The age of the Large Magellanic Cloud cluster NGC 2193

Abstract

The age of the LMC star cluster NGC 2193 is estimated as 2.2 + or - 0.6 Gyr from CCD photometry that reaches below the cluster main-sequence turnoff. The cluster is thus another member of the large set of LMC red clusters that have ages in the range of 1 to 3 Gyr. The principal cause of uncertainty in the estimated age is uncertainty in the LMC distance modulus; at (m - M)0 = 18.2, the age is estimated as 2.5 + or - 0.4 Gyr, while at (m - M)0 = 18.7, the age is 1.8 + or - 0.4 Gyr. A metal abundance of (Fe/H) = -0.5 + or - 0.3 dex is deduced for NGC 2193 from the color of the cluster giant branch. The C-M diagram for the LMC field near NGC 2193 shows the commonly found population of intermediate age stars but, in this case, the diagram is clearly dominated by a population of older stars. Isochrone fits indicate an age for this older population in excess of 7 Gyr, with some indication of ages perhaps as old as 13 Gyr. This latter population is the oldest LMC field population yet dated. 52 references.