8-12 juin, 2014


The centres of galaxy group dark matter haloes

Marie-Pier Neault (McMaster University)

Most galaxies in the local universe are found in the galaxy group environment. Many studies of galaxy groups and their member galaxies depend critically on identifying the centre of galaxy group potentials.It is often assumed that the most massive galaxy resides at the centre of the gravitational potential of a galaxy group, at least in evolved systems. We present a weak gravitational lensing analysis of 53 optically selected groups and 40 high-quality X-ray-selected groups from the GEEC sample in order to investigate group centres. In total our sample is composed of 84 distinct groups (there are 9 in common between the optical and X-ray samples) in the redshift range 0.12 < z < 0.83 with intrinsic velocity dispersions between 84-953 km/s. In this work we explore multiple definitions of group centre including the galaxy mass-weighted centre and the position of the most massive galaxy. We come to the conclusion that for optical groups the mass-weighted centre is the best definition of the centre while for the X-ray selected groups all definitions of centre work equally well.

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