SIMBAD references

We present deep BVRI CCD photometry of the Large Magellanic Cloud cluster NGC 1978 and of fields immediately to the west. From the study of the colour-magnitude diagram and the luminosity function we derive for NGC 1978 an age of slightly more than 2Gyr and a metallicity of [Fe/H]=-0.4. NGC 1978 is, for a globular cluster, rather elliptical which had been explained by a merger origin. No age structure inside NGC 1978 was found, which limits this possibility to a merger of roughly coeval subunits. In the field indications for a higher star formation rate at 1x10⁸ and 6x10⁸yr exist 8' west of the cluster, while no such phases can be found near the cluster. At ages older than 2Gyr the star formation rate appears to have been the same in all analysed fields. On a broader scale, NGC 1978 seems to be one of the oldest of the LMC intermediate age clusters. A coherent redetermination of the ages of the oldest clusters of this age group underlines a sudden enhancement of the cluster formation rate in the LMC about 2 Gyr ago.