Detection of Strong Evolution in the Population of Early-Type Galaxies
Detection of Strong Evolution in the Population of Early-Type Galaxies
复制标题
早期型星系群中强演化的探测
DOI：
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
S. White
中科院分区：
文献类型：
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作者：
G. Kauffmann;S. Charlot;S. White
标准图像认为巨大的椭圆星系是在高红移的单次爆发中形成的。随后恒星种群的老化导致它们褪色并变得更红。加拿大-法国红移巡天提供了约 125 个星系的样本，其亮度和颜色为被动演化的巨型椭圆星系，当仅限于未检测到恒星形成的天体时，0.1 = 0.398；当还包括具有发射线的天体时，0.1 = 0.410。从夏威夷深巡中选择的早期型星系的较小样本也给出了同样重要的结果。随着红移的增加，附近椭圆星系和 S0 星系群中越来越大的部分必须从样本中消失，这要么是因为星系不再是单一单位，要么是因为恒星的形成改变了它们的颜色。如果剩余分数建模为 F=(1+z)^{-gamma}，则数据意味着 gamma = 1.5 ± 0.3。在 z=1 时，只有大约三分之一的明亮 E 和 S0 星系已经组装完毕，并具有旧的被动演化系统的颜色。我们讨论这些结果对我们采用的不完整性修正和恒星种群模型的敏感性。我们的结论是，两者的不确定性都不足以使观察结果与标准图像相一致。分层星系形成模型表明，合并和最近的恒星形成在我们检测到的强烈演化中都发挥着作用。
The standard picture holds that giant elliptical galaxies formed in a single burst at high redshift. Aging of their stellar populations subsequently caused them to fade and become redder. The Canada-France Redshift Survey provides a sample of about 125 galaxies with the luminosities and colours of passively evolving giant ellipticals and with 0.1 = 0.398 when restricted to objects with no detected star formation, and = 0.410 when objects with emission lines are also included. A smaller sample of early-type galaxies selected from tha Hawaii Deep Survey gives equally significant results. With increasing redshift a larger and larger fraction of the nearby elliptical and S0 population must drop out of of the sample, either because the galaxies are no longer single units or because star formation alters their colours. If the remaining fraction is modelled as F=(1+z)^{-gamma}, the data imply gamma = 1.5 +- 0.3. At z=1 only about one third of bright E and S0 galaxies were already assembled and had the colours of old passively evolving systems. We discuss the sensitivity of these results to the incompleteness corrections and stellar population models we have adopted. We conclude that neither is uncertain enough to reconcile the observations with the standard picture. Hierarchical galaxy formation models suggest that both merging and recent star formation play a role in the strong evolution we have detected.