Preprint typeset using LATEX style emulateapj MOLECULAR GAS IN THE Z = 2 . 8 SUBMILLIMETER GALAXY SMM

We report the detection of CO(3!2) emission from the submillimeter{selected hyperluminous galaxy SMM 02399{0136. This galaxy is the brightest source detected in the recent SCUBA surveys of the submillimeter sky. The optical counterpart of the submillimeter source has been identiied as a narrow-line AGN/starburst galaxy at z = 2:8. The CO emission is unresolved, < 5 00 , and is coincident in redshift and position with the optical counterpart. The molecular gas mass derived from the CO observations is 8 10 10 h ?2 75 M , after correcting for a lensing ampliication factor of 2.5. The large CO luminosity suggests that a signiicant fraction of the infrared luminosity of SMM 02399{0136 arises from star formation. The high inferred star{formation rate of 10 3 M yr ?1 and the large gaseous reservoir may suggest that we are seeing the formation phase of a massive galaxy. Future CO observations of other galaxies detected in deep submillimeter surveys will test the generality of these conclusions for the bulk of the faint submillimeter population.