论文标题
低质量孤立的螺旋星系NGC 2403中的低金属球状簇
Low-Metallicity Globular Clusters in the Low-Mass Isolated Spiral Galaxy NGC 2403
论文作者
论文摘要
迄今为止，低质量晚期星系（例如NGC 2403）的球状簇（GC）系统迄今为止的研究很差。作为一个低质量星系（M $ _ {\ ast} $ = 7 $ \ times $ 10 $^{9} $ M $ _ {\ odot} $），宇宙学模拟预测NGC 2403可以包含少数（如果有的话）。它也是孤立的，带有非常不受干扰的HI磁盘。基于文献，斯隆数字天空调查和超级表板成像的候选人，我们使用Keck Cosmic Web Imager选择了几个GC进行后续光谱。从它们的径向速度和其他特性中，我们确定了与内部光环或该无块状银河系的磁盘相关的8个真正的GC。出色的人群分析表明，从大爆炸后不久到今天，大量的GC年龄。我们发现所有旧的GC都与[fe/h] $ \ le $ -1一样贫穷。观察到的GC的年龄 - 金属关系表明它们是在许多GYR上形成的，其有效收率低，类似于SMC中观察到的收率。富集材料的流出可能导致低收率。凭借预期$ \ sim $ 50 GCS的总系统，我们的研究是在时空和时间上完全映射NGC 2403的星团历史的第一步。
The globular cluster (GC) systems of low-mass late-type galaxies, such as NGC 2403, have been poorly studied to date. As a low mass galaxy (M$_{\ast}$ = 7 $\times$ 10$^{9}$ M$_{\odot}$), cosmological simulations predict NGC 2403 to contain few, if any, accreted GCs. It is also isolated, with a remarkably undisturbed HI disk. Based on candidates from the literature, Sloan Digital Sky Survey and Hyper Suprime-Cam imaging, we selected several GCs for follow-up spectroscopy using the Keck Cosmic Web Imager. From their radial velocities, and other properties, we identify 8 bona-fide GCs associated with either the inner halo or the disk of this bulgeless galaxy. A stellar population analysis suggests a wide range of GC ages from shortly after the Big Bang until the present day. We find all of the old GCs to be metal-poor with [Fe/H] $\le$ --1. The age--metallicity relation for the observed GCs suggests that they were formed over many Gyr from gas with a low effective yield, similar to that observed in the SMC. Outflows of enriched material may have contributed to the low yield. With a total system of $\sim$50 GCs expected, our study is the first step in fully mapping the star cluster history of NGC 2403 in both space and time.
