2026/05/20 by Siddhant Manna, Shantanu Desai
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena
paper · pdf · doi:10.1016/j.dark.2026.102404
We present an analysis of the non-thermal properties of the merging galaxy cluster SPT-CL J2012-5649/Abell~3667 (z = 0.0556, M500 = 7.16 × 1014 M_\odot) using the MINOT non-thermal emission modeling framework. The predicted hadronic gamma-ray flux from pp interactions in the 1--300 GeV band is 2.82 × 10-11 \mathrmcm-2 s-1 within R500, rising to 1.15 × 10-10 \mathrmcm-2 s-1 at the truncation radius (3.7 R500), in broad agreement with the Fermi-LAT reported flux of 1.3 × 10-10 \mathrmcm-2 s-1. Approximately 76% of the predicted hadronic flux originates from beyond R500. The Inverse Compton contribution from cosmic-ray electrons is subdominant relative to the hadronic π0-decay gamma-ray component by a factor of ∼20 in the 1--300 GeV energy band, and therefore does not contribute significantly to the observable signal. The best fit of the observed Fermi-LAT data is achieved with a hadronic emission assuming a proton spectrum ∝ E-3.5 and a proton energy density almost in equipartition with the thermal energy density. Even though those parameters may look extreme, they could well be explained by the particle acceleration by low Mach number accretion shocks.