Towards a global understanding of high mass star formation

在过去的20年里，在恒星形成领域取得了重大进展。我们已经确定，所有的恒星都是在深嵌的地方诞生的，随着时间的推移，周围的物质要么被吸积，要么被分散。我们已经发现了红外黑云，这是一种寒冷、密集的气体和尘埃云，在银河面产生的明亮中红外背景下的轮廓，并了解到它们可能是年轻恒星的祖先，包括比太阳质量更大的恒星。我们还了解到，恒星形成区内气体的化学成分会对其物理演化产生影响。我们在恒星形成领域取得的很大一部分进展仅仅集中在低质量恒星的形成上，主要是因为这些天体的形成与附近的其他恒星隔绝，减少了混乱。然而，现在已经认识到，大多数恒星，特别是比太阳质量大的恒星，并不是孤立地形成的。相反，超过90%的恒星是在星团中形成的，这些星团也在形成大质量恒星。在我们对大质量恒星形成的理解方面，类似的进展受到几个因素的阻碍：a)作为大质量恒星诞生地点的巨大分子云距离更远，使得对单个物体的研究变得困难。b)大质量恒星的收缩时间尺度要短得多，这意味着最早阶段的例子很少。c)星团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中能量产生和重元素丰度的关键驱动因素，但它们的形成机制尚不清楚。在这项提案中，资金被要求解决大质量恒星形成领域的一些最紧迫的问题。大质量恒星形成区域的性质（物理和速度结构、密度、温度、化学丰度等）是什么？是什么使它们与形成低质量恒星的区域不同？孕育大质量恒星的云层最初是如何形成的？

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?