We present the rest-frame optical spectral energy distribution (SED) 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 μm. Due to the spatial resolution of
the IRAC observations at the level of 2″, 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 μm,
once combined with Hubble/WFC3 and Keck/NIRC2 data, provide important
constraints on the rest-frame optical SED 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 ×
1010-4 × 1011 M⊙ and
star formation rates of around 100 M⊙
yr-1. This puts these lensed submillimeter 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.