Portrait of the Galaxies in a Young Universe

星系是如何以及何时形成的？对微波背景辐射的研究表明，宇宙在红移大约为1000（对应于大爆炸后的~ 3 × 10**5年）时是非常均匀的。局部，~ 13 Gyr之后，在时间0，我们发现物质的分布是块状的，重子大部分被分配到发光的束缚结构中。比如星系和星系团。这些现今的结构可以用早期宇宙中密度过大的区域的引力坍缩和合并来解释。对这种被称为星系和大规模结构形成的坍缩的详细了解，是当今天体物理学家面临的主要挑战之一。这个项目是一个为期三年的系统观测研究，研究星系形成的最早阶段。它有三个科学目标：(1)识别红移非常高的星系（z 4）。(2)描述早期宇宙时期的星系群。(3)对这些物体的子样本进行详细的物理研究，作为了解整个早期种群的窗口。为了进行这项研究，该项目将使用两种经过验证的技术显著增加对非常遥远（z 4）星系的普查：(1)从深地面和天基成像中选择非常高红移的原星系候选者的光度。(2)深曝光下的高红移线发射的狭缝光谱搜索。一旦这些高红移天体被发现，它们将被用来研究z5的宇宙恒星形成历史，早期宇宙中尘埃的流行，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。在特定的。这两个群体有什么关系？研究这两个星系群对于获得对星系演化早期阶段最真实的理解是必不可少的。本项目由美国国家科学基金会星系外天文学和宇宙学项目（AST/EXC）资助

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).***