Radio properties of nearby groups of galaxies

K. Kolokythas1*, E. O’Sullivan2, S. Raychaudhury3,1, Ishwara C. H. Chandra4 and N. Kantharia4
1School of Physics and Astronomy, University of Birmingham, Birmingham, B15 2TT, UK
2Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
3Department of Physics, Presidency University, 86/1 College Street, 700 073 Kolkata, India
4National Centre for Radio Astrophysics,Tata Institute of Fundamental Research, Post Bag 3, Ganeshkhind, 411 007 Pune, India

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Much of the evolution of galaxies takes place in groups where feedback has the greatest impact on galaxy formation. By using an optically selected, statistically complete sample of 53 nearby groups (CLoGS), observed in Radio (GMRT) and in X-rays (Chandra & XMM-Newton), we aim to characterize the radio-AGN population in groups and examine their impact on the intra-group gas and member galaxies. The sensitivity to older electron populations at 240 MHz and the resolution of 610 MHz is the key to identify past and current AGN activity. Here we will present first results from three different galaxy groups analysed so far. We report an age of ~18 Myr for the radio source 3C270 in NGC 4261 implying that the expansion was supersonic over a large fraction of its lifetime. In NGC 1060 we detect a small-scale (20”/7.4 kpc) jet source with the spectral index of α610 240=0.9 indicating a remnant of an old outburst. Lastly in NGC 5982 the 610 & 235 MHz observations find a radio point source in the central AGN with no evidence of jets or lobes and diffuse emission from the disks (star formation).

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Keywords : galaxies: groups: general — galaxies:active — galaxies: jets