Spitzer IRS spectroscopy of 3CR radio galaxies and quasars: testing the unified schemes

With the Spitzer Space Telescope Infrared Spectrograph (IRS) we have observed seven powerful FR 2 radio galaxies and seven quasars. Both samples, the galaxies and the quasars, are comparable in isotropic 178 MHz luminosity (10$^{\rm 26.5}$ W/Hz $\la$ $ P_{\rm 178\,MHz} \la10^{\rm 29.5}$ W/Hz) and in redshift range (0.05 $\la$ z $\la$ 1.5). We find for both samples similar distributions in the luminosity ratios of high- to low-excitation lines ([NeV] 14.3~ \mu m / [NeII] 12.8~ \mu m ) and of high-excitation line to radio power ([NeV] 24.3~ \mu m / P 178\,MHz ). This solves the long debate about the apparent difference of quasars and radio galaxies in favor of the orientation-dependent unified schemes. Furthermore, the luminosity ratio [OIII] 500.7~ nm / [OIV] 25.9~ \mu m of most galaxies is by a factor of ten lower than that of the quasars. This suggests that the optical emission from the central NLR is essentially absorbed ( A V $\ga$ 3) in the powerful FR 2 galaxies and that the [OIII] 500.7~ nm luminosity does not serve as isotropic tracer for testing the unified schemes.