CLASH: Discovery of a Bright z~6.2 Dwarf Galaxy Quadruply Lensed by MACS
  J0329.6-0211
  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.
