表面之下的SMUDGes：星团证实低表面亮度星系的多样性
SMUDGes Below the Surface: Clusters Confirm the Diversity of Low-Surface-Brightness Galaxies
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中文总结 AI 辅助
本研究通过SMUDGes巡天的44个低表面亮度星系，利用Keck Cosmic Web Imager光谱学发现其普遍存在星团，证实这类星系性质多样，不存在单一形成机制，且星团年龄多样性会影响总晕质量的示踪。
中文摘要 AI 辅助
我们利用空间分辨的Keck Cosmic Web Imager光谱学，对来自SMUDGes巡天的44个低表面亮度星系（其中包括30个超弥散星系）的高表面亮度恒星成分和内部运动学进行研究，这些星系覆盖了星系色-星等图的红序、绿谷和蓝云区域。尽管这些星系在巡天成像中整体呈现平滑形态，但我们在每个星系中都至少探测到一个星团候选体，其中24个星系中存在具有星云发射线的星团，这类星团在蓝云星系中较为常见，在红序星系中则较为罕见。我们还识别出3个核星团候选体，其中1个显示出星云发射线。在无星云发射线的星团中，颜色更蓝的星系往往拥有更明亮的星团光度函数，这表明除了年老的球状星团外，还存在年轻或中年星团。这种年龄多样性可能会干扰将测光选取的球状星团群作为总晕质量示踪物的应用。我们利用具有星云发射线的星团为17个星系测量了旋转速度，利用弥散恒星光为12个星系测量了旋转速度。在0.5个有效半径范围内，推断出的动力学质量通常超过恒星质量，尽管暗物质的贡献推断值存在一个数量级的差异。该超弥散星系和低表面亮度矮星系样本的性质多样性表明，不存在单一的形成机制能够解释低表面亮度星系的整体形成过程。
英文摘要
We use spatially resolved Keck Cosmic Web Imager spectroscopy to study high-surface-brightness stellar components and internal kinematics in 44 low-surface-brightness galaxies from the SMUDGes survey, including 30 ultradiffuse galaxies, spanning the red sequence, green valley, and blue cloud regions of the galaxy color-magnitude diagram. Although these galaxies appear largely smooth in survey imaging, we detect at least one cluster candidate in every galaxy. We identify clusters with nebular emission lines in 24 galaxies. They are common in blue-cloud galaxies but rare in red sequence galaxies. We identify three nuclear star cluster candidates, one of which shows nebular emission lines. Among clusters without nebular emission lines, bluer galaxies tend to have brighter cluster luminosity functions, suggesting the presence of young or intermediate-age clusters in addition to old globular clusters. This age diversity may complicate the use of photometrically selected globular cluster populations as tracers of total halo mass. We measure rotation velocities for 17 galaxies using the clusters with nebular emission lines and for 12 using diffuse stellar light. Within 0.5 effective radii, the inferred dynamical mass generally exceeds the stellar mass, although the inferred dark matter contribution varies by an order of magnitude. The variety in properties for this sample of ultradiffuse galaxies and low-surface-brightness dwarfs suggests that no single formation mechanism explains the population of low-surface-brightness galaxies.
