Astronomy and Astrophysics – Astrophysics
Scientific paper
2008-08-27
Astrophys.J.693:839-846,2009
Astronomy and Astrophysics
Astrophysics
9 pages, 7 figures, accepted for publication in ApJ; extended discussions and 1 new figure
Scientific paper
10.1088/0004-637X/693/1/839
The uniformity of the helium-to-hydrogen abundance ratio in X-ray emitting intracluster medium (ICM) is one of the commonly adopted assumptions in X-ray analyses of galaxy clusters and cosmological constraints derived from these measurements. In this work, we investigate the effect of He sedimentation on X-ray measurements of galaxy clusters in order to assess this assumption and associated systematic uncertainties. By solving a set of flow equations for a H-He plasma, we show that the helium-to-hydrogen mass ratio is significantly enhanced in the inner regions of clusters. The effect of He sedimentation, if not accounted for, introduces systematic biases in observable properties of clusters derived using X-ray observations. We show that these biases also introduce an apparent evolution in the observed gas mass fractions of X-ray luminous, dynamically relaxed clusters and hence biases in observational constraints on the dark energy equation of state parameter, w, derived from the cluster distance-redshift relation. The Hubble parameter derived from the combination of X-ray and Sunyaev-Zel'dovich effect (SZE) measurements is affected by the He sedimentation process as well. Future measurements aiming to constrain w or H_0 to better than 10% may need to take into account the effect of He sedimentation. We propose that the evolution of gas mass fraction in the inner regions of clusters should provide unique observational diagnostics of the He sedimentation process.
Nagai Daisuke
Peng Fang
No associations
LandOfFree
Effect of Helium Sedimentation on X-ray Measurements of Galaxy Clusters does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Effect of Helium Sedimentation on X-ray Measurements of Galaxy Clusters, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Effect of Helium Sedimentation on X-ray Measurements of Galaxy Clusters will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-326602