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Astronomers Have Discovered A Dying Radio Galaxy

Astronomers Have Discovered A Dying Radio Galaxy

Observing the ELAIS N1 region in the constellation Draco using the GMRT (Giant Metrewave Radio Telescope), South African and Indian astronomers discovered a dying radio galaxy with a redshift of 0.33. Its linear size is about 100 kiloparsec. The Preprint of the article is available on

Radio galaxies are called galaxies that have a much larger radio emission compared to the rest — their radiation power can reach 1045 erg/s, while for ordinary galaxies, including the milky Way, it is 1037-1038 erg/s. At the active stage of evolution, which lasts from 10 to 100 million years, these galaxies have a core, "blades" and jets — this indicates a constant emission of relativistic electrons.

This stage of evolution is followed by a stage of dying — the core activity fades, "blades" and jets gradually disappear. The search for the remains of radio galactic nuclei is based on the registration of their spectrum in low frequencies. This dying galaxy was first discovered in 1987. The study of these objects is of interest for understanding the life cycle of radio galaxies.

Zara Randriamanakoto from the South African Astronomical Observatory and her colleagues from India analyzed archived observations on the Indian GMRT radio telescope (Giant Metrewave Radio Telescope) at 150 and 325 megahertz, as well as data obtained using the VLA (Very Large Array) radio telescope system at 1400 megahertz. In the ELAIS-N 1 region (European Large-Area ISO Survey-North 1) in the constellation Draco, they discovered a new dying galaxy with a redshift of 0.33, which was named J1615+5452. It is assumed that it was an elliptical galaxy in its active phase.

According to researchers, the size of this object is about 100 kiloparsec. The galaxy is an amorphous radio source with no hint of a core, "blades" or jets. Observations of this area in high resolution using VLA did not reveal any other compact details visible in the radio band at all. Most likely, J1615+5452 spent at least thirty percent of her life in the dying stage.

Earlier, we talked about how astronomers found the farthest radio galaxy, as well as about an unusual microquasar of a Z-shaped structure and how a second black hole was discovered in the most famous radio source, Cygnus A.