Very high energy gamma-rays from the Galactic Centre measured by H.E.S.S

Loïc Rolland SISSA 2005 – Trieste, 2005 1

Very high energy gamma-rays

from the Galactic Centre

measured by H.E.S.S.

L. Rolland (CEA-Saclay/DSM/DAPNIA/SPP, Gif-sur-Yvette, France)

for the H.E.S.S. collaboration

([email protected])

The H.E.S.S. detector

The Galactic Centre

Observations of the Galactic Centre with H.E.S.S.


The H.E.S.S. experiment


Imaging Atmopheric Cherenkov

TelescopesGamma-ray

Cosmic rayParticle

shower

Che

renk

ov li

ght

muon

Gamma-ray candidate

hadron

Atmosphere = calorimeter

Image of Cherenkov flashs (~3 ns)


Stereoscopic system

Gamma-ray

Cosmic ramy

Particle

shower

Che

renk

ov li

ght

Gamma-ray

Cosmic ray

Particle

shower

Che

renk

ov li

ght

1

2

3

4

Impact

parameter

of the

gamma-ray

Rejection of isolated muons at trigger level

Energy threshold decreased

Hadronic rejection improved

Gamma-ray reconstruction improved Source

direction


The H.E.S.S. experimentSite : Namibia, 23°16'' S, 16°30'' E, altitude 1800 m


Real performancesTrigger rate ~ 400 Hz

Dead time ~ 10%

Field of view 5°

Threshold ~ 100 GeV at zenith

Angular resolution ~ 6' gerbe to gerbe

Energy resolution ~ 15%

Crab Nebula detection at zenith:0,01 Crabe : ~25 h0,05 Crabe : ~1 h0,10 Crabe : ~15 min1,00 Crabe : ~10 s


The first sources seen by H.E.S.S.

16 galactic sources

4 extragalactic sources

May 2005

+ ~5 galactic sources (1 microquasar)

+ ~4 extragalactic sources


H.E.S.S


H.E.S.S. Galactic survey (2004)

HESS J1702-420HESS J1713-381 HESS 1632-478

330°

RX J1713.7-3946HESS J1640-485

HESS J1616-508

HESS J1614-518

359°

HESS J1708-410 HESS J1634-472HESS J1745-303

LS 5039

HESS J1804-216 Gal. Centre HESS J1837-069

G0.9+0.1 HESS J1813-178 HESS J1825-137

HESS J1834-087

30° 0°

Sources > 6 sigma (9 new, 11 total)Sources > 4 sigma (7 new)


Supernova remnants

Excess map

(number of -rays)

X-ray contours:

ASCA

RXJ 1713-


Plerions

Chandra, X

MSH 15-52

Excess map

(number of -rays)

X-ray contours:

ROSAT


New type of VHE sources: microquasarMicroquasar: Microquasar:

LS5039LS5039

H.E.S.S.

Observations

of LS 5039

Aharonian et al. Science (2005)

First VHE detection of a microquasar

Expect a strong attenuation in the photon field of the

star

Emission further away from compact object

Jets (microblazar) ? Or other mechanism

Variablility expected,

needed to constrain the

models (shorter time scale

as in blazars / orbital period)

Being reobserved in 2005,

already significant

signal (16 sigma)

2005 data analysis under way


VHE unidentified sources

Known (2003): TeV 2032 HEGRAGalactic Center CANGAROO, Whipple, HESS, MAGIC

Is there are new population of “dark” TeV emitters ??Extended, structuredPower law energy spectrum, photon index ~2.2

New Sources (2005):J1303-631 HESS J1614-518 HESS J1804-216, “ J1804-216 “

Unconfirmed:3EG J0520+2556 Milagro [Dingus]

IMAGES

SOURCES

HESS


62Unidentified

117AGN (e.g. Mkn 421, PKS 2155 …)

61 Pulsar Wind Nebula (e.g. Crab, MSH 15-52 …)

3212TOTAL

20Diffuse (Cygnus region, GC region)

10Micro-quasar (LS 5039)

10Binary Pulsar (B1259-63)

62Supernova Remnants (e.g. Cas-A, RXJ 1713 …)

2005 2003Source Type*

Gamma-ray source count (ICRC 2005)

* Includes likely associations of HESS unid sources.

Explosion in the number of VHE sources.


The VHE sky - 1995

Mrk421

Mrk501

Crab

R.A.OngAug 2005

Pulsar Nebula

SNR

AGN

Other, UNID


The VHE sky - 2003

Mrk421 H1426

Mrk501

1ES1959

1ES 2344

PKS 2155

Cas A

RXJ 1713

CrabTeV 2032

M87

GC

R.A.OngAug 2005

Pulsar Nebula

SNR

AGN

Other, UNID


The VHE sky - 2005

Mrk421 H1426

Mrk501

1ES1959

1ES 2344

PKS 2155

Cas A

RXJ 1713

CrabTeV 2032

M87

PKS 2005

PSR B1259

RXJ 0852

MSH 15-52

SNR G0.9

HessJ1303

GC

R.A.OngAug 2005

Pulsar Nebula

SNR

AGN

Other, UNID

H2356

1ES 1218

1ES 1101

LS 5039Vela X

+ 8-15 add. sourcesin galactic plane.

