326 research outputs found
BAT AGN Spectroscopic Survey-III. An observed link between AGN Eddington ratio and narrow emission line ratios
We investigate the observed relationship between black hole mass (), bolometric luminosity (), and Eddington ratio
() with optical emission line ratios ([NII]
{\lambda}6583/H{\alpha}, [SII] {\lambda}{\lambda}6716,6731/H{\alpha}, [OI]
{\lambda}6300/H{\alpha}, [OIII] {\lambda}5007/H{\beta}, [NeIII]
{\lambda}3869/H{\beta}, and HeII {\lambda}4686/H{\beta}) of hard X-ray-selected
AGN from the BAT AGN Spectroscopic Survey (BASS). We show that the [NII]
{\lambda}6583/H{\alpha} ratio exhibits a significant correlation with
( = -0.44, -value=,
{\sigma} = 0.28 dex), and the correlation is not solely driven by
or . The observed correlation between [NII]
{\lambda}6583/H{\alpha} ratio and is stronger than the correlation
with , but both are weaker than the
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 the [NII] {\lambda}6583/H{\alpha} is a useful indicator of
Eddington ratio with 0.6 dex of rms scatter, and that it can be used to measure
and thus from the measured ,
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.Comment: Accepted for publication in MNRAS, 9 pages, 5 figures, 1 tabl
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