A combined Optical and X-ray Spectra Study for Type 1 AGN. III.
  Broadband SED Properties
  In this third paper in a series of three, we present a detailed study of the
AGN broadband SED based on a nearby unobscured Type 1 AGN sample. We perform a
systematic cross-correlation study of the following key parameters:
$\Gamma_{2-10keV}$, $L_{2-10keV}$, $L_{bol}$, $L_{bol}/L_{Edd}$,
$\kappa_{2-10keV}$, $\kappa_{5100A}$, FWHM$_{H\beta}$, M$_{BH}$, $\alpha_{ox}$,
$\alpha_{X}$ and $\alpha_{UV}$, and identify various strong correlations among
these parameters. The principal component analysis (PCA) is performed on the
correlation matrix of the above parameters, which shows that the three physical
parameters, i.e. black hole mass, mass accretion rate and Eddington ratio,
drive the majority of the correlations. This is consistent with PCA results
found from previous optical spectral studies.
  We produce various mean SEDs classified by each of the key parameters. Most
parameters, except L$_{bol}$, show similar systematic changes in the mean SEDs
such that the temperature at which the disc peaks is correlated with the ratio
of power in the disc versus the Comptonised components and the hard X-ray
spectral index. This underlying change in SED shape shows that AGN do exhibit
intrinsically different spectral states. This is superficially similar to the
SED differences in BHB seen as $\lambda_{Edd}$ increases, but the analogy does
not hold in detail. Only objects with the highest $\lambda_{Edd}$ appear to
correspond to a BHB spectral state (the disc dominated high/soft state). The
AGN with typical mass accretion rates have spectra which do not match well with
any state observed in BHB. We speculate that this could be due to the presence
of a powerful UV line driven disc wind, which complicates simple mass scaling
between stellar and supermassive black holes.
