Photometric metallicity map of the Small Magellanic Cloud

Abstract

<p>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 ∼2.5. We identify the Red Giant Branch (RGB) in the <em>V</em>, (<em>V</em>−<em>I</em>) colourmagnitude diagrams of small sub-regions of varying sizes in both data sets. We use the slope of the RGB as an indicator of the average metallicity of a sub-region and calibrate the RGB slope to metallicity using available spectroscopic data for selected sub-regions. The average metallicity of the SMC is found to be [Fe/H] = −0.94 dex (σ[Fe/H] = 0.09) from OGLE III and [Fe/H] = −0.95 dex (σ[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 (−0.045  0.004 to −0.067  0.006 dex deg<sup>−1</sup>).</p>