BAT AGN Spectroscopic Survey – III. An observed link between AGN Eddington ratio and narrow-emission-line ratios
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Date
2017-01
Publication Type
Journal Article
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yes
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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.
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published
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Volume
464 (2)
Pages / Article No.
1466 - 1473
Publisher
Oxford University Press
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Subject
Black hole physics; Galaxies: active; Galaxies: nuclei; Quasars: general
Organisational unit
03613 - Lilly, Simon (emeritus) / Lilly, Simon (emeritus)
03968 - Schawinski (SNF-Professur) (ehemalig) / Schawinski (SNF-Professur) (former)
Notes
It was possible to publish this article open access thanks to a Swiss National Licence with the publisher.
Funding
157021 - Piercing Through the Veil: An Optical Spectroscopic Survey of AGN in the Ultra Hard X-rays (SNF)
138979 - From the Dawn of the Universe to Today: The Co-evolution of Galaxies and Black Holes (SNF)
- Uncovering Hidden Black Hole Growth ()
138979 - From the Dawn of the Universe to Today: The Co-evolution of Galaxies and Black Holes (SNF)
- Uncovering Hidden Black Hole Growth ()