The connection between the accretion process that powers AGNs and the formation of jets is still poorly understood. Here we tackle this issue using new, deep Chandra and XMM-Newton observations of the cores of three powerful radio-loud quasars, 1136-135, 1150+497 (Chandra), and 0723+679 (XMM-Newton), in the redshift range z = 0.3-0.8. These sources are known from our previous Chandra snapshot survey to have kiloparsec-scale X-ray jets. In 1136-135 and 1150+497, evidence is found for the presence of diffuse thermal X-ray emission around the cores, on scales of 40-50 kpc and with luminosity L(0.3-2 keV) ~ 1043 ergs s-1, suggesting thermal emission from the host galaxy or a galaxy group. The X-ray continua of the cores in the three sources are described by an upward-curved (concave) broken power law, with photon indices Γsoft ~ 1.8-2.1 and Γhard ~ 1.7 below and above ≈2 keV, respectively. There is evidence for an unresolved Fe Kα line with EW ~ 70 eV in the three quasars. The spectral energy distributions of the sources can be well described by a mix of jet and disk emission, with the jet dominating the radio and hard X-rays (via synchrotron and external Compton radiation) and the disk dominating the optical/UV through soft X-rays. A comparison of the kiloparsec-scale with the parsec-scale jet powers shows that the two agree within a factor of 2, confirming previous findings for γ-ray blazars. This suggests that the power channeled into the jet is stable on timescales of the order of 104-105 yr and that a negligible fraction of the kinetic power of the jet is dissipiated along its path from the innermost regions of the AGN to the hundreds of kiloparsec scales.
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