Jim Hinton, 3rd International Workshop on UHECRs, Leeds, July 2004 H.E.S.S. and (Ultra High Energy) Cosmic Rays Jim Hinton (MPI-K Heidelberg) for the

Jim Hinton, 3rd International Workshop on UHECRs, Leeds, July 2004

H.E.S.S. and (Ultra High Energy)

Cosmic Rays

Jim Hinton (MPI-K Heidelberg) for the H.E.S.S. Collaboration:

MPI Kernphysik, HeidelbergHumboldt Univ. BerlinRuhr-Univ. BochumUniv. HamburgLandessternwarte HeidelbergUniv. KielEcole Polytechnique, PalaiseauCollege de France, ParisUniv. Paris VI-VIIUniv. Montpellier II

CEA SaclayCESR ToulouseLAOG GrenobleParis ObservatoryDurham Univ.Dublin Inst. for Adv. StudiesCharles Univ., PragueYerewan Physics Inst.Univ. PotchefstroomUniv. of Namibia, Windhoek


Outline

VHE -rays as tracers of cosmic-ray acceleration and propagation

The H.E.S.S. experiment

Results from H.E.S.S.The Galactic Centre

The Supernova Remnant RX J1713


-rays from cosmic rays

It is hard to accelerate and propagate cosmic rays without producing -rays

Interactions of cosmic rays with nucleons, radiation fields and magnetic fields all lead to -ray production

often peaks in the GeV-TeV regime

UHECR accelerators within the GZK volume could well be detectable by current TeV gamma-ray detectors


Example: acceleration by supermassive black holes

It has been suggested (Boldt, Levinson,...) that UHCR could be accelerated by compact dynamos at the cores of 'quaser remnants' or ex-AGN.

Fast rotating supermassive black hole embedded in a magnetic field produces a huge emf – could accelerate protons to 1020 eV

Curvature radiation in the TeV regime is the dominant energy loss mechanism

Should be bright TeV sources (Neronov et al 2004)

The supermassive black hole in our galaxy could accelerate to around 1018 eV (AGASA anisotropy?)


-rays from UHECR propagation

Interactions of UHECR with the CMBR lead to the expected GZK cut-off but also produce secondary particles: p + p + 0, p + p + e++ e- and hence to -rays via

0 and Inverse Compton Scattering

These rays in turn interact with the universal radiation fields (CMBR, IR and Optical) and an electromagnetic cascade begins

At energies << 10 TeV the universe becomes transparent to -rays (out to z ~0.1) and the cascade ends

For reasonable assumptions on source strength and on extragalactic magnetic fields, such cascades should be detectable by H.E.S.S. (Ferrigno, Blasi, De Marco 2004)

One complication is that emission may not be point-like

expect extended emission due to magnetic deflections in the cascade, and from diffusion of UHECR out of acceleration region halos (~ 1 degree)


-rays from UHECR propagation

Predicted gamma-ray fluxes for a UHECR accelerator at 100 Mpc (Aharonian 2002):

H.E.S.S. has a wide field of view and very good sensitivity around 1 TeV – ideal for these studies

Auger clusters could be H.E.S.S. targets

within1 degreewithin1 degree

approx HESS Sensitivity1 degree


High Energy Stereoscopic System

In Namibia, 1800 m a.s.l.

Telescopes 4x in 120 m square

15 m focal length

13 m diameter

107 m2 reflectors

Cameras960 PMT pixels

Each 0.16o , 5o FoV

16 ns integration gate

'light-in, light-out'

4 Telescope system completed December 2003


Detection principle:

Stereoscopic imagingof Cherenkov light from air-showers

Large collection area

Multiple views of the showerimproved direction

improved energy

improved rejection of background (cosmic rays!)


