+

Review of the present status
on VHE gamma-ray observations
Takayuki Saito
Kyoto University, Hakubi center+2TeV sky

TeVCat: http://tevcat.uchicago.edu/

Galactic
- SNR

24

- PWN

34

- PSR

2- Binary

5- Clusters

5- Star forming region

1Extragal.

Gal/Extragal.
Galactic

Source ClassBlazer
PWN

Extragalacti
c
UnID

UnID

70

70

- LMC

3- Blazer

61

- FRI

4- Starburst gal.

2

SNR
Binary

UNID

34

Total

174

Clusters

+3

Galactic Sourcesn SNR (4 pages)
n PWN (3 pages)
n Pulsar (2 pages)n Binary (4 pages)n Stellar Cluster (1 page)n Galactic Center (1 page)+4Supernova Remnants (24 detected)

n Supernova Remnants: ~400 in the Galaxy (SNRcat).
Ø Shock wave accelerates proton and e- up to PeV.
Ø Thought to be origins of galactic CR.
Ø 4 types,• Shell-type(~250),• Filled (mainly PWN, ~50),• Plerionic Composite (PWN+Shell, ~50)
• Mixed Morphology (Thermal X-ray at center + Radio Shell, ~40)

Type# of VHE srcs

Tev Source

Shell-type

15Tycho, Cas A, SN1006, Vela Jr. etc

Filled-Counted as PWN

Mixed8Morphology

IC443, W28 (4 sources around),
W49B, W51?, CTB37A

PlerionicComposite

G015

1+5

Young SNRs (Shell-type, < 3000 yrs)
X-rays

VHEVela Jr.
(2500 yrs)

In general, Radio, X-ray and VHE are spaciallywell-correlated, showing shell structure.
Leptonic origin? -> Not very clear yet.
Leptonic

Hadronic[Abdo., ApJ 734,2011][Federici+ A&A 577, 2015]

RX J1713(2000 yrs)

RCW86
(2000 yrs)

Both hadronic and leptonic can explain theGeV-TeV spectrum of RX J1713
Expected hadronic morphology
according to proton column density ->SN1006(1000 yrs)

Nakamori et al., in prep
[Hinton & Hoffmann ARAA, 2009]+

6

Older SNRs (M-M, > 3000 years)
Red: HC0+

No correlation with radio shell.
Good correlation with cloud/gas.

IC443(10000 yrs)

VHE Sources

Actually, pion bump was discovered in
IC443 and W44 spectra. Clear Hadronicemission. (W44 not deteded in VHE)

W28

(30000 yrs)

W51C
(35000 yrs)

Science 339, 2013

+

7

Evolution of spectrum~Mixed Morphology~ShellRadio: Shell
X: Shell
VHE: Shell

Radio: Shell
X: Filled (thermal)
VHE: follow gas/mol.

Relation among Age, Spectrum andMorphology to be studied.

+8Pulsar Wind Nebula (34 detected)
n Pulsar Wind Nebula: 7-80 known in the Galaxy
Ø Termination Shock of the pulsar windØ Powered by the pulsar spindownØ Majority of galactic VHE sources

S. Klepsar, ICRC2015
AgePhase# of VHE srcs

Tev Source

0-7k yrs

Free Expansion? 9Crab, G0.9

7k – 30 kyrs

Interaction?

16

CTA 1

>30 kyrs

Relic?

9

+9Population Study
Young Energetic pulsar
has Nebula

S. Klepsar, ICRC2015

Interaction

Free expansionEdot vs Age

TeV Extension vs Age

TeV Luminosity vs Edot

Correlation is not clear, but more or less consistent with theory.

+10

Crab and 3C58
Crab3C58

MAGIC, JHEA 5, 2015••••

Curved spectra measured up to 20 TeV
Existence of the cutoff unclear due tosystematics
Uniform B field (time dep/indep) cannot
reproduce the spectrum precisely.
Spectral enhancement during GeV flare isnot detected.

