XMM-Newton and INTEGRAL analysis of the Ophiuchus cluster of galaxies
  We investigated the non-thermal hard X-ray emission in the Ophiuchus cluster
of galaxies. Our aim was to characterise the physical properties of the
non-thermal component and its interaction with the cosmic microwave background.
We performed spatially resolved spectroscopy and imaging using XMM-Newton data
to model the thermal emission. Combining this with INTEGRAL ISGRI data, we
modeled the 0.6-140 keV band total emission in the central 7 arcmin region. The
models that best describe both PN and ISGRI data contain a power-law component
with a photon index in a range 2.2-2.5. This component produces ~10% of the
total flux in the 1-10 keV band. The pressure of the non-thermal electrons is
~1% of that of the thermal electrons. Our results support the scenario whereby
a relativistic electron population, which produces the recently detected radio
mini-halo in Ophiuchus, also produces the hard X-rays via inverse compton
scattering of the CMB photons. The best-fit models imply a differential
momentum spectrum of the relativistic electrons with a slope of 3.4-4.0 and a
magnetic field strength B=0.05-0.15 microG. The lack of evidence for a recent
major merger in the Ophiuchus center allows the possibility that the
relativistic electrons are produced by turbulence or hadronic collisions.
