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Title: Limits on the AGN activities in X-ray-underluminous galaxy groups
Authors: Dwarakanath, K.S.
Nath, Biman B.
Keywords: Galaxies: Active
Galaxies: Clusters: General
galaxies: clusters: individual (NGC 524)
galaxies: clusters: individual (NGC 720)
galaxies: clusters: individual (NGC 3607)
galaxies: clusters: individual (NGC 4697)
Galaxies: Intergalactic Medium
Issue Date: Dec-2006
Publisher: The University of Chicago Press for the American Astronomical Society
Citation: Astrophysical Journal, 2006, Vol.653, pL9-L12
Abstract: We have observed four X-ray-underluminous groups of galaxies using the Giant Metrewave Radio Telescope (GMRT). The groups NGC 524, 720, 3607, and 4697 are underluminous in relation to the extrapolation of the LX-T relation from rich clusters and do not show any evidence of current AGN activities that can account for such a departure. The GMRT observations carried out at low frequencies (235 and 610 MHz) were aimed at detecting low surface brightness, steep-spectrum sources indicative of past AGN activities in these groups. No such radio emissions were detected in any of these four groups. The corresponding upper limits on the total energy in relativistic particles is ~3×1057 ergs. This value is more than a factor of 100 less than that required to account for the decreased X-ray luminosities (or enhanced entropies) of these four groups in the AGN-heating scenario. Alternatively, the AGN activity must have ceased ~4 Gyr ago, allowing the relativistic particles to diffuse out to such a large extent (~250 kpc) that their radio emission could have been undetected by the current observations. If the latter scenario is correct, the ICM was preheated before the assembly of galaxy clusters.
Description: Restricted Access. Articles older than 2 years are open to all at the journal site (alternative location)
ISSN: 0004-637X
1538-4357 (online)
Alternative Location:
Copyright: 2006 American Astronomical Society
Appears in Collections:Research Papers (A&A)

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