NGC 4486（M87）球状星团的多色-金属丰度关系
Multicolour-metallicity Relations from Globular Clusters in NGC 4486 (M87)
摘要：
本文对521个球状星团（GC）候选者进行了双子座格里兹测光，观测视场为5.5 × 5.5弧分，中心位于巨大椭圆星系NGC 4486中心以南3.8弧分和以西0.9弧分。所有这些对象以前出版的（C-T1）测光。我们还提出了新的（C-T1）测光的338个球状体，在1.7弧分的银河中心半径，其中（g-z）的颜色在测光系统所采用的室女星系团调查的高级相机的调查哈勃太空望远镜。这些光度数据被用来定义一个自我一致的网格（避免多项式拟合）和初步校准的两个化学丰度尺度。由此产生的色度-化学丰度关系用于测试GC化学丰度分布。这是通过对可以根据Cgriz带定义的十个GC颜色直方图进行建模来实现的。我们的结果表明，GC观察到的颜色直方图的最佳拟合与真正的双峰化学丰度分布NGC（Z）一致。另一方面，每个（蓝色和红色）GC亚群遵循不同的颜色-颜色关系。
英文摘要：
We present Gemini griz photometry for 521 globular cluster (GC) candidates in a 5.5 x 5.5 arcmin field centered 3.8 arcmin to the south and 0.9 arcmin to the west of the center of the giant elliptical galaxy NGC 4486. All these objects have previously published (C-T1) photometry. We also present new (C-T1) photometry for 338 globulars, within 1.7 arcmin in galactocentric radius, which have (g-z) colors in the photometric system adopted by the Virgo Cluster Survey of the Advanced Camera for Surveys of the Hubble Space Telescope. These photometric data are used to define a self-consistent multicolor grid (avoiding polynomial fits) and preliminary calibrated in terms of two chemical abundance scales. The resulting multicolor color-chemical abundance relations are used to test GC chemical abundance distributions. This is accomplished by modelling the ten GC color histograms that can be defined in terms of the Cgriz bands. Our results suggest that the best fit to the GC observed color histograms is consistent with a genuinely bimodal chemical abundance distribution NGC(Z). On the other side, each (blue and red) GC subpopulation follows a distinct color-color relation.
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