Red synchrotron jets in Parkes quasars

Abstract

We present model fits to spectral energy distributions in the optical and near-infrared of >100 flat-spectrum radio quasars from the Parkes Half-Jansky Flat-spectrum Sample. We find that ∼40 per cent of the sources have power-law spectral energy distributions (SEDs), while a similar number show evidence for two primary components: a blue power law and optical synchrotron emission. The blue power law is similar to the dominant component observed in the spectra of optically selected quasars. There is strong evidence that the synchrotron component has a turnover in the ultraviolet-optical rest frame of the spectrum. In the remaining sources, it is likely that the synchrotron peaks at longer wav..