We explore the constraints that can be placed on the evolutionary timescales for typical low redshift galaxies evolving from the blue cloud through the green valley and onto the red sequence .
We utilise galaxies from the GAMA survey with 0.1 < z < 0.2 and classify them according to the intrinsic ( u ^ { * } - r ^ { * } ) colours of their stellar populations , as determined by fits to their multi-wavelength spectral energy distributions .
Using these fits to also determine stellar population ages and star formation timescales , we argue that our results are consistent with a green valley population dominated by galaxies that are simply decreasing their star formation ( running out of gas ) over a timescale of 2-4 Gyr which are seen at a specific epoch in their evolution ( approximately 1.6 e-folding times after their peak in star formation ) .
If their fitted star formation histories are extrapolated forwards , the green galaxies will further redden over time , until they attain the colours of a passive population .
In this picture , no specific quenching event which cuts-off their star formation is required , though it remains possible that the decline in star formation in green galaxies may be expedited by internal or external forces .
However , there is no evidence that green galaxies have recently changed their star formation timescales relative to their previous longer term star formation histories .