The prevalence of Fanaroff–Riley type I radio quasars |
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Authors: | Ian Heywood Katherine M. Blundell Steve Rawlings |
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Affiliation: | University of Oxford Astrophysics, Keble Road, Oxford OX1 3RH |
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Abstract: | We present deep, multi-Very Large Array configuration radio images for a set of 18 quasars, having redshifts between 0.36 and 2.5, from the 7C quasar survey. Approximately one quarter of these quasars have Fanaroff–Riley type I (FR I) type twin-jet structures and the remainder are a broad range of wide angle tail, fat double, classical double, core-jet and hybrid sources. These images demonstrate that FR I quasars are prevalent in the Universe, rather than non-existent as had been suggested in the literature prior to the serendipitous discovery of the first FR I quasar a few years ago, the optically powerful 'radio-quiet' quasar E 1821+643. Some of the FR I quasars have radio luminosities exceeding the traditional FR I/FR II break luminosity; however, we find no evidence for FR II quasars with luminosities significantly below the break. We consider whether the existence of such high-luminosity FR I structures is due to the increasingly inhomogeneous environments in the higher redshift Universe. |
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Keywords: | galaxies: active galaxies: evolution galaxies: jets quasars: general radio continuum: galaxies |
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