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arXiv · 2605.25586

Legacy analysis of Milky Way dwarf spheroidal satellite galaxies: an update

A. Circiello·M. Di Mauro·M. Ajello·C. Karwin·A. Drlica-Wagner·M. Á. Sánchez-Conde
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Abstract

Studies of Fermi-Large Area Telescope (LAT) data coincident with dwarf spheroidal satellite galaxies (dSphs) of the Milky Way (MW) have put the most stringent constraints on models of annihilating dark matter (DM) with candidate masses in the GeV-TeV range. Recent results found the presence of small, local significance excesses from these targets, at the 2-3 sigma level. However, these excesses disagree on the predicted properties of the DM candidate, and their significance vanishes when considering the correction factors for the number of trials. In this work, we apply key improvements to the analysis of the dSphs. We use stricter cuts on the data, implement a method to adaptively model the background, and assume an updated framework for DM annihilation. We find that our improved background modeling leads to a better agreement between the model and the data. This produces an increase in the local and global significance of the dSphs excess compared to previous studies. Finally, we find that the DM properties obtained in this work are less dependent on the sample of dSphs being considered compared to previous studies, while remaining in agreement with the predictions from the Galactic center excess observed by the Fermi-LAT and the antiproton excess observed by the Alpha Magnetic Spectrometer (AMS-02). Considering our improvements, a future significant increase in the number of dwarfs may lead to a definitive confirmation or exclusion of the DM interpretation of the Galactic center excess.

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A. Circiello, M. Di Mauro, M. Ajello, C. Karwin, A. Drlica-Wagner, M. Á. Sánchez-Conde. 2026-06-05. Legacy analysis of Milky Way dwarf spheroidal satellite galaxies: an update. https://doi.org/10.3847/2041-8213%2Fae71c7

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