Wold, M. and Lacy, M. and Armus, L. (2007) The influence of AGN nuclear parameters on the FRI/FRII dichotomy. Astronomy and Astrophysics, 470 (2). pp. 531-538. ISSN 0004-6361 http://resolver.caltech.edu/CaltechAUTHORS:20091118-102624294
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We have investigated the influence of nuclear parameters such as black hole mass and photoionizing luminosity on the FRI/FRII transition in a sample of nearby (z<0.2) radio galaxies from the 3CR catalogue. The sample was observed with medium-resolution, optical spectroscopy and contains some galaxies with unpublished velocity dispersion measurements and emission-line fluxes. The measured velocity dispersions for the sample lie in the range 130-340 km s^(-1) with a mean of 216 km s^(-1). Using the M-σ relation, we convert to black hole mass and find that the black hole mass distribution is identical for FRI and FRII galaxies, with a mean of ≈ 2.5 × 10^8 M_☉. We determine narrow emission-line luminosities from [O III] and [O III] in our spectra, as well as from the literature, and convert them to photoionizing luminosities under the assumption that the gas is ionized by the nuclear UV continuum. Most of the galaxies with FRI morphology and/or low-excitation emission-line spectra have progressively lower black hole masses at lower photoionizing (and jet) luminosities. This agrees with the well-known Ledlow-Owen relation which states that the radio luminosity at the FRI/FRII transition depends on the optical luminosity of the host, L_(radio) ∝ L^(1.8)_(optical), because these two luminosities relate to AGN nuclear parameters. When recasting the Ledlow-Owen relation into black hole mass versus photoionizing luminosity and jet luminosity, we find that the recasted relation describes the sample quite well. Furthermore, the FRI/FRII transition is seen to occur at approximately an order of magnitude lower luminosity relative to the Eddington luminosity than the soft-to-hard transition in X-ray binaries. This difference is also consistent with the Ledlow-Owen relation, which predicts a weak black hole mass dependence in the transition luminosity in Eddington units. We conclude that the FRI/FRII dichotomy is caused by a combination of external and nuclear factors, with the latter dominating.
|Additional Information:||© ESO 2007. Received 24 March 2006; accepted 4 May 2007. The authours thank the referee for comments which helped to improve the original manuscript. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The authors would also like to thank the maintainers of the DRAGN web page (http://www.jb.man.ac.uk/altas) which was used in this work.|
|Subject Keywords:||galaxies: active; galaxies: nuclei; galaxies: jets; X-rays: binaries|
|Official Citation:||The influence of AGN nuclear parameters on the FRI/FRII dichotomy M. Wold, M. Lacy and L. Armus A&A 470 (2) 531-538 (2007) DOI: 10.1051/0004-6361:20065266|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||18 Nov 2009 21:42|
|Last Modified:||26 Dec 2012 11:34|
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