Poster Abstract

P.13 Anwesh Majumder (Universiteit van Amsterdam)

Intense AGN activity in the merging cluster Cygnus A

We report on a detailed spatial and spectral analysis of the large-scale X-ray emission from the merging cluster Cygnus A. We use 2.2 Msec Chandra and 40 ksec XMM-Newton archival datasets to map the thermodynamic properties of the intracluster gas in the merger region between the two sub-clusters in the system. These maps corroborate the presence of complex ICM structure and temperature fluctuations seen previously which show clear evidence of heating along the merger axis. We investigate the source of this heating and quantify the excess energy in the merger region by comparing with simple spherical cluster simulations. The spherical models for the two sub-clusters are constructed using azimuthally averaged density and temperature profiles determined from the data neglecting the merger region. These models for the “undisturbed" sub-clusters were then folded through the MARX and SIXTE instrument simulators to produce realistic mock Chandra and XMM observations. The thermodynamic properties in the merger region from these mock X-ray observations were used as a baseline for comparison with the actual observations. We clearly detect temperature increases of ~3-4 keV along the merger axis compared to the undisturbed models, possibly due to AGN activity, along with a smooth, large-scale temperature excess attributed to the ongoing merger. Based on the location and strength of these features, we derive the energy, age and duration of possible AGN outbursts. The joint analysis from Chandra and XMM provide the strongest constraints to date on the effects of possible AGN activity and the ongoing merger in the Cygnus A cluster.