The Accretion History of AGN: A Newly Defined Population of Cold Quasars
  Quasars are the most luminous of active galactic nuclei (AGN), and are
perhaps responsible for quenching star formation in their hosts. The Stripe 82X
catalog covers 31.3 deg$^2$ of the Stripe 82 field, of which the 15.6 deg$^2$
covered with XMM-Newton is also covered by Herschel/SPIRE. We have 2500 X-ray
detected sources with multi-wavelength counterparts, and 30% of these are
unobscured quasars, with $L_X > 10^{44}\,$erg/s and $M_B < -23$. We define a
new population of quasars which are unobscured, have X-ray luminosities in
excess of $10^{44}\,$erg/s, have broad emission lines, and yet are also bright
in the far-infrared, with a 250$\mu$m flux density of $S_{\rm 250}>30$mJy. We
refer to these Herschel-detected, unobscured quasars as "Cold Quasars". A mere
4% (21) of the X-ray- and optically-selected unobscured quasars in Stripe 82X
are detected at 250$\mu$m. These Cold Quasars lie at $z\sim1-3$, have $L_{\rm
IR}>10^{12}\,L_\odot$, and have star formation rates of
$\sim200-1400\,M_\odot$/yr. Cold Quasars are bluer in the mid-IR than the full
quasar population, and 72% of our Cold Quasars have WISE W3 $<$ 11.5 [Vega],
while only 19% of the full quasar sample meets this criteria. Crucially, Cold
Quasars have on average $\sim9\times$ as much star formation as the main
sequence of star forming galaxies at similar redshifts. Although dust-rich,
unobscured quasars have occasionally been noted in the literature before, we
argue that they should be considered as a separate class of quasars due to
their high star formation rates. This phase is likely short-lived, as the
central engine and immense star formation consume the gas reservoir. Cold
Quasars are type-1 blue quasars that reside in starburst galaxies.
