Investigating the detection of dark matter subhalos as extended sources with Fermi-LAT

Abstract

Cold dark matter (DM) models for structure formation predict that DM subhalos are present in the Galaxy. In the standard paradigm of DM as weakly interacting massive particle, subhalos are expected to shine in gamma rays and to provide a signal detectable with current instruments, notably with the Large Area Telescope (LAT) aboard the Fermi~satellite. This is the main motivation behind searches for DM signals towards dwarf spheroidal galaxies and unidentified Fermi-LAT sources. A significant angular extension detected from unassociated sources located at relatively high latitudes is considered a "smoking gun" signature for identifying DM subhalos. In the present work, we systematically explore, by means of state-of-the-art models of cold DM halos in the Galaxy, the detectability of extended subhalos with Fermi-LAT. We simulate a DM signal exploring different assumptions of subhalos distribution in the Galaxy and DM profile, and reconstruct its flux through a realistic Fermi-LAT analysis pipeline. In the most optimistic case, we show that a detection of extended DM subhalos can be made for annihilation cross sections higher than $3\times 10^{-26}$ cm${}^3$/s (for a 100 GeV DM mass), still compatible with existing gamma-ray constraints, and that, in this case, the preference for extension of the source (vs point-like hypothesis) is significant. For fainter signals, instead, halos not only do not show significant extension, but they are not even detectable significantly as point-like sources.

arXiv comment12 pages, 11 figures. Comments as welcome!

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• Search for dark matter annihilation signals from unidentified Fermi-LAT objects with H.E.S.S
• Spatial extension of dark subhalos as seen by Fermi-LAT and implications for WIMP constraints
• Harnessing the Population Statistics of Subhalos to Search for Annihilating Dark Matter
• Emergent gravity fails to explain color-dependent galaxy-galaxy lensing signals from SDSS Dr7
• Searching for dark matter subhalos in the Fermi-LAT catalog with Bayesian neural networks
• Can prompt cusps of WIMP dark matter be detected as individual gamma-ray sources?
• Dark matter annihilation into leptons through gravity portals
• The viability of low-mass subhaloes as targets for gamma-ray dark matter searches
• Analytical insight into dark matter subhalo boost factors for Sommerfeld-enhanced $s$- and $p$-wave $\gamma$-ray signals
• Impact of baryons on the population of Galactic subhalos and implications for dark matter searches