Hard X-Rays & Gamma-Rays Induced by

Ultra High Energy Proton Accelerationin Cluster Accretion Shocks

Susumu InoueFelix AharonianNaoshi Sugiyama (NAO Japan)

accretion(inc. minor merger)

p acceleration to E~1018-19 eV-> p+CMB→ p+ e+e- E~1015-16 eV-> e+e-+B(~G)→syn. E~101-3 keV e+e-+CMB→IC E~TeV

(MPIK Heidelberg)

paper in prep.

shock formation in clustershierarchical, dark matter-driven structure formation→ merger & accretion shocks→ gas heating+ nonthermal particle acceleration→ nonthermal radiation

accretion(minor merger)

e.g. Ryu et al. 03

strong (high M) shock

nonthermal high energy emission from clusters

Miniati ‘03

thermal >100 MeV>100 keV

• primary electron IC

• LE proton p+p->0

• UHE proton-induced pair syn.+ICc.f. Aharonian 02 Rordorf et al. 04

traces shock

traces gas

e.g. Waxman & Loeb 00 Gabici & Blasi 03

e.g. Dar & Shaviv 95 Völk et al. 96 Berezinsky et al. 97

11

10

9

8

720.520.019.519.018.518.017.5

log E [eV]

maximum proton energy in accretion shocks

accel. vs CMB/adiabatic losses

photopion

adiab.

accel.Bs=0.1 G

photopair

c.f. G.Farrar’s talk

e.g. Kang, Ryu & Jones 96 Kang, Rachen & Biermann 97

accel.Bs=1 G

Rs~3.2 MpcVs~2200 km/s

e.g. Coma-like clusterM=2x1015 M(T=8.2 keV)WMAP cosmo. parameters

Bs,eq~ 6 G

Emax~1018-1019 eV

tacc,Bohm=(20/3) rgc/Vs2

shock radius, velocity, etc.

Bohm limit accel.

SNR observationse.g. Bamba et al. 04

proton injection luminosity in accretion shocks

accretion rate & luminosityM(M,z)=fgasfaccVs

3/GLacc(M,z)=fgasfaccGMM/Rs

~2.7*1046 (fgas/0.16) (facc/0.1) erg/s

proton luminosity & spectrumLp(M,z)=fpLacc(M,z) fp=0.1Fp(E,M,z) E∝ -2 exp(-E/Emax)

facc=0.1 normalization from simulation Keshet et al. ‘04

secondary production and emission processesp+CMB→ p+ e+e-

Ep~1018eV E+-~+-Ep~1015eV, L+-~t+-/tinj f(E>1017.7eV) Lp

→ e+e-+B(~G)→ syn. E~keV-MeV e+e-+CMB→ IC E~TeV-PeV

Aharonian 02 code solve pair kinetic eq.

..

emitted luminosity Coma-like cluster

- large radiative efficiency from protons- hard (~-1.5) spectrum

44

43

42

41

40

39151050

log E [eV]

Lp=2x1045

erg/s

Tinj=2x109 yr, R=3 Mpc

n=10-6

cm-3

B=0.1 (G Ep=8 10x 17 )eV

=0.3 B (G Ep=2.5 10x 18 )eV

=1 B (G Ep=8 10x 18 )eV

e+e- syn

e+e- IC

pp0 ( 10)x

emitted flux > TeV absorption by IRB, CMB

Coma-like cluster at D=100 Mpc

-15

-14

-13

-12

-11

-10

14121086420 log E [eV]

e+e- syn

Lp=2x1045

erg/s

Tinj=2x109 yr, R=3 Mpc

n=10-6

cm-3

D=100 Mpc

B=0.1 (G Ep=8 10x 17 )eV

=0.3 B (G Ep=2.5 10x 18 )eV

=1 B (G Ep=8 10x 18 )eV

pp0 ( 10)x

e+e- IC

emitted flux

extended source sensitivity x (~3 deg/ang. res.)

Coma-like cluster at D=100 Mpccaution: point source sensitivities

-15

-14

-13

-12

-11

-10

14121086420 log E [eV]

e+e- syn

Lp=2x1045

erg/s

Tinj=2x109 yr, R=3 Mpc

n=10-6

cm-3

D=100 Mpc

B=0.1 (G Ep=8 10x 17 )eV

=0.3 B (G Ep=2.5 10x 18 )eV

=1 B (G Ep=8 10x 18 )eV

GLAST

HESS

5 5@

INTEGRAL

HXD

NeXT 5 5HXI 'x '

NeXTSGD

pp0 ( 10)x

e+e- IC

model vs Coma data

perhaps not impossible? but need optimismradio something else

-15

-14

-13

-12

-11

-10

-9

151050-5

log E [eV]

Lp=4*1046

erg/s

Tinj=2*109 yr, R=3 Mpc

n=10-6

cm-3

B=1 (G Ep=4.5*1018 )eV=100 D Mpc

EUVE

RXTEBSAX

EGRET

GLAST5 5@

HESS

INTEGRAL

HXD

NeXT 5 5HXI 'x '

NeXTSGD

implications

UHE p-induced emission in cluster accretion shocks

• probe of UHE proton acceleration• probe of accretion shock• probe of magnetic field at cluster outskirts• probe of IR background

summary

• acceleration to E~1018-1019eV plausible• efficient secondary pair production and emission -> sync. (hard X-MeV) detectable by ASTRO-E2/HXD, imagiable by NeXT -> IC (TeV) detectable by HESS and other current IACTs

UHE p-induced emission in cluster accretion shocks

• contribution to extragalactic gamma background• nonlinear effects in proton acceleration• …

more efficient than primary IC, p-p 0

next steps

Grazie mille! Merci beaucoup!

Monte Bianco from Courmayeur 16.03.05