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Unformatted text preview: y Ways!) Up Radio Lobes: Radio Centaurus A Centaurus A: Ellipitical Galaxy Ellipitical Galaxy with a dust lane with Recent merger? Recent Bright radio galaxy galaxy Radio Lobes Radio Head-Tail Radio Galaxies Some radio galaxies are moving rapidly through gas through (e.g. in a galaxy cluster) The radio lobes are swept back The Radio Galaxies: Radio Unifying ideas Are core-halo and radio halo lobe galaxies the same thing? thing? It may depend on It perspective: perspective: End view: Core-Halo End Side view: Radio Lobes Side Radio Galaxies: Radio Feeding the Beast? Radio Galaxies often visibly show signs of mergers mergers Mergers often result in material flowing to the galaxy nucleus galaxy Do mergers provide fuel for the “engine” of of the active galaxy? the Cygnus A Active Galaxies: Active The Engine Evidence: More light than just stars More Non-starlike spectrum (e.g. radio) Non Rapid variation (small) Rapid Jets and outflows Jets Broad spectral lines: Rapid motions Broad Active Galaxies: Active The Engine The largest galaxies are comparable to 1038 Watts in stars… BUT 10 Active galaxies pack this into a small space space The obvious culprit is a massive black hole massive surrounded by an accretion disk surrounded Active Galaxies: Active The Engine Material falling into Black Holes is super Material heated heated The escape velocity at the event horizon is the speed of light horizon Things falling in achieve close to light speed speed Much of this energy escapes Black Hole Accretion: Black Efficiency How much of E = mc2 can you get? Chemical Fuel 0.0000001 % Chemical Gasoline CO2 and Water Gasoline CO Nuclear fusion 0.7% Nuclear 4 Hydrogen Helium Hydrogen Black Hole Accretion 10% Black Stuff BH Stuff BH Matter-Anti Matter 100% Matter Electron + Positron Gamma Rays Electron Gamma Black Hole: Black The Engine One star has 1030 kg = 1047 Joules One One star per decade could produce 1038 Watts ( Watts = Joules/second) 10 A billion solar mass black hole after 10 billion years billion Black Holes Accretion: Black Getting the Energy out Direct X-rays/ Light Direct rays/ Jets of very fast particles blasted into space blasted Most material falls in – a Most small amount jets out small Black Holes and Accretion Disks: Evidence Disks: Fast rotation in the nucleus of M87 Fast Jet emerges along the axis of rotation as predicted as Viewing Black Holes accretiion in Galaxies accretiion Whether you see Whether mostly the dust accretion torus (IR) or everything up to X-rays depends on rays your viewing angle your Radio Emission: Radio Synchrotron Radiation Accelerating particles in magnetic fields Accelerating emit radio waves emit Seen in: Synchrotrons: Particle Accelerator Labs Synchrotrons: Pulsars (Neutron Stars) Pulsars Radio galaxy jets and lobes Radio Synchrotron Radiation Synchrotron Radiation is non-thermal Radiation A straight line rather than like a black-body straight Quasars Quasars Quasars are “Quasi-Stellar Radio Sources” “Quasi-Stellar” refers to a point-llike source ike like a star like More general name QSO: Quasi-stellar Object More stellar (includes non-radio point-like objects) (includes They are very distant, very powerful active galaxies galaxies Quasars Quasars Quasars were revealed as distant galaxies only recently with very high resolution images resolution 3C 275 Quasars Quasars Quasars initially appeared to have “strange” spectra Actually they are at very high redshifts, redshifts up to billions of light years away up This implies incredible luminosities: This up to 1040-1042 Watts! Watts! Feeding Quasars Feeding 1040 Watts requires 1000 stars per year 10 The largest known black holes are 1 billion solar masses (not 1000 billion) billion Quasars are believed to be temporary phases when the young galaxy’s black phases black hole was unusually voracious hole Summary: Summary: Active Galactic Nuclei: AGN Seyfert Galaxies, Radio Galaxies and Seyfert Galaxies, Quasars are all active galaxies Quasars The origin of the energy output is in the nucleus of the galaxy: an AGN nucleus The power source is a black hole accreting gas and stars radiating at many wavelengths and producing a jet of material of...
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