Collaborative Project: Astrophysics of Early-Type Dwarf Galaxies

AST98-0473018约翰·S·加拉格尔博士和怀斯博士正在合作研究暗矮星系中恒星群的性质。这些星系属于成员最多的星系类型。现在，地面和太空天文台使用新一代仪器进行的一系列定量测量表明，即使仅限于表面上类似的贫气矮星椭圆系统，矮星系也有不同的形态和恒星形成历史。这些矮星为什么变化如此之大还不得而知。这反映的是初始条件、环境影响，还是两者兼而有之？现有的数据表明，矮小的椭圆形行星更喜欢密集的环境--这总是正确的吗？这对小矮人有什么影响，对理清“先天与后天”的关系又有何影响？此外，从恒星速度测量的矮小球状星系的内部动力学，导致推断的暗物质含量很容易相对地超过高表面亮度的巨型星系。微小星系中致密暗物质的含义尚不清楚。这是否意味着在不同类别的星系中存在不同类型的暗物质？如果是这样的话，哪些矮小星系(如果有的话)是巨型星系的组成部分呢？研究小组正在通过对气态贫矮星系进行新的观测和建模来研究这些问题。他们使用新技术ARC望远镜(由约翰·霍普金斯大学组成的联盟)和WIYN 3.5米望远镜(由威斯康星大学组成的联盟)来获得三个星系团：处女座星系团、彗星星系团和英仙座星系团中的矮星系的光谱和光度学数据。***

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. ***