Mapping the Total Gravitating Mass in Three Groups of Galaxies

  • I. Thiering
  • Dahlem M.
Conference paper
Part of the International Astronomical Union / Union Astronomique Internationale book series (IAUS, volume 171)


We report on the detection and analysis of hot ionized gas in three groups of galaxies (MKW4s, AWM5, NGC 6329 group) at distances above 100 Mpc (recession velocities above 8000 km s-1). In all three cases their emission is centered on the dominant member of the group (NGC 4104, NGC 6269, NGC 6329 respectively). The central electron densities of the gas n e,0 are about 0.02 cm-3 decreasing to the outside as: \(n_\textup{e} = n_{\textup{e,0}} \ [1+ (r/r_c)^2]^{3\beta/2}\), with an exponen β=0.40.. 0.77, (see Tab. 1). In each case, the spectra are well-represented by thermal Raymond-Smith spectra with kT ≃ 1.0 to 1.3 keV in the center and a weak increase by ca. 0.5 keV to the outside, indicating a slight cooling flow. The fits suggest that none of the central galaxies hosts an AGN that contributes significantly to the emission in the ROSAT band (0.1 to 2.4 keV). Using the radia temperature and density distributions, the total gravitating mass within a radius r can be derived. This value is 1.7±0.4 1013 M within 300 kpc for all three cases as opposed to to 1014..15 M for rich clusters.

Copyright information

© Springer Science+Business Media Dordrecht 1996

Authors and Affiliations

  • I. Thiering
    • 1
  • Dahlem M.
    • 2
  1. 1.LandessternwarteHeidelbergGermany
  2. 2.STSCIBaltimoreUSA

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