Multi-Component Decompositions for S4G Galaxies

Spitzer Survey of Stellar Structure in Galaxies (S^4G, Sheth et al. 2010) is a deep 3.6 and 4.5 micron imaging survey of over 2000 nearby galaxies. We describe here one of the S4G data analysis pipelines, which is dedicated to 2-dimensional structural surface brightness decompositions, using GALFIT3.0 (Peng et al. 2010). Besides 1-component Sersic fits, and 2-component Sersic bulge + exponential disk fits, we also present multi-component models which include, when appropriate, central point source, bulge, disk, and bar components. Comparison of the derived bulge parameters indicates that multicomponent models are indeed needed to obtain reliable structural parameters for the bulges, confirming earlier results (Laurikainen et al. 2005, Gadotti et al. 2008). Most importantly, we provide all the pipeline decomposition files in electronic form, making it easy to extend these decompositions to suit specific science purposes (i.e. to include spirals/rings). We also provide IDL-based visualization tools (GALFIDL) for displaying/running GALFIT-decompositions.