Probing Dark Matter In X-ray Relaxed Galaxy Groups With Chandra And XMM: Steepening Of The Concentration-Mass Relation
Abstract
We present total mass profiles for 16 relaxed groups/poor clusters,
covering the temperature range 1-3 keV and selected among the ones in the Chandra and XMM archives to have the best constrains for mass determination. Gas densities and temperatures were accurately measured out to at least 0.3 of the virial radius, with the temperature profiles showing similar shape and becoming increasingly similar beyond 0.1 of the virial radius. The total gravitating matter profiles are well described by the NFW model, when accounting for the excess mass of the central galaxy in the inner regions of 9 out of 16 objects. The derived stellar mass-to-light ratio in the K band generally agree with population synthesis models, assuming a Kroupa IMF. Modifying the NFW dark matter halo by adiabatic contraction does not improve the fit and makes the M/L more discrepant. The distribution of concentration parameters versus virial masses, for the first time systematically investigated at this critical mass scale, reveals the steepening predicted by Lambda CDM cosmology. Together with results obtained at the cluster and galaxy scales, X-ray observations provide evidence in favour of the predictions of Lambda CDM, both in terms of the validity of NFW mass density profile and the variation of its concentration with mass. The superposed trend of higher than the average concentrations, as found in X-ray studies, is most likely caused by the X-ray selection of relaxed objects.- Publication:
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AAS/High Energy Astrophysics Division #9
- Pub Date:
- September 2006
- Bibcode:
- 2006HEAD....9.1328G