The end of the electromagnetic spectrum Gamma ray astronomy. The end of the electromagnetic spectrum Christian Stegmann ICHEP, Valencia July, 8th 2014

Gamma rays – Messengers from the High Energy Universe Gamma rays are excellent tracers of the acceleration sites of ultra-relativistic cosmic rays Production protons: pion-decay: π0 → γγ electrons: Inverse Compton Scattering: e± γ → e± γ

Experimental techniques MeV GeV TeV PeV Cherenkov light Satellites (Fermi-LAT) Particle shower Air Cherenkov Systems (MAGIC, VERITAS, H.E.S.S.) Water Cherenkov Systems (HAWC)

Experimental techniques MeV GeV TeV PeV Fermi-LAT MAGIC HAWC Bill Atwood (UCSC): Telescope (LAT) “Like a detector for particle physics, except that it uses less power than a toaster and we talk to it through a telephone line ...” VERITAS H.E.S.S.

Experimental techniques MeV GeV TeV PeV Fermi-LAT MAGIC HAWC Fermi LAT IACTs HAWC Effective area 1 m2 105 m2 Field of view 20% of the sky 3o – 5o 15% of the sky Energy res. 10% 100% – 20% Angular res. 6o – 0.3o 0.1o 1o – 0.2o Duty cycle Full year 1400 h/year VERITAS H.E.S.S.

Closing the gap to Fermi-LAT H.E.S.S. II four 12m telescopes one 28m telescope (FoV 3.5 deg) energy threshold O(30 GeV)

The Vela pulsar seen with H.E.S.S. II τrot = 89 ms Energy distribution <E> = 40 GeV Closing the gap to Fermi-LAT calibration source at the threshold in standard observation mode well prepared for GRB search

The Vela pulsar seen with H.E.S.S. II τrot = 89 ms Energy distribution <E> = 40 GeV Closing the gap to Fermi-LAT calibration source at the threshold in standard observation mode well prepared for GRB search Pulsar physics (not only Vela) what is the spectrum above 20 GeV? constraining the cut-off?

Pulsars seen with Cherenkov Telescopes τrot = 89 ms Energy distribution <E> = 40 GeV Crab pulsar τrot = 33 ms Crab pulsar MAGIC, A&A 565, 12, May 2014

The Vela pulsar spectrum H.E.S.S. II Fermi-LAT arXiv:1002.4050

The HAWC Observatory Altitude: 4100m 20000 m2 covered with 300 water Cherenkov detectors equipped with 1200 PMTs Current status: 256 tanks, 195 with water, 662 PMTs Completion scheduled for this year

The sky seen with HAWC 3 months of data, 1/3rd of array

Experimental techniques MeV GeV TeV PeV Fermi-LAT MAGIC HAWC VERITAS H.E.S.S.

The Gamma-ray Sky at GeV Energies Fermi 2FGL catalogue 1800 sources; significant fraction Extragalactic; many Galactic sources confused with diffuse Emission

The Gamma-ray Sky at TeV Energies TeVCat ~50 extragalactic sources; ~100 Galactic sources

Scientific Highlights Imaging of cosmic particle acceleration sites Physics of pulsars and pulsar winds Full sky surveys Probing the extragalactic background light Extreme variability of AGN Limits on dark matter and new physics Major contributions from all current instruments

Supernova Remnants Gamma rays X rays

GeV-TeV spectra of supernova remnants from S. Funk

GeV-TeV spectra of supernova remnants from S. Funk

Supernova Remnants Fermi-LAT

Detection of the “pion cutoff” in supernovae remnants Supernovae are accelerators of hadronic cosmic rays Science 339, 2013 Science 339, 2013

Extreme SNR HESS J1640-465 The most luminous Galactic TeV source Distance: 8 – 13 kpc SNR G349.7+0.2 Distance 22.4 kpc The farthest SNR discovered so far TeVCat Galactic sources G349.7+0.2

The Galactic Centre

The Galactic Centre at E > 200 GeV H.E.S.S. preliminary H.E.S.S. preliminary Intrinsic GC source spectrum has a stronger cut-off ~ 7 TeV Spectrum of diffuse shows no indication of a cut-off below 25 TeV and follows a power-law up to at least 50 TeV  Indication of a central source accelerating protons to energies > 500 TeV ?

The Galactic Centre with H.E.S.S. II Observation and analysis Life time 68.8 h Signal with 25 σ extended emission Background needs to be further studied Significance map

Dark Matter Search with Gamma Rays Diffuse emission Galactic Centre region Anisotropies, gradients Individual sources Galaxy clusters Milky Way satellite galaxies Spectral signatures Search for line emission e+/e- spectrum Kuhlen et al. (2008) γ-ray predictions for Fermi-LAT

Search for line emission at GeV energies No significant line emission Most significant fit at 133 GeV in smallest search region local significance of 3.3 σ global significance of 1.5 σ Systematics studied in detail Better understanding of energy dispersion Line narrower than instrument response Similar feature seen in Earth-limb data Analysis strategy Study 5 different regions, optimised to test different DM density profiles Exclude Galactic plane and strong gamma-ray sources Define 4 control regions Search for γ-ray lines in sliding energy intervals Phys. Rev. D (2013), 88, 082002 Phys. Rev. D (2013), 88, 082002 Phys. Rev. D (2013), 88, 082002 Phys. Rev. D (2013), 88, 082002 Phys. Rev. D (2013), 88, 082002 Phys. Rev. D (2013), 88, 082002

Dwarf galaxies at TeV energies VERITAS, ICRC 2013 H.E.S.S., MAGIC and VERITAS derived DM limits for different (individual) dwarf spheroidals Dedicated DM search programs for the next ~5 years in place Combine IACT data sets 2013  2018

Electron/Positron Spectra M. Di Mauro, F. Donato, N. Formengo, R. Lineros, A. Vittino, arXiv:1402.0321

Our Neighbourhood

Nearby sources Stefan Klepser, DESY

Pulsarwind Nebulae

PWN Population Study Selection results H.E.S.S., ICRC 2013 Selection results young pulsars (age < 100 kyr) Population plots to benchmark models Spin-down power (erg s-1) Age (kyr) Efficiency L1-10 TeV /Ė PWN extension (pc) Strong variations, probably from surrounding medium or SNR interaction ■ Rough trend of RPWN ~ t0.3 seems quite realistic ■ Some candidates are clearly larger than the general trend ▪ Good candidate evaluation criterion Not a real momentary efficiency, but compares integral electron population to momentary Edot Age (kyr) Age (kyr)

Conclusion Gamma-ray experiments today offer an unique view into the high-energy Universe, from MeV to PeV energies and deliver unprecedented data of high precision resulting in an increased understanding of the astrophysical foreground.

CTA – the Cherenkov Telescope Array A huge improvement in all aspects of performance A factor ~10 in sensitivity, much wider energy coverage, much better resolution, field-of-view, full sky, … A user facility / proposal-driven observatory With two sites with a total of >100 telescopes A 27 nation ~€200M project Including everyone from HESS, MAGIC and VERITAS

Science 339, 2013

GeV Excess in the Galactic Center? Peter Michelson (PI Fermi-LAT): “The Fermi LAT Collaboration continues to examine the extraordinarily complex central region of the galaxy, but until this study is complete we can neither confirm nor refute this interesting analysis."