RUI: Clocking the formation of today's largest galaxies: Wide Field Integral Spectroscopy of Brightest Cluster Galaxies and their surroundings

宇宙中的质量并不是均匀分布的。附近星系的地图显示，它们是星系团，这些星团被巨大的空洞隔开，那里几乎没有物质存在。每个星系团都有一个最亮的星系。奇怪的是，这些最亮的星系团(BCG)通常位于其宿主星系团的中心，并且通常包含周围最古老和最红的恒星。河外天文学领域的一个悬而未决的问题是：星系是如何以及何时增加质量的？该项目将测量从核心到外围的BCG的年龄和化学成分。它还将计算BCG需要多长时间才能通过与附近系统的合并而发展壮大。这一结果将帮助天文学家区分不同的星系演化情景。将收集和分析25个局部星系团星系及其附近伴星的成像光谱(IFU)。除了将IFU研究的BCG及其伴星的样本增加一倍外，从这项工作中获得的宽视场观测还代表了对星系团内光(ICL)样本的首次光谱研究。专注于局部宇宙意味着可以对其组成部分进行细致的研究。为了帮助阐明卡介苗的性质及其形成，拟议工作期间的目标是确定支配样本中恒星质量积累的机制和时间尺度。主要成果包括：1)BCG、亲密伴星和ICL的运动学性质和恒星群的地图。星系中最古老和最年轻的恒星的位置可以为星系是否由内而外形成提供证据。如果BCG和星团内的光有相似的恒星群，以及表面亮度轮廓是否破裂，则可以确定BCG是否与星团内的光同龄；2)估计大合并和小合并对BCG和ICL最近恒星质量积累的时间尺度和相对贡献；3)限制任何新的或原位的数量？恒星质量积聚。这可以通过检查恒星群来确定，从寻找湿的次要合并，或者从热晕寻找冷却。确定这些局域系统的性质将为宇宙学模型提供强有力的约束，并将形成一个重要的比较样本，用于已经编制的高红移BCG。本科生将深入参与这个项目的方方面面。通过使用尖端数据进行研究，访问国家天文台站点，并向同事展示他们的工作，他们将体验进入STEM领域所需的技术和社交技能培训，作为研究生或在行业中。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Mass in the universe is not smoothly distributed. Maps of nearby galaxies show that they are clustered and that these clusters are separated by large voids, where little matter is present. Each cluster has one galaxy that is the brightest. Curiously, these Brightest Cluster Galaxies (BCGs) are often found at the center of their host cluster, and often contain the oldest and reddest stars around. One outstanding question in the field of extragalactic astronomy is the following: How and when do galaxies build-up their mass? This project will measure the ages and chemical compositions of BCGs from their cores to their outskirts. It will also calculate how long it would take a BCG to grow by merging with nearby systems. The results will help astronomers discriminate between various galaxy evolution scenarios. Imaging spectroscopy (IFU) of 25 local cluster galaxies and their nearby companions will be collected and analyzed. In addition to doubling the sample of IFU studied BCGs and companions, wide field observations obtained from this work represent the first spectroscopic study of a sample of intra-cluster light (ICL). Focusing on the local universe means that its components can be studied in exquisite detail. To help elucidate the nature of the BCG and its formation, the objectives for the period of proposed work are to determine mechanisms and timescales that govern stellar mass build-up in the sample. The main deliverables include: 1) Maps of the kinematic properties and stellar populations of the BCGs, the close companions and the ICL. The location of the oldest and youngest stars within the galaxies can lend credence to whether or not the galaxies formed inside out. Whether the BCG is coeval with the intra-cluster light can be determined if the two have similar stellar populations, and if the surface brightness profile breaks; 2) Estimates of the timescale and relative contribution to the recent stellar mass buildup of BCGs and the ICL from major and minor mergers; 3) Constraints on the amount of any new or ?in situ? stellar mass buildup. This can be determined by examining the stellar populations, from searching for wet minor merging, or looking for cooling from a hot halo. Determining the properties of these local systems will provide powerful constraints for cosmological models and will form an important comparison sample for higher-redshift BCGs already being compiled. Undergraduates will be heavily involved in every aspect of this project. Through performing their research with cutting edge data, visiting a national observatory site, and presenting their work to colleagues they will experience training in the technical and social skills required to enter STEM fields as graduate students or in industry.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.