A catalog of extended clusters and ultra-compact dwarf galaxies - An analysis of their parameters in early- and late-type galaxies
A catalog of extended clusters and ultra-compact dwarf galaxies - An analysis of their parameters in early- and late-type galaxies
复制标题
DOI：
10.1051/0004-6361/201219693
复制
发表时间：
2012-09
影响因子：
6.5
通讯作者：
R. Bruens;P. Kroupa
中科院分区：
文献类型：
--
作者：
R. Bruens;P. Kroupa
在各种环境中都发现了有效半径大于10pC的扩展星团。质量与球状星系团(GC)相当的天体被称为扩展星系团(ECs)，而质量在矮星系区的天体被称为超致密矮星系(UCDs)。本文分析了所有已知的ECS和UCDs的观测参数光度、有效半径和到宿主星系的投影距离，以及这些参数与其宿主星系的类型和光度的关系。我们搜索了现有的文献，编制了一个大于10PC的星系团的星表。由于ECs和UCDs之间没有明确的区别，这两种类型的天体都将被称为扩展恒星对象(Eos)。我们总共发现了813个Eos，其中171个与晚型星系有关，642个与早型星系有关。Eos覆盖的光度范围约为mV=-4到-14毫安。然而，绝大多数亮度高于-10 MAG的Eos都与椭圆星系有关。在每个星等处，Eos的有效半径在10pC和大小上限之间，这显示出一个明显的趋势：物体越亮，大小上限越大。对于与早、晚类型星系有关的EOS，光度函数的峰值分别为-6.40和-6.47，比GC光度函数的峰值弱一个数量级。Eos和GCs在Reff vs.MV参数空间形成了一个相干结构，而Eos和早期类型矮星系之间存在着明显的差距。然而，在高质量端有一个小的势能重叠，那里最扩展的Eos接近致密椭圆星系的参数。我们将EO样本与数值模型进行了比较，得出结论：EO样本的参数作为一个整体可以很好地用星团起源来解释，其中Eos是合并的团簇复合体的结果。
Extended stellar clusters with effective radii larger than 10 pc have been found in various environments. Objects with masses comparable to globular clusters (GCs) are called extended clusters (ECs), while objects with masses in the dwarf galaxy regime are called ultra-compact dwarf galaxies (UCDs). The paper analyses the observational parameters luminosity, effective radius, and projected distance to the host galaxy, of all known ECs and UCDs and the dependence of these parameters on the type and the luminosity of their host galaxy. We searched the available literature to compile a catalog of star clusters larger than 10 pc. As there is no clear distinction between ECs and UCDs, both types of objects will be called extended stellar objects (EOs). In total, we found 813 EOs of which 171 are associated with late-type and 642 with early-type galaxies. EOs cover a luminosity range from about MV = -4 to -14 mag. However, the vast majority of EOs brighter than -10 mag are associated with elliptical galaxies. At each magnitude EOs are found with effective radii between 10 pc and an upper size limit, which shows a clear trend: the more luminous the object the larger is the upper size limit. For EOs associated with early-and late-type galaxies, the luminosity functions peak at -6.40 and -6.47 mag, respectively, which is about one magnitude fainter than the peak of the GC luminosity function. EOs and GCs form a coherent structure in the reff vs. MV parameter space, while there is a clear gap between EOs and early type dwarf galaxies. However, there is a small potential overlap at the high-mass end, where the most extended EOs are close to the parameters of compact elliptical galaxies. We compare the EO sample with numerical models and conclude that the parameters of the EO sample as a whole can be very well explained by a star cluster origin, where EOs are the results of merged cluster complexes.