We present Hubble Space Telescope WFC3-IR imaging in the fields of six apparently bright dusty star-forming galaxies ( DSFGs ) at z = 2 – 4 identified by their rest-frame far-infrared colors using the Planck and Herschel space facilities .
We detect near-infrared counterparts for all six submillimeter sources , allowing us to undertake strong-lensing analyses .
One field in particular stands out for its prominent giant arcs , PLCK G165.7+67.0 ( G165 ) .
After combining the color and morphological information , we identify 11 sets of image multiplicities in this one field .
We construct a strong-lensing model constrained by this lensing evidence , which uncovers a bimodal spatial mass distribution , and from which we measure a mass of ( 2.6 \pm 0.11 ) \times 10 ^ { 14 } M _ { \odot } within \sim 250 kpc .
The bright ( S _ { 350 } \approx 750 mJy ) DSFG appears as two images : a giant arc with a spatial extent of 4 \farcs 5 that is merging with the critical curve , and a lower-magnification counterimage that is detected in our new longer-wavelength ground- and space-based imaging data .
Using our ground-based spectroscopy , we calculate a dynamical mass of 1.3 ^ { +0.04 } _ { -0.70 } \times 10 ^ { 15 } M _ { \odot } to the same fixed radius , although this value may be inflated relative to the true value if the velocity distribution is enhanced in the line-of-sight direction .
We suggest that the bimodal mass taken in combination with the weak X-ray flux and low SZ decrement may be explained as a pre-merger for which the intracluster gas is diluted along the line of sight , while the integrated surface mass density is supercritical to strong-lensing effects .