Sommerfeld-enhanced dark matter searches with dwarf spheroidal galaxies

TL;DR

This paper investigates signals from Sommerfeld-enhanced dark matter annihilation in dwarf spheroidal galaxies, emphasizing the importance of accurate velocity-dependent J-factors derived from improved density profile priors, and assesses detection prospects with the Cherenkov Telescope Array.

Contribution

It introduces a method to compute more realistic J-factors using informed priors from recent structure formation models, impacting dark matter detection strategies.

Findings

J-factors are reduced by a factor of a few with realistic priors.

Cherenkov Telescope Array can detect thermal Wino dark matter in promising dSphs.

Realistic priors significantly influence dark matter annihilation signal estimates.

Abstract

We study observable signals from dark matter that self-annihilates via the Sommerfeld effect in dwarf spheroidal galaxies (dSphs). Since the effect of the Sommerfeld enhancement depends on the velocity of dark matter, it is crucial to determine the profile of dSphs to compute the J-factor, i.e., the line-of-sight integral of density squared. In our study we use the prior distributions of the parameters for satellite density profiles in order to determine the J-factor, making most out of the recent developments in the N-body simulations and semi-analytical modeling for the structure formation. As concrete models, we analyze fermionic dark matter that annihilates via a light scalar and Wino dark matter in supersymmetric models. We find that, with the more realistic prior distributions that we adopt in this study, the J-factor of the most promising dSphs is decreased by a factor of a few, compared with earlier estimates based on non-informative priors. Nevertheless, the Cherenkov Telescope Array should be able to detect the thermal Wino dark matter by pointing it toward best classical or ultrafaint dSphs for 500 hours.