Measuring the geometry of the universe from weak gravitational lensing behind galaxy groups in the HST COSMOS survey

Taylor, J.E.; Massey, R.J.; Leauthaud, A.; George, M.R.; Rhodes, J.; Kitching, T.D.; Capak, P.; Ellis, R.; Finoguenov, A.; Ilbert, O.; Jullo, E.; Kneib, J.-P.; Koekemoer, A.M.; Scoville, N.; Tanaka, M.

doi:10.1088/0004-637x/749/2/127

Measuring the geometry of the universe from weak gravitational lensing behind galaxy groups in the HST COSMOS survey

Taylor, J.E.; Massey, R.J.; Leauthaud, A.; George, M.R.; Rhodes, J.; Kitching, T.D.; Capak, P.; Ellis, R.; Finoguenov, A.; Ilbert, O.; Jullo, E.; Kneib, J.-P.; Koekemoer, A.M.; Scoville, N.; Tanaka, M.

Authors

J.E. Taylor

Professor Richard Massey r.j.massey@durham.ac.uk
Professor

A. Leauthaud

M.R. George

J. Rhodes

T.D. Kitching

P. Capak

R. Ellis

A. Finoguenov

O. Ilbert

E. Jullo

J.-P. Kneib

A.M. Koekemoer

N. Scoville

M. Tanaka

Abstract

Gravitational lensing can provide pure geometric tests of the structure of spacetime, for instance by determining empirically the angular diameter distance-redshift relation. This geometric test has been demonstrated several times using massive clusters which produce a large lensing signal. In this case, matter at a single redshift dominates the lensing signal, so the analysis is straightforward. It is less clear how weaker signals from multiple sources at different redshifts can be stacked to demonstrate the geometric dependence. We introduce a simple measure of relative shear which for flat cosmologies separates the effect of lens and source positions into multiplicative terms, allowing signals from many different source-lens pairs to be combined. Applying this technique to a sample of groups and low-mass clusters in the COSMOS survey, we detect a clear variation of shear with distance behind the lens. This represents the first detection of the geometric effect using weak lensing by multiple, low-mass groups. The variation of distance with redshift is measured with sufficient precision to constrain the equation of state of the universe under the assumption of flatness, equivalent to a detection of a dark energy component Ω X at greater than 99% confidence for an equation-of-state parameter –2.5 ≤ w ≤ –0.1. For the case w = –1, we find a value for the cosmological constant density parameter ΩΛ = 0.85+0.044 –0.19 (68% CL) and detect cosmic acceleration (q 0 < 0) at the 98% CL. We consider the systematic uncertainties associated with this technique and discuss the prospects for applying it in forthcoming weak-lensing surveys.

Citation

Taylor, J., Massey, R., Leauthaud, A., George, M., Rhodes, J., Kitching, T., …Tanaka, M. (2012). Measuring the geometry of the universe from weak gravitational lensing behind galaxy groups in the HST COSMOS survey. Astrophysical Journal, 749(2), Article 127. https://doi.org/10.1088/0004-637x/749/2/127

Journal Article Type	Article
Publication Date	Apr 20, 2012
Deposit Date	Jan 31, 2012
Publicly Available Date	Feb 27, 2015
Journal	Astrophysical Journal
Print ISSN	0004-637X
Electronic ISSN	1538-4357
Publisher	American Astronomical Society
Peer Reviewed	Peer Reviewed
Volume	749
Issue	2
Article Number	127
DOI	https://doi.org/10.1088/0004-637x/749/2/127
Keywords	Cosmology: observations, Dark energy, Distance scale, Galaxies: groups: general, Gravitational lensing: weak, Large-scale structure of Universe.