The XMM deep survey in the CDF-S. IX. An X-ray outflow in a luminous
  obscured quasar at z~1.6
  In active galactic nuclei (AGN)-galaxy co-evolution models, AGN winds and
outflows are often invoked to explain why super-massive black holes and
galaxies stop growing efficiently at a certain phase of their lives. They are
commonly referred to as the leading actors of feedback processes. Evidence of
ultra-fast (v>0.05c) outflows in the innermost regions of AGN has been
collected in the past decade by sensitive X-ray observations for sizable
samples of AGN, mostly at low redshift. Here we present ultra-deep XMM-Newton
and Chandra spectral data of an obscured (Nh~2x10^{23} cm^-2), intrinsically
luminous (L2-10keV~4x10^{44} erg/s) quasar (named PID352) at z~1.6 (derived
from the X-ray spectral analysis) in the Chandra Deep Field-South. The source
is characterized by an iron emission and absorption line complex at observed
energies of E~2-3 keV. While the emission line is interpreted as being due to
neutral iron (consistent with the presence of cold absorption), the absorption
feature is due to highly ionized iron transitions (FeXXV, FeXXVI) with an
outflowing velocity of 0.14^{+0.02}_{-0.06}c, as derived from photoionization
models. The mass outflow rate - ~2 Msun/yr - is similar to the source accretion
rate, and the derived mechanical energy rate is ~9.5x10^{44} erg/s,
corresponding to 9% of the source bolometric luminosity. PID352 represents one
of the few cases where indications of X-ray outflowing gas have been observed
at high redshift thus far. This wind is powerful enough to provide feedback on
the host galaxy.
