Do the spectral energy distributions of type 1 active galactic nuclei show diversity?

Abstract

We create broadband SEDs of 761 type 1 AGN. The Scott et al. sample, created by a cross-correlation of the optical SDSS DR5 quasar catalogue and the 2XMMi catalogue of serendipitous X-ray sources, is further matched with the FIRST catalogue of radio sources, the WISE MIR all-sky data release, the 2MASS NIR point source catalogue, the UKIDSS DR9 Large Area Survey and the GALEX all-sky and medium UV imaging surveys. This allows broadband SEDs covering log(nu)~9.2-18.1 to be created. We investigate variations in the SED shape by binning a subsample of 237 AGN with the best quality SEDs according to their X-ray spectral parameters, their AGN sub-type and their luminosity, black hole mass and Eddington ratio. The AGN sub-populations show some significant differences in their SEDs; X-ray absorbed AGN show a deficit of emission at X-ray/UV frequencies and an excess in the MIR consistent with absorption and re-emission, radio-loud AGN show increased radio and X-ray emission, consistent with the presence of a jet component in addition to the emission seen from radio-quiet AGN and the SEDs of NLS1s only differ from other type 1s in the X-ray regime, suggesting any physical differences are limited to their X-ray emitting region. Binning the AGN according to underlying physical parameters reveals more subtle differences in the SEDs. The X-ray spectral slope does not appear to have any influence or dependence on the multiwavelength emission in the rest of the SED. The contribution of X-rays to Lbol is lower in higher luminosity sources, and relatively more emission in the optical/UV is seen in AGN with higher Lx. Variations in the relative flux and peak frequency of the BBB are observed and may suggest higher inner disc temperatures with increasing accretion rates. Overall, we find that the diversity in the SED shapes is relatively small, and we find no apparent single driver for the variations.