ARE DISK GALAXIES THE PROGENITORS OF GIANT ELLIPTICALS?
ARE DISK GALAXIES THE PROGENITORS OF GIANT ELLIPTICALS?
复制标题
盘状星系是巨型椭圆星系的祖先吗？
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
J. Ostriker
中科院分区：
文献类型：
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作者：
T. Naab;J. Ostriker
一种流行的巨型椭圆星系形成假说认为，它们可能是由盘状星系的双星合并形成的。早期研究中出现的困难包括提供必要的恒星质量和金属丰度，维持紧密的颜色-星等关系，以及避免相空间限制。在这篇文章中，我们重新讨论了这个问题，并对基于盘状星系的恒星群的双盘合并方案施加了限制。我们得出以下结论：低红移、无碰撞或气态合并的今天类银河系的盘状星系不会形成今天的椭圆星系。如果今天类银河系盘状星系的祖先的双星合并早于≈3-4 Gyr前的合并，那么它们可能已经演化成中等质量的椭圆星系(M<；M*)。假设大多数今天的盘状星系的形成方式类似于这里给出的银河系模型，那么一般情况下，更大质量的巨型椭圆星系不可能是由今天盘状星系的祖先的双星合并而形成的。得出这些结论的一个主要原因是，一个典型的盘状星系的金属质量大约比一个典型的早期类型星系的金属质量小4-8倍，并且随着红移的增加，这一比例增大到更大的值。
A popular formation scenario for giant elliptical galaxies proposes that they might have formed from binary mergers of disk galaxies. Difficulties with the scenario that emerged from earlier studies included providing the necessary stellar mass and metallicity, maintaining the tight color–magnitude relation, and avoiding phase-space limits. In this paper we revisit the issue and put constraints on the binary disk merger scenario based on the stellar populations of disk galaxies. We draw the following conclusions: low-redshift collisionless or gaseous mergers of present-day Milky-Way-like disk galaxies do not form present-day elliptical galaxies. Binary mergers of the progenitors of present-day Milky-Way-like disk galaxies could have evolved into intermediate-mass elliptical galaxies (M < M*) if they merged earlier than ≈ 3–4 Gyr ago. Assuming that most present-day disk galaxies formed in a way similar to the Milky Way model presented here, more massive giant ellipticals in general could not have formed from binary mergers of the progenitors of present-day disk galaxies. A major reason for these conclusions is that the mass in metals of a typical disk galaxy is approximately a factor of 4–8 smaller than the mass in metals of a typical early-type galaxy, and this ratio grows to larger values with increasing redshift.