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Galaxies with Active Nuclei

Galaxies with Active Nuclei. Seyfert Galaxies. Broad emission lines of highly ionized atoms. Velocities of matter near center ~ 10,000 km/s  supermassive black holes. 2% of all galaxies are Seyferts. Seyfert 1: very luminous at X and UV, broad emission lines with sharp, narrow cores.

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Galaxies with Active Nuclei

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  1. Galaxies with Active Nuclei

  2. Seyfert Galaxies • Broad emission lines of highly ionized atoms. • Velocities of matter near center ~ 10,000 km/s  supermassive black holes. • 2% of all galaxies are Seyferts. • Seyfert 1: very luminous at X and UV, broad emission lines with sharp, narrow cores. • Seyfert 2: No strong X-ray emission, width of lines greater than normal galaxies but smaller than Seyfert 1. • Rapid fluctation of core brightness  nucleus smaller than a few light minutes. • Brightest have luminosities about100 times that of the Milky Way Galaxy. • Activity due to interactions with othergalaxies.

  3. Radio Galaxies • Double lobed radio sources with a galaxy between the two lobes. • Deformed or interacting with other galaxies. • Complex shapes of some radio lobes related to motions of galaxies. • Due to matter flowing into an accretion disk around a black hole. • Emit synchrotron radiation, indicating the presence of relativistic charged particles moving in a magnetic field. • “Hot” spots at outer extremes of the lobes. Cygnus A 500,000 ly

  4. Centaurus A

  5. Supermassive Black Holes • M87: Accretion disk + jet along rotation axis. 60 ly from center gas orbits at 750 km/s  2.4 billion solar mass black hole. • NGC7052: 300 million solar mass black hole. • Milky Way galaxy: 2.6 million solar mass black hole. • Most galaxies observed so far contain black holes with mass equal to about 0.05 times the mass of their nuclear bulges. • In these galaxies, the nuclear bulge formed first, material with low angular momentum settled into the center and evolved to become a black hole. • Disk material accumulated later.

  6. Unified Model • Supermassive black hole. • Hot, thick inner disk. • Outer disk, cooler, thick, dusty, and doughnut shaped. • Inclination of accretion disk  inclination of the galaxy. • Accretion disk seen edge-on – Seyfert 2. • Accretion disk seen tipped at a small angle – Seyfert 1. • Line of sight into the central cavity – Blazar (BL Lac object) – 10,000 times more luminous than the Milky Way Galaxy.

  7. Quasars (QSO’s) • Initially observed as star-like points of light. • Very large redshifts (as large as 6+): Hubble law  very distant. • First one discovered: 3C48 (redshift = 0.37). • L = 10 – 1000 times the L of a large galaxy. • Rapid fluctuations  small objects. • Quasar “fuzz” with spectrum like that of a normal galaxy (stellar absorption lines) suggests that quasars are distant galaxies. • About 100,000 have been found.

  8. QSO 0957+561: Gravitational Lens Effect Images of QSO 0957+561 (z = 1.4136) Galaxy between Earth and the QSO bends space to produce two images of the QSO (z = 0.36).

  9. Gravitational Lensing by a Cluster of Galaxies 7 Billion Light Years Away

  10. Quasar with Jets and Radio Lobes

  11. LBQS 1429-008 (z = 2.1)(3 Distinct QSO’s in Interacting Galaxies) This false-color composite of the triple quasar system was made using a combination of Keck Observatory's and the European Very Large Telescope's visible and infrared data. S. G. Djorgovski and colleagues, Caltech, and EPFL

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