EDP Sciences
Free access
Issue
A&A
Volume 385, Number 2, April II 2002
Page(s) L5 - L9
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20020243


A&A 385, L5-L9 (2002)
DOI: 10.1051/0004-6361:20020243

Letter

The first detection of weak gravitational shear in infrared observations: Abell 1689

L. J. King1, 2, D. I. Clowe1, C. Lidman3, P. Schneider1, 2, T. Erben1, 4, 5, J.-P. Kneib6 and G. Meylan7

1  Institut für Astrophysik und Extraterrestrische Forschung, Auf dem Hügel 71, 53121 Bonn, Germany
2  Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, 85741 Garching, Germany
3  European Southern Observatory, Casilla 19, Santiago, Chile
4  Institut d'Astrophysique de Paris, 98 bis Boulevard Arago, 75014 Paris, France
5  Observatoire de Paris, DEMIRM, 61 avenue de l'Observatoire, 75014 Paris, France
6  Observatoire Midi-Pyrénées, 14 Av. E. Belin, 31400 Toulouse, France
7  Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA

(Received 14 January 2002 / Accepted 13 February 2002)

Abstract
We present the first detection of weak gravitational shear at infrared wavelengths, using observations of the lensing cluster Abell 1689, taken with the SofI camera on the ESO-NTT telescope. The imprint of cluster lenses on the shapes of the background galaxy population has previously been harnessed at optical wavelengths, and this gravitational shear signal enables cluster mass distributions to be probed, independent of whether the matter is luminous or dark. At near-infrared wavelengths, the spectrophotometric properties of galaxies facilitate a clean selection of background objects for use in the lensing analysis. A finite-field mass reconstruction and application of the aperture mass ( $M_{\rm ap}$) statistic are presented. The probability that the peak of the $M_{\rm ap}$ detection ( $\frac{S}{N}\sim 5$), arises from a chance alignment of background sources is only ~ $4.5\times 10^{-7}$. The velocity dispersion of the best-fit singular isothermal sphere model for the cluster is $\sigma_{\rm 1D}=1030^{+70}_{-80}\,{\rm km}\,{{\rm s}^{-1}}$, and we find a K-band mass-to-light ratio of ~ $40\,M_{\odot}/L_{\odot}$ inside a $0.44\,{\rm Mpc}$ radius.


Key words: gravitational lensing -- galaxies: clusters individual: Abell 1689 -- dark matter -- infrared: galaxies

Offprint request: L. J. King, lindsay@astro.uni-bonn.de

SIMBAD Objects in preparation



© ESO 2002