Ground Based Gamma-Ray Telescopes · 2010. 7. 24. · Imaged supernova remnant shells Galaxy is full of VHE pulsar-wind-nebulae Pulsed VHE emission in Pulsars Galactic Center Source:

GroundGround BasedBased GammaGamma--RayRayGroundGround BasedBased GammaGamma Ray Ray TelescopesTelescopespp

Mathieu deMathieu de NauroisNauroisMathieu de Mathieu de NauroisNauroisLLR IN2P3LLR IN2P3--CNRSCNRS--Ecole PolytechniqueEcole Polytechnique

denauroi@in2p3 [email protected]

Victor HESS, 1912

SNRs and origin of cosmic raysg yCosmic ray problem at the origin of the field ∝E−2.7,

lfield

SNRs are believed to be the sources of CREnergetics are OK (10% efficiency) n

mostly protons

eEnergetics are OK (10% efficiency)Robust conceptual framework (DSA)

In the last years, many observation dula

tiofm

agni

tude

progresses

Young SNRs in TeV - Evidence for ultrarelativisitic electrons ar

mod

∝E−3.1,mostly Fe?0

orde

rs o

f

ultrarelativisitic electronsMiddle aged/old SNRs in GeV(Fermi)

sol mostly Fe?30

Open questions:Up to what energy?Wh h d i l i

> 10 orders of magnitudeWhat are the dominant acceleration channels?What acceleration efficiency?

Mathieu de Naurois PPC, July 2010, Torino 2

y(CR content of SNRs)

2 Complementary Techniquesp y qAtmospheric Cherenkov Telescopes:

Small F.O.V.Sampling experiments (Water Cerenkov, Particle Arrays,…)

Low duty cycleHigh rejectionHi h l ti

Large F.O.V.High duty cyclePoor rejectionHigh resolution

Detailed study of a few sources

Poor rejectionPoor resolution

Long term survey instruments

e μ γMilagro Cross Section Schematic

g yNot sensitive enough (yet)

8 m

80 m50 m

φ 2

80 m

φ

φ 2

φ3

φ 4


φ 1

Very High Energy γ-ray WorldMAGIC

TIBETMILAGROSTACEE

y g gy γ y

TIBET

STACEEMILAGRO

ARGO-YBJ

PACT

TACTIC

PACT

GRAPESVERITASTACTIC

HESS CANGAROO

Mathieu de Naurois PPC, July 2010, Torino 4Complementarity between imagers and survey instruments

H.E.S.S. Galactic Plane SurveyyInner part of the Galaxy: |b|<3°, -80 < l < 60°, 1400 h of data + dedicated pointing56 sources, very narrow distribution (RMS(b) ∼0.3°)⇒ M l l l⇒ Molecular gaz scale, young sourcesPopulation: PWN (29), SNRs (9), Binary systems (3), Dark sources, Interacting stellar winds,...


Young (TeV bright) SNRsg ( g )

5 h ll lik bj d d i5 shell-like objects, detected in TeV gamma-raysY hi t i l SNR

RX J1713.7-3946

Young historical SNRsRX J1713.7-3946 Vela JuniorVela JuniorRCW 86

RCW 86SN 1006HESS J1731-347

RCW 86

Unresolved: Kepler (Veritas)

SN 1006

Cas A (Veritas/MAGIC)All show rather clear correlation HESS J1731-347


with non-thermal X-ray emissionHESS J1731 347

X-ray vs γ -ray morphologiesy γ y p gRX J1713.7-3946 SN 1006

B?NE

XMM N tSWH.E.S.S. XMM Newton

2 - 4.5 keV H.E.S.S.


Morphology depends on environment (dense, ...)

Leptonic Acceleratorpradio infrared visible X γ

e UdN×

2BdEdN e ×

dE

Starsrad

eU

dE×dEe

2dN

/d

Dust

ElectronsE2

CMBElectrons

accelerator

Synchrotron Radiation Inverse Compton

Leptonic accelerator probe photon field and magnetic field

Compton


Ratio γ/X is a measure of B

Hadronic Acceleratorradio infrared visible X γ

densityMatter

×p

p

dEdN

E

Stars

dN/d

E

Dust

H d iE2

CMBHadronic

Accelerator

Inverse Comptonπ0→γγS h t R di ti f

Hadronic Accelerator Probe Matter Density

π0→γγSynchrotron Radiation ofsecondary electrons


Hadronic Accelerator Probe Matter Densityγ Spectrum mimic underlying proton spectrum

Magnetic field in SNRsgUchiyama & Aharonian, 2008

Berezhko, Ksenofontov, Völk 2003Bamba et al, 2003;

RX J1713 7 3946

Chandra (X-rays)

