A study of CO emission in high-redshift QSOs using the Owens Valley Millimeter Array

Searches for CO emission in high-redshift objects have traditionally suffered from the accuracy of optically derived redshifts for lack of bandwidth in correlators at radio observatories. This problem has motivated the creation of the new COBRA continuum correlator with 4 GHz available bandwidth at the Owens Valley Radio Observatory Millimeter Array. Presented here are the first scientific results from COBRA. We report detections of redshifted CO (J = 3 --> 2) emission in the QSOs SMM J04135+10277 and VCV J140955.5+562827, as well as a probable detection in RX J0911.4+0551. At redshifts of z = 2.846, 2.585, and 2.796, we find integrated CO flux densities of 5.4, 2.4, and 2.9 Jy km s(-1) for SMM J04135+10277, VCV J140955.5+562827, and RX J0911.4+0551, respectively, over line widths of DeltaV(FWHM) similar to 350 km s(-1). These measurements, when corrected for gravitational lensing, correspond to molecular gas masses of order M(H-2) similar to 10(9.6) -10(11.1) M. and are consistent with previous CO observations of high-redshift QSOs. We also report 3 sigma upper limits on CO (3 --> 2) emission in the QSO LBQS 0018-0220 of 1.3 Jy km s(-1). We do not detect significant 3 mm continuum emission from any of the QSOs, with the exception of a tentative (3 sigma) detection in RX J0911.4+0551 of S-3mm 0.92 mJy beam(-1).