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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?. Cygnus A VLA, 21-cm radio emission. RADIO GALAXIES. - PowerPoint PPT Presentation
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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?
RADIO GALAXIES
Cygnus AVLA, 21-cm radio emission
hot spot
lobe
nucleus
CYGNUS A - VLA, 6cm
CYGNUS A - VLA, 6cm
bow shock
undisturbed intergalactic gas
“cocoon” (shocked jet gas)
splash point
backflow
Abell 4059 (Chandra image)
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”
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
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
M87 - 3 billion solar masses
M87’s RADIO HALO
www.nrao.edu/~fowen/M87.html
M87’s RADIO HALO
www.nrao.edu/~fowen/M87.html
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
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.
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
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?
