Quasars and Active Galactic Nuclei

Quasars and their kin remain among the most fascinating and mysterious of cosmic phenomena. This collection provides an introduction to the whole subject of active galactic nuclei. It started as the WWW version of a slide set produced for the Astronomical Society of the Pacific; this is still available as 35mm slides in their online catalog. (I don't get royalties for this, but the ASP is always a worthy recipient of your business). Newcomers may want to start with an introduction, note how many colleagues have contributed, or check for an unfamiliar term in the glossary. Since the initial image set, I've added a few more images, often driven by something that was especially useful in the classroom.

New: An essay on quasar astronomy after forty years, being the Director's Cut of an article first written for Astronomy magazine.

The list below points to images and graphics with detailed captions. In each case, click on the image for a bigger (and often more legible) version.

General aspects:

  • Comparing optical spectra of various classes of AGN,
  • The broadband spectrum of Markarian 421 from 20 cm to 1 TeV
  • Variability of active nuclei in the radio, ultraviolet, and X-ray domains

    Seyfert galaxies:

  • A gallery of Seyfert galaxies
  • HST closeups of Seyfert nuclei
  • The broad-band emission spectrum of NGC 4151
  • A wide view of NGC 1275 and its gaseous filaments
  • An HST view of the enigmatic nucleus of NGC 1275
  • Finding the hidden active nucleus of IC 5063 in the infrared
  • Interactions between jets and gas in NGC 4151
  • The radio jet and obscuring torus in NGC 1068
  • The hidden nucleus of NGC 1068 revealed by polarization
  • Color image of the nearby Seyfert galaxy NGC 1068
  • Comparison of Seyfert and non-Seyfert nuclei in HST images

    Radio galaxies:

  • Radio structures of radio galaxies
  • HST closeups of nearby radio galaxies
  • HST images of high-redshift radio galaxies in the early Universe
  • The blowtorch jet of NGC 6251
  • The jet of M87
  • The nucleus and central mass in M87
  • Optical jets in four radio galaxies
  • The nearby powerful radio galaxy Cygnus A
  • The nearby radio galaxy Centaurus A
  • The inner and outer parts of the radio galaxy M87


  • A typical quasar: PKS 1117-248
  • The jet of 3C 273
  • The gravitationally lensed double quasar 0957+561
  • An HST view of the Einstein Cross 2237+030
  • The evolution of quasars with cosmic time
  • Anomalous QSO/galaxy associations and the redshift controversy
  • Quasars as lighthouses: the Lyman alpha forest at low and high redshifts
  • The absorbing galaxy seen in front of 3C 196
  • Quasar host galaxies from HST
  • Superluminal motion in 3C 279
  • The hidden quasar nucleus in the ultraluminous infrared galaxy IRAS 09104+4109

    Usage and reproduction:

    Want to make copies of these for use in teaching? Feel free with appropriate acknowledgements - that's what they're here for. Plan to use them commercially or otherwise make money? That's a bit different - take it up with ASP director Alex Filippenko, since they're handling the distribution of the original 35mm slides and can use all the financial gain they can get. And if you do use these for classes or presentations, I'd appreciate your dropping me a note - I'll feel more motivated next time around if I know that they're actually being used out there.
    Bill Keel's home page | UA Astronomy image collection | UA Astronomy

    Last updates: November 2002