Examining The Fermi-LAT Third Source Catalog In Search Of Dark Matter Subhalos

TL;DR

This study searches for dark matter subhalos in Fermi-LAT gamma-ray data, identifying promising candidates with spectra consistent with 20-70 GeV dark matter particles, and constrains annihilation cross sections using subhalo distribution models.

Contribution

It introduces a method to identify potential dark matter subhalos among unassociated gamma-ray sources and provides new constraints on dark matter annihilation cross sections.

Findings

24 candidate sources consistent with 20-70 GeV dark matter annihilation

One source shows spatial extension at 4.2σ significance

Constraints on dark matter annihilation cross section are competitive with other methods

Abstract

Dark matter annihilations taking place in nearby subhalos could appear as gamma-ray sources without detectable counterparts at other wavelengths. In this study, we consider the collection of unassociated gamma-ray sources reported by the Fermi Collaboration in an effort to identify the most promising dark matter subhalo candidates. While we identify 24 bright, high-latitude, non-variable sources with spectra that are consistent with being generated by the annihilations of ~20-70 GeV dark matter particles (assuming annihilations to $b\bar{b}$), it is not possible at this time to distinguish these sources from radio-faint gamma-ray pulsars. Deeper multi-wavelength observations will be essential to clarify the nature of these sources. It is notable that we do not find any such sources that are well fit by dark matter particles heavier than ~100 GeV. We also study the angular distribution of the gamma-rays from this set of subhalo candidates, and find that the source 3FGL J2212.5+0703 prefers a spatially extended profile (of width ~0.15$^{\circ}$) over that of a point source, with a significance of 4.2$\sigma$ (3.6$\sigma$ after trials factor). Although not yet definitive, this bright and high-latitude gamma-ray source is well fit as a nearby subhalo of $m_{\chi} \simeq$ 20-50 GeV dark matter particles (annihilating to $b\bar{b}$) and merits further multi-wavelength investigation. Based on the subhalo distribution predicted by numerical simulations, we derive constraints on the dark matter annihilation cross section that are competitive to those resulting from gamma-ray observations of dwarf spheroidal galaxies, the Galactic Center, and the extragalactic gamma-ray background.