Reaching the Peak of the Quasar Spectral Energy Distribution I: Observations and Models

Abstract

We perform a spectral analysis of a sample of 11 medium redshift (1.5 < z < 2.2) quasars. Our sample all have optical spectra from the SDSS, infrared spectra from GNIRS and TSPEC, 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 broadband spectral energy distribution (SED) to our multi-wavelength data. Five 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_5100A and L_2-10keV may be unreliable, as has been also noted for a low-redshift, X-ray selected AGN sample.

22 pages, 11 figures, 7 tables; accepted for publication in MNRAS

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• The SOUX AGN Sample: SDSS-XMM-Newton Optical, Ultraviolet and X-ray selected active galactic nuclei spanning a wide range of parameter space -- Sample definition
• Searching for Super-Eddington Quasars using a Photon Trapping Accretion Disc Model
• Testing the Completeness of the SDSS Colour Selection for Ultramassive, Slowly Spinning Black Holes
• Disentangling the AGN and Star-Formation Contributions to the Radio-X-ray Emission of Radio-Loud Quasars at 1<z<2
• The broad band SEDs of four 'hypervariable' AGN