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A global analysis of dark matter signals from 27 dwarf spheroidal galaxies using 11 years of Fermi-LAT observations

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Title: A global analysis of dark matter signals from 27 dwarf spheroidal galaxies using 11 years of Fermi-LAT observations
Authors: Hoof, S
Geringer-Sameth, A
Trotta, R
Item Type: Journal Article
Abstract: We search for a dark matter signal in 11 years of Fermi-LAT gamma-ray data from 27 Milky Way dwarf spheroidal galaxies with spectroscopically measured J-factors. Our analysis includes uncertainties in J-factors and background normalisations and compares results from a Bayesian and a frequentist perspective. We revisit the dwarf spheroidal galaxy Reticulum II, confirming that the purported gamma-ray excess seen in Pass 7 data is much weaker in Pass 8, independently of the statistical approach adopted. We introduce for the first time posterior predictive distributions to quantify the probability of a dark matter detection from another dwarf galaxy given a tentative excess. A global analysis including all 27 dwarfs shows no indication for a signal in nine annihilation channels. We present stringent new Bayesian and frequentist upper limits on the dark matter cross section as a function of dark matter mass. The best-fit dark matter parameters associated with the Galactic Centre excess are excluded by at least 95% confidence level/posterior probability in the frequentist/Bayesian framework in all cases. However, from a Bayesian model comparison perspective, dark matter annihilation within the dwarfs is not strongly disfavoured compared to a background-only model. These results constitute the highest exposure analysis on the most complete sample of dwarfs to date. Posterior samples and likelihood maps from this study are publicly available.
Issue Date: 13-Feb-2020
Date of Acceptance: 27-Jan-2020
URI: http://hdl.handle.net/10044/1/77354
DOI: 10.1088/1475-7516/2020/02/012
ISSN: 1475-7516
Publisher: IOP Publishing
Journal / Book Title: Journal of Cosmology and Astroparticle Physics
Volume: 2020
Issue: 02
Copyright Statement: © 2020 IOP Publishing Ltd and Sissa Medialab. This is an author-created, un-copyedited version of an article accepted for publication in Journal of Cosmology and Astroparticle Physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher authenticated version is available online at https://iopscience.iop.org/article/10.1088/1475-7516/2020/02/012
Sponsor/Funder: European Commission
Science and Technology Facilities Council
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Funder's Grant Number: H2020-MSCA-RISE-2015-691164
ST-N000838
ST/N000838/1
ST/P000762/1
Keywords: astro-ph.CO
astro-ph.CO
astro-ph.HE
hep-ph
astro-ph.CO
astro-ph.CO
astro-ph.HE
hep-ph
0201 Astronomical and Space Sciences
0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics
Nuclear & Particles Physics
Notes: 26+3 pages, 7 figures
Publication Status: Published
Appears in Collections:Physics
Astrophysics
Statistics
Mathematics