2006/11/29 by A. Finoguenov, T. J. Ponman, J. P. F. Osmond +1 · 1 citation
Physics and Astronomy · #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2006.11194.x
11 pages, MNRAS in press, the 25 page version with all 176 figures included is at ftp://ftp.xray.mpe.mpg.de/people/alexis/2dxgs_astroph.ps.gz
arxiv created 2006/11/29 · arxiv updated 2009/12/01
We study the thermodynamic properties of the hot gas in a sample of groups in the 0.012-0.024 redshift range, using XMM-Newton observations. We present measurements of temperature, entropy, pressure and iron abundance. Non-parametric fits are used to derive the mean properties of the sample and to study dispersion in the values of entropy and pressure. The scaling of the entropy at 0.2r500 matches well the results of Ponman et al. (2003). However, compared to cool clusters, the groups in our sample reveal larger entropy at inner radii and a substantially flatter slope in the entropy in the outskirts, compared to both the prediction of pure gravitational heating and to observations of clusters. This difference corresponds to the systematically flatter group surface brightness profiles, reported previously. The scaled pressure profiles can be well approximated with a Sersic model with n=4. We find that groups exhibit a systematically larger dispersion in pressure, compared to clusters of galaxies, while the dispersion in entropy is similar.