Journal Article

A deep <i>Chandra</i> observation of the poor cluster AWM 4 – I. Properties of the central radio galaxy and its effects on the intracluster medium

Ewan O'Sullivan, Simona Giacintucci, Laurence P. David, Jan M. Vrtilek and Somak Raychaudhury

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 407, issue 1, pages 321-338
Published in print September 2010 | ISSN: 0035-8711
Published online August 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.16895.x
A deep Chandra observation of the poor cluster AWM 4 – I. Properties of the central radio galaxy and its effects on the intracluster medium

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Using observations from the Chandra X-ray Observatory and Giant Metrewave Radio Telescope, we examine the interaction between the intracluster medium and central radio source in the poor cluster AWM 4. In the Chandra observation a small cool core or galactic corona is resolved coincident with the radio core. This corona is capable of fuelling the active nucleus, but must be inefficiently heated by jet interactions or conduction, possibly precluding a feedback relationship between the radio source and cluster. A lack of clearly detected X-ray cavities suggests that the radio lobes are only partially filled by relativistic plasma. We estimate a filling factor of φ= 0.21 (3σ upper limit φ < 0.42) for the better constrained east lobe. We consider the particle population in the jets and lobes, and find that the standard equipartition assumptions predict pressures and ages which agree poorly with X-ray estimates. Including an electron population extending to low Lorentz factors either reduces (γmin= 100) or removes (γmin= 10) the pressure imbalance between the lobes and their environment. Pressure balance can also be achieved by entrainment of thermal gas, probably in the first few kiloparsecs of the radio jets. We estimate the mechanical power output of the radio galaxy, and find it to be marginally capable of balancing radiative cooling.

Keywords: galaxies: active; galaxies: clusters: general; galaxies: clusters: individual: AWM 4; galaxies: clusters: intracluster medium; galaxies: individual: NGC 6051; X-rays: galaxies: clusters

Journal Article.  17022 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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