The XMM-Newton $Ω$ Project

J. G. Bartlett, N. Aghanim, M. Arnaud, J. -Ph. Bernard, A. Blanchard, M. Boer, D. J. Burke, C. A. Collins, M. Giard, D. H. Lumb, S. Majerowicz, Ph. Marty, D. Neumann, J. Nevalainen, R. C. Nichol, C. Pichon, A. K. Romer, R. Sadat, C. Adami

Published 2001-06-06Version 1

The abundance of high-redshift galaxy clusters depends sensitively on the matter density $\OmM$ and, to a lesser extent, on the cosmological constant $\Lambda$. Measurements of this abundance therefore constrain these fundamental cosmological parameters, and in a manner independent and complementary to other methods, such as observations of the cosmic microwave background and distance measurements. Cluster abundance is best measured by the X-ray temperature function, as opposed to luminosity, because temperature and mass are tightly correlated, as demonstrated by numerical simulations. Taking advantage of the sensitivity of XMM-Newton, our Guaranteed Time program aims at measuring the temperature of the highest redshift (z>0.4) SHARC clusters, with the ultimate goal of constraining both $\OmM$ and $\Lambda$.