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MACS J1423.8+2404 : gravitational lensing by a massive, relaxed cluster of galaxies at z = 0.54.

Limousin, M. and Ebeling, H. and Ma, C.-J. and Swinbank, A.M. and Smith, G.P. and Richard, J. and Edge, A.C. and Jauzac, M. and Kneib, J.-P. and Marshall, P. and Schrabback, T. (2010) 'MACS J1423.8+2404 : gravitational lensing by a massive, relaxed cluster of galaxies at z = 0.54.', Monthly notices of the Royal Astronomical Society., 405 (2). pp. 777-782.


We present results of a gravitational lensing and optical study of MACS J1423.8+2404 (z= 0.545, MACS J1423), the most relaxed cluster in the high-redshift subsample of clusters discovered in the MAssive Cluster Survey (MACS). Our analysis uses high-resolution images taken with the Hubble Space Telescope in the F555W and F814W passbands, ground-based imaging in eight optical and near-infrared filters obtained with Subaru and Canada–France–Hawaii Telescope, as well as extensive spectroscopic data gathered with the Keck telescopes. At optical wavelengths, the cluster exhibits no sign of substructure and is dominated by a cD galaxy that is 2.1 mag (K band) brighter than the second brightest cluster member, suggesting that MACS J1423 is close to be fully virialized. Analysis of the redshift distribution of 140 cluster members reveals a Gaussian distribution, mildly disturbed by the presence of a loose galaxy group that may be falling into the cluster along the line of sight. Combining strong-lensing constraints from two spectroscopically confirmed multiple-image systems near the cluster core with a weak-lensing measurement of the gravitational shear on larger scales, we derive a parametric mass model for the mass distribution. All constraints can be satisfied by a unimodal mass distribution centred on the cD galaxy and exhibiting very little substructure. The derived projected mass of M[< 65 arcsec (415 kpc)]= (4.3 ± 0.6) × 1014 M⊙ is about 30 per cent higher than the one derived from X-ray analyses assuming spherical symmetry, suggesting a slightly prolate mass distribution consistent with the optical indication of residual line-of-sight structure. The similarity in shape and excellent alignment of the centroids of the total mass, K-band light and intracluster gas distributions add to the picture of a highly evolved system. The existence of a massive cluster like MACS J1423, nearly fully virialized only ∼7 Gyr after the big bang, may have important implications for models of structure formation and evolution on cosmological time scales.

Item Type:Article
Additional Information:
Keywords:Gravitational lensing, Galaxies: clusters: individual: MACS J1423.8+2404
Full text:(NA) Not Applicable
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Date accepted:No date available
Date deposited:No date available
Date of first online publication:June 2010
Date first made open access:No date available

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