3D template-based Fermi-LAT constraints on the diffuse supernova axion-like particle background

Axion-like particles (ALPs) may be abundantly produced in core-collapse (CC) supernovae (SNe); hence, the cumulative signal from all past supernova (SN) events can create a diffuse flux peaked at energies of about 25 MeV. We improve upon the modeling of the ALPs flux by including a set of CC SN models with different progenitor masses, as well as the effects of failed CC SNe, which yield the formation of black holes instead of explosions. Relying on the coupling strength of ALPs to photons and the related Primakoff process, the diffuse SN ALP flux is converted into gamma rays while traversing the magnetic field of the Milky Way. The spatial morphology of this signal is expected to follow the shape of the Galactic magnetic field lines. We make use of this via a template-based analysis that utilizes 12 years of Fermi-LAT data in the energy range from 50 MeV to 500 GeV. In our benchmark case of the realization of astrophysical and cosmological parameters, we find an upper limit of g(alpha gamma) less than or similar to 3.76 x 10(-11) GeV-1 at a 95% confidence level for m(a) << 10(-11) eV, while we find that systematic deviations from this benchmark scenario induce an uncertainty as large as about a factor of two. Our result slightly improves the CAST bound, while still being a factor of six (baseline scenario) weaker than the SN1987A gamma-ray burst limit.

Automated summary

Axion-like particles (ALPs) can be abundantly produced in core-collapse supernovae (SNe), creating a diffuse flux peaked at energies of about 25 MeV. By improving the modeling of the ALPs flux, this study reveals the spatial morphology of the signal can follow the shape of the Galactic magnetic field. Utilizing 12 years of Fermi-LAT data, the analysis provides an upper limit for the coupling strength of ALPs to photons, while also assessing the uncertainty caused by systematic deviations from the benchmark scenario.