3C 223
3C 66B
9 nearby FR-I radio galaxies
Centaurus A
Centaurus A
Active Galactic NucleiAbout 10% of galaxies exhibit a very bright and compact core, emitting the large majority of the galaxy's radiation output at all wavelengths. These are labeled "Active Galactic Nuclei" (AGN). AGN are amongst the most powerful sources in the universe. Their total energy output can exceed 1000-10000 times that of the Milky Way. Such an enormous power output is now convincingly explained in terms of relativistic accretion onto a supermassive (M ~ 106-9 solar masses) black hole. Viscous friction heats the accretion disk up to X-ray temperatures. Part of the emitted radiation is further upscattered in energy through inverse Compton scattering due to relativistic electrons very close to the black hole event horizon, whose existence is witnessed by the large and powerful radio/X-ray jets observed, for instance, in radio galaxies. AGN are also amongst the best probes of the theory of relativity, due to the distortion in the X-ray emission line profiles induced by the gravitational potential of the supermassive black hole.AGN show a large variety of phenomenologies. Although several classification schemes exist, depending on their morphological or spectral properties, the most important classes can be summarized as radio galaxies, Blazars & BLLac, and Seyfert galaxies (see corresponding image gallery sub categories for additional info). |
| Radio Galaxies (11 images)
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| 3C 223 | 3C 66B | 9 nearby FR-I radio galaxies | Centaurus A | Centaurus A | more > |
| Seyfert Galaxies (12 images)
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 1H0707-495 |  ESO 198-G24 |  NGC 1068 |  NGC 1365 |  NGC 1808 | more > |
| Quasars (5 images)
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 APM 08279 5255 |  BAL quasar |  PDS 456 |  SDSS J104433.04-012502.2 |  SDSS J143029.88 133912.0 |