Spectral Structure In Fr II Radio Galaxies And Jets

Using spectral tomography to separate overlapping spectral features in a sample of FR II radio galaxies, we Ðnd a variety of spatial/spectral features that are not easily described in the context of current models. In particular, we Ðnd mixtures of Ñat- and steep-spectrum features in the hot spot regions and nonmonotonic spectral index gradients along jets. Additional Ðndings include spectral gradients in compact hot spots and possible transitions in jet properties at the downstream ends of the di use lobes. The complexity of behaviors uncovered here points to the need for a thorough investigation of numerical models for radio galaxies, as well as for detailed observational studies of larger, unbiased samples. We also perform the Ðrst quantitative assessment of errors in the use of spectral tomography for spectral index measurements.