••••

Young (τ=5kyr) and energetic(log10(Edot) = 37.5, 10% Crab)
Lowest VHE luminosity
Most inefficient conversion to VHE
Conversion to X-ray is OK

+11Pulsars (2 detected)

n Pulsars: ~ 2500 in the Galaxy.
Ø Rapidly rotating neutron star with strong B field.

10-8J0007+7303
CrabGeminga
VelaJ1028-5819
J1048-5832
J1413-6205
J1709-4429
J1809-2329
J1836+5925
Dragonfly
J2229+6114
J0614-3325
Other Pulsars
Crab by MAGIC-2-1s ]Spectra of gamma-ray pulsars

102E F [TeV cmn Gamma-ray pulsars: > 150 in the Galaxy
Ø 1/3 are milisecond pulsars
Ø Some are radio quietØ Curvature radiation from outer magnetosphereØ Spectral break/cutoff at a few GeV
Ø Lowering the IACT threshold is the key

10101010

10-9-10-11-12-13-14103104

VHE Source

AgeSpindown Luminosity

BLC

Crab1260 yrs

4.5e38 erg/s

2e6 Gauss

Vela

11300 yrs

6.9e36 erg/s

9.5e4 Gauss

510
10Energy [MeV]

6

+

12

Crab and Vela pulsar

Crab by MAGIC
1 TeVBroken power law
rather than cutoff PL.
At least Crab emission
should be inverse
Compton, rather thanCurvature radiation.

Vela by HESS IIΓ1EcΓ2

Crab2.0

5~3Vela1.5

3~4Geminga

1.0

1~5[GeV]

+13Binary (5 detected)

n X-ray binary (XB), 299 in the Galaxy.
Ø A binary system containing a compact object withmatter accretion from the companion starn High mass X-ray binary (HMXB), 114 in the Galaxy
Ø XB with O or B type companionn Low mass X-ray binary (LMXB), 185 in the Galaxy
Ø The rest of XBn Microquasar, >15 in the Galaxy
Ø XB with relativistic jets. Some are LMXB, some are HMXB.
VHE Source

periodeMcomp/Msun

LS 5039

Compact + O6.5V star

3.9 days

0.35

23B1259

NS + Be star

3.4 years

0.87

31

LS I 61

Compact + Be star

26.5 days

0.55

12HESS J1018

Compact + O6V star

16.6 days--31

HESS J0632

Compact + B0V star

315 days

0.83

16

TeV J2032

NS + Be star

20-30 yrs

0.94

,riend tion!?
fdloa
Very ategoriz 15)0c
New AS 451, 2
10-20 (MNR

+14LS 5039 & PSR B1259

LS 5039 (3.9 days)<Flux vs orbital phase>
Orbital modulation is seen.

< SED vs orbital phase>
Orbital modulation is seen.

Modulation can be explained by photosphere absorption.

PSR B1259 (3.4 yrs)
<Flux vs orbital phase>
Two peaks near priastron.

Two peaks can be explained interaction between pulsar
wind and inclined circumstellar disc.

+15

LSI +61 303
periastron

Apastron

A possible scenar<Flux vs orbital phase>ioOrbital modulation is seen.

This disc oscillates with 1667 days = superorbital
period.
propeller stateejector state
Low accretion<Apastron flux vs superorbital phase>Superorbital modulation is also seen.

flip-flop

High accretion

Ralfven > RLC

Ralfven < RLC

Pulsar Wind blowPulsar Wind disrupted

Strong shock, & emission

No shock, no emission

+16Microquasors• TeV emission expected from the Jets.
• The following 4 are deeply observed by HESS,MAGIC and Veritas. None of them are detected.
• GRS 1915
• Cyg X-1
• Cyg X-3
• SS 443• Upper limits are a few % Crab level.

• There was a 4 sigma hint of hourly scale flare fromCyg X-1 reported by MAGIC

+17

Stellar/globular clusters (5 detected)

n Massive Stellar Clusters (4 srcs)
Westerlund 1

Westerlund 2

n Globular Cluster: Tarzan 5HESS J1614

HESS J1848• Massive Steller cluster can accelerate particles by
Ø Colliding winds
Ø Collective wind bubble
Ø SN explosions• It is not clear which mechanism is at work for eachsystem

•
•
•
•

The only VHE GC.
Extended large than the GC tidal radius
4 arcmin offset from the GC center
Millisecond pulsars in GC produce leptonic VHE?

