TeV-Gamma Ray Astrophysics with the H.E.S.S. Telescopes Thomas Lohse Humboldt University Berlin Physikalisches Kolloquium June 26, 2007

The Cosmic Ray Spectrum Power Laws Shock Acceleration predicts F Source  E  2 Discovery Balloon Flight Victor Hess, 1912 solar modulation  E  2.7, mostly protons transition to heavier nuclei  E  3.1 mostly Fe? Knee ? Ankle EAS Detectors Direct Measurements transition to lighter nuclei ?

Open questions after  90 years  What and where are the sources?  How do they work?  Are the particles really accelerated?...  …or due to new physics at large mass scales?  And how do cosmic rays manage to reach us?

Production in Cosmic Accelerators protons/nuclei electrons/positrons p 00  radiation fields and matter p  ee  Inverse Compton (+Bremsstr.)

1.Detection techniques 2.The H.E.S.S. telescope array 3.Selected results from H.E.S.S. 1.Detection techniques 2.The H.E.S.S. telescope array 3.Selected results from H.E.S.S.

Experimental Techniques ( E  10 GeV ) Instrumented Water / Ice Scintillator or Water Č   Č-Telescope Č Fluorescence Detector Hadron- Detector Fluorescence Primary (Hadron,Gamma) Air Shower Atmospheric (4  )  Primary (4  ) , e,  R&D Radio-Detection Acoustic-Detection

At 100 GeV ~ 10 Photons/m 2 (300 – 600 nm) ~ 120 m Focal Plane ~ 10 km Particle Shower Image Shape  Primary Particle Intensity  Shower Energy Image Orientation  Shower Direction 5 nsec Detection of Cosmic Rays and Gamma Rays Cherenkov Light 120 m 

several viewing angles for precise event-by-event source location! Stereoscopic Observation Technique source direction source image is on image axis 

Source Similar to Meteorite Showers: M

H.E.S.S.CANGAROO III MAGIC Veritas in construction Cherenkov Telescopes (3 rd Generation)

1.Detection techniques 2.The H.E.S.S. telescope array 3.Selected results from H.E.S.S.

H.E.S.S. H igh E nergy S tereoscopic S ystem MPI für Kernphysik, Heidelberg Humboldt-Universität zu Berlin Ruhr-Universität Bochum Universität Erlangen-Nürnberg Universität Hamburg Landessternwarte Heidelberg Universität Tübingen Ecole Polytechnique, Palaiseau APC, Paris Universite Paris VI-VII CEA Saclay CESR Toulouse GAM Montpellier LAOG Grenoble Paris Observatory LAPP Annecy Durham University Dublin Inst. for Advanced Studies NCAC Warsaw Astronomical Observatory Cracow Charles University Prag Yerewan Physics Institute North-West University, Potchefstroom University of Namibia, Windhoek

H.E.S.S. Site Clear sky Galactic centre culminates in zenith Mild climate Easy access Good local support (UNAM etc.) 23 o 16’ S, 16 o 30’ E, 1800 m asl Farm Göllschau, Khomas Hochland, 100 km from Windhoek

H.E.S.S. Phase I 4 telescopes operational since December 2003 Energy threshold (for spectroscopy): 100 GeV Single shower resolution: 0.1  Pointing accuracy: ≲ 20  Energy resolution:  20% June 2002September 2003February 2003December 2003

960 pixel PMT camera Pixel size: 0.16° On-board electronics Weight: 900 kg 13m dish, mirror area 107 m spherical mirrors, f =15m Point spread 0.03°-0.06°

1.Detection techniques 2.The H.E.S.S. telescope array 3.Selected results from H.E.S.S.

Supernovae

Synchrotron radiation Pulsar Wind Nebula: Electron wind from central pulsar heats the cloud The Standard Candle for TeV  -Astronomy Crab Supernova 1054 a.D. d = 2 kpc optical 1 lightyear But what about hadrons (protons and nuclei)?

Cassiopaeia A Supernova 1658 a.D. d = 2,8 kpc X ray picture “Shell Type” SNR: no electron wind from pulsar gamma signal from shell regions not totally drowned in that of electron wind good source class to observe hadron acceleration

resolution H.E.S.S E   210 GeV RX J  3946 resolution H.E.S.S E   210 GeV RX J  3946 First Resolved Supernova Shells in  -Rays H.E.S.S E   500 GeV RX J  4622 Strong correlation with X-ray intensities SN-Shells are accelerating particles up to at least 200 TeV! But are these particles protons/nuclei or electrons?

E 2 dN/dE log(E) Stars radio infrared visible light X-rays VHE  -rays CMB Dust Cosmic Electron Accelerators BEeBEe Electron or Hadron Accelerator? Synchrotron Radiation Inverse Compton BB EeEe Cosmic Proton Accelerators Matter Density  0  Synchrotron Radiation of Secondary Electrons

EGRET   2.0 B  7, 9, 11  G Electron accelerator fits for RX J  3946 : Continuous electron injection over 1000 years Injection spectrum: power law with cutoff IC peak not well described B-field low for SNR shell large  & injection rate  bremsstrahlung important needs tuning at low E B  10  G   2.0, 2.25, 2.5 H.E.S.S.

