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We present CO observations of 9 ULIRGs at z~2 with S(24\mu m)>1mJy,previously confirmed with the mid-IR spectra in the Spitzer First Look Survey.All targets are required to have accurate redshifts from Keck/GEMINI near-IRspectra. Using the Plateau de Bure millimeter-wave Interferometer (PdBI) atIRAM, we detect CO J(3-2) [7 objects] or J(2-1) [1 object] line emission from 8sources with integrated intensities Ic ~(5-9)sigma. The CO detected sourceshave a variety of mid-IR spectra, including strong PAH, deep silicateabsorption and power-law continuum, implying that these molecular gas richobjects at z~2 could be either starbursts or dust obscured AGNs. The measuredline luminosity L'[CO] is (1.28-3.77)e+10[K km/s pc^2]. The averaged moleculargas mass M(H2) is 1.7e+10Msun, assuming CO-to-H2 conversion factor of0.8Msun/[K km/s pc^2]. Three sources (33%) -- MIPS506, MIPS16144 & MIPS8342 --have double peak velocity profiles. The CO double peaks in MIPS506 andMIPS16144 show spatial separations of 45kpc and 10.9kpc, allowing the estimatesof the dynamical masses of 3.2e+11*sin^(-2)(i)Msun and 5.4e+11*sin^{-2}(i)Msunrespectively. The implied gas fraction, M(gas)/M(dyn), is 3% and 4%, assumingan average inclination angle. Finally, the analysis of the HST/NIC2 images,mid-IR spectra and IR SED revealed that most of our sources are mergers,containing dust obscured AGNs dominating the luminosities at (3-6)um. Together,these results provide some evidence suggesting SMGs, bright 24um z~2 ULIRGs andQSOs could represent three different stages of a single evolutionary sequence,however, a complete physical model would require much more data, especiallyhigh spatial resolution spectroscopy.

Detections of CO Molecular Gas in 24um-Bright ULIRGs at z~2 in the Spitzer First Look Survey