+18

Galactic Center
G0.9

Apart from Sgr A* and G0.9,• Point-like source coinciding with radio arc
Ø PWN?
• 0.1 degree source at GC
Ø Radial gradient of CR in central
molecular zone?
• Diffuse emission tracing CS line
• Large Scale diffuse emission

Sgr A*

Central source spectrum shows cutoff at 10 TeV,
while diffuse emission shows no cutoff.

Radio arc+

19

Olaf Reimer, TeVPa 2015

+

20

Extragalactic Sources
n LMC – 50 kpc (1 page)n Star Burst Galaxies – 4 Mpc (1 pages)n AGN• Blazer (z = 0.03 – 0.944)• FR I (4 – 200 Mpc)

+

21

Large Magellanic Cloud (3 srcs)

LMC
•
•
•
•

6 deg
N132 D

Satellite galaxy ofthe Milky way
48.5 kpc away,
10% of Milky way
mass,
5% of Milky waysize••••••N157 B•••

SNR (shell?)
2500 yrs
Bright Sync. Radio
Bright thermal X
Leptonic?
Hadronic?

30 DorCPWN
PSR J0537-6910 init. Crab twin (Edotlarger than Crab!)
Eefficient gammaray emitter, but
spindown power
lost somewhere••
HESS, Science 347, 2015

Superbubble –collectivemechanical outputof massive starcluster into ISM
OB assoc. LH90 is
the power. 5 SN
explosions andstellar winds

+

22Starburst Galaxies (2 detected)
n Galaxy with a high star forming region. CR density is higher there.
n “Diffuse” VHE emission is expected through interaction withinterstellar gas and radiation in the galaxy.
M82NGC 253••••

2.6 – 3.9 Mpc away
Starburst core size ~ a few 100 pc
Supernova rate 0.03 /year in the core
Based on VHE obs. CR density isestimeted to be 2000 times larger
than the Milky way••••

3.5- 3.8 Mpc away
Starburst core size ~ 300 pc
Supernova rate 0.1 – 0.3 /year in the core
Based on VHE obs. CR density isestimeted to be 500 times larger than theMilky way.

“High Supernova rate = High Cosmic ray density” proved.

+23(radio loud) Active Galactic Nuclei
n Supermassive Black hole with a relativistic jet.
n Majority of VHE sources (65 sources, 1/3 of all VHE sources)n Jet pointing at us -> Blazer
Ø 4 types, based on synchrotron peak
• HBL: Peak > 1015 GHz (UV, X)• IBL: 1014 GHz < Peak < 1015 GHz (UV, IR)• LBL: Peak < 1014 GHz (IR)• FSRQ: Radio index >-1.5. Normally peak < 1013
GHz. Line emission visible.
n Jet not pointing at us -> FR ITypeSub-Type# of srcs

TeV SourcesBlazar

HBL46

Mrk 421, 501, PKS 1424 etc.

IBL

83C66A, BL Lac, W Comae, etc

LBL

1AP Librae

FSRQ

53c279, PKS 1441, PKS1510, S4 0954, 4C+21.35

Gravitationally lensed
blazer

1

S3 0218+35

4NGC 1275, PKS0625, M87, Centaurus A

FR I

+24Blazar Spectrum (General)n Picture: Radiative Blob moving toward us.
n In general, one zone SSC model with a Doppler boosting can explain thebroad band SED of BL Lacs (especially HBLs).
n For FSRQs, external photon field or two zone is needed.

One zone SSC model
HBL, Mrk 501, SSC
IBL, 3C66A, SSC+EC

Input parameters.
•••••Broken PL electron spectrum
Electron number density
Blob size
B field strength
Doppler factor

LBL, AP Libre, ??

+25Broad IC peak: e.g. Mrk 421
n IC peak is too broad for SSC?

