AAS 205th Meeting, 9-13 January 2005
Session 82 Dark Matter, Weak and Strong Lensing
Oral, Tuesday, January 11, 2005, 2:00-3:30pm, Golden Ballroom

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[82.04] Weak Lensing by Galaxy Groups at Intermediate Redshifts

L. C. Parker, M.J. Hudson (University of Waterloo), R.G. Carlberg (University of Toronto), H. Hoekstra (University of Victoria)

I will present the results from our weak lensing survey of CNOC2 galaxy groups. The detected shear is used to calculate the M/L of these groups and constrain the matter density of the universe. Galaxy groups are excellent cosmological probes because they dominate the mass and luminosity densities of the Universe, and thus their properties reflect closely the global properties of the universe.

The mass-to-light ratio of the groups was calculated as a function of radius, and found to have an average value of 206 ±27 M\odot/LR\odot. The mass-to-light ratio appeared to rise in the outer regions of the galaxy groups, beyond the virial radius where dynamical estimates are valid. The signal-to-noise of the shear measurement was sufficient to allow us to split the sample into two halves: the ``rich'' galaxy groups and the ``poor'' galaxy groups. The rich galaxy groups were found to have an average velocity dispersion of 260 ±9 km/s while the small galaxies were found to have a velocity dispersion of 176 ±7 km/s. The mass-to-light ratio of the rich groups was nearly twice that of the poor groups. This indicates that the rising mass-to-light ratio of the full sample of galaxy groups is an artifact of averaging together many groups with different inherent mass-to-light ratios.

The author(s) of this abstract have provided an email address for comments about the abstract: lcparker@astro.uwaterloo.ca

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© 2004. The American Astronomical Society.