Abstract

Understanding the formation and evolution of cosmological structure is one of the most outstanding challenges of Astronomy. One of the cornerstones of this quest is the study of galaxy clusters, the largest gravitationally bound structures in the Universe, and tracers of the cosmic large-scale structure. Forthcoming Sunyaev-Zeldovich (SZ) and X-ray galaxy cluster surveys should reveal many thousands of clusters, which combined with observations in other wavebands, are expected to provide important puzzle pieces to solve some of the most challenging riddles of observational cosmology at the present. This includes unveiling the nature of dark-energy and understanding how cosmological structure forms and evolves.

The central objective of this project is the implementation of a cosmological distance determination algorithm to estimate distances to clusters, by combining their SZ and X-ray emissions. This method is independent from traditional distance-ladder indicators (i.e. provides a direct way to measure distances), but it has not yet been fully assessed to test its potential to constrain cosmological parameters (and most notably dark-energy models) from an upsurge of near-future cluster observations. We propose to do this study for the correlation of observations from the XCS (an international collaboration for the serendipitous detection of clusters in public XMM-Newton data) and Planck Surveyor catalogues. Both XMM-Newton and Planck Surveyor satellites are key ESA space missions and will provide the largest cluster catalogues of their kind for many years to come.

With this project we also propose to extend our work on the study and characterization of the observable properties of galaxy clusters in the context of future and ongoing observations. Our objective is to characterize structural and scaling properties of distant clusters to quantify the role of dark-energy and non-gravitational gas physics in the formation and evolution of galaxy clusters, and to study and test for different models of structure formation and cosmology. Our goal is to contribute to develop optimal methods that maximize the extraction of scientific information from cross-correlations between different observational strategies and datasets.

Our analysis combines both analytical and numerical simulation tools that have been developed by our group and collaborators in the context of our participation in the XCS and Planck Surveyor structures. For the analytical approach we will use the formalism that we have developed (see eg Nunes, da Silva, Aghanim, 2006, A&A, 450, 899) to investigate the role of dark energy in the gravitational collapse that leads to cluster formation and for predicting cluster abundances in different models of dark energy. Regarding simulation tools, we will use state-of-the-art hydrodynamic techniques to produce realistic cluster simulation of Planck, and XCS observations. We will also use hydrodynamic simulations featuring different dark-energy models that we have carried out to assess the impact of dark-energy on the cluster formation process and evolution of their scaling properties.

The researchers involved in this project have complementary expertise in different domains of cluster physics, structure formation, and cosmology and are active participants in the construction of the XCS catalogue and in the Planck Surveyor galaxy-cluster working group. They also participate in the CLEF-SSH international collaboration for the study of cluster physics using supercomputer simulations.

Our project is timely and addresses fundamental aspects for the preparation and interpretation of near-future cluster surveys. It spans over a period that optimally includes the launch of the Planck Surveyor satellite (due to 2008) and the building-up of thousands of cluster observations in the XCS catalogue. Although there is a maximum of 3 years of funding for this project, our research interests extend beyond this timescale, being one of our objectives to lay the groundwork to take full advantage of the research and data processing opportunities that will come forth with the Planck space mission and future ESA and ESO observing instruments such as XEUS and ALMA.

Start
1 September 2007
End
28 February 2011