超高エネルギーガンマ線天体物理学
Very-high-energy Gamma-ray Astrophysics

森 正樹
東京大学宇宙線研究所
第18回理論懇シンポジウム「高エネルギー天体物理学の最前線」
2005年12月25日(日) - 27日(火)京都大学基礎物理学研究所 湯川記念館 大講演室

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Detection of gamma-rays (1)> TeV gamma-rays2

Atmospheric
Cherenkov telescopes
Cherenkov light from gamma-ray showers
Lateral distribution & Timing distribution

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Imaging Cherenkov Telescopes
Shower profile
Gamma
Regular

Focal plane image
ProtonGamma

Proton

Sharp

DiffuseIrregularα (image orientation angle)

4Detection of gamma-rays (2)BaseSatellite

Gamma-raydetection

DirectIndirect(pair creation) (atmosphericCherenkov)< 30 GeV>100 GeV(→ 100 GeV) (→ 50 GeV)High S/N
Large area
Large FOV
Good Δθ
Small area
Low S/N (CRbkgd.)
High cost

EnergyPros
ConsGround(but imaging overcomes this!)

Small FOV

GroundIndirect(shower array)>3 TeV(→ 1 TeV)
24hr operation
Large FOV
Low S/N (CRbkgd.)
Moderate Δθ
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R.Ong, rapporteur talk, ICRC2005(closed)6

Galactic sources: basics
 Supernova remnants = Origin of CR?
 Energetics – OK (if 10% of ESN goes to CR)
 Maximum energy – Up to “Knee region”
 How much of them?
 Some evidences, which can be ascribed to HE electrons:

where are HE protons?

 Pulsar and pulsar wind nebula (plerions) Crab – “The standard candle”
 Up to a few 10GeV: pulsed+unpulsed
 Above: unpulsed only
 - Unpulsed: SSC (Synchrotron-Self-Compton) model - Where is the cutoff?
 - (Pulsar emission models) Others? Vela, PSR1706-44,…
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Particle acceleration in SNR
Non-linear kinetic theoryt0 = R0/v0; sweep up time

Particle spectrum

Maximum momentum
100 TeV

Berezhko & Voelk, APh 1997

Berezhko & Voelk, APh 2000
Cf. Lagage and Cesarsky 19848

Nuclear gamma-ray flux from SNR

Berezhko & Voelk, APh 19979

Gamma-ray emission from SNR
n=10 cm-3
Dot: IC
Dash: π0Dot-dash:brems

n=1 cm-3(Data: EGRETIC443)

n=0.1 cm-3

e/p = 0.01

0.1

1

Baring et al. 1999 ApJ 513, 311

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Pulsar nebulaA shock is formed when pulsar
wind balances with ambient gas
pressure, and the wind shines bysynchrotron emission by
thermalization

Shock !!

Pulsar windPulsar

K.Mori, talk at ICRR, Dec 2003

Synchrotron emission
By thermalization
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The Crab
Inner ring
=Shock front

Crab (pulsed)

Synchrotron Self Compton
Crab (unpulsed)

Optical + X-ray image
Asahara et al., SPIE 2002

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“Known” galactic sources:
Supernova remnants Crab “The standard candle”
 Well established (many observations since 1989)
 Supernova remnant RX J1713.7-3946
 CANGAROO 2000/2002, H.E.S.S. 2004
 Supernova remnant Cas A HEGRA CT system 2001
 Supernova remnant RX J0852.0-4622
 CANGAROO 2005, H.E.S.S. 2005

 Supernova remnant G0.9+0.1 [H.E.S.S. 2005]
 Possible SNRs: G338.3-0.0, G8.7-0.1, G18.0-0.7,
G23.3-0.3, G25.5+0.0, AX J1813-178 [H.E.S.S. 2005]
 Pulsar PSR 1706-44, Vela pulsar, SN1006
 CANGAROO-I claims, but H.E.S.S. upper limits
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SNR RX J1713.7-3946 (1)Gamma-ray signal = (ON) – (OFF) Detected in X-rays
 Non-thermal X-ray spectrum

Energy spectrum
Significance map

Enomoto et al. Nature 416 (2002) 823 14

SNR RX J1713.7-3946 (2)Hard to explain byemission from electrons(Brems, IC)⇒Emission fromprotons (π0)?
⇒ Cosmic rayorigin?
NANTEN results :Distance ~ 1 kpc

Age ~ 1600yr→ Lp~1048erg ~ 0.001LSN(Fukui et al. PASJ 55, 2003)
Enomoto et al. Nature 416 (2002) 823

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SNR RX J1713.7-3946 (3)0.8°Counter arguments* Reimer & Pohl, A&A 390 (2002) L43* Butt et al., Nature 418 (2002) 489

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H.E.S.S.: Aharonian et al., astro-ph/0511678

SNR RX J1713.7-3946 (4)17H.E.S.S.: Aharonian et al., astro-ph/0511678

SNR RX J1713.7-3946 (5)CO18

H.E.S.S.: Aharonian et al., astro-ph/0511678

SNR RX J1713.7-3946 (6)Electron origin modelProton origin model⇒ Protons favored (?)

