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Gamma-rays above 10 TeV
Dieter Horns University Hamburg
RXJ1713-3946 [HESS Coll. 2004, 2007]

Crab pulsar wind nebula in X-rays (Chandra) [DH et al. 2010]

Exploring the Accelerator Sky

The accelerator sky

Is it a good deal?

The indirect path to the accelerator sky
Dieter Horns University Hamburg

Is it a good deal?
[astro-ph/0607109]

Unveiling Cosmic Ray accelerators:
Interstellar medium (B-field + gas + photons)

Accelerated Nuclei Meson production via inelastic scattering

Gamma-rays, Neutrinos

Cosmic rays

Neutral particles (photons&neutrinos) retain directional information: Accelerator sky Charged particles ("Cosmic Rays") are deflected and appear (almost) isotropic

(Main) conclusions from Cosmic Ray measurements:

Cosmic-ray confined in a volume: V=hR210 Cosmic-ray escape: esc107 yrs Required Cosmic-ray power:

67 3

cm

3

Local Cosmic-ray energy density: uCR1 eV/cm

Prime suspect: Shell-type supernova-remnants:

Acceleration efficiency of ~10% sufficient (required) to power galactic cosmic rays with shell-type SNR!

SN 1006 SN Ia Color composite: Radio (red) Optical green X-rays: blue D=2.2 kpc ь:0.48° 18 pc

[Cassam-ChenaО et al. 2008]

Shock velocity 6000 km/s

Cassiopeia A Core Collapse Color X-ray composite: Red: Si Blue: Fe Blue: Continuum Age 330 yrs, d=3.4 kpc Diameter 0.08° 5 pc

[Hwang et al. 2004]

Gamma-rays (and neutrinos) from Supernova-remnants
Signatures of 1050 ergs of energetic protons:

Within the SNR:

p+ISM/ejecta baryons+mesons gamma-rays, neutrinos, and secondary electrons uCR modifies the shock structure non-linear feedback on diffusive shock acceleration changes of the cosmic-ray spectrum ucr increases the B-field trapping+efficient radiation signatures from co-accelerated electrons Interaction/trapping of CR in molecular clouds Re-Acceleration in ambient medium/SNR

In the environment:

Gamma-rays (and neutrinos) from Supernova-remnants
Signatures of 1050 ergs of energetic protons:

Within the SNR:

p+ISM/ejecta baryons+mesons gamma-rays, neutrinos, and secondary electrons uCR modifies the shock structure non-linear feedback on diffusive shock acceleration changes of the cosmic-ray spectrum ucr increases the B-field trapping+efficient radiation signatures from co-accelerated electrons Interaction/trapping of CR in molecular clouds Re-Acceleration in ambient medium/SNR
[Drury, Aharonioan, VЖlk 1994]

In the environment:

The evolution of Gamma-ray telescopes
Fermi 2008-?? COS B (1975-1982) CGRO (1991-2000)

Chudakov Krimean 1950s Whipple 10m/ 1989: The first VHE signal from The Crab nebula

MAGIC (2003-)

MAGIC II (2009CTA (2014-)

Whipple 10m/ 1968

HEGRA CT1 (1991-2003)

H.E.S.S. (2003-

HEGRA CtSystem (1997-2002)

H.E.S.S. Phase II (2012-

CAT (1996-2001)

VERITAS (2008-)

HESS coll. (2006)

HESS coll. (2006)

1 year/20 hours

3 years/ 91 hours

RXJ 0852.0-4622 RCW 86 3 year/31 hours

RX J1713.7-3946 SN 1006 5 years/130 hrs

Broad band spectrum from RXJ1713-3946 Fermi-c
Nucleonic gamma-rays Leptonic gamma-rays

oll. [arxiv:1103.5727]

Hard spectrum (=1.5) evidence in favor of leptonic origin of gamma-rays. Not consistent with efficient, non-linear acceleration (filaments, X-ray variability)

VHE specific luminosities

Proton Cut-off energy at ~100 TeV Small (<10%) CR acceleration efficiency

Trouble maker: Cassiopeia A

The youngest (fastest shock) SNR in the Galaxy B-field ~ mG, We~WB~1048 ergs Bremsstrahlung+IC origin of gamma-rays WCR<1049 ergs!

