(J − K_s,K_s) and (H − K_s,K_s) CMDs for the resolved stars detected in near-infrared observation (upper) and for the commonly detected stars in the near-infrared and optical data of Battinelli et al. (2007a) (lower). The magnitude and color range of TRGB (Valenti et al. 2004) for the given metallicity of [Fe/H] = −1.75 ~ − 1.3 is indicated by the solid line. The estimated magnitude in K_s of TRGB in this study is indicated by an arrow at K_s = 18.2. The open circles are 82 C stars cross-identified in both the giJHK_s photometry (this study) and CNTiO photometry of Albert et al. (2000).