Decoding the thermal history of the merging cluster Cygnus A

Author:

Majumder Anwesh12ORCID,Wise M W21,Simionescu A234ORCID,de Vries M N5

Affiliation:

1. Astronomical Institute ‘Anton Pannekoek’, University of Amsterdam , Science Park 904, NL-1098 XH Amsterdam , the Netherlands

2. SRON, Netherlands Institute for Space Research , Niels Bohrweg 4, NL-2333 CA Leiden , the Netherlands

3. Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden , the Netherlands

4. Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo , Kashiwa, Chiba 277-8583 , Japan

5. Department of Physics/KIPAC, Stanford University , Stanford, CA 94305-4060 , USA

Abstract

ABSTRACT 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 Ms Chandra and 40 ks XMM–Newton archival data sets to determine the thermodynamic properties of the intracluster gas in the merger region between the two subclusters in the system. These profiles exhibit temperature enhancements that imply significant heating along the merger axis. Possible sources for this heating include the shock from the ongoing merger, past activity of the powerful AGN in the core, or a combination of both. To distinguish between these scenarios, we compare the observed X-ray properties of Cygnus A with simple, spherical cluster models. These models are constructed using azimuthally averaged density and temperature profiles determined from the undisturbed regions of the cluster and folded through marx to produce simulated Chandra observations. The thermodynamic properties in the merger region from these simulated X-ray observations were used as a baseline for comparison with the actual observations. We identify two distinct components in the temperature structure along the merger axis, a smooth, large-scale temperature excess we attribute to the ongoing merger, and a series of peaks where the temperatures are enhanced by 0.5–2.5 keV. If these peaks are attributable to the central AGN, the location, and strength of these features imply that Cygnus A has been active for the past 300 Myr injecting a total of ∼1062 erg into the merger region. This corresponds to ∼10 per cent of the energy deposited by the merger shock.

Publisher

Oxford University Press (OUP)

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