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Dark matter astrometry : accuracy of subhalo positions for the measurement of self-interaction cross-sections.

Harvey, D. and Massey, R. and Kitching, T. and Taylor, A. and Jullo, E. and Kneib, J.-P. and Tittley, E. and Marshall, P.J. (2013) 'Dark matter astrometry : accuracy of subhalo positions for the measurement of self-interaction cross-sections.', Monthly notices of the Royal Astronomical Society., 433 (2). pp. 1517-1528.


Direct evidence for the existence of dark matter and measurements of its interaction cross-section have been provided by the physical offset between dark matter and intracluster gas in merging systems like the Bullet Cluster. Although a smaller signal, this effect is more abundant in minor mergers where infalling substructure dark matter and gas are segregated. In such low-mass systems the gravitational lensing signal comes primarily from weak lensing. A fundamental step in determining such an offset in substructure is the ability to accurately measure the positions of dark matter subpeaks. Using simulated Hubble Space Telescope observations, we make a first assessment of the precision and accuracy with which we can measure infalling groups using weak gravitational lensing. We demonstrate that using an existing and well-used mass reconstruction algorithm can measure the positions of 1.5 × 1013 M⊙ substructures that have parent haloes 10 times more massive with a bias of less than 0.3 arcsec. In this regime, our analysis suggests the precision is sufficient to detect (at 3σ statistical significance) the expected mean offset between dark matter and baryonic gas in infalling groups from a sample of ∼50 massive clusters.

Item Type:Article
Keywords:Gravitational lensing: weak, Cosmological parameters, Dark matter, Galaxies: clusters general.
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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society © 2013 The Authors Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved.
Date accepted:No date available
Date deposited:19 August 2014
Date of first online publication:August 2013
Date first made open access:No date available

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