Specifications

Energy range100 GeV 10 TeV

Energy resolution15 - 20%

Angular resolution0.05 - 0.1 degrees

Sensitivity1% of the flux from the Crab Nebula in 25 hours


Performance

Trigger rate versus threshold agrees well with simulations

Array is triggering on a two telescope coincidence

Operating range is well outside region dominated by the night sky background light Operating thresholdd

NSB


Crab Nebula

Preliminary3-Telescope data (2003)

54 , (27 /hr0.5)10.8 +/- 0.2 /minute

@ 45 degree zenith angle


Comparison with simulations

Very good agreement between simulations and real -rays:

the excess -ray events from the Crab Nebula

(so we always optimise our cuts on simulated -rays, not on data)

Image Width

Angular Resolution

Image Length


Crab Nebula

Spectrum agrees well with previous measurements

dN/dE E-2.63+/-0.04

Flux > 1 TeV:

1.98 x 10-7 m-2 s-1 PRELIMINARY


Updated sensitivity

Simulations agree well with observed data

-ray rate, trigger rate, image shapes

can confidently predict time required to detect source at 20o zenith with E-2.6

spectrum:

0.01 Crab in ~25 hours

0.05 Crab in ~1 hour

0.10 Crab in ~20 minute

1.00 Crab in ~30 seconds

Threshold is 100 GeV at zenith, 120 GeV after cuts


Official detections by H.E.S.S. so far…

Crab Nebula (2003, 3 Tel.) - 54 sigma

PKS 2155 (2003, 2 Tel.) - 45 sigma

Mrk 421 (2004, 4 Tel.) - 71 sigma

PSR B1259 (2004, 4 Tel.) - 8 sigma

RX J1713 (2003, 2 Tel.) - 20 sigma

Sagittarius A* (2003. 2 Tel.) - 11 sigma

Very confident detections – all but Mrk 421 and PSR B1259 were confirmed independantly in datasets from two hardware configurations


The Galactic Centre

-rays detected by CANGAROO and Whipple but:

Very complex region - lots of potential sources of -raysSagittarius A* - supermassive black hole - curvature radiation of accelerated protons?

Several SNR, including Sag-A East, 'standard' CR acceleration?

Dark matter annihilation?

To resolve the ambiguity we needprecise spectrum

well determined position


Sagittarius A*

H.E.S.S. 20032 telescopes, 16 hours

Ethresh = 160 / 250 GeV(2 data sets)

11 significance

Good source localisation

Hard energy spectrum

-ray candidates (hard cuts)


Sagittarius A* - Source Location

Chandra GC surveyNASA/UMass/D.Wang et al.

CANGAROO (80%)

Whipple

(95%)

H.E.S.S.

Contours from Hooper et al. 2004


Point-like emission from Sgr A* direction

H.E.S.S.

ChandraF. Banagoff et al.

95%

68%


Sgr A EastChandra & Radio NASA/G.Garmire (PSU)F.Baganoff (MIT)Yusef-Zadeh (NWU)

Sgr-A East not ruled out

H.E.S.S.limit on rmssource size


Sagittarius A* - Spectrum

DM annihilation: ?Curvature radiation: ?SNR Shocks: ?Shocks in winds: ?


Galactic Centre – Dark Matter

Neutralino annihilation?Use DarkSusy

Expect two lines and continuum

Power law index - 2.2 - 2.4

Cut off at roughly m / 3

We see no lines and no cut off exponential cut off is limited to < 4 TeV

Which implies m > 12 TeV


Supernova Remnant RX J1713

CANGAROO claim proton acceleration in RX J1713Nature 416, 823 (25 April 2002)

Extended, unresolved source

Soft energy spectrumdN/dE E-2.84

0

IC


SNR-Molecular Cloud Interaction?

Fukui et al 2003NANTEN CO Map

+ ASCA X-rays

X-ray hot spots correspond to dense regions in the north and west of the remnant

cloud provides target for accelerated protons:

Yasunobu Uchiyama

RA


RX J1713 - X-ray

ASCA 1-3 keV

Dat

a fr

om Y

asun

obu

Uch

iyam

a


RX J1713 - TeV -ray

Off source dataOn source data


RX J1713

H.E.S.S. smoothed gamma-candidate map after image size cuts (> 800 GeV) - no background subtraction or acceptance correction

Only two telescopes

18 hours

20 sigma

c.f. ASCA (1-3 keV)Flux = 70% of Crab


Conclusions

1) TeV -rays are good tracers of UHECR acceleration and H.E.S.S is a good instrument for this search

2) One century of work on the cosmic ray mysteryand now we are getting close...

Documents

Jim Hinton, 3rd International Workshop on UHECRs, Leeds, July 2004 H.E.S.S. and (Ultra High Energy) Cosmic Rays Jim Hinton (MPI-K Heidelberg) for the