Breaks in the X-ray spectra of high redshift blazars and the intervening
  medium
  The flat spectrum radio quasars (FSRQs) are a sub-class of blazars
characterised by prominent optical emission lines and a collimated large-scale
jet along the observer line of sight. An X-ray spectral flattening has been
reported in FSRQs (at relatively high redshifts), attributable to either
absorption from gas along the line of sight or intrinsic jet based radiative
processes. We study a sample of 16 high redshift FSRQs (z of 1.1 -- 4.7; rest
frame energy upto 50 keV) observed with XMM-Newton and Swift satellites
spanning 29 epochs. The X-ray spectra are fit with a power law including free
excess absorption and one multiplied by an exponential roll off to account for
the intrinsic jet based processes. A statistical analysis is used to
distinguish between these models to understand the origin of the spectral
flattening. The model selection is unable to distinguish between them in ten of
the sixteen FSRQs. Intrinsic jet based radiative processes are indicated in
four FSRQs where we infer energy breaks consistent with their expectation from
the external Compton scattering of low energy ambient photons. Two of the FSRQs
indicate mixed results, supportive of either scenario, illustrating the
difficulty in identifying X-ray absorption signatures. A clear detection can be
employed to disentangle the relative contributions from the inter-galactic
medium and the intra-cluster medium, the methodology of which is outlined and
applied to the latter two sources.
