From Clusters to Voids: Gas and Galaxy Evolution

该项目由三个相辅相成的观测工作组成，旨在测试星系可能从其周围获得质量的概念性图景，即星系可能不是通过吸收进入银河系时冷却的热等离子体，而是通过积累已经在星际环境中冷却并在流入银河系时保持低温的气体，可能是在有优先方向的有序流上。近年来，通过对星系形成的流体力学模拟，这一理论得到了理论支持；PI将进行的观测测试包括射电观测，主要是在21厘米的中性氢线上，对(1)附近的室女座星系团的外部，(2)红移z=0.2的两个截然不同的星系团周围的大体积，以及(3)位于密度极低的空洞区域的星系。这项工作将利用荷兰的韦斯特堡综合射电望远镜(WSRT)和美国的扩展甚大阵列(EVLA)最新增强的能力。新的数据将与存档的数据相结合，以比较有或没有空间扩展的冷气体的星系团内的形态、恒星形成属性、环境和(适当时)位置。这些观测将与该项目合作者进行的高分辨率流体动力学模拟所作的预测进行比较；特别是处女座的观测将通过一个网站向研究界提供。这项工作将涉及来自代表性不足群体的本科生和研究生的参与，并将在学校和其他场所的公开演讲中得到强调。

This project consists of three complementary observational efforts, intended to test the conceptual picture that galaxies may gain mass from their surroundings not by accretion of hot plasma that cools as it settles into the galaxy, but rather by accretion of gas that has already cooled in the intergalactic environment and remains cold as it flows into the galaxy, possibly on orderly streams with preferred directions. This idea has gained theoretical support in recent years through hydrodynamical simulations of galaxy formation; observational tests to be performed by the PI consist of radio observations, primarily in the 21 cm neutral hydrogen line, of (1) the outer parts of the nearby Virgo cluster of galaxies, (2) large volumes surrounding two distinctly different clusters at redshift z=0.2, and (3) galaxies located in extremely under-dense void regions. This work will exploit the newly enhanced capabilities of the Westerbork Synthesis Radio Telescope (WSRT) in the Netherlands and the Expanded Very Large Array (EVLA) in the US. The new data will be combined with archived data to compare the morphologies, star forming properties, environments, and (where appropriate) locations within the clusters of galaxies with, and without, spatially extended cold gas. The observations will be compared against predictions made by high-resolution hydrodynamical simulations performed by a collaborator on the project; and the Virgo observations, in particular, will be made available to the research community through a website. The work will involve the participation of undergraduate and graduate students from under-represented groups, and will be highlighted in public presentations in schools and other venues.