Ponente
Descripción
Galaxy clusters are the most massive gravitationally bound structures in the Universe. Even if clusters are nearly virialized structures, they undergo merging processes, creating merging shocks, and suffer from feedback from galaxies and AGNs; causing complex turbulent motions and amplifying their magnetic fields. These processes act as acceleration mechanisms for the plasma of the intracluster medium (ICM), originating a population of cosmic rays (CRs). Leptonic CRs have been long detected, but we should also expect a CR hadronic population that, through interactions with the ICM, should produce neutral pions that decay into gamma-rays. The detection of diffuse gamma-ray emission from galaxy clusters is one of the long-awaited milestones for the high-energy astroparticle physics community. Still, no unambiguous detection has been yet obtained.
In this talk, we will present the results of a combined cluster analysis searching for CR-induced gamma-ray signals, using 16 years of Fermi-LAT data. In our previous work (di Mauro et al. 2023) we obtained from the combined analysis of 49 local galaxy clusters (12 years of data) a hint of signal between 2.5-3 sigmas, depending on the DM model considered. These results are aligned with the most recent works on searches for gamma-ray emission from clusters on Fermi-LAT data, which consistently find a non-vanishing hint of signal around the detection threshold. In this new work, we use a sample of near, well-known galaxy clusters and develop CR-induced emission templates using well-established X-ray measurements for calibration, assuming self-similarity for the members of our sample. To strengthen the robustness of our analysis, we define benchmark models to encapsulate the uncertainties in the spectral and spatial profiles for the CR-induced emission and perform the standard template-fitting analysis using the likelihood ratio test.
