The Evolution of Galaxies in X-Ray-luminous Groups
The Evolution of Galaxies in X-Ray-luminous Groups
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DOI：
10.1086/511852
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发表时间：
2006-10
期刊：
影响因子：
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通讯作者：
T. Jeltema;J. Mulchaey;L. Lubin;C. Fassnacht
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文献类型：
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作者：
T. Jeltema;J. Mulchaey;L. Lubin;C. Fassnacht
我们研究了7个x射线选择的中间红移群（0.2 < z < 0.6）的星系群。总的来说，这些系统中的星系群与相同红移的星团中的星系群相似；它们有大比例的早期型星系（fe ~ 70%）和小比例的恒星形成显著的星系（f[O II] ~ 30%）。在低红移的x射线发光群中，我们没有观察到星系群的强烈演化。fe和f[O II]均与半径相关，但在~r500以内不达到场值。然而，我们发现星系群之间的星系群有很大的差异，有些星系群的星系群像田野一样。群星系的形态和光谱特性的比较揭示了贫气合并和被动螺旋的种群。与低红移的x射线发射星系群不同，在这些星系群中，最亮的星系并不位于x射线发射的中心，在几个有中心BGG的星系群中，BGG有多个组成部分。这些群体似乎代表了BGG形成过程中的一系列进化阶段。一些星系群的中心星系密度相对较大，其中一个星系群包含一个由7个明亮星系组成的星系串，其半径为200kpc，其速度色散比系统的其他星系要低。没有一个中心星系，包括那些有多个组成部分的星系，有明显的[O II]发射。这些观测结果支持这样一种假设，即bgg是在相对较晚的时候通过缺乏气体的合并形成的。
We investigate the galaxy populations in seven X-ray-selected, intermediate-redshift groups (0.2 < z < 0.6). Overall, the galaxy populations in these systems are similar to those in clusters at the same redshift; they have large fractions of early-type galaxies (fe ~ 70%) and small fractions of galaxies with significant star formation (f[O II] ~ 30%). We do not observe a strong evolution in the galaxy populations from those seen in X-ray-luminous groups at low redshift. Both fe and f[O II] are correlated with radius but do not reach the field value out to ~r500. However, we find significant variation in the galaxy populations between groups, with some groups having fieldlike populations. Comparisons between the morphological and spectral properties of group galaxies reveal both gas-poor mergers and a population of passive spirals. Unlike low-redshift, X-ray-emitting groups, in some of these groups the brightest galaxy does not lie at the center of the X-ray emission, and in several of the groups that do have a central BGG, the BGG has multiple components. These groups appear to represent a range of evolutionary stages in the formation of the BGG. Some groups have relatively large central galaxy densities, and one group contains a string of seven bright galaxies within a radius of 200 kpc that have a lower velocity dispersion than the rest of the system. None of the central galaxies, including those with multiple components, have significant [O II] emission. These observations support a scenario in which BGGs are formed relatively late through gas-poor mergers.