Is The Gamma-Ray Source 3FGL J2212.5+0703 A Dark Matter Subhalo?

TL;DR

This paper investigates whether the gamma-ray source 3FGL J2212.5+0703 is a dark matter subhalo by analyzing its spatial extension and considering alternative astrophysical explanations, with implications for dark matter particle properties.

Contribution

The study provides the first detailed analysis of the spatial extension of 3FGL J2212.5+0703 and evaluates astrophysical alternatives, offering constraints on dark matter particle mass and annihilation cross section.

Findings

The source prefers a spatially extended profile with 5.1 sigma significance.

A pair of nearby gamma-ray sources could explain the observed extension.

Dark matter interpretation suggests particles of 18-33 GeV with cross section ~10^-26 cm^3/s.

Abstract

In a previous paper, we pointed out that the gamma-ray source 3FGL J2212.5+0703 shows evidence of being spatially extended. If a gamma-ray source without detectable emission at other wavelengths were unambiguously determined to be spatially extended, it could not be explained by known astrophysics, and would constitute a smoking gun for dark matter particles annihilating in a nearby subhalo. With this prospect in mind, we scrutinize the gamma-ray emission from this source, finding that it prefers a spatially extended profile over that of a single point-like source with 5.1 sigma statistical significance. We also use a large sample of active galactic nuclei and other known gamma-rays sources as a control group, confirming, as expected, that statistically significant extension is rare among such objects. We argue that the most likely (non-dark matter) explanation for this apparent extension is a pair of bright gamma-ray sources that serendipitously lie very close to each other, and estimate that there is a chance probability of ~2% that such a pair would exist somewhere on the sky. In the case of 3FGL J2212.5+0703, a model with a second gamma-ray point source at the location of a known BZCAT/CRATES radio source yields fits that are comparable in quality to those obtained for a single extended source. If 3FGL J2212.5+0703 is a dark matter subhalo, it would imply that dark matter particles have a mass of ~18-33 GeV and an annihilation cross section on the order of sigma v ~ 10^-26 cm^3/s (for the representative case of annihilations to bb), similar to the values required to generate the Galactic Center gamma-ray excess.