Fermi-LAT Sensitivity to Dark Matter Annihilation in Via Lactea II Substructure

TL;DR

This paper assesses Fermi-LAT's potential to detect dark matter annihilation signals from Galactic subhalos, using simulations and improved modeling to estimate detectability over a ten-year mission.

Contribution

It introduces an improved formalism for boost factor estimation and detailed Monte Carlo simulations to evaluate Fermi-LAT's sensitivity to dark matter signals from subhalos.

Findings

A few subhalos could be detected with >5 sigma significance.

Detectable subhalos would likely appear extended rather than point sources.

Detection is feasible for WIMP masses up to about 150 GeV.

Abstract

We present a study of the ability of the Fermi Gamma-ray Space Telescope to detect dark-matter annihilation signals from the Galactic subhalos predicted by the Via Lactea II N-body simulation. We implement an improved formalism for estimating the boost factor needed to account for the effect of dark-matter clumping on scales below the resolution of the simulation, and we incorporate a detailed Monte Carlo simulation of the response of the Fermi-LAT telescope, including a simulation of its all-sky observing mode integrated over a ten year mission. We find that for WIMP masses up to about 150 GeV in standard supersymmetric models with velocity-averaged cross section 3*10^-26 cm^3 s^-1, a few subhalos could be detectable with >5 standard deviations significance and would likely deviate significantly from the appearance of a point source.