First results from the Complete Local-Volume Groups Sample

E. O’Sullivan1*, K. Kolokythas2, S. Raychaudhury3,2, J. Vrtilek1 and N. Kantharia4
1Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
2School of Physics and Astronomy, University of Birmingham, Birmingham, B15 2TT, UK
3Department of Physics, Presidency University, 86/1 College Street, 700 073 Kolkata, India
4National Center for Radio Astrophysics, Tata Institute of Fundamental Research, Post Bag 3, Ganeshkhind, 411 007 Pune, India

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Galaxy groups form the environment of the majority of galaxies in the local Universe, and many host an extended hot intra-group medium whose radiative cooling appears to fuel, and be stabilised by, feedback from AGN in group-central galaxies. Unfortunately studies of the physical properties of groups and the influence of AGN on their member galaxies and gaseous haloes have been limited by a lack of reliable representative samples of groups in the local Universe. To address this problem, we have assembled the Complete Local-Volume Groups Sample (CLoGS), an optically-selected statistically-complete sample of 53 groups within 80 Mpc, which we aim to observe in both low-frequency radio and X-ray wavebands. We here describe results from the first half of the sample, for which X-ray and radio observations are complete. Roughly 55% of the groups have group-scale X-ray halos, of which ∼65% have cool cores a similar fraction to that found in galaxy clusters. While 25 of the 26 group central galaxies host radio AGN, among the X-ray bright groups only the cool core systems are found to support central jet sources.

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Keywords : galaxies: clusters: general — galaxies:active— galaxies: jets