COSMIC RAY ORIGINS. Stella Bradbury, University of Leeds, U.K. g -ray sources the cosmic ray connection detection technique galactic and extragalactic accelerators future instruments and new targets Ultra High Energies. Cosmic Rays ?.
Stella Bradbury, University of Leeds, U.K.
On 7th August 1912, Victor Hess demonstrated that the flux of “ionising radiation” increased above 2 km altitude
cosmic ray nuclei should produce g-raysin collisions with interstellar material diffuse g-raybackground along galactic plane?
Simulated Cherenkov lateral distribution at ground:
a single 12.5 mm Ø photomultiplier pixel of the Whipple Telescope camera subtends 0.12º
local muon ?
EGRET 100 MeV - 30 GeV
EGRET solar flare spectrum :
Diffuse background due to p+CR + Hnuclei p0 g g observed but where do we get the p+CR from?
Chandra X-ray image
VLT optical image
TeV g-rays - point source
TeV spectrum consistent with e- synchrotron self-Compton emission magnetic field ~16 nT within 0.4 pc of the pulsar.
1st order Fermi acceleration
Detection of TeV g-rays from Cassiopeia A by HEGRA can still be explained as e- inverse Compton without e.g. a po decay component
Chandra X-ray image of Cas A
Still no conclusive evidence for acceleration of relativistic nuclei
Giant molecular clouds could act as a target for p+CR + H p0 g + g if bathed in uniform cosmic rays or as a cosmic beam dump for a neighboring particle accelerator
such as a black hole binary:
Cosmic ray production must be high in starburst galaxies where there is a high supernova rate and strong stellar winds?
~ 1 % of galaxies have a bright central nucleus that outshines the billions of stars around it
Radio and X-ray observations reveal relativistic jets presumed to be powered by a central supermassive black hole
Rapid TeV g-ray flares emission region only ~ size of solar system!
Whipple Telescope - Mkn 421
Assume emission region is associated with shock accelerated particles, then pick any combination of :
Common feature is a cut-off at E0 ~ 4 - 6 TeV. Is this intrinsic to such objects - limit of accelerator?
There are only 6 established TeV g-ray emitting AGN; the most recent flared to a detectable level on 17/05/02
may cut-off g-ray flux from distant AGN as gg-ray + gIR e- + e+ ( cross-section peaks ateg-ray etarget~ 2 (mec2)2 )
TeV g-ray detection of AGN 600 million light years away limits on IR background density 10 more restrictive than direct satellite measurement in 4 - 50 mm range plagued by foreground starlight
20 keV - 1 MeV
VLT optical afterglow of GRB000131 - at redshift 4.5 1013 light years distant
(epoch of galaxy formation?)
In 1969-70 the Vela 5 nuclear test detection satellites discovered g-ray bursts.
Cosmological distances require an astronomical energy source!
Invoke shocks in beamed jets!
Merging neutron stars ?
> 5 years
20 MeV - 300 GeV
Solar arrays: very large mirror area but small field of view.
STACEE (2001 - ) 50 GeV - 250 GeV > 2000 m2 of heliostats reflect Cherenkov light via a secondary mirror onto a photomultiplier camera in the tower.
CELESTE, Solar II & GRAAL use the same principle.
Imaging telescope with a single 17m diameter dish.
bridging the gap between ground-based instruments and satellite data
Simulated GLAST detection above diffuse background
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