Galaxy and Mass Assembly (GAMA): Morphological transformation of
  galaxies across the green valley
  We explore constraints on the joint photometric and morphological evolution
of typical low redshift galaxies as they move from the blue cloud through the
green valley and onto the red sequence. We select GAMA survey galaxies with
$10.25<{\rm log}(M_*/M_\odot)<10.75$ and $z<0.2$ classified according to their
intrinsic $u^*-r^*$ colour. From single component S\'ersic fits, we find that
the stellar mass-sensitive $K-$band profiles of red and green galaxy
populations are very similar, while $g-$band profiles indicate more disk-like
morphologies for the green galaxies: apparent (optical) morphological
differences arise primarily from radial mass-to-light ratio variations.
Two-component fits show that most green galaxies have significant bulge and
disk components and that the blue to red evolution is driven by colour change
in the disk. Together, these strongly suggest that galaxies evolve from blue to
red through secular disk fading and that a strong bulge is present prior to any
decline in star formation. The relative abundance of the green population
implies a typical timescale for traversing the green valley $\sim 1-2$~Gyr and
is independent of environment, unlike that of the red and blue populations.
While environment likely plays a r\^ole in triggering the passage across the
green valley, it appears to have little effect on time taken. These results are
consistent with a green valley population dominated by (early type) disk
galaxies that are insufficiently supplied with gas to maintain previous levels
of disk star formation, eventually attaining passive colours. No single event
is needed quench their star formation.
