The Next Generation Virgo Cluster Survey. XXXIII. Stellar Population Gradients in the Virgo Cluster Core Globular Cluster System
The Next Generation Virgo Cluster Survey. XXXIII. Stellar Population Gradients in the Virgo Cluster Core Globular Cluster System
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DOI：
10.3847/1538-4357/ac63cf
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发表时间：
2022-04
期刊：
影响因子：
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通讯作者：
Youkyung Ko;E. Peng;Patrick Cot'e;L. Ferrarese;Chengze Liu;A. Longobardi;A. Lançon;R. Muñoz
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文献类型：
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作者：
Youkyung Ko;E. Peng;Patrick Cot'e;L. Ferrarese;Chengze Liu;A. Longobardi;A. Lançon;R. Muñoz
我们对室女座星团核心的球状星团（GCs）进行了一项研究，在距离M87长轴距离R maj = 840 kpc的范围内，用均匀光谱表记录了692个GCs。我们利用共加光谱研究了蓝色（贫金属）和红色（富金属）gc的平均年龄、总金属丰度、[Fe/H]和α元素丰度的径向和方位角变化。我们发现，在R maj = 165 kpc范围内，蓝色gc在[Z/H]有一个陡峭的径向梯度，[Fe/H]和[α/Fe]的贡献大致相等，而在[Fe/H]之外的梯度是平坦的。相比之下，红色gc在[Z/H]上的梯度要浅得多，这完全是由[Fe/H]驱动的。我们使用GC标记的Illustris模拟来演示一个吸积场景，即质量较大的卫星（含更多富含金属和α的GC）比质量较小的卫星更深地沉入中央星系，并且由于低质量矮星的低GC占据率在较大距离上被破坏，梯度变平发生。M87周围的致密环境也可能导致蓝色GCs的陡峭[α/Fe]梯度，反映了在矮星系群中看到的情况。与蓝色gc相比，红色gc的前身具有较窄的质量范围，这使得它们的梯度较浅。我们还探讨了GC丰度的空间不均匀性，发现M87西北部的红色GC的金属丰度略高。未来对GC恒星人口梯度的观测将有助于诊断光晕合并的历史。
We present a study of the stellar populations of globular clusters (GCs) in the Virgo Cluster core with a homogeneous spectroscopic catalog of 692 GCs within a major-axis distance R maj = 840 kpc from M87. We investigate radial and azimuthal variations in the mean age, total metallicity, [Fe/H], and α-element abundance of blue (metal-poor) and red (metal-rich) GCs using their co-added spectra. We find that the blue GCs have a steep radial gradient in [Z/H] within R maj = 165 kpc, with roughly equal contributions from [Fe/H] and [α/Fe], and flat gradients beyond. By contrast, the red GCs show a much shallower gradient in [Z/H], which is entirely driven by [Fe/H]. We use GC-tagged Illustris simulations to demonstrate an accretion scenario where more massive satellites (with more metal- and α-rich GCs) sink further into the central galaxy than less massive ones, and where the gradient flattening occurs because of the low GC occupation fraction of low-mass dwarfs disrupted at larger distances. The dense environment around M87 may also cause the steep [α/Fe] gradient of the blue GCs, mirroring what is seen in the dwarf galaxy population. The progenitors of red GCs have a narrower mass range than those of blue GCs, which makes their gradients shallower. We also explore spatial inhomogeneity in GC abundances, finding that the red GCs to the northwest of M87 are slightly more metal-rich. Future observations of GC stellar population gradients will be useful diagnostics of halo merger histories.