The nature of X-ray absorbed QSOs
  There exists a significant population of broad line, z~2 QSOs which have
heavily absorbed X-ray spectra. Follow up observations in the submillimetre
show that these QSOs are embedded in ultraluminous starburst galaxies, unlike
most unabsorbed QSOs at the same redshifts and luminosities. Here we present
X-ray spectra from XMM-Newton for a sample of 5 such X-ray absorbed QSOs that
have been detected at submillimetre wavelengths. We also present spectra in the
restframe ultraviolet from ground based telescopes. All 5 QSOs are found to
exhibit strong C IV absorption lines in their ultraviolet spectra with
equivalent width > 5 Angstroms. The X-ray spectra are inconsistent with the
hypothesis that these objects show normal QSO continua absorbed by
low-ionization gas. Instead, the spectra can be modelled successfully with
ionized absorbers, or with cold absorbers if they posess unusually flat X-ray
continuum shapes and unusual optical to X-ray spectral energy distributions. We
show that the ionized absorber model provides the simplest, most
self-consistent explanation for their observed properties. We estimate that the
fraction of radiated power that is converted into kinetic luminosity of the
outflowing winds is typically ~4 per cent, in agreement with recent estimates
for the kinetic feedback from QSOs required to produce the M - sigma relation,
and consistent with the hypothesis that the X-ray absorbed QSOs represent the
transition phase between obscured accretion and the luminous QSO phase in the
evolution of massive galaxies.
