2011ApJ...739L..32R

We report the detection of CO(J = 1{x2192}0) emission in the strongly lensed high-redshift quasars IRAS F10214+4724 (z = 2.286), the Cloverleaf (z = 2.558), RX J0911+0551 (z = 2.796), SMM J04135+10277 (z = 2.846), and MG 0751+2716 (z = 3.200), using the Expanded Very Large Array and the Green Bank Telescope. We report lensing-corrected CO(J = 1{x2192}0) line luminosities of L'_CO= (0.34-18.4)x10¹⁰ K km/s pc2 and total molecular gas masses of M(H₂) = (0.27-14.7)x10¹⁰ M_☉ for the sources in our sample. Based on CO line ratios relative to previously reported observations in J ≥ 3 rotational transitions and line excitation modeling, we find that the CO(J = 1{x2192}0) line strengths in our targets are consistent with single, highly excited gas components with constant brightness temperature up to mid-J levels. We thus do not find any evidence for luminous-extended, low-excitation, low surface brightness molecular gas components. These properties are comparable to those found in z > 4 quasars with existing CO(J = 1{x2192}0) observations. These findings stand in contrast to recent CO(J = 1{x2192}0) observations of z ≃ 2-4 submillimeter galaxies (SMGs), which have lower CO excitation and show evidence for multiple excitation components, including some low-excitation gas. These findings are consistent with the picture that gas-rich quasars and SMGs represent different stages in the early evolution of massive galaxies.