The bolometric luminosity of type 2 AGN from extinction-corrected [OIII]

Abstract

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