To understand cosmic mass assembly in the Universe at early epochs , we primarily rely on measurements of stellar mass and star formation rate of distant galaxies .
In this paper , we present stellar masses and star formation rates of six high-redshift ( 2.8 \leq z \leq 5.7 ) dusty , star-forming galaxies ( DSFGs ) that are strongly gravitationally lensed by foreground galaxies .
These sources were first discovered by the South Pole Telescope ( SPT ) at millimeter wavelengths and all have spectroscopic redshifts and robust lens models derived from ALMA observations .
We have conducted follow-up observations , obtaining multi-wavelength imaging data , using HST , Spitzer , Herschel and the Atacama Pathfinder EXperiment ( APEX ) .
We use the high-resolution HST /WFC3 images to disentangle the background source from the foreground lens in Spitzer /IRAC data .
The detections and upper limits provide important constraints on the spectral energy distributions ( SEDs ) for these DSFGs , yielding stellar masses , IR luminosities , and star formation rates ( SFRs ) .
The SED fits of six SPT sources show that the intrinsic stellar masses span a range more than one order of magnitude with a median value \sim 5 \times 10 ^ { 10 } M _ { \sun } .
The intrinsic IR luminosities range from 4 \times 10 ^ { 12 } L _ { \sun } to 4 \times 10 ^ { 13 } L _ { \sun } .
They all have prodigious intrinsic star formation rates of 510 to 4800 M _ { \sun } { yr } ^ { -1 } .
Compared to the star-forming main sequence ( MS ) , these six DSFGs have specific SFRs that all lie above the MS , including two galaxies that are a factor of 10 higher than the MS. Our results suggest that we are witnessing the ongoing strong starburst events which may be driven by major mergers .