Can gamma rays from a merging cluster match what Fermi actually sees?

Using the MINOT framework, researchers modeled gamma-ray production in the merging galaxy cluster Abell 3667 from collisions between cosmic rays and gas. Their hadronic model predicts a 1–300 GeV flux matching Fermi-LAT observations, with most emission from the cluster's outer regions. But the observed spectrum is much steeper than theory expects—a tension suggesting either missing physics or systematic uncertainties in the measurements.