| Grant number: | 12/00578-0 |
| Support Opportunities: | Research Grants - Young Investigators Grants |
| Start date: | September 01, 2012 |
| End date: | December 31, 2017 |
| Field of knowledge: | Physical Sciences and Mathematics - Astronomy - Extragalactic Astrophysics |
| Principal Investigator: | Tatiana Ferraz Laganá |
| Grantee: | Tatiana Ferraz Laganá |
| Host Institution: | Centro de Ciências Exatas e Tecnológicas. Universidade Cruzeiro do Sul (UNICSUL). São Paulo , SP, Brazil |
| Associated scholarship(s): | 16/08024-4 - Revising scaling-relations in groups and galaxy clusters,
BP.IC 12/13251-9 - Matter distribution in galaxy clusters: A comprehensive picture of baryons in the largest virialized structures in the Universe, BP.JP |
Abstract
It is believed that the baryon mass fraction of galaxy clusters is representative of the value in the Universe, and can, therefore, be used to reliably constrain the matter density cosmological parameter (White et al. 1993; Evrard et al. 1997; Allen et al. 2008). The baryons in galaxy clusters consist of the stars in cluster galaxies, the intra-cluster light, and hot intra-cluster gas (which exceeds the mass of the two former components by a factor of ~6). The baryon mass fraction is believed to be constant for galaxy clusters (at radii beyond r2500; e.g., Allen et al. 2004). This assumption is challenged by the growing evidence from observations that the baryon mass fraction increases with cluster total mass shown for a few dozens of clusters (David et al. 1990; Lin et al. 2003; Gonzales et al. 2007; Giodini et al. 2009; Laganá et al. 2011) and the baryon mass fraction increases dramatically with cluster radius for the Perseus cluster (Simionescu et al. 2011), which is one of the few clusters having deepest X-ray data to measure the baryon mass fraction up to the virial radius (approximately the equilibrium radius). Also the comparison between the observed baryon mass fraction of those galaxy clusters and the prediction of the 7-year Wilkinson Microwave Anisotropy Probe (WMAP7) presents controversial mass dependence of missing baryons. Up to now, there are no homogeneous observations for a large representative sample of galaxy clusters to robustly compute both the stellar and gas masses. Under these circumstances, we propose to investigate the matter distribution for a large representative sample, consisting of more than 130 clusters, of which both optical and X-ray data are available. This project will enable us to analyze both the mass and the radial dependence of the baryonic components, namely, the stellar mass fraction and gas mass fraction for one of the largest sample in the literature. Furthermore, the observational baryon mass fraction will be compared to the theoretical predictions to constrain the systematic uncertainties in using the baryon mass fraction of galaxy clusters to determine the cosmological parameters. (AU)
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