B-R Colors of Globular Clusters in NGC 6166 (A2199)

Abstract

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 (1990), we obtain B$-$R colours for $\sim$ 40 globular clusters in NGC 6166. The mean B$-$R is 1.26 $\pm$ 0.11, corresponding to a mean [Fe/H] = $-$1 $\pm$ 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$_N$ $\sim$ 9, with a possible range between 5 and 18. This value is inconsistent with the value of S$_N$ $\leq$ 4 determined earlier by Pritchet \& Harris (1990) 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.