The H.E.S.S. Experiment

The H.E.S.S. Experiment

Christan Stegmann

Universität Erlangen

Content

• The breakthroughs of H.E.S.S.

• How was this achieved

• Some Galactic …

• … and some extra-galactic highlights

• The bright future

By 2002, only a handful of sources, very sparse sky coverage

Extragal. Galactic Milky Way in ~TeV gamma rays

H.E.S.S. Breakthroughs

• Survey of the inner Galaxy

• First astronomical image in

VHE gamma-rays

Discovery of TeV Sources

0 5 10 15 20 25 30 35 40 45 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 S o u rces d isco ver ed WHIPPLE HEGRA CANGAROO OTHER HESS MAGIC Total

Das H.E.S.S.

Telescope System

MPI Kernphysik, Heidelberg, Humboldt Universität Berlin, Ruhr Universität Bochum,

Universität Erlangen-Nürnberg Universität Hamburg,

LSW Heidelberg,

Ecole Polytechnique, Palaiseau, College de France, Paris,

Universite Paris VI-VII, LEA Saclay, CESR Toulouse, GAM Montpellier, LAOG Grenoble, Paris Observatory, Durham University,

Dublin Inst. For Adv. Studies, Yerewan Physics Inst.,

Univ. Potchefstroom,

Namibia

• Clear sky

• Centre of the Milky Way

culminates at zenith

• Milde climate

• Easy access

Namibia

• Clear sky

• Centre of the Milky Way

culminates at zenith

• Milde climate

• Easy access

Telescope

• Alt-Az mount

– Steel frame – Weight ~60 t

• Reflector

– Area ~107m2_,

– segmented into 380 single mirrors with 60 cm

diameter each – Diameter 13 m, – Focal length 15 m

Camera

• 960 Pixel, 0.16

o

_size

• Electronics integrated into the camera

• 5

o

_{field of view (1.4 m)}

© 2006 Philippe Plailly. www.eurelios.com

4 Telescopes in operation since December 2003

Energy threshold: 100 GeV

Single shower resolution: < 0.1

o

Energy resolution: ~15 %

Gamma-ray ~ 10 km Particle shower

Detection of

TeV gamma

rays

using Cherenkov

telescopes

~ 1o Che renk ov li ght ~ 120 m

(from Sky & Telescope)

M

Air showers

look a bit like

Cherenkov Light on the Ground

(looking along shower axis)

1 TeV

Photon

area: 600 x 600 m

2

duration: 32 ns

Cherenkov Light on the Ground

(looking along shower axis)

3 TeV

Proton

area: 600 x 600 m

2

duration: 32 ns

Image intensity

Ä Shower energy

Image orientation

Ä Shower direction

Image shape

Ä Primary particle

Collection area

~ 120 m

Energy threshold & detection area

100000 m2

Highest rate of events “Threshold”

Whipple 1989 (discovery): 50 h

HEGRA 1997: 10 min

H.E.S.S. 2004: 30 sec

Progress in sensitivity and energy threshold

Veritas

H.E.S.S. CANGAROO III

MAGIC

artist view

Status F.o.V (o₎ Energy threshold (GeV) 3.5 30-50 100 ~250 ~100 5 4 4.5 Data taking 08/2004 Data taking 12/2003 Data taking 03/2004 Start 10/2006 MAGIC H.E.S.S. CANGAROO III Veritas # Tel Mirror (m2₎ 1 239 4 108 4 57 4 100

