A non-zero helicity of cosmological magnetic fields could, if detected, have important implications for models of the electroweak phase transition in the early Universe. It has been suggested that the helicity of such a field could be related to the handedness of photon arrival directions in the diffuse gamma-ray sky observed by the \emph{Fermi} Large Area Telescope (LAT). \cite{tashiro_search_2014} found a left-handedness when applying this method, implying the existence of an extragalactic magnetic field with negative helicity. In this work the same method is applied, using twice as much data from the LAT due to the longer exposure time, providing higher statistical certainty. Additionally, the potential effects of the non-uniform LAT exposure and contamination of galactic emission are studied using simulated data sets. The results obtained indicate no significant signal, as the simulations suggest that the uncertainty was highly underestimated in \cite{tashiro_search_2014}, and any observed handedness using the updated LAT data is found to be compatible with zero within this new error estimate.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:su-169518 |
| Date | January 2019 |
| Creators | Asplund, Julia |
| Publisher | Stockholms universitet, Institutionen för astronomi, Nordita |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | Julia Asplund |
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