星系团中的质量-金属丰度关系：星系团成员对局部环境的相对重要性
The mass-metallicity relation in galaxy clusters: the relative importance of cluster membership versus local environment
摘要：
使用一个大的（14,857），均匀选择的样本中确定的斯隆数字巡天数据发布4（SDSS DR 4）的星系团星系，我们调查的影响，星系团成员和本地密度的恒星质量气相金属丰度关系（MZR）。我们表明，恒星金属丰度不适合这项工作，相对不敏感的MZR的微妙变化。在我们的样本中，可以获得1318个星系团的准确星云丰度，我们表明，这些星系是从星系团，是完全representative的母样本的质量，大小，速度色散和丰富。通过比较的MZR的星系团星系与样本控制的星系匹配的质量，红移，纤维覆盖分数和静止框架的g-r色星系团星系被发现，平均而言，更高的金属丰度高达0.04德克斯。这个偏移量的大小并不强烈依赖于星系的半光半径或星系团的性质，如速度色散或星系团的质量。局部密度对MZR的影响进行了研究，使用近邻和二维和三维密度估计的存在。对于所有这三个指标，它被发现，在本地丰富的环境中的星系团星系有更高的中值金属丰度高达~ 0.05德克斯比那些在本地贫穷的环境（或没有近邻）。在局部高密度的控制（非星系团）星系表现出类似的金属增强。总的来说，这些结果表明，星系团中的星系，平均而言，略高于场的金属丰富，但这种效果是由局部密度过大，而不仅仅是集群成员。
英文摘要：
Using a large (14,857), homogenously selected sample of cluster galaxies identified in the Sloan Digital Sky Survey Data Release 4 (SDSS DR4), we investigate the impact of cluster membership and local density on the stellar mass-gas phase metallicity relation (MZR). We show that stellar metallicities are not suitable for this work, being relatively insensitive to subtle changes in the MZR. Accurate nebular abundances can be obtained for 1318 cluster galaxies in our sample and we show that these galaxies are drawn from clusters that are fully repesentative of the parent sample in terms of mass, size, velocity dispersion and richness. By comparing the MZR of the cluster galaxies with a sample control of galaxies matched in mass, redshift, fibre covering fraction and rest-frame g-r colour cluster galaxies are found to have, on average, higher metallicities by up to 0.04 dex. The magnitude of this offset does not depend strongly on galactic half-light radius or cluster properties such as velocity dispersion or cluster mass. The effect of local density on the MZR is investigated, using the presence of a near neighbour and both two- and three-dimensional density estimators. For all three metrics, it is found that the cluster galaxies in locally rich environments have higher median metallicities by up to ~ 0.05 dex than those in locally poor environments (or without a near neighbour). Control (non-cluster) galaxies at locally high densities exhibit similar metal-enhancements. Taken together, these results show that galaxies in clusters are, on average, slightly more metal-rich than the field, but that this effect is driven by local overdensity and not simply cluster membership.
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