RUI: Reconstructing Galaxy Histories

了解星系的起源和演化是现代天体物理学的主要目标之一。人们普遍认为，星系是由原始物质分布中的微小密度波动产生的，这种波动随着时间的推移被引力放大了。然而，我们对星系形成过程细节的了解仍远未完成，许多重要问题仍未得到解答。星系是如何以及何时形成的？它们是如何随着时间进化的？它们的环境如何影响星系的性质？在过去的几年里，迈克尔·韦斯特博士一直在进行一些原始的研究，包括观察和理论，以解决这些问题。有了这个奖项，他将建立在以前的成功和探索新的途径，可能导致进一步了解星系的起源。该项目的具体目标包括：o了解星系形成秘密的最有希望的方法之一是研究它们的球状星团数量。球状星团是由多达一百万颗恒星组成的密集聚集体，它们通过相互的引力吸引而聚集在一起。大多数星系都被由数十个、数百个或数千个球状星团组成的系统所包围，这些球状星团围绕着它们，就像蜜蜂围绕着蜂巢一样。今天的球状星系群反映了数十亿年持续的星系形成和演化的累积效应，包括合并和碰撞、吸积、一代又一代的恒星形成和其他过程。因此，对星系球状星团数量的仔细分析可以让天文学家重建它的历史。韦斯特博士项目的一个主要目标是对室女座和后发星团中数百个星系组成的球状星团系统进行迄今为止最全面的研究。o韦斯特博士及其合作者最近发现了大量星系间球状星团存在的证据，它们不受单个星系的引力约束，而是在星系团的核心自由漫游。这类新天体的发现是一个令人兴奋的结果，它邀请了进一步的研究，在几个附近的星系团中搜索星系间球状星团目前正在进行中。这些星系间球状星团的颜色、光度函数、空间和速度分布将对它们的起源产生强烈的限制。o越来越多的证据表明，星系的毁灭可能比以前认为的要普遍得多，星系的诞生和死亡是交织在一起的。丰富的星系团是特别恶劣的环境，在那里小星系可能会被大星系蚕食，星系之间的碰撞会从它们的晕中剥离物质，烧蚀会去除它们的星际气体，当星系穿过星系团核心时，它们可能会部分甚至完全被潮汐场撕裂。然而，一些星系的消亡也可能产生新的星系，因为溢出到星系间空间的物质最终会被回收到其他星系中。这个研究项目的一个目标是进行第一个系统的调查，寻找星系团中被破坏的星系的微弱残骸，以便对致密环境中星系破坏的当前速度进行定量限制。该奖项是在美国国家科学基金会本科院校研究（RUI）项目的支持下颁发的。* * *

AST 0205960WestUnderstanding the origin and evolution of galaxies is one of the major goals of modern astrophysics. It is generally believed that galaxies arose from small density fluctuations in the primordial matter distribution that were amplified over time by gravity. However, our knowledge of the details of the galaxy formation process is still far from complete, and many important questions remain unanswered. How and when did galaxies form? How have they evolved over time? How do their environs influence galaxy properties? Over the past few years, Dr. Michael West has been pursuing a number of original lines of research, both observational and theoretical, to address these questions. With this award he will build upon previous successes and explore new avenues that may lead to further insights about the genesis of galaxies. Specific goals of this project include the following: o One of the most promising ways to learn the secrets of galaxy formation is by studying their globular cluster populations. Globular clusters are dense aggregates of up to a million stars that are held together by their mutual gravitational attraction. Most galaxies are surrounded by systems of tens, hundreds, or thousands of globular clusters that swarm around them like bees around a hive. The present-day globular populations of galaxies reflect the cumulative effects of billions of years of ongoing galaxy formation and evolution via mergers and collisions, accretion, generations of star formation, and other processes. Careful analysis of a galaxy's globular cluster population can thus allow astronomers to reconstruct its history. A major goal of Dr. West's project is to undertake the most comprehensive study yet of the globular cluster systems of hundreds of galaxies in the Virgo and Coma clusters. o Dr. West and collaborators recently found evidence of the existence of a sizeable population of intergalactic globular clusters that are not gravitationally bound to individual galaxies but instead roam freely throughout the cores of galaxy clusters. The discovery of this new class of objects is an exciting result that invites further study, and searches for intergalactic globulars in several nearby galaxy clusters are currently underway. The colors, luminosity function, and spatial and velocity distributions of these intergalactic globulars will place strong constraints on their origin. o A growing body of evidence suggests that galaxy destruction might be a much more common occurrence than previously thought, and that the births and deaths of galaxies are intertwined. Rich galaxy clusters are especially harsh environments, where small galaxies can be cannibalized by larger ones, collisions between galaxies can strip material from their halos, ablation removes their interstellar gas, and galaxies may be partially or even completely torn apart by tidal fields as they travel through the cluster core. Yet the demise of some galaxies may also give rise to new ones, as material spilled into intergalactic space is eventually recycled into other galaxies. A goal of this research project is to conduct the first systematic survey to look for the faint remains of disrupted galaxies in galaxy clusters, in order to place quantitative constraints on the current rate of galaxy destruction in dense environments. This award is made under the auspices of the Research at Undergraduate Institutions (RUI) program at the NSF. ***