We have created an estimated metallicity map of the Small Magellanic Cloud ( SMC ) using the Magellanic Cloud Photometric Survey ( MCPS ) and Optical Gravitational Lensing Experiment ( OGLE III ) photometric data .
This is a first of its kind map of metallicity up to a radius of \sim 2.5 ^ { \circ } .
We identify the RGB in the V , ( V - I ) colour magnitude diagrams of small subregions of varying sizes in both data sets .
We use the slope of the RGB as an indicator of the average metallicity of a subregion , and calibrate the RGB slope to metallicity using available spectroscopic data for selected subregions .
The average metallicity of the SMC is found to be [ Fe/H ] = - 0.94 dex ( \sigma [ Fe/H ] = 0.09 ) from OGLE III , and [ Fe/H ] = - 0.95 dex ( \sigma [ Fe/H ] = 0.08 ) from MCPS .
We confirm a shallow but significant metallicity gradient within the inner SMC up to a radius of 2.5 ^ { \circ } ( - 0.045 \pm 0.004 dex deg ^ { -1 } to - 0.067 \pm 0.006 dex deg ^ { -1 } ) .