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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 ...
The most accepted theory for the energy source of Seyfert galaxies is the presence of an accretion disk around a supermassive black hole. The supermassive hole in the nucleus of NGC 7682 is estimated to be 17–62 million (10 7.56 ± 0.33 ) M ☉ . [ 7 ]
Seyfert's Sextet is a group of galaxies about 190 million light-years away [2] in the constellation Serpens. The group appears to contain six members, but one of the galaxies, NGC 6027d , is a background object (700 million light years behind the group) and another "galaxy," NGC 6027e , is actually a part of the tail from galaxy NGC 6027 .
1ES 1927+654 was first cataloged during the Einstein Slew Survey, which aimed to identify X-ray sources in the sky. It was classified as a Seyfert galaxy due to its emission-line features. [15] A dramatic increase in brightness was detected in 2017, with the galaxy brightening by a factor of about 40 in the ultraviolet spectrum.
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It is classified as a Type 2 Seyfert galaxy [4] and was discovered by Francis Leavenworth in 1886. [1] [7] The galactic plane is inclined at an angle of 73°, giving it an oval, nearly edge-on appearance with the major axis aligned along a position angle of 150°. [4] Seyfert galaxies such as NGC 5793 are known to house megamasers.
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.
Second, this galaxy has an active nucleus. This caused Carl Seyfert in 1943 to include it in his list of galaxies, which are now called Seyfert Galaxies. However, NGC 3077, though an emission line galaxy, is today no longer classified as a Seyfert galaxy. NGC 3077 was discovered by William Herschel on November 8, 1801. He remarked that "On the ...