037-B327 in M31: Luminous Globular Cluster or Core of a Former Dwarf Spheroidal Companion to M31?
037-B327 in M31: Luminous Globular Cluster or Core of a Former Dwarf Spheroidal Companion to M31?
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DOI：
10.1086/500257
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发表时间：
2005-12
期刊：
影响因子：
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通讯作者：
Jun Ma;S. van den Bergh;Hong Wu;Yanbin Yang;Xu Zhou;Jian-sheng Chen;Zhenyu Wu;Zhao-ji Jiang;Jianghua Wu
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文献类型：
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作者：
Jun Ma;S. van den Bergh;Hong Wu;Yanbin Yang;Xu Zhou;Jian-sheng Chen;Zhenyu Wu;Zhao-ji Jiang;Jianghua Wu
星团037-B327是M31中已知的最明亮和最红的星团，因此它很有意义。利用哈勃太空望远镜上的高级巡天照相机进行的深度观测提供了F606 W波段的光度数据，还显示这个星团被一条尘埃带穿过。我们通过将观测到的表面亮度分布拟合到King模型，确定了037-B327的结构参数，其中rc = 0.″72（=2.69 pc），rt = 5.″87（=21.93 pc），浓度指数c = log（rt/rc）= 0.91。表面亮度轮廓在中心的0.25英寸范围内基本上是平坦的，没有显示出核心塌陷的迹象。虽然尘埃带影响测光，国王模型拟合地表亮度轮廓很好，除了严重影响的地区的尘埃带。我们还计算了半光半径rh = 1.″11（=4.15 pc）。结合以前的测光结果，我们发现这个天体与银河系中的半人马座ω星、M54和NGC 2419以及M31中的大质量星系团G1落在MV-log Rh图的同一区域。所有这四个物体都被认为是前矮星系的剥离核心。这表明037-B327也可能是M31的前矮伴星的剥离核心。
The cluster 037-B327 is of interest because it is both the most luminous and the most highly reddened cluster known in M31. Deep observations with the Advanced Camera for Surveys on the Hubble Space Telescope provide photometric data in the F606W band and also show that this cluster is crossed by a dust lane. We have determined the structural parameters of 037-B327 by fitting the observed surface brightness distribution to a King model with rc = 0.″72 (=2.69 pc), rt = 5.″87 (=21.93 pc), and a concentration index c = log (rt/rc) = 0.91. The surface brightness profile appears to be essentially flat within 0.″25 of the center and shows no signs of core collapse. Although the dust lane affects the photometry, the King model fits the surface brightness profile well except for the regions badly affected by the dust lane. We also calculate the half-light radius, rh = 1.″11 (=4.15 pc). Combined with previous photometry, we find that this object falls in the same region of the MV versus log Rh diagram as do ω Centauri, M54, and NGC 2419 in the Milky Way and the massive cluster G1 in M31. All four of these objects have been claimed to be the stripped cores of former dwarf galaxies. This suggests that 037-B327 may also be the stripped core of a former dwarf companion to M31.