Old Stellar Populations at High Redshifts

AST-0307335斯托克顿基于标准冷暗物质（CDM）理论的半解析模型表明，大多数椭圆星系都是在红移1和2之间形成的，其中质量最大的星系是最近形成的。 然而，也有一些观察结果与这一图景相矛盾。 虽然有些问题可以通过对局部椭圆星系的仔细和详细的研究来解决，但对高红移星系的观测仍然是至关重要的，这些星系中的恒星在对应于这些红移的时代已经很老了（简称为“老星系”）。 该项目的核心是在8米级望远镜上使用自适应光学（AO）获取红移在1.5和2.5之间的具有代表性的老星系样本的图像，可能也在3：4到3：8的范围内，提供比哈勃太空望远镜更好的三到四倍的分辨率。 重点是红外成像，从已经存在的深层光学数据的领域开始，以产生体积密度，聚类特性和形态的分布。 在一定的红移范围内识别和确定最明亮的老星系的物理性质将对它们的形成和早期演化理论提出新的限制，这项建议中包括确保在科学界和感兴趣的非专业观众中广泛和及时传播结果的程序，该项目将为本科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.***