JETS How are jets observed? Where do they come from? 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 A lobe hot spot nucleus VLA, 21-cm radio emission RADIO GALAXIES lobe hot spot nucleus

CYGNUS A - VLA, 6cm

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

Abell 4059 (Chandra image)

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”

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 MONTAGE Jet already exists at F. Owen (NRAO), J. Biretta (STScI), J. Eilek (NMIMT) 1999 Jet already exists at 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 0.8c Flash 1 1 lt-day 0.8 lt-day Flash 2 0.2 lt-day Day 0 Day 1 Flashes emitted 1 day apart, received 0.2 days apart.

EXPLANATION OF SUPERLUMINAL MOTION Consider continuously glowing blob, moving almost directly toward you at Day 1  0.8 sin 0.8 cos 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

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?