Locating the Starburst in the SCUBA Galaxy SMM J14011+0252

We present new, multiwavelength, high-resolution imaging of the luminous, submillimeter galaxy SMM J14011+0252, an interacting starburst at z = 2.56. Our observations comprise optical imaging from the Hubble Space Telescope, sensitive radio mapping from the Very Large Array, and CO observations from the Owens Valley Radio Observatory and Berkeley-Illinois-Maryland Association array. Aided by well-constrained gravitational amplification, we use these new data to map the distribution of gas and both obscured and unobscured starlight. The maps show that the gas and star formation are extended on scales of ≳10 kpc, much larger than starbursts seen in local ultraluminous galaxies and larger than the rest-frame UV-bright components of SMM J14011+0252, J1/J2. The most vigorous star formation is marked by peaks in both the molecular gas and radio emission, ~1'' north of J1/J2, in the vicinity of J1n, an apparent faint extension of J1. Using new sub-0.″5 K-band imaging from the United Kingdom Infrared Telescope, we identify J1n as an extremely red object. We suggest that while J1 and J2 are clearly associated with the submillimeter source, they are merely windows through the dust, or unobscured companions to a large and otherwise opaque star-forming system. Hence, their rest-frame UV properties are unlikely to be relevant for understanding the detailed internal physics of the starburst.