1. 銀河団における超(非)熱的過程 井上 進 （国立天文台） GLAST Suzaku + other topics GeV 100 keV
ZeV CR TA
TeV
CANGAROO III
PeV n
GMRT
m eV
IceCube

2. 2. nonthermal processes in clusters
outline
1. introduction
observational status, structure formation shocks, …
2. nonthermal processes in clusters
primary electron syn+IC
proton-proton p0g, e+- syn+IC, n
UHE proton-g e+- syn+IC
- VHE g-g e+- syn+IC
- structure formation
(merger & accretion) shocks
SN-driven galactic winds
AGN outflows
- UHECR protons+nuclei
3. probing cluster/IGM evolution
IC g-rays
p-p g-rays
4. latest observations
radio
INTEGRAL
HESS

3. observational status: Coma
1. introduction
observational status: Coma
radio
hard X-ray
Giovannini+ 93
4.8s detection
Fusco-Femiano+ 04
Rossetti &
Molendi 04
EUV
no detection
Bowyer+ 04
Eckert+ 07?
gamma-ray
no clear evidence yet
GeV Reimer+ 03
TeV Aharonian+

4. large scale structure formation (SF) shocks
1. introduction
large scale structure formation (SF) shocks
formation of galaxies, groups, clusters...
= hierarchical, dark matter-driven mergers and accretion
→ shock formation → gas heating + particle acceleration
→ nonthermal radiation
clusters are forming this very moment!
thermal emission
shock velocities
cosmological hydro simulations by Ryu+ 03

5. shock acceleration - power-law spectrum dN/dE~∝E-2 for strong shock
very efficient
up to ~50% of kinetic energy
upstream
downstream
shock front
consistent with observations
in-situ: interplanetary shocks, …
SNRs, radio galaxy hot spots, …

6. shock Mach numbers & particle spectra
u1/u M2 -1
Not all SF shocks are equal.
p=1+ =2
(test particle)
major merger
weak (low M) shock
-> soft spectra (p>2), low injection
minor merger, accretion
Ryu+ 03
strong (high M) shock
-> hard spectra (p~2), high injection
also Gabici & Blasi 03
SI & Nagashima 05

7. X-ray observations of cluster merger shocks
(bullet cluster)
Markevitch+ 02
Clowe+ 06
M~3?

8. cluster accretion shocks
(minor merger)
Ryu+ 03
strong (high M) shock
-> hard spectra,
high efficiency
Mach no.
accretion power estimate
Lacc(M)=fgasGMM/Rs
~1046 erg/s (fgas/0.16) (facc/0.1) (M/1015 MQ)5/3 .
difficult to observe in thermal emission!

9. primary electron syn.+IC
2. high energy emission processes in clusters
e.g. Hwang 97
Ensslin & Biermann 98
Loeb & Waxman 00
primary electron syn.+IC
shock-accelerated e-+gCMB→ e-+g L
schematic
spectrum Ec
(tIC~tshock)
Emax
(tIC~tacc)
accretion
E-2
LIC >~ Lsyn if
B < 3mG(1+z)2
merger eV
keV
MeV
GeV
TeV Eg
GeV-TeV
tIC<<tshock traces shock promptly
keV
tIC~<tshock accumulates over cluster history
scales directly with electron injection efficiency
5%? 0.1%?

10. proton-proton p0g, secondary pairs, neutrinos
pCR+pICM→ p0, p+-
p0→2g
p+-→2nm+ne +e+-
e+-+B(~mG)→ syn
e+-+gCMB→ IC
tloss~(nICMkppsppc)-1~100 Gyr (n/10-3 cm-3)-1
tconf ~R2/6D(E)~200 Gyr (R/Mpc)2 (D/1029cm2s-1) (E/GeV)1/3
>>tH
e.g. Völk+ 96, Berezinsky+ 97
traces gas (centrally peaked)
+cosmic rays accumulated over cluster history (SF, RGs, SNe…)
spectra depends on cumulative Mach no. distribution
-> steep (p>2) if merger dominant?

11. p-p p0 and secondary pair emission
pCR+pICM→ p0, p+-
p0→2g p+- → e+-+B(~mG)→ syn, e+-+gCMB→ IC
assume p=2
GLAST
radio: constraints on CR (B-dependent)
Brunetti+ 07
origin of halo?
e.g. Ensslin+ 00, Miniati+ 00
mm-submm: SZ “contamination”? (more interesting?)
keV-MeV: detectable contribution?
Blasi & Colafrancesco 99

12. p-p neutrinos pCR+pICM→ p0, p+- p+- →2nm, ne Murase, SI+, in prep.
Berezinsky+ 97
Colafrancesco & Blasi 98
pCR+pICM→ p0, p+-
p+- →2nm, ne
Murase, SI+, in prep.
IceCube
- promising for near future detectors
- probe of PeV CR confinement
(difficult with g)

