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Title: Diffuse radio emission in Abell 754
Authors: Kale, Ruta
Dwarakanath, K.S.
Keywords: acceleration of particles
galaxies: clusters: individual (A754)
galaxies: halos
radiation mechanisms: non-thermal
radio continuum: galaxies
Issue Date: 10-Jul-2009
Publisher: IOP Publishing Ltd.
Citation: Astrophysical Journal, 2009, Vol. 699, p1883
Abstract: We present a low-frequency study of the diffuse radio emission in the galaxy cluster A754. We present a new 150 MHz image of the galaxy cluster A754 made with the Giant Metrewave Radio Telescope and discuss the detection of four diffuse features. We compare the 150 MHz image with the images at 74, 330, and 1363 MHz; one new diffuse feature is detected. The flux density upper limits at 330 and 1363 MHz imply a synchrotron spectral index, α>2 (S vprop ν–α), for the new feature. The "west relic" detected at 74 MHz is not detected at 150 MHz and is thus consistent with its nondetection at 1363 MHz and 330 MHz. Integrated spectra of all the diffuse features are presented. The fourth diffuse feature is located along the proposed merger axis in A754 and 0.7 Mpc away from the peak of X-ray emission; we refer to it as a relic. We have made use of the framework of the adiabatic compression model to obtain spectra. We show that the spectrum of the fourth diffuse feature is consistent with that of a cocoon of a radio galaxy lurking for about 9 × 107 yr; no shock compression is required. The other three diffuse emission have spectra steeper than 1.5 and could be cocoons lurking for longer time. We discuss other possibilities such as shocks and turbulent reacceleration being responsible for the diffuse emission in A754.
Description: Restricted Access. An open-access version is available at (one of the alternative locations. Articles older than 2 years are open to all at the journal site (alternative location)
ISSN: 0004-637X
1538-4357 (online)
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Copyright: 2009 IOP Publishing Limited
Appears in Collections:Research Papers (A&A)

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