Post-Starburst Quasars: Bridging the Gap Between Post-Starburst Galaxies
  and Quasars
  In order to better understand the nature of post-starburst quasars (PSQs) in
the context of galaxy evolution, we compare their properties to those of
post-starburst galaxies and quasars from appropriately selected samples
possessing similar redshift ($z \sim 0.3$), luminosity ($M_r \sim -$23), and
data quality. We consider morphologies, spectral features, and derived physical
properties of the stellar populations and central supermassive black hole. PSQs
themselves come in two types: the more luminous AGNs with more luminous
post-starburst stellar populations hosted by elliptical galaxies, some which
are clearly merger products, and the less luminous systems existing within
relatively undisturbed spiral galaxies and possessing signs of a more extended
period of star formation. Post-starburst galaxies (PSQs) have elliptical and
disturbed/post-merger morphologies similar to those of the more luminous PSQs,
display similar spectral properties, but also can have younger stellar
populations for a given starburst mass. Quasars at similar redshifts and
luminosities around the Seyfert/quasar transition possess similar AGN
characteristics, in terms of black hole mass and accretion rate, compared with
those of PSQs, but do not appear to be hosted by galaxies with significant
post-starburst populations. Recent studies of more luminous quasars find hosts
consistent with those of our luminous PSQs, suggesting that these PSQs may be
in transition between post-starburst galaxies and a more luminous quasar stage
when the post-starburst stellar population remains dominant. The lower
luminosity PSQs appear to differ from lower luminosity quasars (Seyfert
galaxies) in terms of more significant star formation in their past.
