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For refcode 1999MNRAS.309.1017W:
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Copyright by Royal Astronomical Society. 1999MNRAS.309.1017W The emission line-radio correlation for radio sources using the 7C Redshift Survey Chris J. Willott, Steve Rawlings, Katherine M. Blundell and Mark Lacy Accepted 1999 June 24. Received 1999 June 24; in original form 1998 April 17 ABSTRACT We have used narrow emission-line data from the new 7C Redshift Survey to investigate correlations between the narrow-line luminosities and the radio properties of radio galaxies and steep-spectrum quasars. The 7C Redshift Survey is a low-frequency (151 MHz) selected sample with a flux density limit about 25 times fainter than the 3CRR sample. By combining these samples, we can for the first time distinguish whether the correlations present are controlled by 151-MHz radio luminosity L_151_ or redshift z. We find unequivocal evidence that the dominant effect is a strong positive correlation between narrow-line luminosity L_NLR_ and L_151_, of the form L_NLR_ is proportional to L_151_^0.79+/-0.04. Correlations of L_NLR_ with redshift or radio properties, such as linear size or 151-MHz (rest frame) spectral index, are either much weaker or absent. We use simple assumptions to estimate the total bulk kinetic power Q of the jets in FR II radio sources, and confirm the underlying proportionality between jet power and narrow-line luminosity first discussed by Rawlings & Saunders. We make the assumption that the main energy input to the narrow-line region is photoionization by the quasar accretion disc, and relate Q to the disc luminosity, Q_phot_. We find that 0.05<~ Q/Q_phot_ <~ 1, so that the jet power is within about an order of magnitude of the accretion disc luminosity. Values of Q/Q_phot_ ~1 require the volume filling factor {eta} of the synchrotron-emitting material to be of the order of unity, and in addition require one or more of the following: (i) an important contribution to the energy budget from protons; (ii) a large reservoir of mildly relativistic electrons; and (iii) a substantial departure from the minimum-energy condition in the lobe material. The most powerful radio sources are accreting at rates close to the Eddington limit of supermassive black holes (M_BH_~>10^9^ M_sun_), whilst lower power sources are accreting at sub-Eddington rates. Keywords: galaxies: active - galaxies: jets - quasars: emission lines - quasars: general
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