Revisiting the search for dark matter subhalos using the Fermi-LAT 4FGL-DR4 catalog

TL;DR

This paper reanalyzes Fermi-LAT gamma-ray data to identify potential dark matter subhalo candidates, finding 32 new candidates with properties consistent with dark matter annihilation, but further validation is needed.

Contribution

It introduces a new search for dark matter subhalos using the latest Fermi-LAT data and compares spectral fits with empirical and dark matter models to identify candidates.

Findings

Identified 32 potential dark matter subhalo candidates.

Candidates have J-factors from 0.2 to 5.8 x 10^{20} GeV^2 cm^{-5}.

Further observations are needed to confirm the nature of these candidates.

Abstract

Numerical simulations suggest that dark matter halos surrounding galaxies host numerous small subhalos, which might be detectable by the Fermi-LAT. In this work, we revisit the search for gamma-ray subhalo candidates using the latest Fermi-LAT 4FGL-DR4 catalog. The search is performed by fitting the spectral data of unassociated point sources in the catalog through an unbinned maximum likelihood method. We consider two models in the fitting. One is an empirical function provided by the catalog, and another is a DM model in which DM particles within nearby subhalos annihilate into gamma rays and other Standard Model particles. Based on the fitting results, we identify 32 candidates for which the maximum likelihood value of the DM model fit exceeds that of the empirical function fit. The estimated J-factors of these candidates range from $0.2$ to $5.8 \times 10^{20}\,{\rm GeV^{2}\,cm^{-5}}$, the DM particle masses vary from $30$ to $500\,{\rm GeV}$ and 12 of them are within the range of $[30, 80]\,{\rm GeV}$. Candidate 4FGL J2124.2+1531 is an exception with a J-factor of $4.52 \times 10^{21}\,{\rm GeV^{2}\,cm^{-5}}$ and a particle mass of $3108.44\,{\rm GeV}$. Interestingly, the identified candidates do not overlap with those reported in previous works, and we discuss the possible reasons for the discrepancy. At the current stage, we cannot rule out the possibility that these candidates are gamma-ray pulsars, and further confirmation through multi-band observations is required.