最近的Seyfert II星系Circinus的球状星团系统
The globular cluster system of the nearest Seyfert II galaxy Circinus
摘要：
上下文圆规座星系的球状星团（GC）系统以前没有被探测过，部分原因是该星系位于银河系纬度-3.8 $^\circ$处，受到星际消光、恒星拥挤和银河系前景污染的严重影响。然而，通过Via Láctea扩展巡天（VVVX）中的VISTA变量的深近红外（NIR）测光与盖亚EDR 3的精确天体测量相结合，使我们能够绘制该地区的GC。目的。我们的长期目标是研究和验证距离我们最近的Seyfert II星系Circinus星系的GC和超致密矮星的分布。在这里，我们进行了第一次试点搜索GC在这个星系。方法.我们使用近红外VVVX测光结合Gaia EDR 3天体测量特征，如天体测量多余噪声和BP/RP多余因子，建立了第一个在Circinus星系GC的均匀目录。选择标准的强大组合使我们能够有效地清除样本中的干扰物。结果我们报告的检测$\sim$ 70 GC候选人在这个星系在3 $σ$的置信水平。它们显示出双峰颜色分布，其中蓝色峰在（G-Ks）$_0$ = 0.985 $\pm$ 0.127 mag，分散度为0.211 $\pm$ 0.091 mag，红色峰在（G-Ks）$_0$ = 1.625 $\pm$ 0.177 mag，分散度为0.482 $\pm$ 0.114 mag。（S $_N$）为1.3 $\pm$ 0.2，我们估计该星系的总人口为120 $\pm$ 40 GC。基于投影的径向分布，似乎Circinus具有与MW和M31不同的GC候选物分布。结论.我们证明，圆规星系主机相当数量的集群候选人。这一结果是理解该星系中古老星团演化的第一次飞跃。
英文摘要：
Context. The globular cluster (GC) system of Circinus galaxy has not been probed previously partly because of the location of the galaxy at - 3.8$^\circ$ Galactic latitude which suffers severely from interstellar extinction, stellar crowding, and Galactic foreground contamination. However, the deep near-infrared (NIR) photometry by the VISTA Variables in the Via Láctea Extended Survey (VVVX) in combination with the precise astrometry of Gaia EDR3 allow us to map GCs in this region. Aims. Our long-term goal is to study and characterise the distributions of GCs and Ultra-compact dwarfs of Circinus galaxy which is the nearest Seyfert II galaxy. Here we conduct the first pilot search for GCs in this galaxy. Methods. We use NIR VVVX photometry in combination with Gaia EDR3 astrometric features such as astrometric excess noise and BP/RP excess factor to build the first homogeneous catalogue of GCs in Circinus galaxy. A robust combination of selection criteria allows us to effectively clean interlopers from our sample. Results. We report the detection of$\sim$ 70 GC candidates in this galaxy at a 3 $σ$ confidence level. They show a bimodal colour distribution with the blue peak at (G-Ks)$_0$ = 0.985$\pm$0.127 mag with a dispersion of 0.211$\pm$0.091 mag and the red peak at (G-Ks)$_0$ = 1.625$\pm$0.177 mag with a dispersion of 0.482$\pm$0.114 mag. A GC specific frequency (S$_N$) of 1.3$\pm$0.2 was derived for the galaxy, and we estimated a total population of 120$\pm$40 GCs. Based on the projected radial distribution it appears that Circinus has a different distribution of GC candidates than MW and M31. Conclusions. We demonstrate that Circinus galaxy hosts a sizeable number of cluster candidates. This result is the first leap towards understanding the evolution of old stellar clusters in this galaxy.
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