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.

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. InstrumentPrevious TeV observations of

SgrA regionH.E.S.S. Observations of the

galactic center regionSpectrumVariabilityMorphology

G 0.9+0.1

Mathieu de Naurois for the HESS CollaborationLPNHE - In2p3/CNRS - Universities Paris VI/VII

[email protected]

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 (105 m2)

>> light collection area

Background Cosmic Rays

> 300 Hz against < 1 Hz for strongest sources Use image shape (rejection factor > 100)

Night Sky Background Short integration time Defines low energy threshold

1

2

3

4

candidatehadron


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


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


Previous TeV observations

10 by Cangaroo (Australia)

Appears stable

Point like at 0.3° resolution

Very steep spectrum(index 4.60.5)

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


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 0.09inconsistent with Cangaroo

Aharonian et al, A&A 425 (2004) L13-L17

0.4 0.3 0.2 0.1 0 -0.1 -0. 2-0.4

-0.3

-0.2

-0.1

0

0.1

0.23EGJ1746-2851

(95%)

Whipple(95%)

CANGAROO(80%)

SgrA*

Arches

Quintuplet

G1G2

XRay1

SNR1

SNR2

L(deg)

B(d

eg)

H.E.S.S.position/extension


2004-Data 35 live hour good quality data, 4 telescopes (system complete) > 30 signal, > 1500

2003 2004


Spectrum Consistent with pure power low

2003 : index 2.21 0.092004 : 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%)

1035 erg. s-1 in 1-10 TeV,similar to other wavelenghtes

H.E.S.S. Preliminary


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


Radio (VLA 90cm) TeV H.E.S.S.

Sgr A*

Sgr A EastSNR

Systematicpointing error

Position Position: 4'' ± 10''

stat ± 20''

syst from Sgr A* (1 pc)

3EG J1746-2851 excluded (>95%)

Integral

Integral


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'

-0,05º

-0,05º

HESS PSF

longitude latitude

Point-like core

Extended tail

Further analysis in progress...

Sgr A East(20 cm)

Radio 20cm

dist. of angular distance betweenSgr A* and direction (squared)


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 1018 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


SNRG0.9+0.1

13 2% of Crab flux

Region around Galactic Center


Supernova Remnant G0.9+0.1

Radio 90 cm (VLA) TeV H.E.S.S.

Gamma rays frompulsar wind, not from supernova shell

H.E.S.S. collaboration, F. Aharonian et al., Astron. Astrophys. 432 (2005) L25-L29


G009+0.1 Spectrum Spectrum compatible with

pure power low

Index 2.4 ± 0.11stat

± 0.2syst

Total gamma energy in 2 1034 erg. s-1(one of faintest source sofar)

Inverse compton on starlightfits spectrum if B ≈ 6 G


Conclusions Very significant (>30 ) 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

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.

Documents

high energy phenomena

energy range

galacic center

event energy resolution

low energy threshold

zenith slide

preliminary slide

h cangaroo marginal