Radio Galaxies and Quasars

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Radio Galaxies and Quasars
Powerful natural radio transmitters associated
with Giant elliptical galaxies
Demo
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How we know distances to radio galaxies
redshifts (Doppler shifts) Hubbles Law
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The discovery of quasars a history lesson that
teaches something about the universe

• Some of the brightest radio sources, 3C48, 3C273,
  did not seem to be associated with galaxies, but
  with star-like objects

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Spectra of quasars showed strong emission lines,
highly redshifted
See Figure 24.2 of text
Application of Hubbles Law indicates enormously
distant, Brilliant objects. But where are the
galaxies?
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With Hubble Space Telescope, we have imaged
Quasars
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What are quasars?
Physically what They are
Artistic view of an early quasar
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Whether we see a radio galaxy or quasar depends
on how we view them
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In quasars and radio galaxies, there is a
connection from the small to the extremely large
M87
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M87 at radio wavelengths it exists on many scales
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The Central Engines of quasars and radio
galaxies black holes of 1 - 10 billion solar
masses
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Summary of Quasar Characteristics

• Clearly are a brilliant, energetic phenomenon in
  centers of galaxies
• Quasars are very distant. We see them as they
  were long ago
• Lets look at the distribution of quasar
  redshifts

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Question what does this mean?
7236 quasars
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Extragalactic Astronomy as a Time Machine
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Observations of quasars and radio galaxies allow
us to look out billions of light years into space

• NVSS survey of the sky at radio wavelengths found
  1.8 million sources, almost all of which are
  radio galaxies and quasars
• The Sloan Digital Sky Survey (SDSS) measured
  positions, brightness, and spectra (therefore
  distances) of 675,000 galaxies and 90,000 quasars
• What do we see? What is the shape of the
  universe as a whole?

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Galactic filaments and voids
Figure 25.29 from book
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Why are there filaments and voids in the
distribution of galaxies?