The bolometric luminosity of type 2 AGN from extinction-corrected
  [OIII]: no evidence for Eddington-limited sources
  There have been recent claims that a significant fraction of type 2 AGN
accrete close or even above the Eddington limit. In type 2 AGN the bolometric
luminosity (L_b) is generally inferred from the [OIII] emission line luminosity
(L_OIII). The key issue, in order to estimate the bolometric luminosity in
these AGN, is therefore to know the bolometric correction to be applied to
L_OIII. A complication arises from the fact that the observed L_OIII is
affected by extinction, likely due to dust within the narrow line region. The
extinction-corrected [OIII] luminosity (L^c_OIII) is a better estimator of the
nuclear luminosity than L_OIII. However, so far only the bolometric correction
to be applied to the uncorrected L_OIII has been evaluated. This paper is
devoted to estimate the bolometric correction C_OIII=L_b/L^c_OIII in order to
derive the Eddington ratios for the type 2 AGN in a sample of SDSS objects. We
have collected from the literature 61 sources with reliable estimate of both
L^c_OIII and X-ray luminosities (L_X). To estimate C_OIII, we combined the
observed correlation between L^c_OIII and L_X with the X-ray bolometric
correction. We found, contrary to previous studies, a linear correlation
between L^c_OIII and L_X. We estimated C_OIII using the luminosity-dependent
X-ray bolometric correction of Marconi et al. (2004), and we found a mean value
of C_OIII in the luminosity ranges log L_OIII=38-40, 40-42, and 42-44 of 87,
142 and 454 respectively. We used it to calculate the Eddington ratio
distribution of type 2 SDSS AGN at 0.3<z<0.4 and we found that these sources
are not accreting near their Eddington limit, contrary to previous claims.
