One leading theory said that Seyfert galaxies have been disturbed by close encounters with neighboring galaxies, thus stirring up their gas and bringing more of it within the gravitational reach of the black hole. CREDIT: Kuo et al., NRAO/AUI/NSF Click on image for more graphics. Optical/ Radio Comparison Visible-light (left) and radio (right) image of galaxy pair: Radio image shows gas streaming between galaxies. However, they could not see how the material is started on its journey toward the black hole. Astronomers have long suspected that the extra-bright cores of spiral galaxies called Seyfert galaxies are powered by supermassive black holes consuming material. Radio-telescope images have revealed previously-unseen galactic cannibalism - a triggering event that leads to feeding frenzies by gigantic black holes at the cores of galaxies. Radio Telescopes Reveal Unseen Galactic Cannibalism
We find that the core RLF is obviously different from the total RLF at the 408 MHz band which is mainly contributed by extended lobes, implying that the cores and extended lobes could not be co-evolving at radio emission. Both results are consistent and show that the comoving number density of radio cores displays a persistent decline with redshift, implying a negative density evolution. Based on the combined sample with incomplete core flux data, we also estimate the core RLF using a modified factor of completeness. Using core flux density data of the complete sample 3CRR, we investigate the core RLF at 5.0 GHz. Our results support a luminosity-dependent evolution. Using a large combined sample of 1063 radio-loud AGNs selected at low radio frequency, we investigate the RLF at 408 MHz of steep-spectrum radio sources. The work in this paper aims at determining the evolution and possible co-evolution of radio-loud active galactic nuclei (AGNs) and their cores via their radio luminosity functions (i.e., total and core RLFs, respectively).
On the Evolution of the Cores of Radio Sources and Their Extended Radio Emission
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