Suzaku study of gas properties along filaments of A2744

¹ Department of PhysicsNara Women’s University, Kitauoyanishimachi, Nara, 630-8506 Nara Japan
e-mail: naomi@cc.nara-wu.ac.jp
² SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
³ Argelander Institute for Astronomy, Bonn University, Auf dem Hügel 71, 53121 Bonn, Germany
⁴ Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2a, 00014 Helsinki, Finland

Received: 7 October 2013
Accepted: 5 November 2013

Abstract

Context. We present the results of Suzaku observations of a massive galaxy cluster A2744, which is an active merger at z = 0.308.

Aims. By using long X-ray observations of A2744, we aim to understand the growth of the cluster and the gas heating process through mass accretion along the surrounding filaments.

Methods. We analyzed data from two-pointed Suzaku observations of A2744 to derive the temperature distribution out to the virial radius in three different directions. We also performed a deprojection analysis to study radial profiles of gas temperature, density, and entropy and compared the X-ray results with multiwavelength data to investigate correlations with the surface density of galaxies and with radio relics.

Results. The gas temperature was measured out to the virial radius r₂₀₀ in the north-eastern region and to about 1.5r₂₀₀ in the northwestern and southern regions. The radial profile of the gas temperature is rather flat and the temperature is very high (even near r₂₀₀), which makes it comparable to the mean temperature of this cluster (kT = 9 keV). These characteristics have not been reported in any other cluster. We find a hint of temperature jump in the north-eastern region whose location coincides with a large radio relic, indicating that the cluster experienced gas heating because of merger or mass accretion onto the main cluster. The temperature distribution is anisotropic and shows no clear positive correlation with the galaxy density, which suggests an inhomogeneous mass structure and a complex merger history in A2744.