Clash: Discovery of a bright z ≃ 6.2 dwarf galaxy quadruply lensed by MACS J0329.6-0211

A. Zitrin, J. Moustakas, L. Bradley, D. Coe, L. A. Moustakas, M. Postman, X. Shu, W. Zheng, N. Benítez, R. Bouwens, T. Broadhurst, H. Ford, O. Host, S. Jouvel, A. Koekemoer, M. Meneghetti, P. Rosati, M. Donahue, C. Grillo, D. KelsonD. Lemze, E. Medezinski, A. Molino, M. Nonino, S. Ogaz

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Abstract

We report the discovery of a z phot = 6.18+0.05 - 0.07 (95% confidence level) dwarf galaxy, lensed into four images by the galaxy cluster MACS J0329.6-0211 (zl = 0.45). The galaxy is observed as a high-redshift dropout in HST/ACS/WFC3 CLASH and Spitzer/IRAC imaging. Its redshift is securely determined due to a clear detection of the Lyman break in the 18-band photometry, making this galaxy one of the highest-redshift multiply lensed objects known to date with an observed magnitude of F125W =24.00 0.04 AB mag for its most magnified image. We also present the first strong-lensing analysis of this cluster uncovering 15 additional multiply imaged candidates of five lower-redshift sources spanning the range zs ≃ 2-4. The mass model independently supports the high photometric redshift and reveals magnifications of 11.6+8.9 - 4.1, 17.6+6.2 - 3.9, 3.9+3.0 - 1.7, and 3.7+1.3 - 0.2, respectively, for the four images of the high-redshift galaxy. By delensing the most magnified image we construct an image of the source with a physical resolution of 200 pc when the universe was 0.9Gyr old, where the z ≃ 6.2 galaxy occupies a source-plane area of approximately 2.2kpc2. Modeling the observed spectral energy distribution using population synthesis models, we find a demagnified stellar mass of , subsolar metallicity (Z/Z 0.5), low dust content (AV 0.1mag), a demagnified star formation rate (SFR) of yr -1, and a specific SFR of 3.4Gyr-1, all consistent with the properties of local dwarf galaxies.

Original languageEnglish
Article numberL9
JournalAstrophysical Journal Letters
Volume747
Issue number1
DOIs
StatePublished - 1 Mar 2012
Externally publishedYes

Keywords

  • dark matter
  • galaxies: clusters: general
  • galaxies: clusters: individual (MACS J0329.6-0211)
  • galaxies: high-redshift
  • gravitational lensing: strong

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