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arXiv 0704.3097astro-ph
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最亮星系团和星系群的空间分辨运动学和恒星星族

Spatially resolved kinematics and stellar populations of brightest cluster and group galaxies

S. Brough, R. Proctor, D. Forbes, W. Couch, C. Collins, D. Burke, R. Mann

摘要:

本文研究了3个布里渊星系团半导体(BGG)和3个布里渊星系团半导体(BCGs)的X射线群和星系团的运动学和恒星星族。我们获得了这些星系的高信噪比Gemini/GMOS(Gemini South Multi-Object Spectrograph)长缝光谱,并使用Lick指数来确定年龄,金属丰度和α元素丰度比,至少在其有效半径范围内。我们发现BGG和BCG具有非常均匀的质量、中心年龄和中心金属丰度。检查径向依赖的恒星星族,我们没有发现显着的速度色散,年龄,或α增强梯度。然而,我们发现了一个广泛的金属丰度梯度,提出了各种各样的形成机制。考虑到这些星系探测的均匀环境和它们均匀的中心恒星星族,观察到的金属丰度梯度范围令人惊讶。然而,我们的研究结果与任何单一的星系形成模型是不一致的,并强调需要更多的理论理解的起源金属丰度梯度和星系形成本身。我们假设两种可能的物理原因不同的形成机制。

英文摘要:

We present an examination of the kinematics and stellar populations of a sample of 3 Brightest Group Galaxies (BGGs) and 3 Brightest Cluster Galaxies (BCGs) in X-ray groups and clusters. We have obtained high signal-to-noise Gemini/GMOS (Gemini South Multi-Object Spectrograph) long-slit spectra of these galaxies and use Lick indices to determine ages, metallicities and alpha-element abundance ratios out to at least their effective radii. We find that the BGGs and BCGs have very uniform masses, central ages and central metallicities. Examining the radial dependence of their stellar populations, we find no significant velocity dispersion, age, or alpha-enhancement gradients. However, we find a wide range of metallicity gradients, suggesting a variety of formation mechanisms. The range of metallicity gradients observed is surprising given the homogeneous environment these galaxies probe and their uniform central stellar populations. However, our results are inconsistent with any single model of galaxy formation and emphasize the need for more theoretical understanding of both the origins of metallicity gradients and galaxy formation itself. We postulate two possible physical causes for the different formation mechanisms.

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