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。

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 pre­protostellar 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.