2009ApJ...696.1693F

We present Spitzer Infrared Spectrograph spectra and Multiband Imaging Photometer for Spitzer photometry of 12 radio-loud QSOs with FR II morphologies at z ∼ 0.3. Six of the sources are surrounded by luminous extended emission-line regions (EELRs), while the other six do not have such extended nebulae. The two subsamples are indistinguishable in their mid-infrared (MIR) spectra and overall IR spectral energy distributions (SEDs). For both subsamples, the MIR aromatic features are undetected in either individual sources or their stacked spectra, and the SEDs are consistent with pure quasar emission without significant star formation. The upper limits to the star formation rate (SFR) are sufficiently low that starburst-driven superwinds can be ruled out as a mechanism for producing the EELRs, which are instead likely the result of the ejection of most of the gas from the system by blast waves accompanying the launching of the radio jets. The FR II quasars deviate systematically from the correlation between host galaxy SFR and black hole accretion rate apparently followed by radio-quiet QSOs, implying little or no bulge growth coeval with the current intensive black hole growth. We also present a new Spitzer estimate of the SFR for the starburst in the host galaxy of the compact steep-spectrum radio quasar 3C 48.