Gerrit Schellenberger
Argelander-Institut für Astronomie, University of Bonn

Abstract
Galaxy clusters are known to be the largest virialized objects in the Universe. Based on the theory of structure formation one can use them as cosmological probes. The HIgest X-ray FLUx Galaxy Cluster Sample (HIFLUGCS) is a complete sample of 64 very bright and nearby galaxy clusters. The X-ray regime provides a unique possibility to analyze these important objects by directly measuring the density and temperature of the hot intra cluster medium (ICM). This hot gas is not only the most massive visible component, but can also reveal insights on the Dark Matter content by assuming hydrostatic equilibrium.
Using the Chandra X-ray observatory I provide total mass and gas mass estimates of these clusters in order to constrain cosmological parameters. Analyzing the galaxy cluster substructure found in X-ray observations shows that these are complex objects that provide prospects to study the interaction with galaxies or other clusters.
Since cosmological constraints from clusters rely on accurate gravitational mass estimates, which strongly depend on cluster gas temperature measurements, systematic calibration differences may result in biased, instrument-dependent cosmological constraints. By comparing the two current major X-ray missions, Chandra and XMM-Newton, I find significant and systematic calibration uncertainties, which affect cosmological constraints.

2015 October 05, 11:00

IA/U.Lisboa
Observatório Astronómico de Lisboa (Seminar room)
Tapada da Ajuda, 1349-018 Lisboa