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H.E.S.S.: Aharonian et al., astro-ph/0511678

SNR RX J1713.7-3946 (7)20B. Aschenbach, Nature, 396, 141 (1998)

SNR RX J0852.0-4622 [G266.2-1.2, Vela Jr.](1)21

SNR RX J0852.0-4622 (2)CANGAROO-II: Katagiri et al.,ApJ, 619, (2005) L163

H.E.S.S.: Aharonian et al., AA437, L7 (2005)22

SNR RX J0852.0-4622 (3)ICSpectral index 2.2
Crab-like fluxπ0

H.E.S.S. (Hofmann,Cherenkov2005)
CANGAROO-II: Katagiri et al., ApJ, 619,(2005) L163

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W.Hofmann, ICRC 2005, Pune

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H.E.S.S.: F. Aharonian et al., astro-ph/0510397

Other SNRs?

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“New” galactic sources The Galactic center Whipple 2004, CANGAROO 2004, H.E.S.S. 2004
 Pulsar wind nebulae
 MSH15-52 [CANGAROOH.E.S.S. 2005]
 Vela X [H.E.S.S. 2005]
 Pulsar binary PSR 1259-63/SS2883
 H.E.S.S. 2005
 X-ray binary/microquasar LS5039
 H.E.S.S. 2005
 UnID HEGRA J2032+4130
 H.E.S.S. J1303-631
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The Galactic center [Sgr A*]

CANGAROO-II (Tsuchiya etal., ApJ 606, L115, 2004)

H.E.S.S.: W.Hofmann,ICRC2005
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Dark matter signal from Sgr A*?

Horns, Phys.Lett. B607 (2005) 225

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Pulsar wind nebula MSH15-52

PSR 1509-58

CANGAROO-I.:
Sako et al., ApJ 537, 422 (2000)

H.E.S.S.:
Aharonian et al., A&A 435, L17 (2005)
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Pulsar binary PSR 1259-63/SS2883 (1)3.4 year highly
eccentric orbit
around ~10 M~Be starclosest approach~1013 cmor ~20 stellar
radii

Obs.A
Obs.B

(i)

aligned disc to the orbital plane andinteraction throughout the orbit(ii) mis-aligned disc and interaction in the~200-day period around periastron (τ ),during which the radio emission isdepolarized(iii) mis-aligned disc and interaction in two
short periods, [(τ -18 d) ~(τ ~ -8d)] and [(τ+12 d) ~ (τ +22 d)]
2001
MarCANGAROO-II: Kawachi et al., ApJ, 607(2004) 949

2000
Dec30F. Aharonian et al., Astron. Astrophys. 442 (2005) 1Pulsar binary PSR 1259-63/SS2883 (2)HESSJ1303-631

PSR
B1259-63

Feb. 04

early March 04

Apr./May 04
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F. Aharonian et al., Science 309 (2005) 746

X-ray binary/microquasar LS5039
compact 4 (?) M~ object in eccentric 4 day orbit around 20-30 M~ starclosest approach ~1012 cm or ~2 stellar radii

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Extragalactic sources: basics
Active galactic nuclei
Blazars
 Wide-band spectrum – nonthermal Quasars – LBL (RBL) – HBL (XBL) sequence Leptonic models
SSC or EC (External Compton)

 Hadronic models
Infrared photon field: uncertain

Center of galaxies
Radio galaxy,…

Gamma-ray absorption by EBL (Extragalactic Background Radiation)Proton-initiated cascades

Accumulation of dark matter??

Extragalactic background radiation
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Blazars
Beaming factorδ≡1/Γ (1-βcosθ) >1
Observed frequencyν ∝ ν 0δ
Apparent luminosity
L ∝ L 0δ 434

“Known” extragalactic sources Mrk421 (z=0.031)
 First detection in 1992 [Punch et al. Nature 1992]
 Flares in 1994, 1996, 2001, 2002-3

 Mrk501 (z=0.034)
 First detection in 1995 [Quinn et al. ApJ 1996]
 Large flares in 1997

 1H1426+428 (z=0.129)
 First detection in 2001 [Horan et al. 5th Compton 2001]
 Flares in 2001
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Multiwavelength spectra of blazars
TeV

