Galaxies with Active Nuclei

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Galaxies with Active Nuclei

• It has been found that many galaxies are actively
  emitting energy in many wavelengths
• The Milky Way is not one of them
• They are referred to as active galaxies and they
  have active galactic nuclei this is where the
  energy is coming from
• Many of them are radio galaxies

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• One type of active galaxies are the Seyfert
  galaxies
• They are all spiral galaxies with extremely
  bright nuclei
• The material in the centers of the galaxies is
  moving at about 10,000 km/sec
• This tells astronomers that they contain
  supermassive black holes
• How?
• The cores of the brightest Seyferts will produce
  hundreds of times more energy than the entire
  Milky Way

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Seyfert Galaxy
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• Some of the galaxies were found to be double
  lobed radio galaxies
• This is where a galaxy is found to have 2 radio
  lobes blasting out of them
• All of the evidence says that they contain
  supermassive black holes that drive the lobes

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Cygnus A, a double lobed radio galaxy
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• Sometimes it appears that the jets are pointed
  directly at us
• When this happens we see what we call a blazar
• All of these strange objects seem to have one
  thing in common a supermassive black hole
• Where did they come from?
• It is thought that as the galaxy forms, a small
  amount of mass sinks to the center and forms a
  supermassive black hole

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• One of the really bizarre objects are the quasars
• It stands for quasi-stellar radio sources
• In the 1960s radio sources were discovered that
  showed points of light in the visible spectrum
• The first of these were 3C48 and 3C273
• The spectra of objects was really strange and
  they couldnt figure them out
• It was discovered that the spectra was shifted by
  a significant amount

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• The hydrogen lines of 3C273 had been shifted
  15.8 from normal
• That meant it was moving at 15.8 the speed of
  light or 47,400 km/sec away from us
• 3C48 had its hydrogen lines shifted 37 so it was
  moving at 111,000 km/sec
• They are far away and are 10 to 1000 times more
  luminous than the Milky Way
• They are unique because they are very small, very
  far away and very bright

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• 3C273 must be about 677 Mpc away from us ( 2
  billion ly)
• About 100,000 quasars have been discovered
• By studying them we have determined that they are
  found within galaxies