X-ray concentration-mass relation: theory and observations
Abstract
The concentration-mass relation represents a valuable tool to constrain cosmological parameters such as matter density and sigma_8. In the last few years, X-ray data led to the conclusion that the observed relation has higher normalization and slope than those predicted by dark matter only simulations. In this work, we explore whether this disagreement is real or artificially due to an unfair comparison between the two approaches. To this purpose, we consider ~50 clusters simulated by progressively increasing the simulation complexity: (i) dark-matter only, (ii) non-radiative hydrodynamics, (iii) adding cooling, star-formation and feedback by Supernovae, (iv) adding feedback by AGN. We produced X-ray synthetic catalogues to derive the concentration-mass relation following an observational approach. We find that even if cooling has the effect of steepening the concentration- mass relation with respect to the DM-only simulations, the introduction of AGN makes this difference small. A larger variation is expected when reducing the radial range over which density profiles are fitted to a NFW profile. In particular if the external radius is about half R500 the slope can double its value. Therefore, observations, suffering from background contamination, are more inclined to detect a steeper c-M relations. Finally, we analyze the effect of X-ray selection function using an X-ray synthetic catalogue. We conclude by indicating the best strategy to follow to conduct a fair theory-observation comparison and to lead an observational campaign.
- Publication:
-
Half a Century of X-ray Astronomy
- Pub Date:
- September 2012
- Bibcode:
- 2012hcxa.confE..53R