Krawczynski, astro-ph/0309443

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Synchrotron self-Compton modelSynchrotron+ inverse
Comptonmodel works
well→ e± origin(SSC: Synchrotron
Self Compton)

Mrk 421synchrotron

InverseComptonOne-zone SSC model
δ=14, B=0.14G

Takahashi et al. ApJ 542, 2000

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Synchrotron proton blazar model (1)Targetphotonp-synchcascadeμ-synchcascadeπ0cascadeπ±cascadeMuecke et al. APh 18, 2003

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Synchrotron proton blazar model (2)Mrk 421

dF/dE∝Ep-2, δ=10,
B=30G,
γmax,p=4×1010,
Ljet=9×1044erg/s

Muecke et al. APh 18, 2003

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TeV gamma-ray absorption on EBL (1)γTeV+ γIR→ e+ + eMean free path for e+e- pair production

EBL (ExtragalacticBackground Light)

Opacity at z=0.031

Dwek, “Universe Viewed in Gamma-rays”, Kashiwa, 2002

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Protheroe et al. astro-ph/0005349

W.Hofmann, ICRC2005

TeV gamma-ray absorption on EBL (2)

XXXX

9941

W.Hofmann, ICRC2005

EBL SpectraX

measurements

upperlimits

EBL resolved
Universe moretransparent

X
HESS limits

lower limits
from galaxy
countsReference shape42

R.Ong, Rapporteur talk, ICRC2005

AGN summary
SourceRedshift

TypeFirst
detection

M87

0.004

FR I

HEGRA

H.E.S.S.

Mrk 4210.031

BL LacWhippleMany

Mrk 501

0.034

BL LacWhippleMany

1ES 2344+514

0.044

BL LacWhippleHEGRA

1ES 1959+650

0.047

BL Lac7TAMany

PKS 2005-4890.071

BL Lac

H.E.S.S.

PKS 2155-304

0.116

BL LacDurham

H.E.S.S.

H1426+428

0.129

BL LacWhippleMany

H2356-309

0.165

BL Lac

H.E.S.S.

1ES 1218+304

0.182

BL LacMAGIC

1ES 1101-232

0.186

BL Lac

H.E.S.S.

⇒ Reaching further out in redshift!

Confirmation

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TeV gamma-ray absorption on EBL (3)We need many
samples of AGNs atvarious redshifts!

Redshift44

Costamante and Ghisellini A&A 384 (2002) 56

TeV blazar population

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Galactic diffuse gamma-rays (1) EGRET “GeV bump” (Hunter et al. ApJ 1997)

60%
ExcessData

E-2.5
Prediction

E-2.7

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R.Ong, Rapporteur talk, ICRC2005

Galactic diffuse gamma-rays (2)47

F.Aharonian, TAUP 2005

Diffuse gamma-rays along the plane?

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R.Ong, Rapporteur talk, ICRC2005

Diffuse source in Cygnus?

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Gamma Ray Bursts
 Ground-based experiments?
 TeV gamma-rays (afterglow)
 MAGIC a few per year expected Air shower rate Tibet-III

 Single particle rate

1 TeV

Totani ApJ (2000)
Opacity GRAND ARGO-YBJ
 Tibet-III

 Need fast and precise

GRB alerts!

100 GeV50

Dark matter annihilation
Signal enhancement due to `cusp’ structure toward the center?
“Explosive annihilation” by non-perturvative effect

LineContinuum
Photon energy (GeV)

Flux (cm -2sec-1 ) ΔΩ = 10−3
10 −17
10 −1510 −11

10 −1310 −9Hisano, Matsumoto, Nojiri PRL 92 (2004)

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R.Ong, rapporteur talk, ICRC2005“Evolution” of the TeV gamma-ray sky

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R.Ong, rapporteur talk, ICRC2005“Evolution” in number of objects
Logscale53

VERITAS: VERITAS-4 by 2006
New site: Horseshoe canyon,
Kitt Peak, ArizonaSmithonian Inst. etc.

Prototype (Aug ’03)

Nov 2005: New Environmental
Assessment
Oct 2006: Completion of Phase I:
4 telescope array
Then VERITAS-7 in 200X

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Near future?

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International coordination
 Monitoring of time-variable objects (e.g. blazars)
 Multiwavelength observation campaign

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An example: MAGIC & H.E.S.S.
campaign on Mrk 421

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Summary Very high energy sources may contain large varieties,

including both galactic and extragalactic objects.
 Supernova remnants are confirmed to be very-high-energy
particle accelerators: an important evidence of cosmic ray
origin!
 TeV gamma-ray astronomy is becoming an indispensable
field of astronomy.
 The “third generation” Cherenkov telescopes are working
hard (and “fourth” ones are planned)– more fun!
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