The TeV view of the Galactic Centre R. Terrier APC

The TeV view of the Galactic Centre

R. Terrier APC


2 point like sources: HESS J1745-290 compatible with GC Composite SNR G0.9+0.1

Extended source associated with unid 3EG J1744-3011

HESS > 380 GeV

SF2A 2004

The TeV emission from the Galactic Centre

HESS J1745-290: data up to 2004 total of ~50h live time

(Aharonian et al. 2004 & Aharonian et al 2006)

Flux ~ 10% crab

F(E>1TeV) = 1.87± 0.1 10-12 cm-2s-1

Luminosity: ~ 1035 erg/s

No significant variability detected

Detection confirmed by MAGICobservations (Albert et al, 2005)

Position and spectrum compatible

SF2A 2004




Flux ~ 10% crab

F(E>1TeV) = 1.87± 0.1 10-12 cm-2s-1


Position compatible with Sgr A* (<7'') a = 17h45m39.44s ± 0.6s

d = -29d00'30.3'' ± 9.7''

Statistical error: 10''Systematic pointing error: 20''

SF2A 2004




Flux ~ 10% crab

F(E>1TeV) = 1.87± 0.1 10-12 cm-2s-1


Spectrum: power-law: ~2.25 ± 0.1

No indication of cut-off < 9 TeV

=2.25 +- 0.1

SF2A 2004


Presence of underlying diffuse emission along Galactic plane

90% of total flux due to point-like source

Once diffuse emission removed:Source size compatible with point source : <1.2' (95%CL)

SF2A 2004


HESS J1745-290:

Origin of the emission?:

•Dark matter annihilation

•Non-thermal emission from SgrA east

•Pulsar Wind Nebula

•Emission from particles accelerated around SgrA*

SF2A 2004

Dark matter annihilation at the origin of the Galactic centre TeV emission?

HESS J1745-290 spectrum inconsistent with DM annihilation(Aharonian et al. 2006, PRL)

MSSM & KK models deviate from simple PL above a few TeV

Contribution of DM < 10% of total HESS J1745-290 flux

SF2A 2004


HESS J1745-290:


•Dark matter annihilation: No spectral cut off

•Non-thermal emission from SgrA east



SF2A 2004


HESS J1745-290:



•Non-thermal emission from SgrA east•Position and size constraints



1.2'

VLA 90cm

SF2A 2004

A PWN close to the Galactic Centre

G359.95-0.04 : a candidate PWN at 7'' (0.3pc) of SgrA* (Wang et al 2006)

Non-thermal cometary structure detected in X-rays (1-9 keV)

Luminosity ~ 1034 erg/s Spectral index = 1.94 ± 0.2

10''

Chandra 1-9 keV

Sgr A*

IRS 13

G359.95-0.04

SF2A 2004

A PWN close to the Galactic Centre

G359.95-0.04 : a candidate PWN at 7'' (0.3pc) of SgrA* (Wang et al 2006)

Clear indication of spectral cooling of electrons

Ram pressure confined pulsar wind nebula

SF2A 2004

G359.95-0.03 = HESS J1745-290?

G359.95-0.04 as a TeV emitter (Wang et al 2006, Hinton & Aharonian, 2006)

Position and extension compatible

X-ray flux 1 order of magnitude lower than TeV flux

Huge radiation field due to largenumber of massive stars in central pc

up to UNIR

~ 5 103 eV.cm-3

IC losses are dominant ( LX<< L )

Lifetime of 50 TeV e- ~ 20 yr

SF2A 2004


HESS J1745-290:






•Hadrons, leptons?

SF2A 2004

Particles accelerated in the vicinity of the SMBH?

Several mechanisms of particle acceleration in the central pc have been proposed:

Stochastic acceleration around Sgr A* (Liu et al 2006)Massive stars wind collisions (Quataert & Loeb

2005)Others...

Electrons radiate their energy very quickly in high ambient field

Hadrons accelerated in the vicinity of Sgr A* can diffuse away

Will be confined by stronger mag field in circum-nuclear disk

1.5 pc radius, height ~ 0.5 pcdensity ~ 105 cm-3

5 1045 erg can account for TeV luminosity(Ballantyne et al 2006)

SF2A 2004


HESS J1745-290:





•Emission from particles accelerated around • SgrA*• Stochastic acceleration of p• Massive stars wind collisions

• production in the dense CND : 1’ extended source

And many other possibilities...

