We present the rest-frame optical spectral energy distribution and stellar masses of six Herschel -selected gravitationally lensed dusty , star-forming galaxies ( DSFGs ) at 1 < z < 3 .
These galaxies were first identified with Herschel /SPIRE imaging data from the Herschel Astrophysical Terahertz Large Area Survey ( H-ATLAS ) and the Herschel Multi-tiered Extragalactic Survey ( HerMES ) .
The targets were observed with Spitzer /IRAC at 3.6 and 4.5 \mu m. Due to the spatial resolution of the IRAC observations at the level of 2 ^ { \prime \prime } , the lensing features of a background DSFG in the near-infrared are blended with the flux from the foreground lensing galaxy in the IRAC imaging data .
We make use of higher resolution Hubble /WFC3 or Keck/NIRC2 Adaptive Optics imaging data to fit light profiles of the foreground lensing galaxy ( or galaxies ) as a way to model the foreground components , in order to successfully disentangle the foreground lens and background source flux densities in the IRAC images .
The flux density measurements at 3.6 and 4.5 \mu m , once combined with Hubble /WFC3 and Keck/NIRC2 data , provide important constraints on the rest-frame optical spectral energy distribution of the Herschel -selected lensed DSFGs .
We model the combined UV- to millimeter-wavelength SEDs to establish the stellar mass , dust mass , star-formation rate , visual extinction , and other parameters for each of these Herschel -selected DSFGs .
These systems have inferred stellar masses in the range 8 \times 10 ^ { 10 } to 4 \times 10 ^ { 11 } M _ { \odot } and star-formation rates of around 100 M _ { \odot } yr ^ { -1 } .
This puts these lensed sub-millimeter systems well above the SFR- M ^ { * } relation observed for normal star-forming galaxies at similar redshifts .
The high values of SFR inferred for these systems are consistent with a major merger-driven scenario for star formation .