The largest gravitational lens: MACS J0717.5+3745 (z = 0.546)

Adi Zitrin*, Tom Broadhurst, Yoel Rephaeli, Sharon Sadeh

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

86 Scopus citations


We identify 13 sets of multiply-lensed galaxies around MACS J0717.5+3745 (z = 0.546), outlining a very large tangential critical curve of major axis ∼2′8, filling the field of the Hubble Space Telescope/Advanced Camera for Surveys. The equivalent circular Einstein radius is θe = 55″± 3″ (at an estimated source redshift of zs ∼ 2.5), corresponding to re ≃ 350 ±20 kpc at the cluster redshift, nearly three times greater than that of A1689 (re ≃ 140 kpc for zs = 2.5). The mass enclosed by this critical curve is very large, 7.4± 0.5 × 1014 M and only weakly model dependent, with a relatively shallow mass profile within r < 250 kpc, reflecting the unrelaxed appearance of this cluster. This shallow profile generates a much higher level of magnification than the well-known relaxed lensing clusters of higher concentration, so that the area of sky exceeding a magnification of >10 times, is ≃3.5□′ for sources with z ≃ 8, making MACS J0717.5+3745 a compelling target for accessing faint objects at high redshift. We calculate that only one such cluster, with θe ≥ 55″, is predicted within 10 7 Universes with z ≥ 0.55, corresponding to a virial mass ≥3 × 1015 M , for the standard ΛCDM (WMAP5 parameters with 2σ uncertainties).

Original languageEnglish
Pages (from-to)L102-L106
JournalAstrophysical Journal
Issue number1 PART 2
StatePublished - 2009


  • Dark matter
  • Gravitational lensing


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