The morphological identification of the rapidly evolving population of faint galaxies
The morphological identification of the rapidly evolving population of faint galaxies
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DOI：
10.1093/mnras/275.1.l19
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发表时间：
1995-03
影响因子：
4.8
通讯作者：
K. Glazebrook;R. Ellis;B. Santiago;R. Griffiths
中科院分区：
文献类型：
--
作者：
K. Glazebrook;R. Ellis;B. Santiago;R. Griffiths
数量过多的微弱蓝色星系是一个长期存在的宇宙学难题。我们将新的数量-星等计数作为星系形态的函数，来自第 4 周期哈勃太空望远镜{\it 中深度巡天}项目的第一个深场。从 301 个星系的样本中，我们将椭圆形、螺旋形和不规则/特殊星系的计数定义为 $I=22$。我们发现两个主要结果。首先，椭圆星系和螺旋星系的计数都遵循所有星等的高归一化无演化模型的预测，这表明常规哈勃类型仅缓慢演化至 $z\sim 0.5$。其次，我们发现不规则/特殊星系，包括多峰的、可能合并的物体，具有非常陡峭的数量-幅度关系，并且大大超出了基于当地调查比例的预测。这些系统占总计数的一半（$I=22$），这意味着微弱星系群中快速演化的部分已经被识别出来。
The excess numbers of blue galaxies at faint magnitudes are a long-standing cosmological puzzle. We present new number-magnitude counts as a function of galactic morphology from the first deep fields of the Cycle 4 Hubble Space Telescope {\it Medium Deep Survey} project. From a sample of 301 galaxies we define counts for elliptical, spiral and irregular/peculiar galaxies to $I=22$. We find two principal results. Firstly the elliptical and spiral galaxy counts both follow the predictions of high-normalisation no-evolution models at all magnitudes, indicating that regular Hubble types evolve only slowly to $z\sim 0.5$. Secondly we find that irregular/peculiar galaxies, including multiple-peaked, possibly merging, objects, have a very steep number-magnitude relation and greatly exceed predictions based on proportions in local surveys. These systems make up half the total counts by $I=22$ and imply the rapidly-evolving component of the faint galaxy population has been identified.