Abstract
EXTRAGALACTIC radio sources of high total luminosity usually contain compact emitting regions. These may be coincident with the optical galaxy or quasar, or they may be situated at the outer edges of extended double structures. Radio interferometers sensitive to structures with an angular scale ≤1 arc s have been used at Jodrell Bank to investigate the frequency of occurrence of such compact regions. Large samples of sources, covering a wide range of flux densities, were studied. This work extends to lower flux densities than previous investigations based on observations of sources showing interplanetary scintillations1,2. The frequency of occurrence of compact regions varies as a function of flux density. This is best explained as a cosmological effect involving the strong evolution of source properties with redshift. Several forms of this evolution, similar to those deduced from the radio source counts (see ref. 3), and the relationship between largest angular size and flux density4,5 are discussed elsewhere6.
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ANDERSON, B., PALMER, H., RICHARDS, P. et al. Statistical investigation of compact emitting regions in extragalactic radio sources. Nature 271, 636–638 (1978). https://doi.org/10.1038/271636a0
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DOI: https://doi.org/10.1038/271636a0
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