# Sommerfeld-Enhanced $J$-Factors For Dwarf Spheroidal Galaxies

## TL;DR

This paper models the dark matter distribution in dwarf spheroidal galaxies to compute Sommerfeld-enhanced J-factors, revealing that velocity-dependent effects can alter the ranking of promising targets for dark matter detection.

## Contribution

It provides the first detailed calculations of Sommerfeld-enhanced J-factors for dSphs, accounting for astrophysical uncertainties and their impact on indirect detection prospects.

## Key findings

- Sommerfeld enhancement significantly alters J-factor rankings.
- Astrophysical uncertainties affect the predicted J-factors.
- Target prioritization for dark matter searches may change with velocity-dependent models.

## Abstract

For models in which dark matter annihilation is Sommerfeld-enhanced, the annihilation cross section increases at low relative velocities. Dwarf spheroidal galaxies (dSphs) have low characteristic dark matter particle velocities and are thus ideal candidates to study such models. In this paper we model the dark matter phase space of dSphs as isotropic and spherically-symmetric, and determine the $J$-factors for several of the most important targets for indirect dark matter searches. For Navarro-Frenk-White density profiles, we quantify the scatter in the $J$-factor arising from the astrophysical uncertainty in the dark matter potential. We show that, in Sommerfeld-enhanced models, the ordering of the most promising dSphs may be different relative to the standard case of velocity-independent cross sections. This result can have important implications for derived upper limits on the annihilation cross section, or on possible signals, from dSphs.