examples of the earliest phases are rare. c) The very nature of clustered star formation increases the chances for confusion. As a result, even though massive stars are key drivers of energy production and heavy element abundance in the Galaxy, their formation mechanism is unclear. In this proposal, funding is requested to tackle some of the most pressing issues in the field of massive star formation. What are the properties (physical & velocity structure, density, temperature, chemical abundances, etc.) of massive star forming regions? What makes them different from regions forming low mass stars? How do the clouds that give birth to massive stars form in the first place?