NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-25 T02:56:31 PDT
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For refcode 1991A&A...242...49J:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
1991A&A...242...49J Relationship between Fe II and radio emission in active galactic nuclei M. Joly DAEC, Observatoire de Meudon, F-92 195 Meudon Cedex, France Received January 2, accepted July 27, 1990 Abstract. We have collected Fe II data for about 200 active galactic nuclei (AGN), including Seyfert 1 galaxies, quasars and Broad-Line Radio Galaxies. Using a sub-sample of about hundred AGN for which radio data are available, we have studied the relation between Fe II and radio emission. More than half of the Fe II-emitting AGN appear to be radio loud. However, the most extreme Fe II emitters might be preferentially radio quiet. From our sample we find that there is a correlation between Fe II {lambda}4570 and the ratio R of the radio core flux density to the extended radio lobe flux density. Furthermore, we find that strong Fe II emission occurs in AGN over the whole range of R. The correlations between R and W (Fe II {lambda}4570) or Fe II {lambda}4570/H{beta} can probably not be explained by inclination effect. Indeed, H{beta} and Fe II{lambda}4570 are likely to be emitted by the same region and would therefore vary in the same way with inclination, while the equivalent width can vary with R only if we admit that the underlying continuum is independent of inclination, excluding any contribution of an accretion disc. We find also that on the average, the radio-loud strong Fe II emitters have higher radio core luminosity than the weak Fe II emitters. This may be interpreted as a proof that the emission region of Fe II is closely associated with the jets responsible for the compact radio source. In this model the heating of the gas is due to internal shocks. Now, computations of the Fe II emission in the region in collisional equilibrium show that Fe II {lambda}4570/H{beta} is proportional to the density and inversely proportional to the temperature of the gas. The observed correlation is thus explained if the higher the radio power, the denser the emitting region. For low-power radio sources, the mechanical heating and therefore the temperature of the gas should be low, strengthening the Fe II emission compared to the Balmer lines. It would account for the radio quiet class of extreme Fe II emitters. Key words: galactic nuclei - broad line region - Fe II - statistics
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