Abstract
The radiative and jet power in active galactic nuclei is generated by accretion of material on to supermassive galactic-centre black holes. For quasars, where the radiative power is by definition very high, objects with high radio luminosities form 10 per cent of the population, although it is not clear whether this is a stable phase. Traditionally, quasars with high radio luminosities have been thought to present jets with edge-brightened morphology (Fanaroff-Riley II—FR II) due to the limitations of previous radio surveys (i.e., FRIs were not observed as part of the quasar population). The LOw Frequency ARray (LOFAR) Two-metre Sky Survey (LoTSS) with its unprecedented sensitivity and resolution covering wide sky areas has enabled the first systematic selection and investigation of quasars with core-brightened morphology (Fanaroff-Riley I—FR). We carried out a Very Large Array (VLA) snapshot survey to reveal inner structures of jets in selected quasar candidates; 15 (25 per cent) out of 60 sources show clear inner jet structures that are diagnostic of FRI jets and 13 quasars (∼22 per cent) show extended structures similar to those of FRI jets. Black hole masses and Eddington ratios do not show a clear difference between FRI and FRII quasars. FRII quasars tend to have higher jet powers than FRI quasars. Our results show that the occurrence of FRI jets in powerful radiatively efficient systems is not common, probably mainly due to two factors: galaxy environment and jet power.
Highlights
Quasars are a class of Active Galactic Nuclei (AGN) that produce immense energy by the fast accretion onto supermassive black holes in the centre of massive galaxies
In a recent study we presented a model of the radio luminosity distribution of the quasars that assumes that every quasar displays a superposition of two sources of radio emission: AGN and star formation [4]
25 per cent show extended structures similar to FRI jets but with the current observations it is not clear whether the bright jet parts are jet knots of an FRI jet or hot spots in FRII jets, our sample size is small we do not see any difference in the range of black hole masses and Eddington ratios of FRI and FRII quasars
Summary
Quasars are a class of Active Galactic Nuclei (AGN) that produce immense energy by the fast accretion onto supermassive black holes in the centre of massive galaxies. An object is called a quasar if it is viewed within a cone of half-angle approximately 45◦. Investigations of quasars are crucial in their own right, and essential for galaxy formation and AGN feedback studies, e.g., [2,3,4]. They allow us to constrain cosmological parameters, e.g., [5] and to investigate the radio emission in low-luminosity (or faint) AGN at moderate/high redshifts, owing to the strong lensing effect which is just one of the powerful tools for studying AGN at moderate/high redshifts [6,7]. For a recent review on radio galaxies and radio-loud quasars we refer the reader to [8]
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