2004ApJ...614L...5S

We report the detection of CO J=3⟶2 line emission from all three multiple images (A, B, and C) of the intrinsically faint (≃0.8 mJy) submillimeter-selected galaxy SMM J16359+6612. The brightest source of the submillimeter continuum emission (B) also corresponds to the brightest CO emission, which is centered at z=2.5168, consistent with the preexisting redshift derived from Hα. The observed CO flux in the A, B, and C images is 1.2, 3.5, and 1.6 Jy.km/s, respectively, with a line width of 500±100 km/s. After correcting for the lensing amplification, the CO flux corresponds to a molecular gas mass of ∼2x10¹⁰ h^–2₇₁M_☉, while the extent of the CO emission indicates that the dynamical mass of the system is ∼9x10¹⁰ M_☉. Two velocity components are seen in the CO spectra; these could arise either from a rotating compact ring or disk of gas or from merging substructure. The star formation rate in this galaxy was previously derived to be ∼100-500 M_☉/yr. If all the CO emission arises from the inner few kiloparsecs of the galaxy and if the Galactic CO-to-H₂conversion factor holds, then the gas consumption timescale is a relatively short 40 Myr, and so the submillimeter emission from SMM J16359+6612 may be produced by a powerful but short-lived circumnuclear starburst event in an otherwise normal and representative high-redshift galaxy.