Berezhko et al, 2003

Growing evidence for magnetic field amplificationRX J1713,7-3946(X rays)

Thin filaments (SN 1006, ...) indicates rapid electron cooling => B ~ 0.1 mG , but alternate explanation possible (field damping)Synchrotron X-Ray variability gives new probe of B-field in SNRs


Synchrotron X Ray variability gives new probe of B field in SNRs(Fast cooling) => B ~ [0.1,0.5] mG )

What have we learnt ?Young SNR are proved to accelerate particles up to 100 TeV (at least)

Effi i b l 50% (P h k CR i )Efficiency can be as large as 50% (Post shock temperature, CR retroaction) Growing evidence for magnetic field amplification, predicted for hadronacceleration), supports acceleration of hadronsacceleration), supports acceleration of hadrons

No definive proof concerning mechanism

100 TeV difficult to reach with IC (Klein Nishina)100 TeV difficult to reach with IC (Klein Nishina)High B favours hadronic origin, B amplification as wellClose TeV/X correlation in favour of leptonic scenario

Answer might come from GeV region (FERMI) and highest energies (CTA)

L i HadronicLeptonic


Gamma emission from molecular cloud near SNRnear SNR

Non-thermal emission from aNon-thermal emission from a molecular cloud in the proximity of a SNR: interactions of cosmic rays ypenetrating the cloud.CRs contribution from:

galactic background: steep spectrum, steady in time, peaks at GeV energy region;region;runaway from SNR: hard spectrum, variable in timeSuperposition of both: concave spectra, variable in time

Can be use to probe CR overdensityCan be use to probe CR overdensityin clouds

Mathieu de Naurois PPC, July 2010, Torino 12500 yr32000 yr

Gamma emission from molecular cloud near SNRnear SNR

Several cases: W28 (HESS), W51C (MAGIC), IC443 W44 + did t (5 ?)IC443, W44, + many candidates (5 ?)

Galactic centre ridgeWindow on CR propagation

MAGIC

Window on CR propagation

Strong indication of hadronic accelerators

Overdensities of the order of 10Overdensities of the order of 10

FERMI

HESS

FERMIpions

HESS

IC

Bremsstrahlung


Pulsar Wind NebulaeHigh ISMdensity Reverse shock density

crushes PWN

Low ISM@Chandra

Low ISMdensity Blondin et al.

ApJ 563 (2001) 806

Relativistic e-/e+ plasma wind driven by pulsar - confined by SNR of pulsar progenitor

Efficient conversion of rotation power into relativistic particlesAssociated with young pulsars - high ‘spin-down power’


Expansion in non-uniform medium may lead to complex morphology.

Lots of Gamma-ray PWNey

HESS J1640-465 G54.1+0.3

VERITAS

Major galactic TeV source population, Associated with relatively young (<105 year old) j g p p y y g ( y )and energetic pulsars

Extended sources, often displaced from pulsar (expansion into inhomogenous medium)


Generally believed that we see inverse Compton emission of 1-100 TeV electrons

Cooling in actiong

Young electronsYoung electrons

Old Electrons

S t l t i f lSpectral steeping away from pulsar=> First observation of radiative cooling of electrons


Gamma Flux: ∼1% of pulser rotational energy

Crab Pulsar Science 322 (2008) 1221

Crab pulsar detected above 25 GeVth k t i l t i tthanks to special trigger setup

Pulsed emission detected at the 6.4σ i ifi l l (MAGIC)significance level (MAGIC)

First pulsar detection by Cherenkov telescopestelescopesCutoff around 20 GeV favours outer gap modelsgap models


Dark Sources50% of TeV source (same in GeV)Old PWN not seen in other a elengths?Old PWN, not seen in other wavelengths?Old SNRs, interacting with molecular clouds?


Other Galactic sourcesBinary Systems:

PSR B1259-63, HESS J0632+057, Cyg X-1, LSI +61 303Only variable galactic TeV sources Varying, but regularly repeating,

i t l ditienvironmental conditions Lots a good MWL quality data

Massive star clustersAcceleration as the result ofAcceleration as the result of colliding stellar winds collective effects or SNRsWesterlund 2, Westerlund 1, HESS J1614-581, HESS J1848-018


018

Extragalactic Skyg y

TeV Blazars

Radio GalaxiesRadio Galaxies

Starbust Galaxies NGC 4261 @HST


TeV BlazarsActive Galactic Nuclei

S i bl k h lSupermassive black hole surrounded by an accretion diskUltrarelativistic jets (Mpc) Blazars: jets pointing towards the earthHighly variable TeV emission: two model classes:

LeptonicHadronic (through π0 decay)( g y)

Possible connection with UHECRSScience drivers:

