B-R colours of globular clusters in NGC 6166 (A2199)

We have analysed new R-band photometry of globular clusters in NGC 6166, the cD galaxy in the cooling flow cluster A2199. In combination with the earlier B photometry of Pritchet & Harris, we obtain B-R colours for ~40 globular clusters in NGC 6166. The mean B-R is 1.26+/-0.11, corresponding to a mean [Fe/H]=-1+/-0.4. Given that NGC 6166 is one of the most luminous cD galaxies studied to date, our result implies significant scatter in the relationship between mean cluster [Fe/H] and parent galaxy luminosity. We obtain a globular cluster specific frequency of S_N~9, with a possible range between 5 and 18. This value is inconsistent with the value of S_N<=4 determined earlier by Pritchet & Harris from B-band photometry, and we discuss possible reasons for the discrepancy. Finally, we reassess whether or not cooling flows are an important mechanism for forming globular clusters in gE/cD galaxies.