title: A Study of Very High Energy Gamma-Ray Emission from Extragalactic Objects with H.E.S.S.
creator: Nedbal, Dalibor
subject: ddc-530
subject: 530 Physics
description: 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.
date: 2008
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/8945/1/Dalibor_Nedbal_Dissertation.pdf
identifier: DOI:10.11588/heidok.00008945
identifier: urn:nbn:de:bsz:16-opus-89459
identifier:   Nedbal, Dalibor  (2008) A Study of Very High Energy Gamma-Ray Emission from Extragalactic Objects with H.E.S.S.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/8945/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng