Old Stellar Populations at High Redshifts

AST-0307335基于标准冷暗物质(CDM)理论的斯托克顿半解析模型表明，大多数椭圆星系是在红移一到二之间形成的，最近形成的最大质量星系。然而，有一些观察结果与这张照片格格不入。虽然一些问题可以通过仔细和详细地检查局部椭圆体来解决，但对具有高红移的星系进行观测是至关重要的，这些星系的恒星群在与这些红移相对应的纪元上已经很老了(简单地称其为“旧星系”)。该项目的核心是获取红移在1.5到2.5之间，也可能在3：4到3：8之间的重要和有代表性的老星系样本的图像，使用8米级望远镜的自适应光学(AO)来提供比哈勃太空望远镜获得的分辨率高三到四倍的图像。重点放在红外成像上，从已经存在深层光学数据的领域开始，以产生体积密度、团簇属性和形态分布。在一系列红移中识别和确定最明亮的古老星系的物理性质，将对它们的形成和早期演化理论产生新的限制。这项提议包括确保结果广泛和及时地在科学界和感兴趣的非专业观众中传播的程序，该项目将为本科生教学和一般公众宣传提供材料。

AST-0307335StocktonSemi-analytic models based on the standard cold dark matter (CDM) theory suggest that most elliptical galaxies formed between redshifts one and two, with the most massive forming most recently. However, there are observations which sit uneasily with this picture. Although some questions can be addressed by careful and detailed examination of local ellipticals, it is nevertheless crucial to have observations of galaxies at high redshifts with populations of stars that were already old at the epoch corresponding to those redshifts (simply called 'old galaxies'). The centerpiece of this project is acquiring images of a significant and representative sample of old galaxies at redshifts between 1.5 and 2.5, and possibly also in the range 3:4 to 3:8, using adaptive optics (AO) on 8-m-class telescopes to deliver resolutions three to four times better than can be obtained with the Hubble Space Telescope. Emphasis is on infra-red imaging, starting with fields for which deep optical data already exist, to yield volume density, clustering properties, and the distribution of morphologies. Identifying and determining physical properties for the most luminous old galaxies over a range of redshifts will place new constraints on theories of their formation and early evolution.Integrated into this proposal are procedures to ensure wide and timely dissemination of the results, both within the scientific community and to interested lay audiences, and the project will provide material for both undergraduate teaching and general public outreach.***