A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. August 2015. / This work investigates the impact of the extragalactic background light fluctuations
on very high energy !-ray spectra from distant blazars. We calculate
the extragalactic background light spectral energy distribution using a
model that extends those proposed by Razzaque et al. (2009ApJ.697.483R)
and Finke et al. (2010ApJ.712.238F). We introduce a model for fluctuations
in the extragalactic background light based on fluctuations in the star formation
rate density, since these two fluctuations can reasonably be expected to
be correlated. Fluctuations in the star formation rate are estimated from the
semi-analytical galaxy catalogue of Guo et al. (2013MNRAS.428.1351G), we
use his model to derive the resulting opacities for !-rays from distant sources.
We determine the mean, lower and upper limits for the scatter of the star
formation rate density, which then allow us to compute corresponding limits
on the extragalactic background light spectrum. We then calculate the impact
of these fluctuations limits on the !-ray optical depth. This appears to
be the first detailed analytical model that aims to account for the impact of
extragalactic background light fluctuations on the !-ray opacity. The model
predicts relatively high variations ( 15%) on the opacity in the energy range
less than 100 GeV for nearby sources. The impact is found to be smaller
(⇠ 5%) for very high energy !-rays from distant sources.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/19295 |
| Date | January 2016 |
| Creators | Kudoda, Ayman Mohamed ELhadi Mohamed |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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