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Properties of galaxy dark matter halos from weak lensing

Published online by Cambridge University Press:  26 May 2016

Henk Hoekstra ,
Howard K.C. Yee  and
Michael D. Gladders
Henk Hoekstra
Affiliation:
Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, M5S 3H8, Toronto, Canada
Howard K.C. Yee
Affiliation:
Department of Astronomy and Astrophysics, University of Toronto, 60 St. George Street, M5S 3H8, Toronto, Canada
Michael D. Gladders
Affiliation:
Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101, USA

Abstract

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We present the results of a study of the average mass profile around galaxies using weak gravitational lensing. We use 45.5 deg2 of RC band imaging data from the Red-Sequence Cluster Survey (RCS) and define a sample of ~ 1.2 × 105 lenses with 19.5 < RC < 21, and a sample of ~ 1.5 × 106 background galaxies with 21.5 < R < 24.

We constrain the power law scaling relations between the B-band luminosity and the mass and size of the halo, and find that the results are in excellent agreement with observed luminosity–line-width relations. Under the assumption that the luminosity does not evolve with redshift, the best fit NFW model yields a mass M200 = (8.8±0.7) × 1011h–1M⊙ and a scale radius rs = I6.7+3.7–3.0h–1 kpc for a galaxy with a fiducial luminosity of Lb = 1010h–2LB⊙. the latter result is in excellent agreement with predictions from numerical simulations for a halo of this mass. We also observe a signficant anisotropy of the lensing signal around the lenses, implying that the halos are flattened and aligned with the light distribution. We find an average (projected) halo ellipticity of 〈ehalo〉 = 0.20+0.04–0.05, in fair agreement with results from numerical simulations of CDM. Alternative theories of gravity (without dark matter) predict an isotropic lensing signal, which is excluded with 99.5% confidence. Hence, our results provide strong support for the existence of dark matter.

Type
Part 13: The Shapes and Extents of Dark Halos
Information
Symposium - International Astronomical Union , Volume 220: Dark Matter in Galaxies , 2004 , pp. 439 - 445
Copyright
Copyright © Astronomical Society of the Pacific 2004 

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