Deep observation of the NGC 1275 region with MAGIC: search of diffuse gamma-ray emission from cosmic rays in the Perseus cluster

Understand

Clusters of galaxies are expected to be reservoirs of cosmic rays (CRs) that should produce diffuse gamma-ray emission due to their hadronic interactions with the intra-cluster medium.

• The nearby Perseus cool-core cluster, identified as the most promising target to search for such an emission, has been observed with the MAGIC telescopes at very-high energies (VHE, E>100 GeV) for a total of 253 hr from 2009 to 2014.
• The active nuclei of NGC 1275, the central dominant galaxy of the cluster, and IC 310, lying at about 0.6$^\circ$ from the centre, have been detected as point-like VHE gamma-ray emitters during the first phase of this campaign.
• We report an updated measurement of the NGC 1275 spectrum, which is well described by a power law with a photon index of $3.6\pm0.2_{stat}\pm0.2_{syst}$ between 90 GeV and 1.2 TeV.