SPT 0538-50: Physical conditions in the ISM of a strongly lensed dusty star-forming galaxy at z=2.8

TL;DR

This paper studies a gravitationally-lensed dusty star-forming galaxy at z=2.8, analyzing its physical conditions and ISM properties using multi-wavelength data, revealing merger-driven starburst activity similar to local galaxies.

Contribution

The study provides detailed physical and ISM conditions of a high-redshift DSFG using extensive multi-wavelength observations and high-resolution imaging, highlighting its merger-driven star formation.

Findings

Derived physical properties indicate compact, merger-driven star formation.

ISM excitation conditions suggest similarities to local starburst galaxies.

Magnification factor of 21 +/- 4 from lens modeling.

Abstract

We present observations of SPT-S J053816-5030.8, a gravitationally-lensed dusty star forming galaxy (DSFG) at z = 2.7817, first discovered at millimeter wavelengths by the South Pole Telescope. SPT 0538-50 is typical of the brightest sources found by wide-field millimeter-wavelength surveys, being lensed by an intervening galaxy at moderate redshift (in this instance, at z = 0.441). We present a wide array of multi-wavelength spectroscopic and photometric data on SPT 0538-50, including data from ALMA, Herschel PACS and SPIRE, Hubble, Spitzer, VLT, ATCA, APEX, and the SMA. We use high resolution imaging from HST to de-blend SPT 0538-50, separating DSFG emission from that of the foreground lens. Combined with a source model derived from ALMA imaging (which suggests a magnification factor of 21 +/- 4), we derive the intrinsic properties of SPT 0538-50, including the stellar mass, far-IR luminosity, star formation rate, molecular gas mass, and - using molecular line fluxes - the excitation conditions within the ISM. The derived physical properties argue that we are witnessing compact, merger-driven star formation in SPT 0538-50, similar to local starburst galaxies, and unlike that seen in some other DSFGs at this epoch.