CygnusDiffuse


The Galactic Centre


VHE candidates at the Galactic Centre

4° × 5°

A supermassive black hole:

Sgr A*


In the vicinity of the black hole

A supernova remnant

Sgr A East

20 cm- VLA

~4x3 pc

<1x1 pc


The GC seen by INTEGRAL

20-40 keV

40-100 keV

2° × 2°


The 2004 signal: HESS J1745-290

48 hours live time from March 30 to September 4, 2004

● pointing within 2 degrees of Sgr A*

● 0° to 60° zenith angle

<0.11° within Sgr A*:

● 38

● 1862


A new plerion: G0.9+0.1

● G0.9+0.1

● mixte morphology type SNR

● photon index ~2.3

● 3% Crabe flux


HESS J1745-290 - Angular distribution

Compatible with point-source in the very centre

Tail at larger distance


HESS J1745-290 - Position and extension

Assuming point-like source

compatible with Sgr A* 5.6''±10''±20''Diffuse emission

Assuming symmetric gaussian

distance to Sgr A* 3.9''±13''±20''

extension: 1.9' ± 0.23' 20 cm- VLA


Other high energy observations

Compatibility with

● INTEGRAL source (G1)

● black hole Sgr A*

● supernova Sgr A East

Incompatibility with

● unidentified EGRET source (99% CL)


HESS J1745-290 - Spectrum

Energy range:

166 GeV-37 TeV

Compatible with 2003 spectrum:

=2.2±0.09±0.15

(>1TeV)=(2.0±0.4±0.3)x10-12 cm-2s-1

Search for exponential cut-off:

Ecut

> 6 TeV (95% CL)

95% CL

upper limits


HESS J1745-290 - Light curves

Fit light curve by a constant:

2 probability

projection of the reduced flux

Night average flux

15% systematic errors added


HESS J1745-290 - Light curves

Light curves compatible with constant flux

15% systematic errors

added to every light curve points

Sensitivity of the method for a 5 detection of a flare:

nightly: x 2

28 minutes: x 4

10 minutes: x 7

Dataset P(Chi2) Sigmanightly 2003 73% 0.9 0.2nightly 2004 65% 1.0 0.1

nightly 2003-2004 50% 1.1 0.228-minutes 2004 41% 1.0 0.110-minutes 2004 94% 0.95 0.04


Astrophysical candidates


Emission from Sgr A*Sgr A* : supermassive black hole

variability energy spectrum


Emission from Sgr A EastSgr A East :supernova remnant

extension energy spectrum


Emission from Sgr A EastSgr A East : supernova remnant

extension energy spectrum

Source Photon index Luminosity (10̂ {34} erg/s) distance (kpc)

Crab 2,6 9 2

G0.9+0.1 2,3 4 8,5

MSH15-5-2 2,3 10 5

CG 2.3 12 8.5


Other possibilities

● Cosmic-ray interaction with dense medium

● Collision of stellar winds

● Other contributions:● transient sources observed in X-rays


Dark matter at the Galactic Centre


Shape of the DM halo

Halo density profiles

Extrapolations

Predictions

Large scale structure formation models


Gamma-ray: DM annihilation flux

WIMP nature

Neutralino annihilationlines are loop suppressedhadronisation (W± and Z

0 )

Kaluza-Klein annihilation

lines are loop suppressedcharged leptons and quarks

Dark matter halo

● Predicted gamma-ray annihilation flux:

continuum MSSM

Power law mKK

= 10 TeV

Cut-off


Gamma-ray: DM indirect detection

WIMP nature DM halo shape

Energy spectrum Angular distribution

● Predicted gamma-ray annihilation flux:


Only dark matter - Halo shape

Cherenkov telescopes

constraints DM halo shape

Diffuse emission

BUT

Angular distributioncompatible with cuspy halo ~ 1

Point-like source:

> 1.2


Only dark matter - Spectrum shape

Different spectra than Bergström and Profumo

Misuse of PYTHIA ?

Different spectra between Dark Susy and PYTHIA ?


Dark matter and astrophysical background

2 composonant spectrum:power lawDM annihilation

Spectrum compatible with power law

Upper limits on .v

● Shape of the halo: NFW

Uncertainties in density > 106


Dark matter and astrophysical background

99% CL upper limits


38 detection of

HESS J1745-290

in 2004

Position compatible

with Sgr A* within 6'' Slightly extended ? = 1.8'

Uncurved power law spectrum = 2.27

No indication of

variability in 2003-2004

Possible origin for the gamma-rays:● Sgr A*● Sgr A East● stellar wind collisions● cosmic-ray interactions in the dense medium● dark matter annihilations


38 detection of

HESS J1745-290

in 2004

Pure DM annihilation

spectrum incompatible

with the data

Loose constraints on .v

in case of astrophysical

background

Looking for other DM source candidates:

Sgr A Dwarf (25 kpc)

Canis Major (8 kpc)75.05.0~2.01.0~

GC

CMaj

GC

Sgr

Documents

Very high energy gamma-rays from the Galactic Centre measured by H.E.S.S