Searching for TeV Dark Matter in Irregular dwarf galaxies with HAWC Observatory

TL;DR

This study searches for TeV-scale dark matter signals in 31 dwarf irregular galaxies using HAWC, setting new exclusion limits on WIMP annihilation and decay, and comparing these to limits from dwarf spheroidal galaxies.

Contribution

First to analyze dwarf irregular galaxies with HAWC for dark matter, providing complementary exclusion limits and insights into different galaxy evolution histories.

Findings

No significant dark matter signal detected.

Exclusion limits are comparable to classical dwarf spheroidals.

Limits are about 100 times weaker than ultrafaint dwarf spheroidal constraints.

Abstract

We present the results of dark matter (DM) searches in a sample of 31 dwarf irregular (dIrr) galaxies within the field of view of the HAWC Observatory. dIrr galaxies are DM dominated objects, which astrophysical gamma-ray emission is estimated to be negligible with respect to the secondary gamma-ray flux expected by annihilation or decay of Weakly Interacting Massive Particles (WIMPs). While we do not see any statistically significant DM signal in dIrr galaxies, we present the exclusion limits ($95\%~\text{C.L.}$) for annihilation cross-section and decay lifetime for WIMP candidates with masses between $1$ and $100~\text{TeV}$. Exclusion limits from dIrr galaxies are relevant and complementary to benchmark dwarf Spheroidal (dSph) galaxies. In fact, dIrr galaxies are targets kinematically different from benchmark dSph, preserving the footprints of different evolution histories. We compare the limits from dIrr galaxies to those from ultrafaint and classical dSph galaxies previously observed with HAWC. We find that the contraints are comparable to the limits from classical dSph galaxies and $\thicksim2$ orders of magnitude weaker than the ultrafaint dSph limits.