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Session 27 - Gravitational Lensing & Dark Matter.
Oral session, Monday, January 13
Frontenac Ballroom,

[27.08] Distribution of Very Faint Galaxies (B>26) from the Magnification Bias in Cl0024+1654

B. Fort (Obs. de Paris)

The distribution of mass in cluster of galaxies or the interpretation of the cosmic shear in terms of power spectrum of the initial density fluctuation and cosmological parameters could be obtained from weak lensing studies. In this case the redshift distribution of very faint galaxies far beyond B=26 or I = 24.which are used as distorted images of the distant sources is a crucial parameters. In this presentation we will show how it is possible to determine statistically the color redshift dependance of this extremely faint galaxy population down to the limit of the sky backgroud noise by using well selected clusters of galaxies as very low resolution spectrographs. Preliminary results obtained with the strong cluster lense Cl0024+1654 as well as a first unexpected consequence for the possibility to constrain the existence of a cosmological constant will be given.

Program listing for Monday