M h i f l i i i jMechanisms of relativistic jet productionBlazars as probes of the pextragalactic background light (EBL) through pair absorption (characteristic absorption feature)


(characteristic absorption feature)Tests of Lorentz Invariance

Testing modelsgSimple SSC Model(Blazar Sequence)γ2

Fast variability (down to 1 mn) allow precise tests

B-2

Very small emitting region << RsOne zone SSC excluded by Fγ/FXy γ Xratio∼ 40 TeV Blazars known

H E S S

HESS28th J l 2006

H.E.S.S.arXiv:0706.0797

H E S SCrab Flux

28th July 2006MAGIC: Mrk 501


H.E.S.S.PKS 2155-304

Crab Flux

Radio GalaxiesRadio Galaxies not seen face-on, can be very close

M 87

very closeIdentification of emission regionLess effects of relativistic beamingLess effects of relativistic beaming

M87 (HESS, Veritas, Magic)E i i ( ) l t tEmission (very) close to centerVariability on time scale of days

C A (HESS) 3C 66B (MAGIC/V it )Cen A (HESS), 3C 66B (MAGIC/Veritas)


M 87 Joint campaignp g2007-2008 : VERITAS/MAGIC/H E S S /VLBAVERITAS/MAGIC/H.E.S.S./VLBA campaign

VHE flare accompanied by radio flareVHE flare accompanied by radio flare from BH vicinityHST-1 unlikelyHST 1 unlikelyVLBA resolves jet formation with 30 x 60 Schwarzschild radii

ore

ST-1

ot-A

VLBA

Co

HS

Kno

CoreVLBA

Mathieu de Naurois PPC, July 2010, Torino 24Walker et al., 2007 data

EBL Tomographyg p y

x

γVHEγEBL → e+e-

xx

EBL

Combined limits from all VHE blazars

Direct limits

High redshift blazars allow test of light propagationRecent limits on EBL close to lower limit from galaxy counts Mazin+Raue 2007

Galaxy Counts


Test of Lorentz InvarianceSearch for time lags between energy bands (test of invariance

PKS2155-304: cross-correlation function vs. time lag

Phys Rev Lett 101(2008)170402energy bands (test of invariance of c)Limit: 73 s TeV-1 (95% CL)

Phys. Rev. Lett. 101(2008)170402

Lower limit on Quantim Gravity Scale: EQG > 0.7 x 1018 GeV

PKS2155-304: 200<E<800 GeV Δt/ΔE (s TeV-1) vs

redshiftredshift

MQG > 7% Planck mass

Mathieu de Naurois PPC, July 2010, Torino 26PKS2155-304: E>800 GeV

QG 7% a c ass

Starburts GalaxiesNew class of sources: NGC 253 (HESS) and M82 (Veritas)Very deep observations (100h)Compact starburst region (a few 100pc) at nucleus, ∼0.03/0.2 SN/yrCompact starburst region (a few 100pc) at nucleus, 0.03/0.2 SN/yrVery high cosmic ray and gas density n∼ 600/150 cm-3 vs ∼ 1 in Milky Wayy


ConclusionsExploding field, major discoveries since 2003:

Massive flares of Active Galactic NucleiImaged supernova remnant shellsGalaxy is full of VHE pulsar-wind-nebulaePulsed VHE emission in PulsarsGalactic Center Source: possible accreting SMBHBinary Systems: VHE modulationDiffuse gamma rays from interacting molecularclouds and star-forming regionsStarburst GalaxiesDark AcceleratorsExtra-galactic background light constraintsCosmic Ray Electron and Iron spectra


Still exciting discoveries ahead (MAGIC-II, HESS-II, CTA)

TeV Catalogueg

first source in 1989,∼ 10 sources in 2000

∼100

110 sources today.

Mathieu de Naurois PPC, July 2010, Torino 29 2010Rome 2005

20102000

Backupp


What was not covered

Dark Matter searchesCosmic ray physics (electron flux)Galactic CentreClusters of Galaxies


RX J1713.7-3946 with FERMIS. Funk

Faint source in a complicated regionp gSources to the north coincide with molecular material (CO and HII region)

Hard spectrum in the Fermi-LATpband

Slightly favours simple π0 decaySlightly favours simple π decayNot very conclusive yet


Galactic Centre – Diffuse Emission

2 point like sources (PWNs)Diffuse emission associated to molecular clouds (CS)CR Interaction with interstellar matter? Gamma-rays probe local spectrumHarder than on earth (2.3=> Propagation effects?


CS Lines (dense clouds) pp → π0 → γγ ?

Documents

Ground Based Gamma-Ray Telescopes · 2010. 7. 24. · Imaged supernova remnant shells Galaxy is full of VHE pulsar-wind-nebulae Pulsed VHE emission in Pulsars Galactic Center Source: