The bolometric luminosity of type 2 AGN from extinction-corrected [OIII] No evidence of Eddington-limited sources

Context. There have been recent claims that a significant fraction of type 2 AGN accrete close to 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 estimating the bolometric luminosity in these AGN, is therefore to know the bolometric correction to be applied to L(OIII). A complication arises from the observed L(OIII) being affected by extinction, most likely from dust within the narrow line region. The extinction-corrected [OIII] luminosity (L(OIII)(c)) is a better estimator of the nuclear luminosity than L(OIII). However, only the bolometric correction to be applied to the uncorrected L(OIII) has been evaluated so far. Aims. This paper is devoted to estimating the bolometric correction C(OIII) = L(b)/L(OIII)(c) for deriving the Eddington ratios for the type 2 AGN in a sample of SDSS objects. Methods. We collected 61 sources from the literature with reliable estimates of both L(OIII)(c) and X-ray luminosities (L(X)). To estimate C(OIII), we combined the observed correlation between L(OIII)(c) and L(X) with the X-ray bolometric correction. Results. In contrast to previous studies, we found a linear correlation between L(OIII)(c) and L(X). We estimated C(OIII) using an earlier luminosity-dependent X-ray bolometric correction, 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 found that these sources are not accreting near their Eddington limit, contrary to previous claims.