论文标题
矮球星系中球状簇的空间分布和时间问题
The spatial distribution of globular clusters in dwarf spheroidal galaxies and the timing problem
论文作者
论文摘要
矮球（DSPH）星系中cuspy暗光环的内部区域中大量球状簇（GC）的动态摩擦时间尺度可能比哈勃时间短得多。这意味着预计GC的一小部分将被吸引到这些星系的中心附近。我们比较了简单的蒙特卡洛模型中预测的GC的径向分布与光谱确认的$ 38 $样本的GC和17个GC候选者的径向分布，这主要与低亮度DSPH星系相关。如果暗物质光环遵循NFW曲线，则观察到的预计距离的中心GC数量小于一半，Galaxy有效半径明显高于模型的预测。这个时序问题可以看作是开始GC距离的微调。由于中央区域的GC的沉没时间尺度短，GC的径向分布有望在接下来的1-2 GYR中显着发展。但是，具有与星系有效半径相当的大小核心的暗物质光环会导致这些星系中央区域中GC的慢速轨道内刺激性，从而为时序问题提供了简单的解决方案。我们还检查了我们的GC样品的求和分布中质量分离的任何迹象。
The dynamical friction timescale of massive globular clusters (GCs) in the inner regions of cuspy dark haloes in dwarf spheroidal (dSph) galaxies can be much shorter than the Hubble time. This implies that a small fraction of the GCs is expected to be caught close to the centre of these galaxies. We compare the radial distribution of GCs predicted in simple Monte Carlo models with that of a sample of $38$ spectroscopically confirmed GCs plus 17 GC candidates, associated mainly to low-luminosity dSph galaxies. If dark matter haloes follow an NFW profile, the observed number of off-center GCs at projected distances less than one half the galaxy effective radius is significantly higher than models predict. This timing problem can be viewed as a fine-tuning of the starting GC distances. As a result of the short sinking timescale for GCs in the central regions, the radial distribution of GCs is expected to evolve significantly during the next 1-2 Gyr. However, dark matter haloes with cores of size comparable to the galaxy effective radii can lead to a slow orbital in-spiral of GCs in the central regions of these galaxies, providing a simple solution to the timing problem. We also examine any indication of mass segregation in the summed distribution of our sample of GCs.
