We present a source-plane reconstruction of a ${ \it Herschel}$ and ${ \it Planck}$-detected gravitationally-lensed dusty star-forming galaxy (DSFG) at $z=1.68$ using { \it Hubble}, Sub-millimeter Array (SMA), and Keck observations. The background sub-millimeter galaxy (SMG) is strongly lensed by a foreground galaxy cluster at $z=0.997$ and appears as an arc of length $\sim 15^{ \prime \prime}$ in the optical images. The continuum dust emission, as seen by SMA, is limited to a single knot within this arc. We present a lens model with source plane reconstructions at several wavelengths to show the difference in magnification between the stars and dust, and highlight the importance of a multi-wavelength lens models for studies involving lensed DSFGs. We estimate the physical properties of the galaxy by fitting the flux densities to model SEDs leading to a magnification-corrected star formation rate of $390 \pm 60$ M$_{ \odot}$ yr$^{ -1}$ and a stellar mass of $1.1 \pm 0.4\times 10^{ 11}$ M$_{ \odot}$. These values are consistent with high-redshift massive galaxies that have formed most of their stars already. The estimated gas-to-baryon fraction, molecular gas surface density, and SFR surface density have values of $0.43 \pm 0.13$, $350 \pm 200$ M$_{ \odot}$ pc$^{ -2}$, and $\sim 12 \pm 7~$M$_{ \odot}$ yr$^{ -1}$ kpc$^{ -2}$, respectively. The ratio of star formation rate surface density to molecular gas surface density puts this among the most star-forming systems, similar to other measured SMGs and local ULIRGS.
Categories: astro-ph.GA