Scan regio

First sensitive scan of the Galactic plane

Sensitivity ~ 3% of Crab flux

Galactic Plane Survey

Survey of the inner Galaxy

• H.E.S.S. 2004 Galactic survey: 230 hours

• 8 new sources above 6 sigma post-trials

• 7 new sources above 4 sigma post-trials

• At least 3 source classes

The New Sources

HESS J1804-216 Gal. Centre

HESS J1837-069 330° G0.9+0.1 HESS J1813-178 HESS J1825-137 HESS J1834-087 30° _0°

Conservative 6 sigma post trials

RX J1713.7-3946 HESS J1640-485

HESS J1616-508

HESS J1614-518

The New Sources

HESS J1702-420 HESS J1713-381 HESS 1632-478 330° RX J1713.7-3946 HESS J1640-485 HESS J1616-508 HESS J1614-518 359° HESS J1708-410 HESS J1634-472 HESS 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 Sources > 4 sigma

330° 359°

30° _0°

Pulsar Wind Nebulae, X-ray binary,

Unknown

,

Supernova remnants

Source classes

Source classes

330° 359°

30° _0°

Pulsar Wind Nebulae, X-ray binary,

Supernova remnants, Unknown

Ionisation

Hight

[m]

The Discovery of Cosmic Rays

• 1912 discovered by Viktor Hess

Nobel price 1936

Nobel price 1936

Supernova remnants as CR

accelerators?

• Large energy release

(dE/dt)_SN = 10._(dE/dt) CR

• Diffuse shock

acceleration

• Element composition

of CR

The Shockwave Accelerator

(Inventor: Enrico Fermi)

sound speed Alvén speed

u

<

shock front

plasma “at rest”

plasma from

supernova

u

4

3

proton

v = c > u

E

E+dE

shock front

plasma “at rest”

plasma from

supernova

u

4

3

u

4 1

new reference

system:

The Shockwave Accelerator

(Inventor: Enrico Fermi)

E´

E´+dE´

Prediction:

2 −

∝ E

dE

dN

The shell-type SNR RX J1713.7—3946

ROSAT 0.5-2.4 keV ASCA

Location of RX J1713.7—3946

Constellation Scorpius

AD393

“Guest Star”

“A GUEST STAR APPEARED WITHIN THE ASTERISM WEI DURING THE SECOND LUNAR MONTH OF THE EIGHTEENTH YEAR OF THE TAI-YUAN REIGN PERIOD (Feb. to March AD393), AND DISAPPEARED DURING THE NINTH LUNAR MONTH (Oct. to

H.E.S.S. RX J1713.7-3946

Point source

H.E.S.S. 2004

33 h with 4 telescopes 210 GeV threshold

Energy spectrum

What have we learned?

Supernova shock waves accelerate

particles up to O(100 TeV)!

But:

• are supernovae accelerators of hadronic cosmic rays? • produce supernovae a spectrum up to E=1015 _eV?

E

2

dN/dE

ln(E)

stars

radio infrared visble X-rays VHE γ-radiation

dust

Electron or Hadron Accelerators?

cosmic electron accelerator

Synchrotron radiation Inverse Compton Scattering cosmic proton accelerators

B

B

Bremsstrahlung

Proton accelerator

F.A. Aharonian

Electron spectrum

matched to radio and X-ray, for 10 µG

Other supernovae: Vela Junior

Vela (Rosat)

Vela Junior d ≈200 pc age ≈ 700 y

The centre of our Galaxy

330° 359°

30° _0°

The source at the Galactic centre

• No significant variability on any time scale

• Pure power law spectrum • Sgr A*, Sgr A East,

The source at the Galactic centre

For pure DM origin

• rather large mass

• large x-section or density

Extended emission from

the Galactic center region

Extended emission from

the Galactic center region

Point sources subtracted

GC molecular clouds Tsuboi et al. 1999

Extended emission from

the Galactic center region

Point sources subtracted

1050 _ergs

D ~ 1030_/cm2_s

Interpretation:

we see (for the first time) interaction between CR and molecular clouds

Æ πo _{(production and decay)}

Diffusion Model:

Point Source at GC ~ 10000 yrs old

Extended emission from

the Galactic center region

Spectral index 2.29 ± 0.07 ± 0.20 Implies harder CR spectrum than in solar neighborhood  Proximity of accelerator and target

