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We present high-resolution CO(1-0) observations of the lensed submillimetergalaxy (SMG) SMM J14011+0252 at z=2.6. Comparison to the previously-detectedCO(3-2) line gives an intensity ratio of r_3,1=0.97+/-0.16 in temperatureunits, larger than is typical for SMGs but within the range seen in the low-zultraluminous infrared galaxy population. Combining our new data with previousmid-J CO observations, we perform a single-phase large velocity gradient (LVG)analysis to constrain the physical conditions of the molecular gas. Acceptablemodels have significant degeneracies between parameters, even when we rule outall models that produce optically thin emission, but we find that the bulk ofthe molecular gas has T_kin=20-60 K, n_{H_2}~10^4-10^5 cm^-3, andN_CO/Delta-v=10^{17.00+/-0.25} cm^-2 km^-1 s. For our best-fit models toself-consistently recover a typical CO-to-H_2 abundance and a plausible degreeof virialization, the local velocity gradient in the molecular gas must besubstantially larger than its galaxy-wide average. This conclusion isconsistent with a scenario in which SMM J14011+0252 has a fairly face-onorientation and a molecular ISM composed of many unresolved clouds. Usingprevious H-alpha observations, we find that SMM J14011+0252 has a spatiallyresolved star formation rate vs. molecular gas surface density relationinconsistent with those of "normal" local star-forming galaxies, even if weadopt a local "disk-like" CO-to-H_2 conversion factor as motivated by our LVGanalysis. This discrepancy supports the inference of a star formation relationfor high-z starbursts distinct from the local relation that is not solely dueto differing choices of gas mass conversion factor.

VLA Mapping of the CO(1-0) Line in SMM J14011+0252