2015/10/20 by Samyaday Choudhury, Annapurni Subramaniam, Andrew A. Cole
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stv2414
28 pages, 40 figures, 7 tables, Accepted for publication in MNRAS. arXiv admin note: text overlap with arXiv:1101.1771, arXiv:1302.6211 by other authors
arxiv created 2015/10/20 · arxiv updated 2015/11/18
We have estimated a metallicity map of the Large Magellanic Cloud (LMC) 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 4 - 5 degrees, derived using photometric data and calibrated using spectroscopic data of Red Giant Branch (RGB) stars. 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 spectroscopic data for field and cluster red giants in selected subregions. The average metallicity of the LMC is found to be [Fe/H] = -0.37 dex (σ[Fe/H] = 0.12) from MCPS data, and [Fe/H] = -0.39 dex (σ[Fe/H] = 0.10) from OGLE III data. The bar is found be the most metal-rich region of the LMC. Both the data sets suggest a shallow radial metallicity gradient up to a radius of 4 kpc (-0.049±0.002 dex kpc-1 to -0.066±0.006 dex kpc-1). Subregions in which the mean metallicity differs from the surrounding areas do not appear to correlate with previously known features; spectroscopic studies are required in order to assess their physical significance.