TY  - GEN
KW  - Astroteilchenphysik 
KW  -  H.E.S.S.Astroparticle physics 
KW  -  Galaxy Clusters 
KW  -  Starburst Galaxies 
KW  -  Gamma Rays
ID  - heidok8945
AV  - public
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/8945/
N2  - Very-high-energy (VHE) gamma-ray astronomy has opened a unique window into the Universe of the highest energies, allowing one to efficiently investigate the question of the origin of high-energy cosmic rays. The H.E.S.S. array of four Imaging atmospheric Cherenkov (IACT) telescopes is utilised in this work to search for VHE gamma-rays from selected candidate extragalactic objects that are expected to contain significant populations of cosmic rays: galaxy clusters Abell 496, Abell 85, Coma cluster, Abell 754, Centaurus cluster and Hydra A, starburst galaxies NGC 253 and M 83, from an ultraluminous infrared galaxy Arp 220 and from an active galactic nucleus (AGN), RGB J0152+017. The instrument is described, giving an overview of the IACT technique, the data acquisition, data-quality determination, calibration, performance, and the actual analysis that was used to obtain the results. In the starburst galaxy NGC 253, a hint of a VHE signal is found at a ~3 sigma significance level. No significant VHE signal is found from the remaining non-AGN objects, and upper limits are presented. The upper limits of Abell 85 and Abell 496 are used to constrain the non-thermal to thermal energy ratio, which is ~8% for Abell 85 and is thus challenging theoretical estimates. The AGN, RGBJ0152+017, is in this work discovered in VHE gamma rays and its first-time broad-band spectral energy distribution is presented. While no new type of a VHE emitter is established, the presented theoretical expectations are very promising for the planned CTA observatory.
TI  - A Study of Very High Energy Gamma-Ray Emission from Extragalactic Objects with H.E.S.S.
Y1  - 2008///
A1  - Nedbal, Dalibor
ER  -