Young star clusters immersed in intermediate-age fields in the Large Magellanic Cloud bar

Abstract

We present Washington System photometry for 11 star clusters immersed in the north-west part of the Large Magellanic Cloud (LMC) bar, centred on the intermediate-age clusters NGC 1865 and SL 244. The fields are heavily populated by the intermediate-age component of the LMC bar. We succeeded in disentangling cluster colour–magnitude diagrams from those of the fields and in deriving reddening and ages for five clusters — SL 218, BRHT4b, and NGC 1839, 1838 and 1863 – with the aid of recent Washington System theoretical isochrones. The resulting cluster ages range between 50 and 125 Myr. Despite their proximity, NGC 1836 and BRHT4b have very different ages. Thus the possibility of these two objects being a binary cluster is very unlikely, although a capture cannot be ruled out a priori. Our results suggest that for each intermediate-age cluster remaining in the LMC bar region, a number of robust young blue star clusters occurs in the same region.