What do the Star Formation Histories of Galaxies tell us about the
  Starburst-AGN connection?
  Using a sample of 229618 narrow emission-line galaxies, we have determined
the normal star formation histories (SFHs) for galaxies with different activity
types: star forming galaxies (SFGs), transition type objects (TOs), Seyfert 2s
(Sy2s) and LINERs. We find that the variation of the SFH with the activity type
is explained by the mass of the galaxies and the importance of their bulge: the
LINERs reside in massive early-type galaxies, the Sy2s and TOs are hosted by
intermediate mass galaxies with intermediate morphological types, and the SFGs
are found in lower mass late-type spirals. Except for the Sy2s, the more
massive galaxies formed the bulk of their stars more rapidly than the less
massive ones. The Sy2s formed their stars more slowly and show presently an
excess in star formation. We have also found that the maximum in star formation
rate in the past increases with the virial mass within the aperture (VMA), the
VMA increasing from the SFGs to the TOs, to the Sy2s, culminating in the
LINERs. This correlation suggests that the bulges and the supermassive black
holes at the center of galaxies grow in parallel, in good agreement with the
M(BH)-sigma relation.
