Multi-wavelength lens reconstruction of a $\textit{Planck}$ $\&$ $\textit{Herschel}$-detected star-bursting galaxy

TL;DR

This paper reconstructs a gravitationally-lensed starburst galaxy across multiple wavelengths, revealing detailed physical properties and emphasizing the importance of multi-wavelength lens modeling for understanding high-redshift dusty star-forming galaxies.

Contribution

It provides a novel multi-wavelength lens model of a lensed DSFG, highlighting differences in magnification between stars and dust, and derives key physical properties of the galaxy.

Findings

Star formation rate of 390 ± 60 M_sun/yr after magnification correction

Stellar mass of 1.1 ± 0.4 x 10^11 M_sun

High gas-to-baryon fraction and star formation surface density

Abstract

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.