Size, shade or shape? The contribution of galaxies of different types to
  the star-formation history of the Universe from SDSS-IV MaNGA
  By fitting stellar populations to SDSS-IV MaNGA survey observations of ~7000
suitably-weighted individual galaxies, we reconstruct the star-formation
history of the Universe, which we find to be in reasonable agreement with
previous studies. Dividing the galaxies by their present-day stellar mass, we
demonstrate the downsizing phenomenon, whereby the more massive galaxies hosted
the most star-formation at earlier times. Further dividing the galaxy sample by
colour and morphology, we find that a galaxy's present-day colour tells us more
about its historical contribution to the cosmic star formation history than its
current morphology. We show that downsizing effects are greatest among galaxies
currently in the blue cloud, but that the level of downsizing in galaxies of
different morphologies depends quite sensitively on the morphological
classification used, due largely to the difficulty in classifying the smaller
low-mass galaxies from their ground-based images. Nevertheless, we find
agreement that among galaxies with stellar masses
$M_{\star}>6\times10^{9}\,M_{\odot}$, downsizing is most significant in
spirals. However, there are complicating factors. For example, for more massive
galaxies, we find that colour and morphology are predictors of the past star
formation over a longer timescale than in less massive systems. Presumably this
effect is reflecting the longer period of evolution required to alter these
larger galaxies' physical properties, but shows that conclusions based on any
single property don't tell the full story.
