1. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galacic Center. 2005 1 H.E.S.S. Observations of the Galactic Center  The H.E.S.S. Instrument  Previous TeV observations of SgrA region  H.E.S.S. Observations of the galactic center region  Spectrum  Variability  Morphology  G 0.9+0.1 Mathieu de Naurois for the HESS Collaboration LPNHE - In2p3/CNRS - Universities Paris VI/VII denauroi@in2p3.fr

2. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galactic Center. 2005 2 Atmospheric Cherenkov technique  Shower development in atmosphere  Imagery of the Cherenkov emission in fast camera  Huge effective area (10 5 m 2 ) >> light collection area  Background  Cosmic Rays > 300 Hz against 100)  Night Sky Background  Short integration time  Defines low energy threshold  1 1  2 2 33  4 4  candidate hadron 

3. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galactic Center. 2005 3 The H.E.S.S. Experiment  Array  Situated in Namibia, 1800 asl  4 telescopes, separated by 120 m  Telescope  Mirror area ≃ 107 m 2  Focal length: 15 m (f/d ~ 1.2)  Camera  960 PMTs (0.16º)  5º field of view  Readout integrated in camera body  16 ns integration, 1 GHz sampling  Central Trigger system  Allows for telescope multiplicity requirement

4. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galactic Center. 2005 4 Performances  Gamma-ray parameters  Angular resolution: ≃ 0.1° per event  Energy resolution: ≃ 15%  Energy Range: 100 GeV – 20 TeV  Trigger rate ~ 300 Hz with ~ 10% dead time  Sensitivity  One order of magnitude gain  0.01 Crab (10 -10 erg. s -1. cm -2 ) in ~25 hrs  0.05 Crab in ~1 hr  0.5 Crab in ~75 sec  ~ 25  /mn for a Crab nebula source at zenith

5. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galactic Center. 2005 5 Previous TeV observations  10  by Cangaroo (Australia)  Appears stable  Point like at 0.3° resolution  Very steep spectrum (index 4.6  0.5) CANGAROO 2001/2002 (> 10  Whipple 1995 – 2003 (3.7  Kosack et al. 2004 26 h Cangaroo  Marginal detection (3.7  )  Not idealy located (northern hemisphere), higher threshold Whipple

6. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galactic Center. 2005 6 2003 - HESS observation of Gal. Centre  During commissioning phase: 2 obs (4.7h / 12.2h) with different hardware setup  Signal in both cases (6.0  / 10.2  )  Position consistent with SgrA* (18± 30’’)  Consistent with point source (@ 0.1 °): (Source size < 2,6’ under Gaus. Assumption) however small indication of extension along Gal. plane.  Hard spectrum: 2.21  0.09 inconsistent with Cangaroo Aharonian et al, A&A 425 (2004) L13-L17

7. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galactic Center. 2005 7 2004-Data  35 live hour good quality data, 4 telescopes (system complete)  > 30  signal, > 1500  20032004

8. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galactic Center. 2005 8 Spectrum  Consistent with pure power low 2003 : index 2.21  0.09 2004 : index 2.29  0.05  Compatible flux: 2003 : (2.5  0.2) 10 -8 m -2 s -1 TeV -1 2004 : (2.4  0.1) 10 -8 m -2 s -1 TeV -1 (  @ 1 TeV)  No hint for spectral cutoff below 6 TeV (95%)  10 35 erg. s -1 in 1-10 TeV, similar to other wavelenghtes H.E.S.S. Preliminary

9. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galactic Center. 2005 9 Variability  Spectra 2003-2004 are consistent  2003 and 2004 lightcurves compatible with constant emission  No variability found sofar at any time scale, analysis still in progress 2004 night by night lightcurve, inc. 15% systematic uncertainty HESS Preliminary Significance distribution

10. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galactic Center. 2005 10 Radio (VLA 90cm) TeV H.E.S.S. Sgr A* Sgr A East SNR Systematic pointing error Position  Position: 4'' ± 10'' stat ± 20'' syst from Sgr A* (1 pc)  3EG J1746-2851 excluded (>95%) Integral

11. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galactic Center. 2005 11 Extension Intrinsic Extension along Gal. Plane. (Source centered on Sgr A*) :  b < 1,5' [~4pc] (95% CL)  l = 2,2' (95% CL) + 0,7' - 0,8' -0,05 º HESS PSF longitude latitude Point-like core Extended tail Further analysis in progress... Sgr A East (20 cm) Radio 20cm dist. of angular distance between Sgr A* and direction (squared)

12. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galactic Center. 2005 12 Interpretations  Sgr A* low luminosity  transparent to gamma rays up to (at least) 10 TeV  access to very central engine?  but source confusion problem !!!  Proton acceleration in the BH vicinity (poss. up to 10 18 eV), gamma production by interaction with IR radiation (10 R s ) (Aharonian & Neronov, 2005) or p-p interactions (See talk by Felix Aharonian)  Electron acceleration: Jet-ADAF (Falcke & Markoff, 2000) or Black Hole Plerion powered by the ADAF wind (Atoyan & Dermer, 2005)  Sgr A East  Dark Matter (See Loic Rolland's talk) ... (X ray sources,...) Atoyan & Dermer, 2005 Aharonian & Neronov, 2005

13. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galactic Center. 2005 13 SNR G0.9+0.1 13  2% of Crab flux Region around Galactic Center

14. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galactic Center. 2005 14 Supernova Remnant G0.9+0.1 Radio 90 cm (VLA) TeV H.E.S.S. Gamma rays from pulsar wind, not from supernova shell H.E.S.S. collaboration, F. Aharonian et al., Astron. Astrophys. 432 (2005) L25-L29

15. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galactic Center. 2005 15 G009+0.1 Spectrum  Spectrum compatible with pure power low  Index 2.4 ± 0.11 stat ± 0.2 syst  Total gamma energy in  2  10 34 erg. s -1 (one of faintest  source sofar)  Inverse compton on starlight fits spectrum if B ≈ 6  G

16. Mathieu de Naurois, H.E.S.S.High Energy Phenomena in the Galactic Center. 2005 16 Conclusions  Very significant (>30 σ) signal from the Galactic Center  Position compatible with Sgr A* within 20''  Power-law spectrum, index 2.29  0.05  Indication for extension along galactic plane (preliminary), still under study  No indication of spectral break below 6 TeV (constraints on possible dark matter component)  No indication of variability  Newly detected plerion G0.9+0.1 in the same field of view  2005 observation campaign already started