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Weak lensing study of low mass groups: implications for Ωm

Published online by Cambridge University Press:  26 May 2016

H. Hoekstra ,
M. Franx ,
K. Kuijken ,
R. G. Carlberg  and
H. K. C. Yee
H. Hoekstra
Affiliation:
1Kapteyn Astronomical Institute, P.O. Box 800, NL-9700 AV, Groningen, The Netherlands
M. Franx
Affiliation:
2Leiden Observatory, P.O. Box 9513, 2300 RA, Leiden, The Netherlands
K. Kuijken
Affiliation:
1Kapteyn Astronomical Institute, P.O. Box 800, NL-9700 AV, Groningen, The Netherlands
R. G. Carlberg
Affiliation:
3Department of Astronomy, University of Toronto, Toronto, ON, M5S 3H8, Canada
H. K. C. Yee
Affiliation:
3Department of Astronomy, University of Toronto, Toronto, ON, M5S 3H8, Canada

Abstract

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We report on the first measurement of the average mass and mass-to-light ratio of galaxy groups by analysing the weak lensing signal induced by these systems. The Canadian Network for Observational Cosmology Field Galaxy Redshift Survey (CNOC2) allows the identification of a large number of groups at intermediate redshifts. For our analysis we use a sample of 50 groups which are selected on the basis of a careful dynamical analysis of group candidates. We detect a signal at the 99% confidence limit. The best fit singular isothermal sphere model yields an Einstein radius rE = 0″.72 ± 0″.29. This corresponds to a velocity dispersion of 〈σ2〉1/2 = 274±+48-59 km/s, which is in good agreement with the dynamical estimate. Under the assumption that the light traces the mass, we find an average mass-to-light ratio of 191 ± 83 h in the restframe B band. Unlike dynamical estimates, this result is insensitive to problems associated with determining group membership. We use the observed mass-to-light ratio to estimate the matter density of the universe, for which we find Ωm = 0.19 ± 0.10 (ΩΛ = 0), in good agreement with other recent estimates. For a closed universe (Ωm + ΩΛ = 1), we obtain Ωm = 0.13 ± 0.07.

Type
Part VIII: Dark Matter and Ω0
Information
Symposium - International Astronomical Union , Volume 201: New Cosmological Data and the Values of the Fundamental Parameters , 2005 , pp. 340 - 343
Copyright
Copyright © Astronomical Society of the Pacific 2005 

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