论文标题
对最亮星系中球状簇系统的光度调查
A Photometric Survey of Globular Cluster Systems in Brightest Cluster Galaxies
论文作者
论文摘要
Hubble空间望远镜成像，用于26个巨型早期型星系，均来自桅杆档案，用于执行其周围球形群集（GC）系统的光度法。这些目标大多数是最明亮的簇星系（BCG），其距离范围为24至210 mpc。用Dolphot完成的光度法目录是公开的。 GC颜色指数通过12-GYR SSP（单个恒星种群）模型和基准颜色指数（F475W-F850LP）的直接光谱校准将GC颜色指数转换为[Fe/H]。所有结果的金属分布函数（MDF）可以通过双峰高斯函数准确地匹配。所有星系中的GC系统还表现出具有较浅的金属性梯度，其平均$ z \ sim r_ {gc}^{ - 0.3} $平均为agractCentric距离。总结了MDF的几个参数，包括均值，分散和蓝色/红色部分。也许最有趣的新结果是蓝色/红色GC与星系质量的趋势，它与大型大星系层次组装中GC形成的最新模拟相关联。观察到的趋势揭示了两个主要的过渡阶段：对于低质量星系，金属富含金属的GC分数$ F（红色）$随着星系质量而稳定增加，直到Halo Mass $ M_H \ M_H \ Simeq 3 \ times 10^{12} M _ {\ odot} $。在这一点之上，超过一半的金属贫困（蓝色）GC来自积聚的卫星和$ f（红色）$开始下降。但是，在$ m_h \ simeq 10^{14} m _ {\ odot} $附近的更高过渡点之上，数据暗示$ f（red）$可能会再次增加，因为金属富含金属的GC也被积聚的系统所支配。
Hubble Space Telescope imaging for 26 giant early-type galaxies, all drawn from the MAST archive, is used to carry out photometry of their surrounding globular cluster (GC) systems. Most of these targets are Brightest Cluster Galaxies (BCGs) and their distances range from 24 to 210 Mpc. The catalogs of photometry, completed with DOLPHOT, are publicly available. The GC color indices are converted to [Fe/H] through a combination of 12-Gyr SSP (Single Stellar Population) models and direct spectroscopic calibration of the fiducial color index (F475W-F850LP). All the resulting metallicity distribution functions (MDFs) can be accurately matched by bimodal Gaussian functions. The GC systems in all the galaxies also exhibit shallow metallicity gradients with projected galactocentric distance that average $Z \sim R_{gc}^{-0.3}$. Several parameters of the MDFs including the means, dispersions, and blue/red fractions are summarized. Perhaps the most interesting new result is the trend of blue/red GC fraction with galaxy mass, which connects with predictions from recent simulations of GC formation within hierarchical assembly of large galaxies. The observed trend reveals two major transition stages: for low-mass galaxies, the metal-rich (red) GC fraction $f(red)$ increases steadily with galaxy mass, until halo mass $M_h \simeq 3 \times 10^{12} M_{\odot}$. Above this point, more than half the metal-poor (blue) GCs come from accreted satellites and $f(red)$ starts declining. But above a still higher transition point near $M_h \simeq 10^{14} M_{\odot}$, the data hint that $f(red)$ may start to increase again because the metal-rich GCs also become dominated by accreted systems.
