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JETS

JETS. How are jets observed? How do they interact with their surroundings? The radiation from jets Where do they come from? Tracing them to their source How are they made? Magnetic propulsion Energy source? Accretion or BH spin?. Cygnus A VLA, 21-cm radio emission. RADIO GALAXIES.

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JETS

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  1. JETS • How are jets observed? • How do they interact with their surroundings? • The radiation from jets • Where do they come from? • Tracing them to their source • How are they made? • Magnetic propulsion • Energy source? Accretion or BH spin?

  2. Cygnus A VLA, 21-cm radio emission RADIO GALAXIES lobe hot spot nucleus

  3. CYGNUS A - VLA, 6cm

  4. CYGNUS A - VLA, 6cm undisturbed intergalactic gas “cocoon” (shocked jet gas) splash point backflow bow shock

  5. Abell 4059 (Chandra image)

  6. How do we know the jets are streams of gas? 3C 449 They produce of kind of “skywriting” when interacting with background NGC 1265 a “radio trail”

  7. SS 433 • An X-ray binary, not an AGN • Only case where Doppler shifts give jet speed: 0.26c • Precesses like a top every 164 days • Not known whether neutron star or BH

  8. M87 RADIO MONTAGE F. Owen (NRAO), J. Biretta (STScI), J. Eilek (NMIMT) 1999 Jet already exists at www.nrao.edu/~fowen/M87.html

  9. M87 - 3 billion solar masses

  10. M87’s RADIO HALO www.nrao.edu/~fowen/M87.html

  11. M87’s RADIO HALO www.nrao.edu/~fowen/M87.html

  12. ONE-SIDEDNESS • Many jets appear “one-sided” but lobes are symmetric: Why? • Clues: • “Jet side” is always side coming toward us (how do we know?) • Superluminal motion • Rapid variability ACCEPTED EXPLANATION: RELATIVISTIC MOTION One-sidedness due to beaming (aberration + Doppler) effect

  13. Flash 1 0.2 lt-day Flash 1 Flash 2 1 lt-day Flash 2 0.8c Flashes emitted 1 day apart, received 0.2 days apart. 0.8 lt-day Flash 1 Day 1 Day 0 THE REAL CATCH:RELATIVISTIC MOTION • Suppose source emits flashes 1 day apart, while moving toward you at

  14. 0.8 sin 0.8 cos  Day 1 EXPLANATION OFSUPERLUMINAL MOTION • Consider continuously glowing blob, moving almost directly toward you at Actual dist. traveled: 0.8 lt-day Apparent travel time: (1- 0.8 cos) day Sideways dist: 0.8 sin Apparent sideways speed: 0.8 sin / (1- 0.8 cos) c 0.8c 0.8 lt-day Day 0

  15. HOW ARE JETS MADE? • Hypothesis: Jet axis = rotation axis • What force “pushes” jets? • Gravity? Wrong direction • Centrifugal force? • Gas or radiation pressure? • Magnetic forces? • Energy source? • Accretion? Jet launched from disk • Black hole spin? BH behaves like flywheel • Why are they focused to narrow streams?

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