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Using Narrow Emission Lines to Test Physical Models Unifying AGNs

Published online by Cambridge University Press:  07 August 2017

Steve Rawlings  and
Richard Saunders
Steve Rawlings
Affiliation:
Mullard Radio Astronomy Observatory, Cavendish Laboratory, Cambridge CB3 0HE, England
Richard Saunders
Affiliation:
Mullard Radio Astronomy Observatory, Cavendish Laboratory, Cambridge CB3 0HE, England

Extract

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We contend that quantitative measurements of nuclear narrow emission line strength can strongly constrain models that unify AGNs. The reasons for the importance of narrow-line luminosity LNLR are:

  1. a) The lines normally arise via photoionisation by the integrated UV/soft X-ray luminosity LPHOT of the central source. Thus LNLR is directly linked to a physical quantity intimately connected with the central engine but not observable from the ground. For constant covering factor we expect an approximate proportionality between LNLR and LPHOT; this has been confirmed observationally for AGNs by estimating LPHOT from either optical non-stellar luminosity or effective ionisation parameter.

  2. b) NLRs are far enough from the photoionising source to avoid the excessive obscuration that appears able to attenuate broad-line and continuum emission. Narrow-lines are radiated isotropically unlike, eg, the radio core which may be Doppler boosted. Their variability timescale of 103–4 years is intermediate between those of LPHOT and any large-scale radio emission.

Type
Part 5: Structure of the Central Object and NLR
Information
Symposium - International Astronomical Union , Volume 134: Active Galactic Nuclei , 1989 , pp. 305 - 307
Copyright
Copyright © Kluwer 1989 

References

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