VHE Gamma Ray Astronomy: a UK strategy for the next decade

Paula Chadwick for the University of Durham

Johannes Knapp for the University of Leeds

Richard Holdaway & John Womersley for RAL

• Definitions & detection

• The international context

• Some recent highlights

• The UK situation

• Our proposed strategy

• (Multiple) Images of showers

• Gamma rays form consistent pattern

• Excellent gamma-hadron separation (~100%)

• Showers located to ~0.1° at threshold

• Point source location to ~ 20”

Imaging

Atmospheric

Cherenkov

Technique

VHE gamma rays can be defined as those detectable from the ground using the:

Generally E > 100 GeV at present

Current Major IACTs

Ntels Et Res. FoVDead Time

Sens.

CANGAROO III 3 X ✓ ✓ ✓ X

H.E.S.S. 4 ✓ ✓ ✓✓ ✓ ✓

MAGIC 1 ✓ ✓ ✓ ✓ ✓

VERITAS 4 ✓ ✓ ✓ ✓✓ ✓

Science topics

Dunkle Materie

Pulsarsand PWN

GRBs

SNRs AGNs

Origin ofcosmic

raysCosmology

Dark matterSpace-time& relativity

VERITAS-4Four 12m diameter telescopes

Davies-Cotton design, 345 mirrors

FoV 3.5°

499 PMTs, pixel spacing 0.15°

Two telescopes operating in stereo mode

Four telescope array by end 2006

USA: Smithsonian Astrophysical Observatory; Iowa State University;University of California, Los Angeles; University of Chicago; University of Utah; Washington University, Saint LouisUK: Leeds UniversityCanada: McGill UniversityIreland: National University of Ireland

Integrated Pulse

First Stereo Observations

Markarian 421 at ~ 2 Crab in Jan/Feb 2006

High Energy Stereoscopic System – H.E.S.S.

Four 13m diameter telescopes

Davies-Cotton design, 382 0.6 m diameter mirrors

FoV 5°

960-pixel cameras

Routine operations since January 2004

Germany: M-PIK Heidelberg; Humboldt University, Berlin; University of Hamburg; Ruhr University, Bochum; Landessternwarte HeidelbergFrance: LLR Ecole Polytechnique, LPNHE, PCC College de France, University of Grenoble, CERS Toulouse, CEA Saclay, Observatoire de Paris-Meudon, University of Montpellier IIUK: Durham UniversityIreland: Dublin Institute for Advanced StudiesCzech Republic: Charles University, PragueArmenia: Yerevan Physics InstituteNamibia: University of NamibiaSouth Africa: North-Western University

Progress in VHE Gamma Rays…

Source Type 2003 2005

Pulsar wind nebula (Crab, MSH15-52…) 1 6

SNRs (Cas A, RXJ1713….) 2 6

Binary Pulsar (PSR B1259-63) 0 1

Microquasar (LS5039) 0 1

Diffuse (Cygnus region) 0 1

AGN (PKS2155-304, Mkn 421…) 7 11

Unidentified 2 6

TOTAL 12 32

X 7

X 11

X 40

X 12

X 2

RXJ1713.7-3946

Aharonian et al., Nature, 75, 432 (2004)

2 telescopes with/without array trigger

E > 800 GeV; angular res. 3 arcmin. 18.1 hours livetime, 20

Enomoto, R. et al.,Nature, 416, 823-826 (2002)

Image from 2004 with all four H.E.S.S. Phase telescopes; 2 arcmin resolution, 33 hours livetime.

Vela region

Vela (Rosat)

Vela Juniord ≈200 pcage ≈ 700 y

H.E.S.S. observations show a source which is consistent with the position of Sgr A* and with a nearby SNR. Significance with 2004 data > 30

Aharonian et al., Astron. Astrophys., 425, L13 (2004)

Galactic Centre

10-13

10-12

10-11

0,1 1 10

E2 F

(E)

[Te

V/c

m2 s]

E [TeV]

Dark matter annihilation?

