Hubble space telescope observations of a spectacular new strong-lensing galaxy cluster: MACSJ1149.5+2223 at z = 0.544

Graham P. Smith, Harald Ebeling, Marceau Limousin, Jean Paul Kneib, A. M. Swinbank, Cheng Jiun Ma, Mathilde Jauzac, Johan Richard, Eric Jullo, David J. Sand, Alastair C. Edge, Ian Smail

Research output: Contribution to journalArticlepeer-review

100 Scopus citations


We present Advanced Camera for Surveys observations of MACSJ1149.5+2223, an X-ray luminous galaxy cluster at z = 0.544 discovered by the Massive Cluster Survey. The data reveal at least seven multiply imaged galaxies, three of which we have confirmed spectroscopically. One of these is a spectacular face-on spiral galaxy at z = 1.491, the four images of which are gravitationally magnified by 8 ≲ μ ≲ 23. We identify this as an L * (MB ≃ -20.7), disk-dominated (B/T ≲ 0.5) galaxy, forming stars at 6 M yr-1. We use a robust sample of multiply imaged galaxies to constrain a parameterized model of the cluster mass distribution. In addition to the main cluster dark matter halo and the bright cluster galaxies, our best model includes three galaxy-group-sized halos. The relative probability of this model is P(N halo = 4)/P(N halo < 4) ≥ 1012 where N halo is the number of cluster/group-scale halos. In terms of sheer number of merging cluster/group-scale components, this is the most complex strong-lensing cluster core studied to date. The total cluster mass and fraction of that mass associated with substructures within R ≤ 500 kpc, are measured to be M tot = (6.7 ± 0.4) × 1014 M and f sub = 0.25 ± 0.12, respectively. Our model also rules out recent claims of a flat density profile at ≳7σ confidence, thus highlighting the critical importance of spectroscopic redshifts of multiply imaged galaxies when modeling strong-lensing clusters. Overall our results attest to the efficiency of X-ray selection in finding the most powerful cluster lenses, including complicated merging systems.

Original languageEnglish (US)
Pages (from-to)L163-L168
JournalAstrophysical Journal
Issue number2 PART 2
StatePublished - 2009
Externally publishedYes


  • Cosmology: observations
  • Galaxies: evolution
  • Gravitational lensing

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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