The Host Galaxies of X-ray Quasars Are Not Strong Star Formers
  We use ultradeep SCUBA-2 850um observations (~0.37 mJy rms) of the 2 Ms
Chandra Deep Field-North (CDF-N) and 4 Ms Chandra Deep Field-South (CDF-S)
X-ray fields to examine the amount of dusty star formation taking place in the
host galaxies of high-redshift X-ray AGNs. Supplementing with COSMOS, we
measure the submillimeter fluxes of the 4-8 keV sources at z>1, finding little
flux at the highest X-ray luminosities but significant flux at intermediate
luminosities. We determine gray body and MIR luminosities by fitting spectral
energy distributions to each X-ray source and to each radio source in an
ultradeep Karl G. Jansky Very Large Array (VLA) 1.4 GHz (11.5uJy at 5-sigma)
image of the CDF-N. We confirm the FIR-radio and MIR-radio correlations to z=4
using the non-X-ray detected radio sources. Both correlations are also obeyed
by the X-ray less luminous AGNs but not by the X-ray quasars. We interpret the
low FIR luminosities relative to the MIR for the X-ray quasars as being due to
a lack of star formation, while the MIR stays high due to the AGN contribution.
We find that the FIR luminosity distributions are highly skewed and the means
are dominated by a small number of high-luminosity galaxies. Thus, stacking or
averaging analyses will overestimate the level of star formation taking place
in the bulk of the X-ray sample. We conclude that most of the host galaxies of
X-ray quasars are not strong star formers, perhaps because their star formation
is suppressed by AGN feedback.
