Constraints on dark matter annihilation from a nearby subhalo candidate

TL;DR

This paper uses 17 years of Fermi-LAT gamma-ray data to set strong constraints on dark matter annihilation from a nearby subhalo candidate, leveraging its large J-factor to improve existing limits.

Contribution

It provides the first gamma-ray constraints on dark matter annihilation from a candidate subhalo with an exceptionally high J-factor, using conservative analysis methods.

Findings

Identified a tentative gamma-ray excess near the subhalo candidate.

Derived upper limits on dark matter annihilation cross-section that are potentially stronger than previous constraints.

Demonstrated the potential of nearby subhalo candidates to improve dark matter searches.

Abstract

A recent analysis of pulsar timing data has reported evidence for a massive ($\sim 6 \times 10^7 M_{\odot}$) dark matter subhalo located only $\sim 0.8$ kpc from Earth. This candidate implies an exceptionally large $J$-factor of $\sim 10^{23}\,{\rm GeV^2\,cm^{-5}}$, exceeding that of known classical dwarf spheroidal galaxies by orders of magnitude and rivaling the Galactic Center. In this work, we utilize more than 17 years of $\textit{Fermi}$-LAT data to search for gamma-ray emission from this subhalo. We identify a tentative excess in the region with ambiguous origin. Adopting a conservative strategy, we retain this excess without modeling additional astrophysical components, treating it instead as unmodeled background to derive upper limits on the dark matter annihilation cross-section for the $b\bar{b}$ and $\tau^+\tau^-$ channels. Despite this conservative treatment, the resulting limits remain stringent due to the exceptionally large $J$-factor. Subject to the dynamical confirmation of the subhalo, these constraints are potentially orders of magnitude stronger than those obtained from combined analyses of dwarf spheroidal galaxies and blind subhalo searches.