20 TeV Neutralino

20 TeV KK particle proposed beforeH.E.S.S. data

proposed based on early H.E.S.S. data

Preliminary

Bergström et al, Phys. Rev. Lett., 94, id. 131301 (2005)

Diffuse Emission

Galactic Plane Scan

1ES 1101-232Z = 0.186

H2356-309 (x 0.1)Z = 0.165

EBL

Source spectrum = 1.5

Preliminary

AGN Spectra & ExtragalacticBackgroundLight

AGN Spectra & ExtragalacticBackgroundLight

1 ES 1101 = 2.9±0.2

H 2356 (x 0.1) = 3.1±0.2

too muchEBL

Source spectrum

Upper limit on EBL

Preliminary

Spectra & ExtragalacticBackgroundLight

1 ES 1101 = 2.9±0.2

H 2356 (x 0.1) = 3.1±0.2

too muchEBL

Not really a solution:

add huge amountof UV photonsto EBL

problems withsource energetics,X-ray/gamma-raySED ratio

UVEBL

Preliminary

Spectra & ExtragalacticBackgroundLight

lower limitsfrom galaxy

counts

measure-ments upper

limits

Reference shape

HESS limits

X

XEBL resolvedUniverse more

transparent

Cosmic Background – hidden quasars

MWB

XRB

IRB

Cosmic

Stars/AGN

AGN

X

The UK VHE Gamma Ray Scene

• A long UK history in VHE gamma ray astronomy• Two UK groups – Leeds (VERITAS) and

Durham (H.E.S.S.)• Both provide a strong contribution to their

respective collaborations based on over 20 years’ experience

• UK thus has access to data from both North and South, but our efforts are divided

• Joint UK strategy defined

Our Strategy• Start a UK Gamma Ray Association to co-ordinate

activities e.g. multi-instrument campaigns, development• Exploit VERITAS – similar performance to H.E.S.S. but

different, Northern sky targets – total cost ~ £100k - £200k p.a. Minimal capital investment.

• Jim Hinton at Leeds to become involved in H.E.S.S.• Sizeable (~ £1M) capital contribution to H.E.S.S. II

aiming at higher sensitivity at low energies.• RAL joins VHE gamma ray effort, other groups also

interested (e.g. Liverpool, Oxford).• H.E.S.S. & H.E.S.S. II to be the experiment towards

which UK gamma ray activities gravitate.• Post-2010 – plan UK contribution to the next major VHE

gamma-ray facility (ESFRI?). Development work to start now.

H.E.S.S. II

A single, 28m diameter dish

Lowers threshold to ~ 20 GeV in standalone mode

Improves overall array sensitivity in coincidence

Key science questions:

AGN population & the EBL; microquasar & XRB models; hadrons vs. leptons in SNR; pulsar detection; EGRET UiD sources; gamma ray bursts; dark matter.

10-16

10-15

10-14

10-13

10-12

10-11

10 100 1000 104 105

E x

F(>

E)

[TeV

/cm

2s]

E [GeV]

After H.E.S.S. II?

Crab

10% Crab

1% Crab

GLAST

MAGIC

H.E.S.S.

Current Simulations

20 wide-angle10 m telescopesde la Calle Perez,Biller, astro-ph 0602284

30 m stereotelescopesKonopelkoAstropart.Phys. 24 (2005) 191

In summary…

2006 2007 2008 2009 2010 2011

Exploitation of VERITAS

H.E.S.S. II Build Exploitation of H.E.S.S. I & II

Array development & design Array build

Why North and South?

• Understanding both AGN & SNR requires population studies

• Specific objects in both hemispheres require investigation (e.g. Cas A, Tycho, Galactic Centre, LMC/SMC…)

• Full sky coverage is desirable for multiwavelength multi-target campaigns

Technical Expertise of UK groups• CCLRC/RAL: large scale project

management/delivery; instrumentation (esp. single photon detection, fast electronics, communications); detector assembly (design/validation, test assemblies); data analysis & physics (data management, ‘gridification’)

• Durham University: mirror design/manufacture, atmospheric monitoring, calibration, simulations.

• Leeds University: fast signal transmission; advanced trigger systems; photodetectors; simulations.

The UK GRA

• Start with a general discussion between all members of involved and interested groups

• Form a small committee of (say) 2 members from each group

• Quarterly meetings to enable updating• Regular reviews of strategy• Eventually a more formal orghanisation

with MoU etc.