论文标题
黑眼星系M64的外磁盘中的一个新的金属球状簇和已解决的星星：对III型磁盘断裂的起源的影响
A New Metal-poor Globular Cluster and Resolved Stars in the Outer Disk of the Black Eye Galaxy M64: Implication for the Origin of the Type III Disk Break
论文作者
论文摘要
M64是一个附近的螺旋星系，具有III型抗截断分量。为了追踪III型组件的起源，我们提出了用于调查的Hubble太空望远镜/高级摄像头$ F606W/F814W $在外部磁盘中的磁场中的已解决星的光度法（$ 2.5'\ lesssim r \ Lessim r \ Lessim r \ Lessim 6.5'$）M64。在东部的$ r \约5.5'$（7 kpc）时，我们发现了一个新的金属贫困球状群集（$ r _ {\ rm eff} = 5.73 \ pm0.02 $ pc和$ m_v = -9.54 \ 9.54 \ pm0.09 $ mag），m64-gc1。这是M64中发现的第一个球状簇。 M64-GC1中已解决的恒星的颜色标记图（CMD）与[Fe/H] $ = -1.5 \ pm0.2 $的12个Gyr等亚线很好地匹配，表明此群集属于Halo。整个ACS场中解决的恒星的CMD显示了两个可区分的红色巨型分支（RGB）：弯曲金属富的RGB和垂直金属贫困RGB。金属丰富的RGB代表旧金属富含（[Fe/H] $ \ -0.4 $）磁盘总体。相比之下，金属贫困RGB星的CMD与M64-GC1的CMD非常相似，表明金属贫困的RGB代表了光环群体。富含金属的RGB恒星的径向数密度曲线由指数磁盘定律描述，而金属贫困的RGB星的轮廓由De Vaucoulers定律描述。从这些结论中，我们得出的结论是，M64中III型成分的起源是一种光环，其金属性比磁盘或凸起的人群低得多。
M64 is a nearby spiral galaxy with a Type III anti-truncation component. To trace the origin of the Type III component, we present Hubble Space Telescope/Advanced Camera for Surveys $F606W/F814W$ photometry of resolved stars in a field located in the outer disk ($2.5' \lesssim r \lesssim 6.5'$) of M64. At $r\approx 5.5'$ (7 kpc) to the east, we discover a new metal-poor globular cluster ($R_{\rm eff}=5.73\pm0.02$ pc and $M_V=-9.54\pm0.09$ mag), M64-GC1. This is the first globular cluster found in M64. The color-magnitude diagram (CMD) of the resolved stars in M64-GC1 is well matched by 12 Gyr isochrones with [Fe/H] $=-1.5\pm0.2$, showing that this cluster belongs to a halo. The CMD of the resolved stars in the entire ACS field shows two distinguishable red giant branches (RGBs): a curved metal-rich RGB and a vertical metal-poor RGB. The metal-rich RGB represents an old metal-rich ([Fe/H] $\approx -0.4$) disk population. In contrast, the CMD of the metal-poor RGB stars is very similar to the CMD of M64-GC1, showing that the metal-poor RGB represents a halo population. The radial number density profile of the metal-rich RGB stars is described by an exponential disk law, while the profile of the metal-poor RGB stars is described by a de Vaucouleurs's law. From these, we conclude that the origin of the Type III component in M64 is a halo which has a much lower metallicity than a disk or bulge population.
