Ages and structural and dynamical parameters of two globular clusters in the M81 group

作者：Ma Jun^*; Wang Song^*; Wu Zhenyu; Zhang TianMeng; Zou Hu; Zhou Zhimin; Nie Jundan; Zhou Xu; Peng Xiyang; Wang Jiali; Wu Jianghua; Du Cuihua; Yuan Qirong

来源：Monthly Notices of the Royal Astronomical Society, 2017, 468(4): 4513-4528.

DOI：10.1093/mnras/stx761

• galaxies: evolution
• galaxies: star clusters: general
• galaxies: star clusters: individual: M81
• galaxies: star clusters: individual: M82

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 Hubble Space Telescope (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 4000-10 000 angstrom. We accurately determine these two clusters' ages and masses by comparing their spectral energy distributions (from 2267 to 20 000 angstrom, comprising photometric data in the near-ultraviolet of the Galaxy Evolution Explorer, 14 BATC intermediate-band and Two Micron All Sky Survey near-infrared JHK(s) filters) with theoretical stellar population-synthesis models, resulting in ages of 15.50+/-3.20 for GC-1 and 15.10+/-2.70 Gyr for GC-2. The masses of GC-1 and GC-2 obtained here are 1.77-2.04 x 10(6) and 5.20-7.11 x 10(6) M-circle dot, respectively. In addition, the deep observations with the Advanced Camera for Surveys and Wide Field Camera 3 on the 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.

• 出版日期2017-7
• 单位中国科学院大学; 中国科学院国家天文台; 北京师范大学