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Active Galactic Nuclei

Active Galactic Nuclei. Ay 16, April 8, 2008. AGN. DEFINITION PROPERTIES GRAVITATIONAL LENSES BLACK HOLES MODELS. WHAT IS AN AGN?. Objects that emit significant amounts of radiation from non-thermal sources (i.e. not stars or dust or thermal gas). In order of discovery:

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Active Galactic Nuclei

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  1. Active Galactic Nuclei Ay 16, April 8, 2008

  2. AGN DEFINITION PROPERTIES GRAVITATIONAL LENSES BLACK HOLES MODELS

  3. WHAT IS AN AGN? Objects that emit significant amounts of radiation from non-thermal sources (i.e. not stars or dust or thermal gas). In order of discovery: Seyfert Galaxies Radio Galaxies Quasars BL Lac Objects LINERS (Low Ionization Emission Regions)

  4. Early History Carl Seyfert & strange emission line galaxies (1943) Birth of Radio Astronomy & discovery of strong sources = radio galaxies (40-50’s) Greenstein & Schmidt & QSO’s (1963) Surveys of Extremely Blue Objects (60-70’s) Surveys at other Wavelengths (70’s > )

  5. SY1 AGN Spectra SY2 QSO

  6. Mean UV QSO Spectrum

  7. LBQSO Spectrum

  8. NGC 4151 Typical SY1

  9. Seyfert 1 galaxy and quasar spectra are dominated by broad line regions, lines often showing doppler velocities of 0.1c Seyfert 2 galaxies spectra are dominated by narrower lines, ~ 1-2000 km/s wide LINER spectra are dominated by stars plus emission lines from multiple ionization states indicative of non-thermal excitation BL Lac spectra show almost no features but strong continua

  10. M87 Core In X-rays

  11. Markarian 231

  12. Markarian 421 BL Lac in an E Galaxy TeV  Source

  13. BL LAC SED’s

  14. Radio Galaxies M87 = Virgo A

  15. M87 in the Radio (VLA)

  16. M87 Central Jet

  17. M87 Jet In 3 bands

  18. Centaurus A Radio on Optical Image

  19. Cygnus A (VLA Conway & Blanco)

  20. Synchrotron Power • = related to kinetic enegy of electron = (1 - (v/c)2)-1/2 = (1 - 2)-1/2 where  = v/c

  21. Synchrotron Spectra

  22. AGN NORMAL LINERS Baldwin, Phillips & Terlevich

  23. Ly Alpha Forest

  24. Eddington Luminosity Largest Luminosity that can pass through a gas in hydrostatic equilibrium : Outward Force of Radiation Pressure > Inward Force of Gravity Gravity dP/dr = -g = -GM/r2 Luminosity dP/dr = -(T/mpc) (L/4r2) T = Thomson Cross section LEdd = 4GMmpc/T = 3.3 x 104 L(M/M)

  25. Gravitational Lensing Deflection of Light passing at a distance b by an object of mass M:  = 4GM/bc2 Bending of light by the Sun: r = 6.96 x 1010 cm M = 1.989 x 1033 g  = 8.47 x 10-6 radians = 1.74”

  26. Gravitational lensing:

  27. 2237+0305 = Einstein’s Cross

  28. Gravitational Redshift Photons lose E as the move out of a gravity well. For a photon E = hc/, “m” = E/c2 = h/c Gravitational Potential E = -GMm/r E = -GMh/cr / = GM/rc2 which generally is pretty small except for NS and BH

  29. Black Holes Curvature around a point mass has a critical radius = Schwarzchild Radius Inside this is a singularity RS = 2GM/c2 In units we know RS = 3.0 km (M/M) Gravitational redshift from RS = 

  30. NGC 4261 X-ray vs Optical

  31. V = 1100 km/s

  32. M87’s central mass: Given the HST observations, what’s the enclosed mass? v = 1100 km/s  ~ 1” D = 16.1 Mpc R = 0.078 kpc (78 pc) GMm/R = 1/2 mV2 for circular orbits M = 0.5 V2R/G G = 4.309 x 10-6 kpc (km/s)2 / M Mcore ~ 1010 M

  33. Reverberation Mapping NGC5548

  34. Lag ~ 20 days Size ~ 20 light days ~ 0.02 pc

  35. Maggorian Relation (Nuker team) Almost every large galaxy has a central BH, and the BH mass is directly correlated with the galaxy’s total bulge mass!

  36. A Unified Model of AGN’s We have come to believe that all AGN are essentially driven by the same phenomena --- a central black hole surrounded by an accretion disk, hot clouds of gas and dust. The disk is hot, 105 K plus. The AGN is powered by accretion onto the BH. And what you actually see is driven by the viewing angle.

  37. Unified AGN ModelBH + Disk + Torus SY2 SY1 BL Lac edge on tilted down the pipe

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