Where are the PeV-accelerators?
A)PeV acceleration only during pre-Sedov stage PeV CR have already left the SN-shell or B)PeV CR are accelerated somewhere else

Large field of view/survey cap. Good sensitivity up to ~100 TeV

Comment on sensitivity

Generic Sensitivity curve:
F(>E) Background

Photon counts

E

CTA Whitepaper [arxiv:1008.3703]

Cherenkov telescope array
Flux sensitivity

Large facility O(100) telescopes, one array in northern and one array in southern hemisphere Three different types of telescopes (ь24 m, 23 m, 7 m) in graded array configuration, covering ~3-4 km2 Superb angular, energy resolution, gamma-hadron separation Currently in preparatory phase (839 persons, 76 parties, 25 countries)

SCORE array

Classical Cherenkov shower front sampling array (40 stations~160 channels)/sqkm Adequate performance above 20 TeV, collection area 10-100 km
2

Currently in proto-typing phase , cooperation with TUNKA, Auger

Physics with gamma-rays above 10 TeV

Cosmic accelerators:

Locating PeV cosmic-ray accelerators Measuring the B-field at Pulsar wind termination shock Locating the sources of ultra-high energy cosmic-rays Measuring dust emission in the universe Measuring the distance of Galactic gamma-ray sources Searching for Axions A new observational window (closer to Neutrino telescopes' energy)

Gamma-ray propagation:

Unknown:

Cosmic accelerators

Looking for run-away cosmic-rays (Aharonian 1995, Caprioli et al. 2009)

Probes of Cosmic ray probagation (interaction with molecular clouds)

100 VHE sources (circles) 1500 HE sources (red dots

Survey prospect:

25 CTA telescopes (10 degree FOV each)

SCORE FOV

The Huge Electron Accelerator

The Crab pulsar and nebula

Pulsed emission with Fermi /MAGIC and now VERITAS!

N. Otte reported on the Fermi symposium last week:

Shocked magnetospheric wind model

Unique opportunity to measure the B-field close to the shock!

[Rees&Gunn 1974] [Kennel&Coroniti 1984]

[Meyer, DH, Zechlin 2010]

Shocked magnetospheric wind model

Unique opportunity to measure the B-field close to the shock!

[Rees&Gunn 1974] [Kennel&Coroniti 1984]

Low B

Hi B

[Meyer, DH, Zechlin 2010]

Surprise in September 2010 and even more so in April 2011: Crab flare

Truly a PeV (Electron) Accelerator!

[Lobanov, Horns, Muxlow accepted 2011]

VHE gamma-rays from Crab flare

Synchrotron self-Compton small contribution/not visible Beamed emission at D>100: sizeable VHE emission Unbeamed inverse Compton on nebula: Could show up at ~400 TeV

Locating ultra-high energy cosmic ray accelerators

Origin of UHECR in local structure with efficient confinement gamma-rays from cascades

[Kneiske, Kulbart, Sigl, DH] (indication for a UHECR anisotropy from TA talk by G. Rubtsov yesterday)

Absorption on the Far infrared EBL

Gamma-ray absorption on the galactic radiation field

Infer the radiation in the galactic plane or Estimate distance based upon optical depth Opportunity to verify pair-absorption
Far Side of the Galaxy

Galactic center [Moskalenko, Porter 2006]

In Summary:

Current gamma-ray data do not support cosmic-rays at knee energy acceleration in young SNRs Rich physics topics for E>10 TeV:

Origin of cosmic-rays at knee energies Extreme accelerators (pulsar wind nebulae) Cascade emission from UHECR ...

Requirement: O(1 km2) surface array/ O(10 km2) Cherenkov array (next talk) or CTA (?)