BAT AGN Spectroscopic Survey - III. An observed link between AGN Eddington ratio and narrow-emission-line ratios
Date Issued
2017
Author(s)
Oh, Kyuseok
•
Schawinski, Kevin
•
Koss, Michael
•
Trakhtenbrot, Benny
•
Lamperti, Isabella
•
Ricci, Claudio
•
Mushotzky, Richard
•
Veilleux, Sylvain
•
Berney, Simon
•
Crenshaw, D. Michael
•
Gehrels, Neil
•
Harrison, Fiona
•
•
Soto, Kurt T.
•
Stern, Daniel
•
Treister, Ezequiel
•
Ueda, Yoshihiro
Abstract
We investigate the observed relationship between black hole mass (MBH), bolometric luminosity (Lbol) and Eddington ratio (λEdd) with optical emission-line ratios ([N II] λ6583/Hα, [S II] λλ6716, 6731/Hα, [O I] λ6300/Hα, [O III] λ5007/Hβ, [Ne III] λ3869/Hβ and He II λ4686/Hβ) of hard X-ray-selected active galactic nuclei (AGN) from the BAT AGN Spectroscopic Survey. We show that the [N II] λ6583/Hα ratio exhibits a significant correlation with λEdd (RPear = -0.44, p-value = 3 × 10-13, σ = 0.28 dex), and the correlation is not solely driven by MBH or Lbol. The observed correlation between [N II] λ6583/Hα ratio and MBH is stronger than the correlation with Lbol, but both are weaker than the λEdd correlation. This implies that the large-scale narrow lines of AGN host galaxies carry information about the accretion state of the AGN central engine. We propose that [N II] λ6583/Hα is a useful indicator of Eddington ratio with 0.6 dex of rms scatter, and that it can be used to measure λEdd and thus MBH from the measured Lbol, even for high-redshift obscured AGN. We briefly discuss possible physical mechanisms behind this correlation, such as the mass-metallicity relation, X-ray heating, and radiatively driven outflows.
Volume
464
Issue
2
Start page
1466
Issn Identifier
0035-8711
Ads BibCode
2017MNRAS.464.1466O
Rights
open.access
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