  We present new multi-wavelength observations of the first submm-selected
galaxy, SMM J02399-0136 at z=2.8. These observations include mapping of the CO
J=1-0 emission using elements of the Expanded VLA, as well as high-resolution
1.4-GHz imaging and optical/IR data from the VLA, HST, Spitzer and Keck.
Together these new data provide fundamental insights into the mass and
distribution of stars, gas and dust within this archetypal SMG. The CO J=1-0
emission, with its minimal excitation and density requirements, traces the bulk
of the metal-rich molecular gas, and reveals a mass of ~10^11 M(sun), extending
over ~5" (~25 kpc in the source plane), although there is tentative evidence
that it may be significantly larger. Our data suggest that three or more
distinct structures are encompassed by this molecular gas reservoir, including
the BAL quasar from which the redshift of the SMG was initially determined. In
particular, the new rest-frame near-IR observations identify a massive,
obscured, starburst coincident with a previously known Ly-alpha cloud. This
starburst dominates the far-IR emission from the system and requires a
re-assessment of previous claims that the gas reservoir resides in a massive,
extended disk around the BAL QSO. Instead it appears that SMM J02399-0136
comprises a merger between a far-IR-luminous, but highly obscured starburst,
the BAL QSO host and a faint third component. Our findings suggest that this
SMG and its immediate environment mark a vast and complex galactic nursery and
that detailed studies of other SMGs are likely to uncover a similarly rich
diversity of properties.
