Patrick Valageas web page

Clusters of galaxies are the most massive non-linear structures we observe in the present universe. They are also rare objects. In particular, by observing their evolution at low redshifts one can constrain the cosmological parameters which define our universe. One advantage of clusters of galaxies as compared with galaxies themselves is that their physics could be expected to be somewhat simpler (since most of the gas is still hot and has not had time to cool). However, it appeared in the 90s that the simplest models could not explain all observations and that one cannot neglect the processes associated with radiative cooling and star formation (supernovae). This is another illustration of one of the main difficulties encountered in observational cosmology: the multiplicity of physical processes which have to be taken into account simultaneously and which span a wide range of scales (there are typically a hundred galaxies and 10^12 stars in a cluster).

Articles:

• 2003, MNRAS, 344, 53
  Are the "anomalous" properties of groups (high entropy and low luminosity) related to the shocks associated with large-scale structures ?
  
• 2001, A&A, 366, 363
  An analytical description of the relationship between the distributions of dark matter matter and baryons: bias of various objects (clusters, galaxies, quasars, Lyman-alpha clouds).
  
• 2000, A&A, 359, 821
  A compared study of clusters and groups of galaxies, galaxies and quasars. Comparison of analytical models with observations.
  
• 1999, A&A, 350, 725
  Evolution with redshift of the entropy of the IGM. Relationship with the entropy of the intra-cluster gas.