Astrophysical Jets

Astrophysical Jets

Robert Laing (ESO)

Galactic black
-
hole

binary system

Gamma
-
ray burst

Young

stellar

object

Jets are everywhere

Jets in Active Galaxies



… with an emphasis on the nearby


Well
-
collimated, bulk relativistic

flows with
Γ

> 5


Powered by accretion onto black

holes M

10
6

-

10
10

M
SUN


Powers can be as high as 10
41

W


Major effects on galaxy formation

and cluster evolution


Efficient accelerators: electrons

10
14

eV; ? protons >10
20

eV

Jets in radio galaxies
–

up to Mpc scales

FRI
–

low power

Deceleration


Morphological

Classification

Correlates with

radio luminosity



FRII
–

high power

Relativistic and

supersonic until

hot
-
spots

Key topics


Where are the emission sites? What are the radiation
mechanisms?


Jet velocity fields


Effects on galaxy formation and cluster evolution


Composition, power thrust


Formation and collimation mechanism



Emission from jets: broad
-
band and on
many scales



Radio
-

TeV Gamma ray

Synchrotron and inverse

Compton
→
broad

electron energy

distribution + B


Protons?

Auger

Cen A
-

X
-
ray synchrotron

Relativistic effects in jets

Energy spectrum

Doppler boosting

Doppler factor

Jet/counter
-
jet ratio

Aberration

v
app
= 30c

Superluminal

motion

Blazars (
θ



0) are bright,

and rapidly
-
varying

Low
-
power radio galaxies are

side
-
on TeV blazars

M87 TeV
-

core or HST
-
1



Look for correlated variability with both core and HST
-
1

Jet velocity fields



Limb
-
brightening and slow

component speeds: gradual

acceleration or fast spine + slow

shear layer?

Kovalev et al.

2007

Acceleration
→ deceleration?



NGC315

Cotton et al. 1999

RL et al. 2006

Hardcastle et al.

2003

Tingay et al.

TeV results require very high
Γ

-

where are jets

accelerated?

Velocity fields on large scales



VLA data




θ

= 58
o





Model

Velocity
β

= v/c: deceleration and
transverse gradients



3C 31

B2 0326+39

NGC 315 3C296

shock

380 kpc

Hydra A

Wise et al. 07

10
61

erg

Environmental Impact

Radio: Lane et al. 04/Taylor

Low Radio Frequency Traces Energy

74 MHz

Wise et al. 07

Feedback from

jets halts cooling

in cores of galaxy

clusters



Quenching of star

formation
→ major

influence on galaxy

formation

(“downsizing”)

Composition?


Electromagnetic


Leptonic (pair plasma)
-

not near black hole


Hadronic (electron
-
proton plasma;
relativistic protons?
)


Composition must change along the jet.

EM → particles

Entrainment of external medium



Faraday rotation?


Bulk Comptonization


Mass, energy, momentum budget



Sunyaev
-
Zeldovich Effect and Radio
Lobe Composition



Pfrommer, Ensslin & Sarazin (2005)

Perseus cluster

(NGC1275/3C84)

Contours: radio

Colour: X
-
ray


Extra pressure

component

Simulation of ALMA

observation of SZ

decrement

in Perseus cluster

Bubble profiles

for different lobe

compositions

Pressure and density

3C31 0326+39 3C296

Mach number and entrainment rate

Stars

Jets must be very light: consistent with electron
-
positron plasma

Power estimates from cavities



Krichbaum et al.
2006

174 R
s

Limits on collimation from mm VLBI

Jet base 70 x 20 R
S

M87

86GHz

Magnetic collimation?



Coming shortly .... we hope

LWA, eLOFAR

mm

VLBI

ALMA

GLAST

VSOP
-
2

EVLA

eMERLIN