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, C. Grillo, D. Kelson, D. Lemze, E. Medezinski, A. Molino, M. Nonino, S. Ogaz
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 \emph{HST}/ACS/WFC3 CLASH and \emph{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 $z_{s}\simeq2-4$. 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
$\sim200$ pc when the universe was $\sim0.9$ Gyr old, where the $z\simeq6.2$
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 $\sim10^{9} \mathcal{M}_{\sun}$, subsolar
metallicity ($Z/Z_{\sun}\sim0.5$), low dust content ($A_{V}\sim0.1$ mag), a
demagnified star formation rate (SFR) of $\sim3.2 \mathcal{M}_{\sun}$
yr$^{-1}$, and a specific SFR of $\sim3.4$ Gyr$^{-1}$, all consistent with the
properties of local dwarf galaxies.
View original:
http://arxiv.org/abs/1111.5006
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