论文标题
Fornax 4是Fornax矮人球形星系的核星簇吗？
Is Fornax 4 the nuclear star cluster of the Fornax dwarf spheroidal galaxy?
论文作者
论文摘要
Fornax 4是Fornax矮人球体中最独特的球状簇。靠近银河系的中心，比其四个同伴（即Fornax簇1、2、3和5）更年轻，并且可能会与银河系中的其他簇不同。在这里，我们使用HST/WFC3光度法来表征该系统的出色种群含量，并为其性质提供了新的启示。 By means of a detailed comparison of synthetic horizontal branch and red giant branch with the observed colour-magnitude diagrams, we find that this system likely hosts stellar sub-populations characterized by a significant iron spread up to $Δ$[Fe/H]$\sim$0.4 dex and possibly by also some degree of He abundance variations $Δ$Y$\sim0.03$.我们认为，这种纯粹的观察证据与表征该系统的其他特殊性相结合，支持Fornax 4是Fornax Dwarf球形星系的核星簇的可能性。需要进行大量已解决的成员恒星的光谱随访来确认这一有趣的结果，并详细研究该系统的形成和早期演化，而更多的是银河系成核的过程。
Fornax 4 is the most distinctive globular cluster in the Fornax dwarf spheroidal. Located close to the centre of the galaxy, more metal-rich and potentially younger than its four companions (namely, Fornax clusters number 1, 2, 3 and 5), it has been suggested to have experienced a different formation than the other clusters in the galaxy. Here we use HST/WFC3 photometry to characterize the stellar population content of this system and shed new light on its nature. By means of a detailed comparison of synthetic horizontal branch and red giant branch with the observed colour-magnitude diagrams, we find that this system likely hosts stellar sub-populations characterized by a significant iron spread up to $Δ$[Fe/H]$\sim$0.4 dex and possibly by also some degree of He abundance variations $Δ$Y$\sim0.03$. We argue that this purely observational evidence, combined with the other peculiarities characterizing this system, supports the possibility that Fornax 4 is the nuclear star cluster of the Fornax dwarf spheroidal galaxy. A spectroscopic follow-up for a large number of resolved member stars is needed to confirm this interesting result and to study in detail the formation and early evolution of this system and more in general the process of galaxy nucleation.