SF2A 2004

TeV and hard X-ray sources at the Galactic Centre

IGR J17456-2901:Luminosity: 5 1035 erg/s (20-200 keV)Spectral index: 3.04 ± 0.08

HESS J1745-290:Luminosity: 1035 erg/s Spectral index: 2.25

XMM integrated over 5'

IGR J17456-2901 is not due to: Sgr A* emission from binaries close

to the GC hot plasma emission G359.95-0.04

(Belanger et al, 2006)

Maybe due to: superposition of large number of faint X-ray sources in central 30pc

(Krivonos et al 2006) non-thermal diffuse emission (~10pc)

(Belanger et al, 2006)



Diffuse emission in the Central Molecular Zone (CMZ):

after subtraction of point sources

Diffuse emission from the CMZ

CS emission (49 Ghz) traces dense cores of massive molecular clouds

~ 5 107 Mo of molecular matter in the CMZ

Tsuboi et al 1998

Diffuse emission from the CMZ

CS emission (49 Ghz) traces dense cores of massive molecular clouds

TeV diffuse emission well correlated with giant molecular clouds

produced through p-p collisions

Tsuboi et al 1998

SF2A 2004

Diffuse emission from CMZ supermassive clouds

Diffuse emission spectrum similar to HESS J1745-290:= 2.29 ± 0.1

Not compatible with spectrumexpected from local CRspectral distribution (~ 2.7)

Existence of a local cosmic-rayaccelerator

1049 erg in CR protons in 4-40 TeV band

SF2A 2004


Origin of the CR producing the TeV diffuse emission?

Deficit at l=1.3° suggests propagation effect

CS distribution

Expected profile for 0.8°gaussian CR distribDiffusion of CR injected by young (<10 kyr) accelerator (e.g. Sgr A east)?

(Aharonian et al 2006)

SF2A 2004


Origin of the CR producing the TeV diffuse emission?

Deficit at l=1.3° suggests propagation effect

CS distribution

Expected profile for 0.8°gaussian CR distribDiffusion of CR injected by young (<10 kyr) accelerator (e.g. Sgr A east)?

(Aharonian et al 2006)Diffusion of CR injected by central source HESS J1745-290

(spectral index similarity) (Ballantyne et al. 2007)

In situ CR production in the molecular clouds(Yusef-Zadeh et al, 2006)

SF2A 2004

Diffuse TeV & hard X-ray emission from CMZ

60-80 keV

6.4 keV Ka Fe line

VHE

SF2A 2004

Diffuse TeV & hard X-ray emission from CMZ

6.4 keV line and hard X-ray cloud emission usually interpreted as:

- fluorescence & Compton echo of a 1039 erg/s flare 300

yr ago

- low energy cosmic-rays electrons (LECRE)

Can a single CR population explain TeV & hard X-ray emissions?

Sgr B (Crocker et al 2007)

CR hadrons

secondaries

LECRE

SF2A 2004

Conclusions & future prospects

HESS J1745-290: a point-like stable source compatible with Sgr A* (<7'')Position error due to pointing systematics (~20'')Extension < 1.2‘ radiusNature still unclear (PWN, accelerated particles around Sgr A*)?Link with hard X-ray source unclear

Diffuse emission from the CMZ:Evidence of active CR accelerator in th GC regionCompatible with CR injected by a single SNR 10 kyr agoSingle CR population cannot reproduce hard X-ray and TeV spectra

Future: Currently improving pointing accuracy CTA (>2012) with better PSF and 10 times better sensitivity:

significantly improved size and position constraints improved diffuse emission imaging and morphology

G0.9+0.1G0.9+0.1

Composite SNR

I0 = 5.7 ± 0.7 ± 1.2 10-12 cm-2s-1 (>0.2 TeV)

Γ = 2.29 ± 0.14

Assuming distance of 8.5 kpc:Lγ = 2 1034 erg/sLX = 5 1034 erg/s (PWN)

TeV emission most likely due to PWN

SED well explained by: 6 μG field strong starlight component

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The TeV view of the Galactic Centre R. Terrier APC