paper

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

arXiv:1705.08587 · doi:10.1093/mnras/stx761

Abstract

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 Å. We accurately determine these two clusters' ages and masses by comparing their spectral energy distributions (from 2267 to 20000~Å, 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 filters) with theoretical stellar population-synthesis models, resulting in ages of for GC-1 and Gyr for GC-2. The masses of GC-1 and GC-2 obtained here are and , 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 versus diagram shows that GC-2 is an ultra-compact dwarf in the M81 group.

arXiv commentMNRAS 468, 4513-4528 (2017), 16 pages, 9 figures and 11 tables

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