JETS
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Transcript of JETS
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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?
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RADIO GALAXIES
Cygnus AVLA, 21-cm radio emission
hot spot
lobe
nucleus
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CYGNUS A - VLA, 6cm
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CYGNUS A - VLA, 6cm
bow shock
undisturbed intergalactic gas
“cocoon” (shocked jet gas)
splash point
backflow
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Abell 4059 (Chandra image)
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How do we know the jets are streams of gas?
3C 449They produce of kind of “skywriting” when interacting with background
NGC 1265a “radio trail”
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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
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M87 RADIO MONTAGEF. Owen (NRAO), J. Biretta (STScI), J. Eilek (NMIMT) 1999
Jet already exists at
SunBH MM 9103~
mR 100
www.nrao.edu/~fowen/M87.html
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M87 - 3 billion solar masses
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M87’s RADIO HALO
www.nrao.edu/~fowen/M87.html
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M87’s RADIO HALO
www.nrao.edu/~fowen/M87.html
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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
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THE REAL CATCH:RELATIVISTIC MOTION
• Suppose source emits flashes 1 day apart, while moving toward you at c8.0
0.8c
Flash 1
1 lt-day
0.8 lt-day
Flash 2
Flash 1
Flash 2
Flash 10.2 lt-day
Day 0 Day 1
Flashes emitted 1 day apart, received 0.2 days apart.
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EXPLANATION OFSUPERLUMINAL MOTION
• Consider continuously glowing blob, moving almost directly toward you at c8.0
0.8c
0.8 lt-day
Day 0
Actual dist. traveled: 0.8 lt-day Apparent travel time: (1- 0.8 cos) daySideways dist: 0.8 sin Apparent sideways speed:
0.8 sin / (1- 0.8 cos) c
Day 1
0.8 sin
0.8 cos
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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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