Most galaxies can be considered as system of two components (bulge & disc) with contrasting properties, origins and formation histories. Separating these components and examining their properties individually provides a more complete picture of galaxy evolution. Performing such a decomposition is challenging, particularly in large surveys, where an automated method is essential. Current solutions use just one image (wasting available data), at a single wavelength, to determine a galaxy”s structural parameters, while modern surveys produce imaging in many near-UV to near-IR bands. Utilising all available data enables us to successfully separate the galaxy components, thanks to their different colour, and is essential to building a complete picture of the assembly histories of galaxies.
I will describe the multi-wavelength approach that MegaMorph takes for this challenge, and will demonstrate that it enables more accurate, robust and physically meaningful multi-wavelength measurements of galaxy structural components, essential for reliably studying the physical properties (stellar mass and age) of spheroids and disks.
Using galaxies from the GAMA survey, I will show how galaxy structural parameters, such as half-light radius and Sérsic index, vary from near-UV to near-IR wavelengths. This provides an alternative way of quantifying colour gradients and studying the relationships between the internal structure of galaxies and their stellar populations. I will further show how bulge-disc decompositions help us to understand the wavelength-dependence of galaxy profiles and the relationships between structure, star-formation history and dust extinction. I will also investigate the distributions of bulge and disc colours for a volume-limited sample of low-redshift galaxies.