我们提出了新的测量的演化莱曼break星系（LBG）人口之间的z~4和z~6。通过利用广泛的多波长数据集在GOODS领域，我们确定2443 B，506 V，和137 i '带辍学星系可能是在z~4，5和6。为了了解z>4时星系中典型恒星形成事件的持续时间，我们研究了恒星质量和年龄的分布作为宇宙时间的函数。我们发现，在一个固定的静止紫外光度，星系的平均恒星质量和年龄并没有显着增加之间的z~6和4。为了保持这种近平衡的平均性能的高红移LBG，我们认为，必须有一个稳定的流量的年轻，新的发光物体在每个连续的红移。当考虑到从集群测量推断的短占空比时，这些结果可能表明星系正在经历恒星形成事件，持续时间只有数亿年。与恒星平均质量和静止紫外光度之间的不变关系相反，我们发现大质量星系的数密度在4<z<6的范围内随时间显著增加。考虑到紫外光大质量星系的快速增加，我们探讨了一个可能性，即在早期，大质量（M*> 1 e11 Msun）z~2-3远距离红星系（DRG）中有相当一部分是在LBG阶段组装的。对4<z<6到z~2范围内活跃形成的LBG的恒星质量函数的增长进行积分，我们发现z>3的LBG可能对静止的DRG种群有很大的贡献，这表明目前亚毫米波观测所探测到的强烈的恒星形成系统并不是z~2处DRG组装的唯一途径。
英文摘要：
We present new measurements of the evolution in the Lyman break galaxy (LBG) population between z~4 and z~6. By utilizing the extensive multiwavelength datasets available in the GOODS fields, we identify 2443 B, 506 V, and 137 i'-band dropout galaxies likely to be at z~4, 5, and 6. With the goal of understanding the duration of typical star formation episodes in galaxies at z>4, we examine the distribution of stellar masses and ages as a function of cosmic time. We find that at a fixed rest-UV luminosity, the average stellar masses and ages of galaxies do not increase significantly between z~6 and 4. In order to maintain this near equilibrium in the average properties of high redshift LBGs, we argue that there must be a steady flux of young, newly-luminous objects at each successive redshift. When considered along with the short duty cycles inferred from clustering measurements, these results may suggest that galaxies are undergoing star formation episodes lasting only several hundred million years. In contrast to the unchanging relationship between the average stellar mass and rest-UV luminosity, we find that the number density of massive galaxies increases considerably with time over 4<z<6. Given this rapid increase of UV luminous massive galaxies, we explore the possibility that a significant fraction of massive (M*>1e11 Msun) z~2-3 distant red galaxies (DRGs) were in part assembled in an LBG phase at earlier times. Integrating the growth in the stellar mass function of actively forming LBGs over 4<z<6 down to z~2, we find that z>3 LBGs could have contributed significantly to the quiescent DRG population, indicating that the intense star-forming systems probed by current sub-millimeter observations are not the only route toward the assembly of DRGs at z~2.
Forecasting cosmic acceleration measurements using the Lyman-$α$ forest
我们提出的结果，从端到端的观测模拟设计约束宇宙膨胀历史的变化率使用的红移漂移的莱曼- $α$森林吸收线沿视线朝向明亮的类星体。在我们的模拟中，我们采用了从$z>3$亮类星体的Keck/HIRES光谱中提取的Lyman-$α$森林线，并将这些真实类星体光谱的结果与通过Monte Carlo实现产生的模拟光谱进行了比较。我们使用这些模拟的结果来评估一个专门的天文台检测红移漂移的潜力，并量化这些观测的望远镜和摄谱仪的要求。相对于Liske et al.（2008），当前工作的两个主要改进是包括来自最近目录的类星体，以及考虑一个现实的观测策略，用于一个专门的红移漂移实验，最大化$\dot{v}/σ_{\dot{v}}$。我们发现，使用一个专门的设施和我们设计的观测计划，在15年的时间内，使用一台25米的望远镜，给出了一个长期稳定的光谱仪与$R=50,000$和25%的总系统效率的$3σ$意义上的红移漂移可以检测。为了达到这个意义，目标的最佳数量是四个类星体，观测时间根据$\dot{v}/σ_{\dot{v}}$和物体可见度加权。这种优化策略导致望远镜直径减少9%或所需时间减少6%，以达到相同的S/N，作为理想情况下，均匀分布的时间相同的类星体。
Lyman-Alpha Forest and its Cross-Correlation with High-Redshift Galaxies in Effective Field Theory at the Field Level
Center for Theoretical Physics – a Leinweber Institute, Massachusetts Institute of Technology（麻省理工学院理论物理中心）；The NSF AI Institute for Artificial Intelligence and Fundamental Interactions（美国国家科学基金会人工智能基础相互作用研究所）；Department of Physics, Columbia University（哥伦比亚大学物理系）；NASA Hubble Fellowship Program（NASA 哈勃奖学金计划）；Theory Center, Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK)（高能加速器研究机构粒子与核研究学院理论中心）
