ACTIVE GALACTIC NUCLEI

Active galactic nuclei (AGN) are galaxies that have very energetic central regions, due to either the presence of a black hole or star formation activity at the core of the galaxy. Three main types of AGN are quasars, ("quasi-stellar objects" or QSOs), which are very compact objects that resemble stars in optical images; Seyfert galaxies, characterized by fluctuations in brightness at their cores; and radio galaxies, which emit massive jets of gas powered by black holes at their cores. In general, AGN have six main properties: (1) very compact angular size; (2) high luminosity, many billions of times brighter than our own Sun; (3) Continuum emission from the core, meaning that the objects emit radiation at a range of wavelengths from radio to x-ray; (4) emission lines; (5) variability of the continuum and spectral line emission, and (6) strong emission of radiation at radio wavelengths. Many of the images on these pages are Double Radio Sources Associated with Galactic Nuclei (DRAGNs), which are large-scale double radio sources produced by jets that are launched by processes in AGN. You can learn more about such sources at this web site.

Click on any Sub-category name below to view all the images in that sub-category, or click any thumbnail to view the details of that image. Other images of AGN can be found in the VLBA 2cm Survey of Compact Radio Sources and the Jodrell Bank Atlas of DRAGNs. Visit this non-NRAO website for more information on active galactic nuclei.


Quasars (20 images)
PKS+B2300-189
PKS B2300-189
3C279
3C279
M87
M87
Z+227-012
Z 227-012
4C+29.45
4C 29.45
3C175
3C175

Radio_Galaxies (36 images)
NGC5128
NGC5128
3C83.1
3C83.1
3C75
3C75
3C75
3C75
M87
M87
Cygnus A
Cygnus A

Seyferts (18 images)
ngc262
ngc262
ngc4151
ngc4151
ngc4151
ngc4151
ngc4258
ngc4258
3C120
3C120
3C84
3C84

Other_AGN (2 images)
PKS 1519-273
PKS 1519-273
8C 1316+708
8C 1316 708

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