Ages and structural and dynamical parameters of two globular clusters in the M81 group
Ages and structural and dynamical parameters of two globular clusters in the M81 group
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DOI：
10.1093/mnras/stx761
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发表时间：
2017-05
影响因子：
4.8
通讯作者：
Jun Ma;Song Wang;Zhenyu Wu;Tianmeng Zhang;H. Zou;J. Nie;Zhi-min Zhou;Xu Zhou;Xiyan Peng;Jiali Wang;Jianghua Wu;C. Du;Q. Z. D. O. Astronomy;National Astronomical Observatories;Chinese Academy of Sciences;C. Astronomy;S. Sciences;U. O. A. Sciences
中科院分区：
文献类型：
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作者：
Jun Ma;Song Wang;Zhenyu Wu;Tianmeng Zhang;H. Zou;J. Nie;Zhi-min Zhou;Xu Zhou;Xiyan Peng;Jiali Wang;Jianghua Wu;C. Du;Q. Z. D. O. Astronomy;National Astronomical Observatories;Chinese Academy of Sciences;C. Astronomy;S. Sciences;U. O. A. Sciences
GC-1和GC-2是Jang等人利用哈勃太空望远镜（{\it HST}）图像发现的M81和M82远晕中的两个球状星团（gc）。这两个gc是作为北京-亚利桑那-台湾-康涅狄格洲（BATC）多色巡天的一部分观测到的，使用了14个中间波段滤波器，覆盖了4000- 10000 \AA的波长范围。我们通过比较这两个星团的光谱能量分布（从2267到20000~{\AA}，包括{\it星系演化探测器}、14 BATC中波段和two Micron All Sky Survey近红外$JHK_{\rm s}$滤光片的光度数据）与理论恒星群合成模型，准确地确定了这两个星团的年龄和质量，得出GC-1的年龄为15.50\pm3.20$， GC-2的年龄为15.10\pm2.70$ Gyr。GC-1和GC-2的质量分别为$1.77-2.04\乘以10^6$和$5.20-7.11\乘以10^6 \rm~M_\odot$。此外，利用{\it HST}上的先进巡天相机和广角相机3进行深度观测，获得了GC-1和GC-2的表面亮度剖面。通过拟合三种不同的模型，得到了结构参数和动力参数；特别是推导了GC-1和GC-2的内部速度色散，可与光谱观测结果进行比较。本文首次用r_h和M_V的对比图表明GC-2是M81群中的一颗超致密矮星。
GC-1 and GC-2 are two globular clusters (GCs) in the remote halo of M81 and M82 in the M81 group discovered by Jang et al. using the {\it Hubble Space Telescope} ({\it HST}) images. These two GCs were observed as part of the Beijing--Arizona--Taiwan--Connecticut (BATC) Multicolor Sky Survey, using 14 intermediate-band filters covering a wavelength range of 4000--10000 \AA. We accurately determine these two clusters' ages and masses by comparing their spectral energy distributions (from 2267 to 20000~{\AA}, comprising photometric data in the near-ultraviolet of the {\it Galaxy Evolution Explorer}, 14 BATC intermediate-band, and Two Micron All Sky Survey near-infrared $JHK_{\rm s}$ filters) with theoretical stellar population-synthesis models, resulting in ages of $15.50\pm3.20$ for GC-1 and $15.10\pm2.70$ Gyr for GC-2. The masses of GC-1 and GC-2 obtained here are $1.77-2.04\times 10^6$ and $5.20-7.11\times 10^6 \rm~M_\odot$, respectively. In addition, the deep observations with the Advanced Camera for Surveys and Wide Field Camera 3 on the {\it HST} are used to provide the surface brightness profiles of GC-1 and GC-2. The structural and dynamical parameters are derived from fitting the profiles to three different models; in particular, the internal velocity dispersions of GC-1 and GC-2 are derived, which can be compared with ones obtained based on spectral observations in the future. For the first time, in this paper, the $r_h$ versus $M_V$ diagram shows that GC-2 is an ultra-compact dwarf in the M81 group.