The Mysterious Gamma-Ray Excess of Andromeda: Comparing Millisecond Pulsars to Dark Matter

The discovery of an excess in gamma rays coming from the center of our Milky Way galaxy in 2009 has opened up an exciting field in the search for dark matter. More recently in 2017, another such an excess has been confirmed to be present in the Andromeda galaxy. In this work we analyze 10 years of Fermi-LAT data in the attempt to rigorously characterize the significance of this excess when accounting for uncertainties coming from difficulties in modeling the gamma-ray background. For this purpose we constructed specific background models for the Andromeda sky region, employing modern inpainting techniques based on algorithms involving neural networks. We furthermore developed models for testing the hypothesis that this signal could be caused by a population of millisecond pulsars (MSPs), which are as of yet unresolved by the Fermi space telescope. Our findings indicate, that the emission of annihilating dark matter is unwarranted when accounting for the emission of the beforementioned pulsars or contributions from interstellar gas and dust. The results of this work build up on previous attempts on this matter, but we use a more sophisticated and robust statistical framework in combination with templates specifically constructed for this purpose alone.