High energy emission from jets – what can we learn?

Amir Levinson, Tel Aviv University

Levinson 2006 (IJMPA, review)

Some open questions

Acceleration and collimation mechanisms? (constraints on Doppler factor from γ-ray and low energy emission, e.g., existing limits for TeV BL)

On what scales dissipation of the bulk energy occurs and how? Internal shocks ? Recollimation shocks ? Dissipation of Poynting flux ? (variability of VHE γ-ray emission + multi waveband obs.)

Jet composition ? (probes: cosmic rays; neutrinos)

Sources of UHECRs and neutrinos ? (probes of new physics?)

If UHECRs are produced in astrophysical sites then emission of high energy neutrinos is expected

The basic picture

Target photons: synchrotron and /or external Electromagnetic: synchrotron, IC, pair production

Hadronic: photopion production, nuclear collisions

MQblazar

Scaling with dimensionless jet parameters

M

Mm BH

BH

L

L

Edd

jj

G m

1042/1

B

1/2

BH

8

jB

magnetic field

3-22

BH

16 cm erg )(m

10

jju

Total energy density

3-22

BH

19 cm )(m

10

jb

bn baryon

density

radius essdimensionl - r

r

s

SourceAGN MQ GRB

j

BHm

(Gauss) 2/1 BB

)cm (erg 3-

2 ju

505 101 42 1010

1~1~ 1210~

810 3 3

Lac BL 10~ 3

parameter

410810 1410

810 1610 2710

5.210

510

X

BBcutoff

ννF

s2/1

MQ - keV 3.0hν AGN - eV 20hν

1s0.5

BB

BB

External radiation field

Intrinsic synchrotron intensityνFν

electrons by thermalemission toscorrespond - νpeak

cooling rapid of casein expected ispeak below νF -1/2

MQ - keV 50

AGN - eV 10hν1

1peak

Energy scales

creationpair - νh

cmε

peak

42e

peakγ,

production photomeson - νh

/2)m(mmε

peak

πNπpeakp,

Threshold energies for interaction with peak synchrotron photons

eV )Γm(106.3ε 1BHjB

16maxp,

r

reBp

L

Confinement limit

• At small radii the proton energy may be limited by losses due to photopion production, and can be well below the confinement limit.

SourceAGN MQ GRB

(eV)ε maxp,

(eV)ε peakp,

energy

2010 1610 2210

2/11210 2/15.1010 2/1710

(eV)ε

(eV)ε maxe,

(eV)ε peak,1110 710 )cm (if

10 2

e

5.1610 5.1210 5.610

175.13 1010 1412 1010 1410

)3.0 ;10( e2 B

observed

observed

rest frame

rest frame

Various energy scales

Electromagnetic emission

Pair production opacity

relevant to 3c279

eeγγ

-spheric radius versus energy:

log

1TeV)/( log

GLAST

external

synchrotron 210

310

410

510

1),(

γjsynsynγ ε

Conclusion: if dissipation occurs over a wide range of radii then flares should propagate from low to high -ray energies.

Will be constrained by GLAST

r(cm)

r0

107 109 1011

1014 1017 1019

MQAGN

GeV)1(r TeV)1(r

,D),ε,s( γνzrsynγ

redshift

measured synchrotron flux

γ- ray energy

Doppler factor

Further constriants from variability using multi-band obs.

z

tDc

1

)(rsynγ

at emission ray - of ty time variabili- t

t),,ε,sD( γν z

Constraints on Doppler factor and radius of emission zone.

Upper limit on neutrino yield

γ-spheric radius for target synchrotron radiation field

Example

TeV 1 ;1.0S 0.03; Z:421Mrk Jy

2.8BH

10/4

32

10/4

316

10/3

3

10/1

2e

B

10m adopting ,s 01

Δt 106 TeV) 1(

cms 01

Δt 103 TeV) 1(r

s 01

Δt

ξ

ξ 35

D

Inconsistent with superluminal motions on pc scale and source statistics.

Jet decelerates ? Other reasons ?

Hadronic emission

321.0

jpbpppp

rn

p + n p + p + - - + e- + e + +

p + n n + n + + + + e+ + e + +

p + n p + n +0 +

Inelastic nuclear collisions

mbn 50~pp

in AGNs, Microquasars (except perhaps for HMXBs where stellar wind may contribute)

May be important in GRBs

1pp

p + + + n + + e+ + e + +

p + 0 + p +

Photomeson production

mbn 1.0~

π - sphere

3 3;mBH 10 ;10m 8BH

log

extsync

maxp,ε

dissipation radius

210

110

310

210

Relations between photo- production and γ pair-production

5.210

p

Same target photons for both processes.

ppp

ths

thpspp

n

n

6,

,

102.1)(

)(

)(

)(

Opacity ratio (target: synchrotron photons)

510210

1BjB 10/mξ

GeV

GeV

TeV

T

eV

Mrk 421 maxp,ε

Opacity ratio (target: external radiation field)

G

eV

GeV

TeV

T

eV

• Regions of significant photo- opacity are opaque to emission of VHE gamma rays.

• Highly variable VHE -ray sources, in particular TeV blazars are not good candidates for km3 neutrino detectors.

• In regions of high photo- opacity, - rays produced through π0 decay will be quickly degraded to GeV energies (in blazars and lower in MQs). Correlation between GeV and neutrino emissions is expected. (Also temporal changes in the -ray spectrum in the GLAST band during intense neutrino emission.)

Conclusions

Neutrino yields (in a km3 detector)

TeV BLLac: < 0.03 event per year for Mrk 421, 501 during

intense flares

MQ: a few events from a powerful flare like the 1994 event seen in GRS 1915

Blazars: ~ 1 event per year at Z~1 for the most powerful

sources (e.g, 3C279). May be constrained further by GLAST.

THE END