Indirect Dark Matter Detection from Dwarf Satellites: Joint Expectations from Astrophysics and Supersymmetry

TL;DR

This paper develops a methodology to predict gamma-ray signals from dark matter annihilation in dwarf galaxies, exploring the impact of halo substructure models and supersymmetric parameters on detection prospects with Fermi.

Contribution

It introduces a formalism for calculating halo substructure boosts and assesses their effects within the CMSSM framework, providing new insights into detection probabilities.

Findings

Boost factors depend strongly on halo substructure extrapolation.

Preferred minimum halo mass range is 10^-9 to 10^-6 solar masses.

Fermi has about a 20% chance to detect signals from Draco after 5 years.

Abstract

We present a general methodology for determining the gamma-ray flux from annihilation of dark matter particles in Milky Way satellite galaxies, focusing on two promising satellites as examples: Segue 1 and Draco. We use the SuperBayeS code to explore the best-fitting regions of the Constrained Minimal Supersymmetric Standard Model (CMSSM) parameter space, and an independent MCMC analysis of the dark matter halo properties of the satellites using published radial velocities. We present a formalism for determining the boost from halo substructure in these galaxies and show that its value depends strongly on the extrapolation of the concentration-mass (c(M)) relation for CDM subhalos down to the minimum possible mass. We show that the preferred region for this minimum halo mass within the CMSSM with neutralino dark matter is ~10^-9-10^-6 solar masses. For the boost model where the observed power-law c(M) relation is extrapolated down to the minimum halo mass we find average boosts of about 20, while the Bullock et al (2001) c(M) model results in boosts of order unity. We estimate that for the power-law c(M) boost model and photon energies greater than a GeV, the Fermi space-telescope has about 20% chance of detecting a dark matter annihilation signal from Draco with signal-to-noise greater than 3 after about 5 years of observation.