论文标题
核星簇
Nuclear Star Clusters
论文作者
论文摘要
我们回顾了当前关于核星簇（NSC）的知识，这是大多数星系中心发现的恒星的壮观和庞大的恒星组合。最近的观察和理论工作表明，包括其质量，密度和恒星种群在内的许多NSC特性随宿主星系的特性而变化。因此，了解NSC的形成，生长和最终命运对于完整的星系进化至关重要。在整个综述中，我们试图将可用证据结合在一起，成为NSC进化的连贯图片。该证据结合在一起表明，〜10^9太阳能的星系中明确的过渡质量，其中核星形簇的特征发生了变化。我们认为，在较低的质量下，NSC主要由启发到星系中心的球形簇形成，而在较高的质量下，核内的恒星形成形成了NSC的大部分。我们还讨论了NSC和中央黑洞的共存，以及它们的增长如何联系在一起。 NSC的极端密度及其与大型黑洞的相互作用导致广泛的独特现象，包括潮汐破坏和重力波事件。最后，我们回顾了证据，表明许多NSC最终都陷入了围绕它们的恒星剥离的大型星系的光环中，从而提供了星系的积聚历史的宝贵示踪剂。
We review the current knowledge about nuclear star clusters (NSCs), the spectacularly dense and massive assemblies of stars found at the centers of most galaxies. Recent observational and theoretical work suggest that many NSC properties, including their masses, densities, and stellar populations vary with the properties of their host galaxies. Understanding the formation, growth, and ultimate fate of NSCs therefore is crucial for a complete picture of galaxy evolution. Throughout the review, we attempt to combine and distill the available evidence into a coherent picture of NSC evolution. Combined, this evidence points to a clear transition mass in galaxies of ~10^9 solar masses where the characteristics of nuclear star clusters change. We argue that at lower masses, NSCs are formed primarily from globular clusters that inspiral into the center of the galaxy, while at higher masses, star formation within the nucleus forms the bulk of the NSC. We also discuss the coexistence of NSCs and central black holes, and how their growth may be linked. The extreme densities of NSCs and their interaction with massive black holes lead to a wide range of unique phenomena including tidal disruption and gravitational wave events. Lastly, we review the evidence that many NSCs end up in the halos of massive galaxies stripped of the stars that surrounded them, thus providing valuable tracers of the galaxies' accretion histories.