Active Galactic Nuclei

Active Galactic Nuclei

• Supermassive black holes, M≈ 109 _M ~

• Accretion disc with relativistic jet

Blazar-Typ: Jet towards Earth

E

dN/dE

Study of the infrared background light → Cosmology

γ

Physics of compact objects and relativistic jets and …

E

dN/dE

Absorption in extragalactic background light (Infrared)

γ(TeV) + γ(IR) →

e

+

_e

-e

+

e

-γ

_γ

The Gamma-ray Horizon

Blanch, Martinez (2005) H.E.S.S. MAGIC Recently Discovered by:

AGN Physics

e.g. Mkn 421 (z=0.031)

Emission spectra

–

Synchrotron-Self-Compton

– bursts

– intrinsic Cut-offs

Konopelko et al. ApJ 597 (2003) 851 Mkn 421 burst 2004 _{Mkn 421 Cut-offs} MJD Flux [10 -1 1 cm -2 s -1 ] Mkn 421 multi-wavelength spectra ν [Hz] νF ν [erg cm -2 s -1 ] E cut [TeV]

Many sources at large z

Many sources at the same z

H.E.S.S. 2004 H.E.S.S.₂₀₀₄

1ES 1101-232

Derive Upper Limit on EBL

Assumption: intrinsic spectrum of blazars can’t be harder than

Γ = 1.5 Parameterization EBL spectrum H 2356-309 shows relatively hard spectrum

γ

e

+

e

-γ

_γ

The good news

The Universe is more transparent to Gamma-Rays than expected

Æ we can “see” further

H.E.S.S. Phase II:

add Large Cherenkov Telescope (600 m2 _Mirror)

• Improved sensitivity at higher energy in coincidence mode • Lower threshold and increased energy range in

stand-alone mode

• Test bed for future large telescopes and image analysis 600 m2

2048 pixel camera

• 600 m2 • f = 36 m • F/D = 1.2 • Parabolic dish • ~560 to total weight • 90 cm hex mirror • 851 mirrors

Phase II Sensitivity

Improved Sensitivity Guaranteed new window Let’s see and learn

H.E.S.S. Phase II:

add Large Cherenkov Telescope (600 m2 _Mirror)

• Construction of mount has started (Jan. 2006) • Installation of mount in 2007 (dry season)

• Camera integration and tests in 2007 • end of 2008 first light

CTA

An advanced facility for ground-based high-energy gamma ray astronomy

XExploring the non-thermal universeW

the

C

herenkov

T

elescope

A

rray as a

facility for gamma ray astronomy in the next decade

CTA

An advanced facility for ground-based high-energy gamma ray astronomy few 1000 m High-energy section ~0.05% area coverage E_th ~ 1-2 TeV 250 m Medium-energy section ~1% area coverage E_th ~ 50-100 GeV 70 m Low-energy section ~10% area coverage E_th ~ 10-20 GeV

Array layout: 2-3 Zones

FoV increasing to 8-10 degr. in outer sections

Not to scale !

Option:

Mix of telescope types

Option:

Single dish type

Not to scale !

Requires further development of trigger system for central cluster, allowing to combine pixel signals from multiple telescopes

Modes of operation

Deep wide-band mode:

all

telescopes track the same source

Survey mode:

staggered fields of

view survey sky

Search & monitoring mode:

subclusters track different sources

Narrow-band mode:

halo

telescopes accumulate high-energy

data, core telescopes hunt pulsars

…

CTA

An advanced facility for ground-based high-energy gamma ray astronomy

(Very optimistic) Schedule

Telescope prototypes Site exploration Full operation Partial operation Array construction Component prototypes Array design 13 12 11 10 09 08 07 06 GLAST FP 7 Design Study “Letter of Intent” (100 pages, physics + conceptual design) Technical proposal W. Hofmann

Conclusion

H.E.S.S. has opened a new window to the Universe:

TeV gamma-ray astronomy is a reality