We present estimates of CN and Mg overabundances with respect to Fe for early-type galaxies in eight clusters over a range of richness and morphology. Spectra were taken from the Sloan Digital Sky Survey Data Release 1 and from William Hershel Telescope and Centro Astronomico Hispano-Aleman observations. Abundances were derived from absorption lines and single-burst population models, by comparing galaxy spectra with appropriately broadened synthetic model spectra. We detect correlations between the [Mg/CN] and [CN/Fe] values and the cluster X-ray luminosity. No correlation is observed for [Mg/Fe]. We also see a clear trend in the richness and morphology of the clusters. This is interpreted as giving varying formation timescales for CN, Mg, and Fe and a varying star formation history in early-type galaxies as a function of their environment: intermediate-mass early-type galaxies in more massive clusters are assembled on shorter timescales than in less massive clusters, with an upper limit of ～1 Gyr.
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机译：我们提出了在丰富度和形态范围内的八个星团中，早期类型星系中相对于Fe的CN和Mg过量。光谱取自Sloan Digital Sky Survey Data Release 1以及William Hershel望远镜和Centro Astronomico Hispano-Aleman观测。通过将星系光谱与适当扩展的合成模型光谱进行比较，可以从吸收线和单爆发种群模型中获得丰度。我们检测[Mg / CN]和[CN / Fe]值与簇X射线光度之间的相关性。没有观察到[Mg / Fe]的相关性。我们还看到了簇的丰富度和形态的明显趋势。这被解释为根据环境的变化给出了CN，Mg和Fe的形成时间尺度的变化以及早期星系中恒星形成历史的变化：更大质量星团中的中等质量早期星系的组装时间要短于在较小质量的团簇中，上限为〜1 Gyr。
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