2 zone model (steady blob + flareing blob)[MAGIC, A&A578, 2015]

External Compton model[Asano, ApJ 780, 2015]

Hadronic model[Abdo, ApJ 736, 2011]+

26

Extreme HBL
1ES 0229, z=0.14• Sync. and IC peak ~2 orders higher
than classical HBLs.
• Very hard at GeV (Bad for Fermi)

1ES 1101, z=0.186

1ES 0347, z=0.188• One zone SSC still works, but input
parameters are largely different
than classical ones. -> Further
understanding of AGN emission
mechanism.
• Substantial EBL absorption. ->Useful for EBL and IGMF study.

+27

Variability
n Variability time scale is a powerful probe for emission region (causality).

FSRQ PKS 1222+21 (z = 0.432)

IC310 (z = 0.0189)

10 min scale variability-> emission region
should be close to BH

5 min variability-> emission region
should be smaller thanSchwarzschild radius.

Black hole Polar Cap model
proposed

No BLR absorption feature-> emission region out of BLR

MAGIC, ApJ 730, 2011

Strong constraints on the emission mechanism

MAGIC, Science 346, 2014

+28

How far we can see?

Gravitationally lensed Blazar
S3 0218+35 (z = 0.944)

FSRQ PKS 1441+25(z = 0.940)

Thanks to the lensing effect and LAT, theflare timing (of the second image)
could be known ~10 days in advanceAlso triggered by LAT detectionThese are the record, important for EBL study.

+29Fanaroff - Riley Class I (4 detected)
n Jet not pointing at us. Thus, no/weak Doppler boosting.
n Emission is not fully dominated by jets.
Cen A,• 3.8 Mpc
• θ=15-80 deg

M87:
VHEM87• 16 Mpc• θ= ~30 deg

radio
NGC 1275• 75 Mpc• θ=30-50 deg

PKS0625• 230 Mpc, z=0.055• θ=50 deg?

NGC 1275•

VHE emission comesfrom the nucleus•

SSC can describe thespectrum•

Hadronic Scenario etc
are also considered.

+30Dark matter indirect Search

+31

Dark Mattern Electrically neutraln Non-baryonicn Stablen Non-relativistic (cold)

No candidate
in Standard modeln Mass 10 GeV to a few TeV
New physics such as SUSY, Kaluza-Klein and etc.
predict weekly-interacting massive particles(WIMPs).
=>The best Dark matter candidates.
In the early hot universe, WIMPs should be in thermal
equilibrium with standard particles.
To explain the relic Dark matter density, crosssection at “freeze-out” should beσannv = 3x10^-26 cm3/s+32

VHE Gamma-rays from WIMPsn WIMP annihilation
X + X -> W + W- -> γ+ …
-> b + b- -> γ+ …
-> τ+τ- -> γ+ …
-> γ+γ-> …
Branching ratio
is particle physics
model dependentdN
1 σ ann v
dN i=J×Br∑ i dEdEdAdt
4π 2m χ2
J= ∫2ΔΩ

γSpectrum fromSM particle is known∫ ρ (l, Ω) dl dΩlosDark matter density profileis also model dependent

VHE observation sets upper limits
on σxx->kk v assumig a certain Jfactor. To convert it toσannv,branching ratio must be assumed.

JCAP 02, 2014

Targets should have
• Large J factor• Low astrophyscal gamma BG+33

Observations:n Galactic Center region by HESS (112 hours)

Dark Matter
profile modelJann~ 1e22 GeV2/cm5(1 deg)Line emission is
expected for γγ

q q- caseγγ case

HESS, PRL 106, 2011

HESS, PRL 110, 2013+34

Observations

n Dwarf Spheroidal Galaxy “Segue 1” by MAGIC (158 hours)
Jann~ 1e19 GeV2/cm5(0.1 deg)

MAGIC,
JCAP 02, 2014
Known to have low baryon,
high DM content

n Fornax Galaxy Cluster by HESS (14.5 hours)
Jann~ 1e17 GeV2/cm5(0.1 deg)

Different Decay Channels
With NFW profileHESS,
ApJ 750, 2012

WW Channel,
DM substructure is assumed.
Sommerfeld effect is taken into accoun

+35Conclusionn VHE astronomy is blooming