A combined optical and X-ray study of unobscured type 1 active galactic nuclei - I. Optical spectra and spectral energy distribution modelling

We present modelling and interpretation of the continuum and emission lines for a sample of 51 unobscured type 1 active galactic nuclei (AGNs). All of these AGNs have high-quality spectra from both XMM-Newton and the Sloan Digital Sky Survey. We extend the wavelength coverage where possible by adding simultaneous ultraviolet data from the OM onboard XMM-Newton. Our sample is selected based on low reddening in the optical and low gas columns implied by their X-ray spectra, except for one case, the broad absorption line quasar PG 1004+130. They also lack clear signatures for the presence of a warm absorber. Therefore, the observed characteristics of this sample are likely to be directly related to the intrinsic properties of the central engine.