High energy emission from jets – what can we learn?
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Transcript of High energy emission from jets – what can we learn?
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
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
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 ?
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)(
)(
)(
)(
• 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.