Galaxy Zoo: the independence of morphology and colour
S. P. Bamford, Robert C. Nichol, I. K. Baldry, Kate Land, Chris J. Lintott, Kevin Schawinski, Anže Slosar, Alexander S. Szalay, D. Thomas, Mehri Torki, Dan Andreescu, Edward M. Edmondson, Christopher J. Miller, Phil Murray, M. Jordan Raddick, Jan Vandenberg · arXiv (Cornell University) · 2008
We analyse the relationships between galaxy morphology, colour, environment and stellar mass using data for 130352 objects from Galaxy Zoo, the largest sample of visually classified morphologies yet compiled. We conclusively show that the colour and morphology bimodalities are largely independent functions of environment. Both colour and morphology fractions are sensitive to stellar mass. However, at fixed stellar mass, while colour is also highly sensitive to environment, morphology displays much weaker environmental trends. A minority of both the morphology–density and colour–density relations can be attributed to the variation in the stellar mass function with environment. The remaining majority of the morphology– density relation is driven by variation in morphological fraction with environment at fixed stellar mass. Galaxies with high stellar masses are mostly red, in all environments and irrespective of their morphology. Low stellar-mass galaxies are mostly blue in low-density environments and mostly red in high-density environments, again irrespective of their morphology. While galaxies with early-type