Документ взят из кэша поисковой машины. Адрес оригинального документа : http://tunka.sinp.msu.ru/en/presentation/horns_vhe.pdf Дата изменения: Sun May 22 11:45:05 2011 Дата индексирования: Mon Feb 4 18:35:50 2013 Кодировка: Поисковые слова: molecular cloud

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 (?)