13. UHE proton-induced emission from accretion shocks
SI, Aharonian & Sugiyama 2005 ApJ 628, L9
proton Emax
accel. vs CMB losses, lifetime
Coma-like cluster
M=2x1015 MQ
photopair
shock radius, velocity, etc.
Rs~3.2 Mpc
Vs~2200 km/s
Bs,eq~ 6 mG
lifetime
escape
Bohm limit shock accel. time
accel.
Bs=0.1 mG
tacc=(20/3) h rgc/Vs2
h~1 (c.f. SNR observations)
photopion
accel.
Bs=1 mG
shock lifetime(?)
tsl~R/V~2 Gyr < tadiab~6 Gyr
Emax~ eV photopair important
c.f. Kang, Rachen & Biermann 97

14. emitted flux & detectability
Coma-like, D=100 Mpc
p(1019eV) +gCMB→ p+ e+e- (1016eV)
e+e-+B(~mG)→keV, e+e-+gCMB→TeV
5s 100h
large radiative efficiency from protons - hard (G~-1.5) spectrum + rollover - sensitive to B
Suzaku, NeXT
Cerenkov

15. secondary g-g pairs from VHE g sources (pair halos)
Aharonian+ 94
Coppi & Aharonian 97
VHE g
source
Timokhin+ 04
synchrotron
hard X
AGN, SF shocks…
Asano, SI & Aharonian
in prep.
→ 浅野君の講演

16. UHECRs as nuclei from clusters
SI, Sigl, Miniati, Armengaud
PRD (astro-ph/ )
UHECRs as nuclei from clusters
spectrum
anisotropy
100 events>4x1019eV
with EGMF
fCR~
no EGMF
fCR~0.002
1000 events>4x1019eV
composition
consistent with current data
(spectrum <2 sigma)
IF Fe/p similar to Galactic CRs
clear predictions for
Auger, Telescope Array,
JEM-EUSO…
1019 eV
1020 eV

17. latest Auger results composition mixed composition at all E
Unger+ arXiv:
mixed composition
at all E
becoming heavier
at highest E?

18. X-ray scaling relations
3. probing cluster/IGM evolution via nonthermal emission
- gravitational heating (structure formation)
- nongravitational effects
(radiative cooling, conduction, SN/AGN heating…)
entropy vs temp.
X-ray scaling relations
luminosity vs temperature

19. probing structure formation with gamma-rays: warm-hot IGM (missing baryons)
SI & Nagashima, in prep.
(see also astro-ph/ )
WHIM
DIOS
SF shocks →
e-+gCMB→ e-+g
GLAST
Dave+ 01
baryon condensation into stars
-> shock suppression affects
contribution to g background,
g-ray source statistics
g background contribution
important constraint on WHIM,
complementary to thermal lines

20. nonthermal protons: probe of entropy history?
“entropy” of thermal gas
s ∝ ln (T/r2/3)
(shock) heating↑
radiative cooling↓
adiabatic pth/r5/3=const.
nonthermal protons
shock injection↑
diffusive escape↓
(only at high Ep )
adiabatic pCR/r4/3=const.
SN heating
metal+CR injection
AGN heating
CR injection only?

21. radio on large scales: Coma
4. latest observations
radio on large scales: Coma
Kronberg+ arXiv:
DRAO+Arecibo
408 MHz
8 deg field
Beq~ mG

22. INTEGRAL observations of Coma
XMM
2-5 keV/0.5-2 keV
Neumann+ 03
INTEGRAL
18-30 keV
Eckert+ 07 arXiv:
hard X: >10 keV gas? displaced from XMM hotspot

23. INTEGRAL observations of Coma
Effelsberg
1.4 GHz
Deiss+ 97
INTEGRAL
18-30 keV
Eckert+ 07 arXiv:
hard X: nonthermal? matches radio peak
-> Suzaku HXD?

24. INTEGRAL observations of Ophiuchus
Eckert+ A&A submitted
3Msec
>20 keV:
extended source >7’
spectral excess >6.4 s
2 temp: T2>50 keV
power-law: G=
ISGRI
20-40 keV
strongest evidence to date
of cluster hard excess!
need confirmation
from Suzaku HXD

25. INTEGRAL observations of Ophiuchus: implications
Eckert+ A&A submitted
syn IC

26. まとめ： 銀河団における超(非)熱的過程はいろいろありうる （決してあやしくない） 電波・ミリ波・硬Ｘ・GeVガンマ・TeVガンマ・
UHE宇宙線・PeVニュートリノまでそれぞれおもしろい
観測は電波以外まだだが、そろそろ見え始めるかも
高エネ現象としておもしろいだけでなく銀河団・
銀河間物質の進化に対して貴重な新情報も得られるかも
いろいろおもろいので皆研究しよう！