Eva Wuyts, L. Felipe Barrientos, Michael D. Gladders, Keren Sharon, Matthew B. Bayliss, Mauricio Carrasco, David Gilbank, H. K. C. Yee, Benjamin P. Koester, Roberto Muñoz
We present the discovery of an extremely bright and extended lensed source
from the second Red Sequence Cluster Survey (RCS2). RCSGA 032727-132609 is
spectroscopically confirmed as a giant arc and counter-image of a background
galaxy at $z=1.701$, strongly-lensed by the foreground galaxy cluster RCS2
032727-132623 at $z=0.564$. The giant arc extends over $\sim 38$\,\arcsec and
has an integrated $g$-band magnitude of 19.15, making it $\sim 20$ times larger
and $\sim 4$ times brighter than the prototypical lensed galaxy MS1512-cB58.
This is the brightest distant lensed galaxy in the Universe known to date. Its
location in the `redshift desert' provides unique opportunities to connect
between the large samples of galaxies known at $z\sim3$ and $z\sim1$. We have
collected photometry in 9 bands, ranging from $u$ to $K_s$, which densely
sample the rest-frame UV and optical light, including the age-sensitive
4000\AA\ break. A lens model is constructed for the system, and results in a
robust total magnification of $2.04 \pm 0.16$ for the counter-image; we
estimate an average magnification of $17.2 \pm 1.4$ for the giant arc based on
the relative physical scales of the arc and counter-image. Fits of
single-component spectral energy distribution (SED) models to the photometry
result in a moderately young age, $t = 115 \pm 65$\,Myr, small amounts of dust,
$E(B-V) \le 0.035$, and an exponentially declining star formation history with
\textit{e}-folding time $\tau = 10-100$\,Myr. After correcting for the lensing
magnification, we find a stellar mass of
$\log(\mathrm{M}/\mathrm{M}_\odot)=10.0 \pm 0.1$. Allowing for episodic star
formation, an underlying old burst could contain up to twice the mass inferred
from single-component modeling. This stellar mass estimate is consistent with
the average stellar mass of a sample of `BM' galaxies ($1.4 < z < 2.0$) studied
by Reddy et al. (2006).
View original:
http://arxiv.org/abs/1005.2621
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