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 (z_{ l}=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\pm0.04 AB mag for its highest-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 z_{ s}~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. With this we construct a source image with a physical resolution of ~200 pc when the universe was ~0.9 Gyr old, where the z~6.2 galaxy occupies a source-plane area of approximately 2.2 kpc^{ 2}. Modeling the observed spectral energy distribution using population synthesis models, we find a demagnified stellar mass of ~10^{ 9} { M}_{ sun}, subsolar metallicity (Z/Z_{ sun}~0.5), low dust content (A_{ V}~0.1 mag), a demagnified star formation rate (SFR) of ~3.2 { M}_{ sun} yr^{ -1}, and a specific SFR of ~3.4 Gyr^{ -1}, all consistent with the properties of local dwarf galaxies.
Categories: astro-ph.CO