We have created an estimated metallicity map of the SmallMagellanic 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 V, (V - I) colour-magnitude 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 shallowbut 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-1).
Bibliographical noteFunding Information:
This research was supported by the KASI-Yonsei Joint Research Program for all Frotiers of Astronomy and Space Science funded by the Korea Astronomy and Space Science Institute. The work is also partially supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF2016R1D1A1B01006608). S.C. acknowledges Dr. Smitha Subramanian (Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing, China) for suggestions during initial area binning of OGLE III and MCPS data, and also for critical reading of the original version of the manuscript and comments. The authors thank the OGLE and the MCPS team for making the data available in public domain. The authors also thank the anonymous referee for constructive suggestions that helped improve the manuscript.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science