We report the detection of CO ( J =3 \rightarrow 2 ) line emission from all three multiple images ( A , B and C ) of the intrinsically faint ( \simeq 0.8 mJy ) submillimeter-selected galaxy SMM J16359+6612 .
The brightest source of the submm continuum emission ( B ) also corresponds to the brightest CO emission , which is centered at z =2.5168 , consistent with the pre-existing redshift derived from H \alpha .
The observed CO flux in the A , B and C images is 1.2 , 3.5 and 1.6 Jy km s ^ { -1 } respectively , with a linewidth of 500 \pm 100 km s ^ { -1 } .
After correcting for the lensing amplification , the CO flux corresponds to a molecular gas mass of \sim 2 \times 10 ^ { 10 } h _ { 71 } ^ { -2 } M _ { \sun } , while the extent of the CO emission indicates that the dynamical mass of the system \sim 9 \times 10 ^ { 10 } M _ { \sun } .
Two velocity components are seen in the CO spectra ; these could arise from either a rotating compact ring or disk of gas , or merging substructure .
The star formation rate in this galaxy was previously derived to be \sim 100–500 M _ { \sun } yr ^ { -1 } .
If all the CO emission arises from the inner few kpc of the galaxy and the galactic CO-to-H _ { 2 } conversion factor holds , then the gas consumption timescale is a relatively short 40 Myr , and so the submm 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 .