论文标题
奇特的巨大星系M85的神秘球状群集系统
Mysterious Globular Cluster System of the Peculiar Massive Galaxy M85
论文作者
论文摘要
我们介绍了一项关于特殊星系M85中球形簇（GC）的恒星种群和运动学的研究。我们使用MMT/hectoSpec以8 kpc $ <r <$ <$ <$ <$ <$ <$ <$ <$ <$ <$ <$ <r <$ <r <$ <$ <r <r <r <r <r <r <r <r <r。我们将它们分为三组，分别是蓝色/绿色/红色GC（B/G/RGC），其$（g-i）_0 $颜色。所有GC亚群的平均年龄为10 GYR，但表现出金属性差异。 BGC和RGC是最贫穷的（[z/h] $ \ sim -1.49 $）和金属富含金属的（分别为[z/h] $ \ sim -0.45 $），而GGCS则介于两者之间。我们发现内部GC系统表现出强烈的总体旋转，这完全是由于RGC系统的磁盘样旋转。 BGC系统几乎没有旋转。 GGC在GC亚群中显示的运动特性明显不同，平均速度高于BGC和RGC，并且沿M85的主要轴对齐。这意味着GGC的起源与其他GC亚群不同。 RGC系统的旋转式速度分散远低于BGC系统的旋转速度分散，表明M85的红色光环的截断。 BGC的平坦速度分散曲线为$ r $ = 67 kpc，反映了M85的暗物质范围。使用BGC系统的速度分散，我们估计M85的动态质量为$ 3.8 \ times 10^{12} m _ {\ odot} $。我们推断M85最近发生了合并事件，从而导致了GC系统的特殊运动学。
We present a study on stellar population and kinematics of globular clusters (GCs) in the peculiar galaxy M85. We obtain optical spectra of 89 GCs at 8 kpc $< R <$ 160 kpc using the MMT/Hectospec. We divide them into three groups, blue/green/red GCs (B/G/RGCs), with their $(g-i)_0$ colors. All GC subpopulations have mean ages of 10 Gyr, but showing differences in metallicities. The BGCs and RGCs are the most metal-poor ([Z/H] $\sim -1.49$) and metal-rich ([Z/H] $\sim -0.45$), respectively, and the GGCs are in between. We find that the inner GC system exhibits a strong overall rotation that is entirely due to a disk-like rotation of the RGC system. The BGC system shows little rotation. The GGCs show kinematic properties clearly distinct among the GC subpopulations, having higher mean velocities than the BGCs and RGCs and being aligned along the major axis of M85. This implies that the GGCs have an origin different from the other GC subpopulations. The rotation-corrected velocity dispersion of the RGC system is much lower than that of the BGC system, indicating the truncation of the red halo of M85. The BGCs have a flat velocity dispersion profile out to $R$ = 67 kpc, reflecting the dark matter extent of M85. Using the velocity dispersion of the BGC system, we estimate the dynamical mass of M85 to be $3.8 \times 10^{12} M_{\odot}$. We infer that M85 has undergone merging events lately, resulting in the peculiar kinematics of the GC system.
