Colour–magnitude diagram (left panel) and metallicity distribution (right panel) of Cole et al. (2005) RGB sample (green) and our selected RGB stars (red). V and I magnitudes are from the OGLE catalogue Udalski et al. (1997, 2000); Szymanski (2005) for the samples of Cole et al. (2005) and the present paper, while black dots in the CMD are photometric data from Zaritsky et al. (2004) catalogue. Metallicities in the right panel are those derived from the infrared Ca ii triplet index by Cole et al. (2005).