Herschel and Hubble study of a lensed massive dusty starbursting galaxy at $z\sim 3$

Abstract

We present the results of combined deep Keck/NIRC2, HST/WFC3 near-infrared and Herschel far infrared observations of an extremely star forming dusty lensed galaxy identified from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS J133542.9+300401). The galaxy is gravitationally lensed by a massive WISE identified galaxy cluster at $z\sim 1$. The lensed galaxy is spectroscopically confirmed at $z=2.685$ from detection of $\mathrm{CO}(1\to 0)$ by GBT and from detection of $\mathrm{CO}(3\to 2)$ obtained with CARMA. We use the combined spectroscopic and imaging observations to construct a detailed lens model of the background dusty star-forming galaxy (DSFG) which allows us to study the source plane properties of the target. The best-fit lens model provide magnification of $\hat{I}{¼}_{\mathrm{star}}=2.10\pm 0.11$ and $\hat{I}{¼}_{\mathrm{dust}}=2.02\pm 0.06$ for the stellar and dust components respectively. Multi-band data yields a magnification corrected star formation rate of $1900(\pm 200)M_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$ and stellar mass of $6.8_{-2.7}^{+0.9}\times 10^{11}{M}_{\odot }$ consistent with a main sequence of star formation at $z\sim 2.6$. The CO observations yield a molecular gas mass of $8.3(\pm 1.0)\times 10^{10}{M}_{\odot }$, similar to the most massive star-forming galaxies, which together with the high star-formation efficiency are responsible for the intense observed star formation rates. The lensed DSFG has a very short gas depletion time scale of $\sim 40$ Myr. The high stellar mass and small gas fractions observed indicate that the lensed DSFG likely has already formed most of its stellar mass and could be a progenitor of the most massive elliptical galaxies found in the local Universe.

15 Pages, 10 Figures, 2 Tables. Accepted to the Astrophysical Journal