Spatially resolved spectra of RX J  3946 TeV / X-ray intensities correlate, but NOT the spectral shapes  very hard to understand for pure electron accelerator ! TeV photon index  const H.E.S.S. preliminary G. Cassam-Chenaï A&A 427, 199 (2004) X-ray photon index

 Continuous proton injection over 1000 years  Injection spectrum: power law, index  2  Different cutoff shapes & diffusion parameters Proton accelerator fit: H.E.S.S. RX J  3946

Galactic Centre HESS J1837  069 HESS J1834  087 HESS J1825  137 HESS J1813  178 HESS J1804  216 G0.9  0.1 HESS J1747  281 Galactic Centre HESS J1745  290 HESS J1713  381 RX J  3946 HESS J1708  410 HESS J1702  420 HESS J1640  465 HESS J1634  472 HESS J1632  478 HESS J1616  508 HESS J1614  518

 no visible cut-off  rather large mass  measured flux  large cross-section and/or DM density Possible Interpretation: Dark Matter annihilation? 20 TeV Neutralino 20 TeV Kaluza Klein particle … unlikely ! H.E.S.S. MAGIC GC Crab

Galactic Centre Neighbourhood ~150 pc Galactic Centre HESS J1745  290 SNR G0.9  0.1 HESS J1747  281 EGRET GeV-  -sources

...point sources subtracted  first resolved detection of diffuse TeV-  -radiation  cosmic rays (hadrons) interacting with molecular clouds ~150 pc Galactic Centre Neighbourhood molecular clouds density profiles HESS J1745  290

Cosmic Ray Spectrum at the GC... diffuse radiation expected flux for CR spectrum observed on earth Cosmic rays are much harder and have 3  larger density around the GC is very different from the one at earth Possible reason: Close-by source population Possibly single SN-explosion

The Gamma Ray Horizon

General Active Galactic Nuclei (AGN): Supermassive black holes, M  10 9 M  accretion disk and relativistic jets Blazar-Typ: Jet points towards the earth Doppler-boost  TeV  -radiation Blazars

E dN/dE Measurement of EBL (  Cosmology )  Physics of compact objects, acceleration/absorption in jets, … E dN/dE Absorption in (infrared) extragalactic background light (EBL)  (TeV) +  (EBL)  e + e - e+e+ e-e-  

Cut-off Energy and  -Ray Horizon PG 1553  113

H 2356 (x 0.1)  = 3.1±0.2 Preliminary EBL Unfolding of Measured Spectra 1 ES 1101  = 2.9±0.2 EBL H 2356 (x0.1)  = 3.1±0.2 Hardest plausible source spectrum  = 1.5 Hardest plausible source spectrum  = 1.5 Too much EBL

Lower Limits (Galaxy Counts) New Upper Bound on EBL Density Direct IRTS Measurements Assumed shape for rescaling H.E.S.S. upper bound from spectral shapes of 1ES (z = 0.186) H (z = 0.165) EBL density seems  2  smaller than expected! Little room for EBL sources other than galaxies (early stars…) Upper Limits excluded by H.E.S.S.

M87 Gamma Rays from the Rim of a Super-Massive Black Hole

M87 Radio Galaxy, Virgo Cluster, d  16 Mpc Central 3  10 9 M ⊙ Black Hole, R S  cm Relativistic Plasma Jet at 30   Blazar Radio VHE  -Rays host galaxy (optical) 99.9% c.l. extension upper limit Is there a better way to constrain the source size?

v   c  Yes, there sometimes is: Source variability!  source R time smearing: R/c source variability:  t* ≳ R/c shortest observable variability:  t ≳   R/c  upper limit on source size: R ≲  c  t relativistic Doppler factor reasonable: 1    50

Radio optical X-ray nucleus knots (jet) Doubling times of 2 days observed during 2005 high state of M87 Knots in jet are excluded as sources High energy particles created close to black hole horizon

Gamma Rays from a Micro-Quasar

LS 5039 Periastron   0 Apastron   0.5 observer inferior conjunction   superior conjunction    Massive star M   20 M ⊙  compact object: M ⊙ neutron star or black hole?  Orbital Period 3.9 days  Eccentric orbit binary separation R *

LS 5039 Periastron   0 Apastron   0.5 observer inferior conjunction   superior conjunction   Paredes et al  Faint X-ray emission slightly variable  Extended pc-scale radio emission possibly from jets (v  0,2 c)

VHE  -Ray Lightcurve folded with orbital period   0  0   0.5 observer     Modulation  absorption in radiation field  central emission (  1au) H.E.S.S.

VHE Spectral Modulation modulation strength strongly energy dependent not explainable by pure absorption effects complicated interplay between production & absorption mechanisms The central engine starts to reveal its physics

The Future: H.E.S.S. Phase II Large telescope under construction Improve sensitivity:  4 small  1 large  better than  8 small  Reduce threshold to O ( 20 GeV )

Summary Very successful initial years of H.E.S.S. Phase I Many new sources & several fundamental discoveries The VHE  -ray sky is well populated and complex Expect “bright” future