Volume 524, December 2010
|Number of page(s)||12|
|Published online||25 November 2010|
The halos of satellite galaxies: the companion of the massive elliptical lens SL2S J08544−0121⋆
Argelander-Institut für Astronomie,
Auf dem Hügel 71,
2 Excellence Cluster Universe, Technische Universität München, Boltzmannstr. 2, 85748 Garching, Germany
3 Tuorla Observatory, Department of Physics & Astronomy, University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland
Accepted: 20 September 2010
Strong gravitational lensing by groups or clusters of galaxies provides a powerful technique to measure the dark matter properties of individual lens galaxies. We study in detail the mass distribution of the satellite lens galaxy in the group-scale lens SL2S J08544−0121 by modelling simultaneously the spatially extended surface brightness distribution of the source galaxy and the lens mass distribution using Markov chain Monte Carlo methods. In particular, we measure the dark matter halo size of the satellite lens galaxy to be with a fiducial velocity dispersion of . This is the first time the size of an individual galaxy halo in a galaxy group has been measured using strong gravitational lensing without assumptions of mass following light. We verify the robustness of our halo size measurement using mock data resembling our lens system. Our measurement of the halo size is compatible with the estimated tidal radius of the satellite galaxy, suggesting that halos of galaxies in groups experience significant tidal stripping, a process that has been previously observed on galaxies in clusters. Our mass model of the satellite galaxy is elliptical with its major axis misaligned with that of the light by ~50deg. The major axis of the total matter distribution is oriented more towards the centre of the host halo, exhibiting the radial alignment found in N-body simulations and observational studies of satellite galaxies. This misalignment between mass and light poses a significant challenge to modified Newtonian dynamics.
Key words: galaxies: halos / galaxies: groups: individual: SL2S J08544 − 0121 / gravitational lensing: strong / methods: data analysis
Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program 10876.
© ESO, 2010
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