AIMSS项目I：连接星团-星系鸿沟
The AIMSS Project I: Bridging the Star Cluster - Galaxy Divide
摘要：
我们描述了AIMSS项目发现的第一个紧凑的恒星系统的结构和运动学特性。这些光谱学确认的物体（$\sim$ 6 $<$ R $_{\rm e}$ [pc] $<$ 500）和质量（$\sim$ 2 $\times$ 10 $^{6}$ $<$ M $_*$ /M $_\odot$ $<$ 6 $\times$ 10 $^{9}$），涵盖大质量球状星团（GC）、超致密矮星（UCD）和致密椭圆星系（cEs），完全填补了星团和星系之间的空隙。有几个天体与cE的原型M32非常相似。这些天体的质量比先前发现的相同大小的UCD更大，进一步质疑了紧凑恒星系统存在紧密的质量大小趋势，同时加强了在质量大小平面中动态热恒星系统的普遍“回避区”的情况。总的来说，我们认为有两类紧凑的恒星系统：1）大质量星团和2）与星系密切相关的人口。我们的数据提供了进一步划分的星系型UCD/cE人口分为两组，一个人口，我们与剥离的有核矮星系形成的对象，和第二个人口，通过剥离的膨胀星系或低质量的类似物的经典椭圆形。我们在低密度到高密度的环境中发现了星系周围的致密恒星系统，这表明形成它们的物理过程不仅在致密星系团中起作用。
英文摘要：
We describe the structural and kinematic properties of the first compact stellar systems discovered by the AIMSS project. These spectroscopically confirmed objects have sizes ($\sim$6 $<$ R$_{\rm e}$ [pc] $<$ 500) and masses ($\sim$2$\times$10$^{6}$ $<$ M$_*$/M$_\odot$ $<$ 6$\times$10$^{9}$) spanning the range of massive globular clusters (GCs), ultra compact dwarfs (UCDs) and compact elliptical galaxies (cEs), completely filling the gap between star clusters and galaxies. Several objects are close analogues to the prototypical cE, M32. These objects, which are more massive than previously discovered UCDs of the same size, further call into question the existence of a tight mass-size trend for compact stellar systems, while simultaneously strengthening the case for a universal "zone of avoidance" for dynamically hot stellar systems in the mass-size plane. Overall, we argue that there are two classes of compact stellar systems: 1) massive star clusters and 2) a population closely related to galaxies. Our data provide indications for a further division of the galaxy-type UCD/cE population into two groups, one population that we associate with objects formed by the stripping of nucleated dwarf galaxies, and a second population that formed through the stripping of bulged galaxies or are lower-mass analogues of classical ellipticals. We find compact stellar systems around galaxies in low to high density environments, demonstrating that the physical processes responsible for forming them do not only operate in the densest clusters.
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