Richard Lieu (Physics Department, University of Alabama, USA)
Par Stephane Charpinet - 21/05/2007
de l’Observatoire Midi-Pyrénées
Séminaire exceptionnel de
(Physics Department, University of Alabama, USA)
Lundi 28 Mai 2007 à 11h
LATT - Salle Coriolis
Can LCDM cosmology explain clusters of galaxies ?
I will focus upon two observational properties of clusters, the `UV excess’ and the surprisingly low level of Sunyaev-Zel’dovich effect (SZE) in the WMAP data of a large sample of clusters. In this seminar I will argue that the two apparent diverse `anomalies’ of clusters might in fact have a common cause. Firstly, I present the evidence as to why, after more than a decade of research, the `UV excess’ in the core region of clusters is increasingly looking like a non-thermal phenomenon. Secondly, this power-law spectrum of emitted photons could account for a substantial fraction of the X-ray luminosity of some clusters, i.e. the actual amount of virialized thermal gas available for producing a SZE on the microwave background may be less than previously expected. I will then discuss the repercussions these aspects of cluster physics have on the standard LCDM cosmological model. If time permits, I will talk a bit about the origin of the non-thermal particles, and ways of testing the content and state of the near Universe by gravitational lensing (even on the 3rd CMB acoustic peak) and time delay observations.