Towards a Global Understanding of High and Low Mass Star Formation

在过去的30年里，我们在恒星形成领域的大部分进展都集中在低质量恒星的形成上（质量小于1太阳的恒星），因为这些天体离我们很近，并且被认为是与其他恒星分离形成的。然而，现在人们认识到大多数恒星（约90%）是在星团中形成的，而不是孤立的。此外，来自赫歇尔空间天文台的观测已经确定了一个遍布星际介质的复杂的细丝网。这些细丝分裂成致密的团块，其中一些从湍流到相干的相变，然后成为恒星的形成地点。这些细丝是如何形成、破碎并随后演变成星团的还不确定。因此，很明显，低质量恒星形成的细节并不像以前认为的那样被很好地理解。大质量恒星（8倍太阳质量或更高质量的恒星）的形成更不为人所知。这些恒星很重要，因为它们是银河系中能量产生和重元素丰度的关键驱动力。然而，我们对它们形成的理解受到一些事实的阻碍：a)它们本质上是罕见的，在它们最早的进化阶段很难找到，所以我们还没有统计上相关的样本；b)我们唯一的大质量恒星形成区域的例子比形成低质量恒星的区域要远得多。因此，星团形成的本质使得研究单个物体变得困难（因为我们望远镜有限的空间分辨率会导致单独的物体混合在一起）。***在本提案中，要求资金用于解决恒星形成领域（低质量和高质量）中一些最紧迫的问题。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）是什么？是什么使它们与形成低质量恒星的区域不同？很明显，为了在我们对大质量恒星形成的理解上取得重大进展，我们需要对大质量恒星在其不同演化阶段的出生环境的物理特性进行系统的、有统计学意义的研究；从必须成为分子形式的原子气体，到引力不稳定的前原恒星核心，再到与新形成的大质量恒星直接相关的小而致密的“热核心”。我们还将探讨一些关于细丝及其与恒星形成的关系的基本问题；例如：这些细丝如何以及在哪里从对抗引力坍缩的湍流支持转变为纯粹的热支持，并最终破碎成恒星形成的核心？磁场在这个过程中起什么作用？我们还计划开发新的创新仪器，以帮助我们在观测上解决这些问题。**

A large part of our progress in the field of star formation over the past 30 years has focused solely on the formation of low-mass stars (stars with ~1 solar mass or less), because these objects are nearby and were thought to form isolated from other stars. However, it is now recognized that most stars (~ 90%) form in clusters instead of in isolation. Furthermore, observations from the Herschel Space Observatory have identified a complex web of filaments that pervade the Interstellar medium. These filaments break up into dense, compact clumps some of which make a phase transition from turbulence to coherence and then become the formation sites of stars. How these filaments form, fragment, and subsequently evolve into clusters of stars is still uncertain. As a result, it has become clear that the details of low mass star formation are not as well understood as it was previously believed. ***The formation of massive stars (stars with 8 solar masses or higher) is even less well understood. These stars are important since they are key drivers of energy production and heavy element abundance in the Galaxy. However, our understanding of their formation has been hampered by a number of facts: a) they are intrinsically rare and hard to find in their earliest evolutionary stages and so we do not yet have statistically relevant samples, b) Our only examples of massive star forming regions are much more distant than regions forming low mass stars. Therefore, the nature of clustered star formation makes it difficult to study individual objects (since the limited spatial resolution of our telescopes will cause separate objects to blend together). ***In this proposal, funding is requested to tackle some of the most pressing issues in the field of star formation (both low and high mass). What are the properties (physical & velocity structure, density, temperature, chemical abundances) of massive star forming regions? What makes them different from regions forming low mass stars? It is clear that in order to make significant progress in our understanding of massive star formation, we require systematic and statistically significant studies of the physical properties of the natal environments of massive stars during their different evolutionary stages; from the atomic gas which must become molecular in form, to gravitationally unstable pre-protostellar cores, to the small & dense “hot cores” directly associated with newly formed massive stars. We will also explore some of the fundamental questions that have arisen regarding filaments and their connection to star formation; such as: how and where do these filaments make the transition from turbulent support against gravitational collapse to pure thermal support and, ultimately, to fragmentation into star forming cores? What role do magnetic fields play in the process? We also plan to develop new and innovative instrumentation that will help us to tackle these questions observationally. **