Collaborative Project: Astrophysics of Early-Type Dwarf Galaxies

AST 98-04706 迷迭香怀斯 加拉格尔博士和怀斯博士正在合作研究暗淡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，即使仅限于表面相似的贫气体矮椭圆系统，矮星系也具有不同的形态和星星形成历史。 为什么这些矮星如此不同还不清楚。 这是否反映了初始条件、环境影响或两者兼而有之？ 现存的数据表明矮椭圆星系更喜欢稠密的环境--这总是正确的吗？ 这对侏儒有什么影响，以及对解开“先天与后天”的关系有什么意义？ 此外，矮球状星系的内部动力学，从恒星速度测量，导致推断的暗物质含量很容易超过，在相对而言，高表面亮度的巨星系。 致密暗物质在微小星系中的含义尚不清楚。 这是否意味着不同类型的星系中存在不同类型的暗物质？ 如果是的话，哪些矮星系（如果有的话）是巨星系的代表性组成部分？ 研究小组正在通过对贫气体矮星系的新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联合）和WIYN 3.5米望远镜（由威斯康星州大学联合）获得三个星系团中矮星系的光谱和测光：室女座星系团、后发座星系团和英仙座星系团。 ***

AST 98-04706 Rosemary Wyse 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. ***