Young massive star clusters in 3D - spectrophotometric mapping with MUSE

大多数恒星形成于星团环境中，其中大多数在几百万年内解散，形成银河系场群。密度最大、质量最大的星团有可能保持引力束缚，并可能长期存在。恒星群与其母星HII区之间的物理过程和相互作用还不是很清楚。由于这些年轻的大质量星团（ymc）位于其他星系中，因此它们的性质很难获得。这使得银河系ymc成为重要的研究对象，然而，与星暴星系相比，ymc在银河系中是罕见的。新的仪器和望远镜第一次使得在合理的望远镜时间内进行详细的、大规模的光谱调查成为可能。在这个为期两年的研究项目中，我计划对YMC进行研究，特别是Westerlund 2 (Wd2)，利用MUSE积分场光谱仪获得的数据，绝对第一次对这样一个YMC的三维结构、形成、现状和未来演变进行结论性的了解。Wd2的年龄为1 - 2 Myr，距离为4 kpc，是MW中质量第二大的YMC（恒星总质量：37000太阳质量）。这个高度质量分离的YMC拥有一个完整的上部主序列，由两个同时期的亚团块组成。这些特性，众多的OB恒星以及周围的HII区域使Wd2成为研究ymc与其母体分子气体云相互作用的完美试验台。与现有的深度、多历元哈勃太空望远镜测光技术一起，这个新仪器给了我一个独特的机会，可以同时观察和检查恒星群和剩余气体，研究它们的反馈和相互作用。确定大量星团恒星样本的速度色散将提供关于大质量星团及其在内部和外部影响下的长期稳定性的信息，例如超新星爆炸和与巨大分子云或银盘的引力相互作用。我还将讨论OB恒星的远紫外线通量对低质量PMS恒星周围原恒星盘的盘面扩散有多大影响。分散速度越快，意味着低质量恒星的质量增长越少，这改变了星团的质量函数，影响了长期稳定性。这个项目将有助于调整n体模拟的初始参数，以在哈勃时间的相当一部分时间内追踪大质量星团的长期演化。这些模拟对于进一步了解观测到的ymc和旧球状星团人口之间的联系至关重要。我将以Wd2为例，开发新的方法来减少和分析这些数据集，并将其扩展到MW中的其他ymc以及麦哲伦云中更遥远、更大质量的ymc。

Most stars form in clustered environments, of which the majority dissolve within a few million years forming the Galactic field population. The densest and most massive star clusters have the potential to remain gravitationally bound and might be long-lived. The physical processes and interactions between the stellar cluster population and its parental HII region are not very well understood. The properties of the majority of these young massive star clusters (YMCs) are difficult to access due to their location in other galaxies. This makes the Galactic YMCs important objects to study, yet, compared to starburst galaxies, YMCs are rare in the Milky Way (MW). For the first time, new instruments and telescopes make it possible to perform detailed, large scale spectroscopic surveys with a reasonable amount of telescope time.For the proposed two-year research project, I plan to perform a study of YMCs, specifically Westerlund 2 (Wd2), using data obtained with the integral field spectrograph MUSE to gain, for the absolute first time, a conclusive insight into the 3D structure, formation, present status, and future evolution of such a YMC. With an age of 1 – 2 Myr at a distance of 4 kpc, Wd2 is the second most massive YMC in the MW (total stellar mass: 37000 solar masses). This highly mass segregated YMC hosts a fully intact upper main sequence and is built from two coeval sub-clumps. These properties, the numerous OB stars, and the surrounding HII region makes Wd2 a perfect test bed to study the interactions of YMCs with their parental molecular gas cloud. Together with the existing deep, multi-epoch Hubble Space Telescope photometry this new instrument gives me the unique opportunity to simultaneously observe and examine the stellar population and the remaining gas to study their feedback and interactions. Determining the velocity dispersion of a large sample of cluster stars will provide information about massive clusters and their long-term stability toward internal and external influences, such as supernova explosions and gravitational interactions with giant molecular clouds or the Galactic disk. I will also address the question on how much the far ultra-violet flux of the OB stars impact the disk dispersal of protostellar disks around low-mass PMS stars. Faster dispersing disks mean that the low-mass stars will grow less in mass, which alters the stellar mass function of the cluster impacting the long-term stability.This project will help to adjust the initial parameters of N-body simulations to trace the long-term evolution of massive clusters over a significant fraction of a Hubble time. These simulations are essential to get a step closer to understand the link between the observed YMCs and the old globular cluster population. I will use Wd2 as an example case to develop new methods for reducing and analyzing such datasets, which will be extended to other YMCs in the MW and the more distant and more massive ones in the Magellanic Clouds.