Collaborative Project: Astrophysics of Early-Type Dwarf Galaxies

John S. Gallagher博士和Wyse博士正在合作研究暗矮星系中恒星群的特性。这些星系属于包含最多成员的星系类型。在地面和太空的观测站，使用新一代仪器进行的一系列定量测量现在表明，即使局限于表面相似的气体贫乏矮椭圆系统，矮星系也具有不同的形态和恒星形成历史。为什么这些小矮星如此多样化还不清楚。这是否反映了初始条件、环境影响，还是两者兼而有之？现存的数据表明，矮椭圆行星更喜欢密集的环境——这是绝对正确的吗？对侏儒的影响是什么，以及解开“先天vs后天”的含义是什么？此外，从恒星速度测量矮球状星系的内部动力学，可以推断出暗物质的含量，相对而言，很容易超过高表面亮度的巨型星系。致密暗物质在小星系中的含义尚不清楚。这是否意味着在不同类型的星系中存在不同类型的暗物质？如果是这样，那么哪些矮星系（如果有的话）代表了巨大星系的组成部分呢？研究小组正在通过新的观测和对贫气矮星系的建模来调查这些问题。他们使用新技术的ARC望远镜（由约翰霍普金斯大学组成的联合体）和WIYN 3.5m望远镜（由威斯康星大学组成的联合体）来获得三个星系团（室女座星系团、后发星系团和英仙座星系团）中的矮星系的光谱和光度。* * *

AST 98-0473018 John S. Gallagher Dr. Gallagher and Dr. Wyse are collaborating to study the properties of the stellar populations in faint dwarf galaxies. These galaxies belong to the type of galaxy that contains the most members. A range of quantitative measurements with new generations of instruments, at observatories on the ground and in space, now show that even when restricted to the superficially similar gas poor dwarf elliptical systems, dwarf galaxies have diverse morphologies and star formation histories. Why these dwarfs are so varied is not known. Does this reflect initial conditions, environmental influences, or both? Extant data suggest that dwarf ellipticals prefer dense environments - is this invariably true? What are the effect on the dwarfs, and the implications for disentangling "nature vs. nurture"? Further, the internal dynamics of dwarf spheroidal galaxies, measured from stellar velocities, leads to an inferred dark matter content easily surpassing, in relative terms, that of high surface brightness giant galaxies. The implications of dense dark matter in tiny galaxies are unclear. Does this mean different types of dark matter in different classes of galaxies? If so, which dwarf galaxies, if any, are representative of the building blocks of giant galaxies? The research team is investigating these questions through new observations and modeling of gas poor dwarf galaxies. They use the new technology ARC telescope (consortium through Johns Hopkins University) and the WIYN 3.5m telescope (consortium through the University of Wisconsin) to obtain spectra and photometry of dwarf galaxies in three clusters of galaxies: the Virgo cluster, the Coma cluster and the Perseus cluster. ***