Abstract
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-1, respectively, with a line width of 500 ± 100 km s-1. After correcting for the lensing amplification, the CO flux corresponds to a molecular gas mass of ~2 × 1010 h M☉, while the extent of the CO emission indicates that the dynamical mass of the system is ~9 × 1010 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-1. If all the CO emission arises from the inner few kiloparsecs of the galaxy and if the Galactic CO-to-H2 conversion 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.
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