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首页> 外文学位 >Faint stellar systems in the Virgo Cluster: The connection between dwarf galaxies and globular clusters.
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Faint stellar systems in the Virgo Cluster: The connection between dwarf galaxies and globular clusters.

机译：处女座星团中微弱的恒星系统：矮星系和球状星团之间的联系。

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摘要

We present observations of faint stellar systems in the Virgo Cluster that have properties similar to both globular clusters and dwarf elliptical galaxies. These systems are not only very faint but are under-represented in the local Universe, factors that make their observation and analysis not only compelling but also challenging. However, using state-of-the-art observing facilities, we can undertake the first ever study of the connection between these two types of stellar systems.; We use optical and near-infrared Hubble Space Telescope images from the Advanced Camera for Survey Virgo Cluster Survey program, and spectroscopy obtained with the Echelle Spectrograph and Imager on the Keck 10-m telescope.; We perform careful dynamical and kinematical analyses, in which the properties of these "Dwarf Globular Transition Objects" (DGTOs) are compared to those of globular clusters and dwarf elliptical galaxies in the Local Supercluster. A few of our DGTOS are just "normal", old, metal-rich globular clusters, although much brighter than the previously known equivalent systems in our Galaxy.; The majority of the DGTOs have properties unlike those of normal globular clusters or dwarf galaxies. We consider them to belong to a recently identified class of faint stellar system, called ultracompact dwarf galaxies (UCDs). On the whole, the UCDs resemble the nuclei of nucleated dwarf elliptical galaxies in the Virgo Cluster. Our analysis generally support two possible scenarios for UCD formation: tidal stripping of the stellar envelopes of nucleated dwarf galaxies, and the amalgamation of multiple young massive clusters.; We find that there is a transition between globular clusters and ultracompact dwarf galaxies in terms of total system mass, at M ∼ (2-3) x 106 M⊙ . This transition is reflected in the onset of a size-luminosity relation for the UCDs, while there is none for the globular clusters. We suggest a quantitative classification scheme for DGTOs based on half-mass relaxation time, where UCDs have relaxation times that exceed a Hubble Time.; The strong concentration of UCDs to the center of the Virgo Cluster (and M87 in particular) suggests that proximity to the cluster center may be of key importance in the formation of UCDs.
机译：我们介绍了处女座星团中微弱的恒星系统的观测结果，该系统具有类似于球状星团和矮椭圆形星系的特性。这些系统不仅非常微弱，而且在本地宇宙中代表性不足，这些因素使得它们的观察和分析不仅引人注目，而且具有挑战性。但是，使用最先进的观测设备，我们可以对这两种类型的恒星系统之间的联系进行有史以来的首次研究。我们使用来自高级相机的光学和近红外哈勃太空望远镜图像进行处女座星团团聚计划，并使用Echelle光谱仪和成像仪在Keck 10米望远镜上获得光谱。我们执行仔细的动力学和运动学分析，将这些“矮球状过渡对象”（DGTO）的属性与局部超集群中的球状星团和矮椭圆形星系进行比较。我们的一些DGTOS只是“正常”的，旧的，富含金属的球状星团，尽管比我们银河系中以前已知的等效系统要亮得多。大多数DGTO具有与正常球状星团或矮星系不同的特性。我们认为它们属于最近确定的微弱恒星系统类别，称为超紧凑矮星系（UCD）。总体而言，UCD类似于处女座星团中有核矮化椭圆星系的核。我们的分析通常支持UCD形成的两种可能情况：潮汐剥夺有核矮星系的恒星包膜，以及合并多个年轻的大质量星团。我们发现，在总系统质量方面，球状星团和超紧凑矮星系之间存在一个过渡，M =（2-3）x 106 M＆odot; 。这种转变反映在UCD大小-光度关系的开始，而球状星团则没有。我们建议基于半质量弛豫时间的DGTO定量分类方案，其中UCD的弛豫时间超过哈勃时间。 UCD高度集中在处女座星团中心（尤其是M87）表明，靠近星团中心可能对UCD的形成至关重要。

著录项

  • 作者

    Hasegan, Ioana Monica.;

  • 作者单位

    Rutgers The State University of New Jersey - New Brunswick.;

  • 授予单位 Rutgers The State University of New Jersey - New Brunswick.;
  • 学科 Physics Astronomy and Astrophysics.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 127 p.
  • 总页数 127
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 天文学;
  • 关键词

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