Dwarf Spheroidal J-factors with Self-interacting Dark Matter
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The next decade of searches in the field of dark matter will focus on the detection of gamma rays from dark matter annihilation in dwarf spheroidal galaxies. This dark matter-induced gamma ray flux crucially depends on a quantity known as the Jfactor. In current research, the J-factor calculations does not include self-interaction between the dark matter particles, but there are indications on galactic scales that dark matter is self-interacting. The purpose of this thesis is to introduce a thorough generalisation of the J-factor to include a self-interacting effect and to compute the factor for 20 dwarf spheroidal galaxies orbiting the Milky Way. We thoroughly study the fundamental theory needed to compute the J-factor, based on Newtonian dynamics and non-relativistic quantum mechanics. A maximum likelihood formalism is applied to velocity data from dwarf spheroidal galaxies, assuming a Gaussian distribution for the line of sight velocity data. From this we extract galactic length and density scale parameters. The acquired parameters are then used to compute the J-factor. Using a binning approach, we present an error estimate in J. The used method is compared to previously published results, by neglecting self-interaction. We perform the first fully rigorous calculation for the J-factor, properly taking into account the dark matter velocity distribution. We can deduce that a previously used approximation of the self-interaction overestimates the J-factor by 1.5 orders of magnitude. Furthermore, we confirm that our method produces three to four orders of magnitudes larger values compared to J-factors without self-interaction.
Fysik , Physical Sciences