GALAXY CLUSTER SAMPL · Multi-wavelength analysis of merging galaxy clusters
FP6 — Marie Curie Actions (Human Resources and Mobility)
- Duration
- 2004-01-01 → 2005-12-31
- EU contribution
- €148,829
- Participants
- 1
- Scheme
- EIF
Lines connect the coordinator with its partners. CORDIS does not always give exact coordinates for projects before 2014. These points are placed at city or country level.
Results in brief
Final Activity Report Summary - GALAXY CLUSTER SAMPL (Multi-wavelength analysis of merging galaxy clusters)
The present project is a study of the complex physics of formation and evolution of galaxy clusters, whose knowledge is essential for cosmological theories. Galaxy clusters are the only systems small enough to have achieved dynamical equilibrium during the Universe lifetime, and large enough to let us estimate the average ratio of baryonic to dark matter in the Universe. While dark matter, whose composition is still unknown, cannot be detected directly, baryons emit electromagnetic radiation at different wavelengths, depending on their nature. Galaxy clusters, in particular, can be observed at optical, X-ray and radio wavelengths due to the presence of galaxies, hot and diffuse gas that fill the intra-cluster medium (ICM), and a non-thermal component, i.e. magnetic fields and relativistic particles. Multi-wavelength observations of galaxy clusters reveal that more than 80% of their total mass is in dark matter, 16% is in gas, while stars and galaxies represent only the 3%. In the framework of the hierarchical model of structures formation, galaxy clusters are supposed to form by accretion and merging of smaller units. By studying lumpy clusters one has then the opportunity to understand the gravitational and non-gravitational processes acting during the formation of the large scale structures of the Universe. In this picture, during my Marie Curie Fellowship I worked on an international project to study the formation of galaxy clusters and the complex physical processes that are driving their evolution. A joint observational and numerical approach was applied, which combined optical, X-ray and radio observations of a sample of galaxy clusters with N-body and hydrodynamic simulations of structures formation and evolution. The complex dynamics and morphologies of the clusters analysed are observational evidence of the hierarchical model of structure formation. We found evidences that the merging event can significantly affect the physical properties of the different cluster components. In addition to its well-known effects on the velocity and density distribution of galaxies, and on the temperature and density distribution of the gas, our combined observational and numerical analysis showed that mergers seem to trigger star formation in galaxies, accelerate the relativistic particles observed at radio wavelengths, and strongly affect the presence and distributions of heavy elements in the ICM. Our analysis also showed that the ICM metallicity distribution is a more powerful diagnostic to determine the dynamical state of clusters than the former methods developed and used up to now. This combined observational and numerical analysis has therefore given new insights to the understanding of the complex physics of merging clusters. New perspectives on the study of galaxy clusters have also been opened.
Data: CORDIS, © European Union
Project objective
The present project is related to the study of galaxy clusters, to their formation and to the physical processes that are leading their evolution. In the hierarchical model of structure formation, clusters of galaxies form by accretion and merging of smaller sub-clusters and groups.We aim at answering to open questions about the dynamical and physical processes that act during the merging event on each component of clusters, i.e. galaxies, intra-cluster plasma and dark matter. Our two-level approach consists in:- observing in optical, X-ray and radio a sample of interacting clusters; and- reproducing by N-body and hydrodynamic simulations the evolution of collisionless matter (i.e. galaxies and dark matter) and intra-cluster gas respectively.A detailed modelling of cluster merger is very difficult at present; by comparing multi-wavelength observations to numerical simulations, we will be able to determine the stage and the geometry of merging clusters. In this way, we will obtain a sequence of clusters in different phases of the merging process; this sample will be the starting point to follow the evolution of cluster properties during their growth from poor groups to rich galaxy systems.In particular, we aim at analyzing how the process of cluster formation acts on the following: the relative distributions of galaxies, gas and dark matter; the large scale structure of clusters; both thermal and non-thermal components of the intra-cluster plasma, observable at X-ray and radio wavelengths respectively; the dynamics and kinematics of the member galaxies, and their internal properties, e.g. star formation rate and AGN activity.As clusters of galaxies are the largest organized structures in the Universe, a clear and complete picture of cluster evolution will bring fundamental clues on cosmological models and structure formation.
Original text from CORDIS.
Participants
- UNIVERSITÄT INNSBRUCK · INNSBRUCKCoordinatorCity levelAustria
Links
Data: CORDIS, © European Union