2009ApJ...690.1706M

We present new Near-Infrared Camera and Multi-Object Spectrometer and attitude control system observations of the quasar jet PKS 0637-752, and we use them, together with existing multiwavelength observations, to produce the most complete spectral coverage of the source to date. We explore the implications of these observations in the context of models for the jet X-ray emission. By relaxing the assumption of equipartition, we undertake an exhaustive study of the parameter space for external Compton off the cosmic microwave background (CMB) (EC/CMB) model. We find that the multiwavelength observations exclude a magnetic-field-dominated jet. Using the method proposed by Georganopoulos et al. for probing the jet matter content, we show that protons are practically needed for all jet configurations, extending a previous application of the method by Uchiyama et al. that was based on exploring three particular jet configurations. We also show that equipartition is the only configuration that can reproduce the observations and have one proton per radiating lepton. We finally present a rather model-independent argument that the jet has a spine-sheath flow pattern, with the spine being faster and emitting most of the infrared-optical X-ray emission.