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The Circinus Galaxy, a Type II Seyfert galaxy. Seyfert galaxies are one of the two largest groups of active galaxies, along with quasar host galaxies. They have quasar-like nuclei (very luminous sources of electromagnetic radiation that are outside of our own galaxy) with very high surface brightnesses whose spectra reveal strong, high-ionisation emission lines, [1] but unlike quasars, their ...
Active galaxies such as these are known as Seyfert galaxies in honor of Seyfert's pioneering work. The development of radio astronomy was a major catalyst to understanding AGN. Some of the earliest detected radio sources are nearby active elliptical galaxies such as Messier 87 and Centaurus A . [ 8 ]
Several dozen nearby large galaxies, including the Milky Way galaxy, that do not have an active center and do not show any activity similar to a quasar, are confirmed to contain a similar supermassive black hole in their nuclei (galactic center). Thus it is now thought that all large galaxies have a black hole of this kind, but only a small ...
NGC 3147 has been characterised as a Seyfert II galaxy. It is considered the best candidate to be a true type II Seyfert galaxy, [4] galaxies which feature optical/UV spectrum lacking broad emission lines due to the lack of the broad line region rather than its obscuration, since the nucleus is simultaneously seen unobscured in the X-rays.
The characteristics of Seyfert galaxies were first observed in M77 in 1908; however, Seyferts were defined as a class in 1943. [23] First radio galaxy: Cygnus A: Cygnus: 1951 Of several items, then called radio stars, Cygnus A was identified with a distant galaxy, being the first of many radio stars to become a radio galaxy. [24] [25] First ...
In 2016, astronomers confirmed NGC 1106 contains a Compton-thick [4] active galactic nucleus, after extensive analysis of the galaxy's X-ray spectra. [5] Due to the AGN in its center, it's also classified as a type II Seyfert galaxy, meaning it has the characteristic bright core of a Seyfert galaxy, as well as appearing bright when viewed at infrared wavelengths.
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A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. [1] [2] The word is derived from the Greek galaxias (γαλαξίας), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System.