An optical/near-infrared survey of GCs in early-type galaxies
A. L. Chies-Santos, S. S. Larsen, E. M. Wehner, H. Kuntschner, J. Strader, J. P. Brodie, J. F. C. Santos
备注：
6 pages, 3 figures, contributed talk to appear in the proceedings of IAU Symp. 266 (Star Clusters - Basic Galactic Building Blocks throughout Time and Space), eds. R. de Grijs and J. Lepine
Optical/near-infrared observations for 14 globular cluster (GC) systems in early- type galaxies are presented. We investigate the recent claims (Yoon, Yi & Lee 2006) of colour bimodality in GC systems being an artefact of the non linear colour - metallicity transformation driven by the horizontal branch morphology. Taking the advantage of the fact that the combination of optical and near-infrared colours can in principle break the age/metallicity degeneracy we also analyse age distributions in these systems.
Massive early-type galaxies typically have two subpopulations of globular clusters (GCs) which often reveal radial colour (metallicity) gradients. Collating gradients from the literature, we show that the gradients in the metal-rich and metal-poor GC subpopulations are the same, within measurement uncertainties, in a given galaxy. Furthermore, these GC gradients are similar in strength to the {\it stellar} metallicity gradient of the host galaxy. At the very largest radii (e.g. greater than 8 galaxy effective radii) there is some evidence that the GC gradients become flat with near constant me…
Metal-poor globular clusters (GCs) are both numerous and ancient, which indicates that they may be important contributors to ionizing radiation in the reionization era. Starting from the observed number density and stellar mass function of old GCs at $z=0$, I compute the contribution of GCs to ultraviolet luminosity functions (UVLFs) in the high-redshift Universe ($10 \gtrsim z \gtrsim 4$). Even under absolutely minimal assumptions - no disruption of GCs and no reduction in GC stellar mass from early times to the present - GC star formation contributes non-negligibly to the UVLF at luminositie…
We present the results of a self-consistent $N$-body simulation following the evolution of a primordial population of thick disc globular clusters (GCs). We study how the internal properties of such clusters evolve under the action of mutual interactions, while they orbit a Milky Way-like galaxy. For the first time, through analytical and numerical considerations, we find that physical encounters between disc GCs are a crucial factor that contributed to the shape of the current properties of the Galactic GC system. Close passages or motion on similar orbits may indeed have a significant impact…
A new perspective on globular clusters, their initial mass function, and their contribution to the stellar halo and to cosmic reionisation
我们研究了各种影响的动力学和化学模型的球状星团（GC），成功地再现了所观察到的丰度模式和多个人口的恒星在这些系统中假设化学富集快速旋转的大质量恒星。使用Decressin et al.（2007）的模型，我们确定了观测到的球状星团的现今质量与它们的初始恒星质量之间的比值，作为恒星初始质量函数（IMF）的函数。我们还计算了低质量恒星喷出的质量，以及原始球状星团发射的氢电离光子的数量。通常，我们发现GC的初始质量必须比现在的恒星质量大8-10倍（如果第二代恒星也从GC逃逸，则可达25倍）。现在的银河系GC星群对星系晕中低质量恒星的贡献率大约为5-8%（10-20%）。我们还表明，第二代恒星的检测在星系晕，最近宣布由不同的团体，GC初始质量函数（GCIMF）提供了一个新的约束。这些意见似乎排除了幂律GCIMF，而他们是兼容的对数正态分布。最后，高的初始质量也意味着GC在早期宇宙中必须发射大量的电离光子。我们的研究结果重新打开的GC的初始质量函数的问题，并加强了早期的结论，老GC可能代表了一个显着的贡献，在高红移再电离的星系间介质。
The SLUGGS Survey: globular clusters and the dark matter content of early-type galaxies
球状星团（GC）系统的总质量与宿主星系的维里晕质量之间存在很强的相关性。然而，在这种相关性中，总晕质量是在空间尺度上进行的统计测量，是典型GC系统的十倍左右。在这里，我们调查GC系统和星系的暗物质在可比的空间尺度之间的联系，使用动态质量测量的星系的基础上。我们的样本包括17个充分研究的大质量（恒星质量$\sim$ 10 $^{11}$ M $_{\odot}$）早期型星系从SLUGGS调查。我们发现，最强的相关性是蓝色（贫金属）GC亚群和暗物质含量。这种相关性意味着星系的暗物质质量可以通过对GC系统的仔细成像来估计，误差在2倍之内。GC系统的质量与封闭的暗物质的质量之比几乎是恒定的。我们还发现，蓝色GC的分数和封闭的暗物质的分数之间有很强的相关性，因此，一个典型的星系与蓝色GC的分数为60%有一个暗物质的分数为86%，在类似的空间尺度。晕的增长和去除（通过潮汐剥离）可能在形成这种趋势中发挥一定作用。在星系形成的两相模型的背景下，我们发现星系的吸积恒星的比例最高，有较高的暗物质分数为一个给定的分数的蓝色GC。
