Portrait of the Galaxies in a Young Universe

AST 0097163 Spinrad星系是如何以及何时形成的？对微波背景辐射的研究表明，宇宙在红移约为1000（相当于大爆炸后约3 x 10**5年）时是非常均匀的。在局部，~ 13 Gyr后，在时间0，我们发现，物质的分布是明亮的，重子主要委托发光，束缚结构。比如星系和星系团。这些现今的结构可以用早期宇宙中高密度区域的引力坍缩和聚合来解释。详细了解这种坍缩，称为星系和大尺度结构的形成，是当今天体物理学家面临的主要挑战之一。该项目是一项为期三年的星系形成早期阶段的系统观测研究。它有三个科学目标：（1）识别具有很高红移（z 4）的星系. (2)描述了早期宇宙时代的星系人口。以及（3）对这些对象的子样本进行详细的物理研究，作为了解早期人口整体的窗口。为了进行这项研究，该项目将使用两种已被证明有效的技术来显著增加对非常遥远（z 4）星系的普查：（1）从深地和天基成像中光度选择非常高红移的原星系候选者。和（2）狭缝光谱搜索深曝光的高红移线发射。一旦这些高红移天体被发现，它们将被研究以发现z 5处的宇宙星星形成历史，早期宇宙中尘埃的普遍性，早期宇宙时间星系的表面密度和分布，以及早期宇宙中光度选择和线发射星系的光度函数。尤其是。这两个种群之间有什么联系研究这两个群体对于获得星系演化最早阶段的最真实理解至关重要。该项目的资金由美国国家科学基金会的河外天文宇宙学计划（AST/EXC）提供。

ABSTRACT AST 0097163Spinrad How and when do galaxies form? Studies of the microwave background radiation show that the universe was spectacularly homogeneous at redshift of approximately 1000 (corresponding to ~ 3 x 10**5 years after the Big Bang). Locally, ~ 13 Gyr later, at time 0, we find that the distribution of matter is lumpy, with baryons largely consigned to luminous, bound structures. such as galaxies and clusters of galaxies. These present-day structures can be explained by the gravitational collapse and coalescence of the overdense regions of the early Universe. A detailed understanding of this collapse, called galaxy and large-scale structure formation, stands as one of the primary challenges to astrophysicists today.This project is a, three year systematic, observational study of the earliest phases of galaxy formation. It has three scientific objectives: (1) identifying galaxies at very high redshift (z 4). (2) characterizing the galaxy population(s) at early cosmic epoch. and (3) performing detailed physical studies on a subsample of these objects as a window toward understanding the early population(s) as a whole. To conduct this study, this project will significantly augment the census of very distant (z 4) galaxies using two proven techniques: (1) photometric selection of very high-redshift protogalaxy candidates from deep ground- and space-based imaging. and (2) slit spectroscopic searches for high-redshift line emission on deep exposures. Once these high redshift objects have been found they will be studied to find the cosmic star formation history at z 5, the prevalence of dust in the early Universe, the surface density and distribution of galaxies at early, cosmic time, and the luminosity function of both photometrically -selected and line-emitting galaxies in the early Universe. In particular. how are these two populations related? Studying both populations is essential for obtaining the truest understanding of the earliest phases of galaxy evolution. Funding for this project was provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC).***