A search for a dark matter annihilation signal towards the Canis Major overdensity with H.E.S.S

TL;DR

This study used H.E.S.S. telescopes to search for gamma-ray signals from dark matter annihilation in the Canis Major overdensity, setting upper limits on the annihilation cross-section and constraining dark matter models.

Contribution

First to analyze H.E.S.S. data for dark matter signals in the Canis Major overdensity, providing new constraints on dark matter properties and halo models.

Findings

No gamma-ray signal detected.

Set upper limits on dark matter annihilation cross-section.

Constrained dark matter models with specific halo assumptions.

Abstract

A search for a dark matter (DM) annihilation signal into $\gamma$-rays toward the direction of the Canis Major (CMa) overdensity is presented. The nature of CMa is still controversial and one scenario represents it as a dwarf galaxy, making it an interesting candidate for DM annihilation searches. A total of 9.6 hours of high quality data were collected with the H.E.S.S. array of Imaging Atmospheric Cherenkov Telescopes (IACTs) and no evidence for a very high energy $\gamma$-ray signal is found. Upper limits on the CMa dwarf galaxy mass of the order of 10$^{9}$ M$_{\odot}$ are derived at the 95% C.L. assuming neutralino masses in the range 500 GeV - 10 TeV and relatively large annihilation cross-sections. Constraints on the velocity-weighted annihilation cross section $<\sigma v>$, are calculated for specific WIMP scenarios, using a NFW model for the DM halo profile and taking advantage of numerical simulations of hierarchical structure formation. 95% C.L. exclusion limits of the order of 5 $\times$ 10$^{-24}$ cm$^{3}$ s$^{-1}$ are reached in the 500 GeV - 10 TeV DM particle mass interval, assuming a total halo mass of 3 $\times$ 10$^{8}$ M$_{\odot}$.