AI 中文总结
该论文研究英仙座和后发座星系团的超弥散与近超弥散星系，发现其恒星族群性质，揭示金属丰度梯度与球状星团丰富度的关联，提出球状星团潮汐瓦解机制可解释相关梯度特征。
AI 中文摘要
我们利用凯克望远镜/KCWI光谱仪研究英仙座星系团中的1个超弥散星系（UDG）和5个近超弥散星系（NUDGEs），以及后发座星系团中的另外1个超弥散星系。作为系列论文的第一篇，我们聚焦于样本星系的整体及径向恒星族群性质。研究发现这些星系拥有中等至年老的恒星族群，典型年龄约7亿年，金属丰度较低（[M/H]≃-0.9 dex），且[Mg/Fe]丰度增强（约0.3 dex），与此前研究结果一致。6个星系位于当前质量-金属丰度关系（MZR）的弥散范围内，而后发座超弥散星系DF11则与高红移（z~2）星系的MZR更为吻合。我们未发现整体恒星族群性质与星系团并合参数之间存在强相关性，表明任何环境影响都难以通过积分恒星族群追踪。我们进一步对3个星系测量了径向梯度：其中2个呈现平坦的年龄梯度和轻微负向的金属丰度梯度，与经典矮星系类似；而1个则呈现上升的金属丰度分布，这与其他超弥散星系的最新发现一致。与经典矮星系对比，我们发现金属丰度梯度与球状星团（GC）丰富度之间存在连续相关性，即GC丰富度越高的系统越倾向于呈现上升分布。我们提出，星系内部区域球状星团的优先潮汐瓦解自然会产生上升的金属丰度分布，这与GC贫乏的经典矮星系不同；该机制若与早期集中恒星形成产生的强恒星反馈相结合，或许能解释在GC丰富的超弥散星系/近超弥散星系中观测到的异常上升金属丰度分布。
英文摘要
We use Keck/KCWI spectroscopy to study one ultra-diffuse galaxy (UDG) and five Nearly-UDGs (NUDGEs) in the Perseus cluster, together with an additional UDG in the Coma cluster. As the first paper in a series, we focus on the global and radial stellar population properties of our sample. We find that these galaxies host intermediate-to old stellar populations, with typical ages of ~7 Gyr, low metallicities ([M/H]$\simeq$ -0.9 dex), and enhanced [Mg/Fe] abundances (~0.3 dex), consistent with previous studies. Six galaxies lie within the scatter of the present-day mass-metallicity relation (MZR), whereas the Coma UDG (DF11) is more consistent with the MZR of high-z galaxies (z ~ 2). We find no strong correlation between global stellar population properties and cluster infall parameters, suggesting that any environmental impact is not easily traceable through integrated stellar populations. We go one step further and measure radial gradients for three galaxies. Two show flat age and mildly negative metallicity gradients, similar to classical dwarfs, while one shows a rising metallicity profile as recently found in other UDGs. Comparing with classical dwarfs, we find a continuous correlation between metallicity gradient and globular cluster (GC) richness, where more GC-rich systems tend to show rising profiles. We propose that preferential tidal disruption of GCs in the inner regions of galaxies naturally produces rising metallicity profiles, unlike GC-poor classical dwarfs. This mechanism, potentially coupled with strong stellar feedback from early concentrated star formation, may explain the unusual rising metallicity profiles observed in GC-rich UDGs/NUDGEs.
Comments14 pages, 11 figures, Accepted for publication in MNRAS
