Reaching the peak of the quasar spectral energy distribution - I. Observations and models

We perform a spectral analysis of a sample of 11 medium redshift (1.5 less than or similar to z less than or similar to 2.2) quasars. Our sample all have optical spectra from the SDSS, infrared spectra from GNIRS and TripleSpec, and X-ray spectra from XMM-Newton. We first analyse the Balmer broad emission line profiles which are shifted into the IR spectra to constrain black hole masses. Then we fit an energy-conserving, three component accretion model of the broad-band spectral energy distribution (SED) to our multiwavelength data. 5 out of the 11 quasars show evidence of an SED peak, allowing us to constrain their bolometric luminosity from these models and estimate their mass accretion rates. Based on our limited sample, we suggest that estimating bolometric luminosities from L-5100 angstrom and L2-10 keV may be unreliable, as has been also noted for a low-redshift, X-ray selected active galactic nucleus sample.