The TeV view of the Galactic Centre
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
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
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
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
Spectrum: power-law: ~2.25 ± 0.1
No indication of cut-off < 9 TeV
=2.25 +- 0.1
SF2A 2004
The TeV emission from the Galactic Centre
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
The TeV emission from the Galactic Centre
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
The TeV emission from the Galactic Centre
HESS J1745-290:
Origin of the emission?:
•Dark matter annihilation: No spectral cut off
•Non-thermal emission from SgrA east
•Pulsar Wind Nebula
•Emission from particles accelerated around SgrA*
SF2A 2004
The TeV emission from the Galactic Centre
HESS J1745-290:
Origin of the emission?:
•Dark matter annihilation: No spectral cut off
•Non-thermal emission from SgrA east•Position and size constraints
•Pulsar Wind Nebula
•Emission from particles accelerated around SgrA*
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
The TeV emission from the Galactic Centre
HESS J1745-290:
Origin of the emission?:
•Dark matter annihilation: No spectral cut off
•Non-thermal emission from SgrA east•Position and size constraints
•Pulsar Wind Nebula
•Emission from particles accelerated around SgrA*
•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
The TeV emission from the Galactic Centre
HESS J1745-290:
Origin of the emission?:
•Dark matter annihilation: No spectral cut off
•Non-thermal emission from SgrA east•Position and size constraints
•Pulsar Wind Nebula
•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)
The TeV view of the Galactic Centre
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
Diffuse emission from CMZ supermassive clouds
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
Diffuse emission from CMZ supermassive clouds
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
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