2018MNRAS.474.3866H

We report the detection of CO(1-0) line emission from seven Planck and Herschel selected hyper luminous (L_ IR (8 -1000µm)_ > 10¹³ L_☉ ) infrared galaxies with the Green Bank Telescope (GBT). CO(1-0) measurements are a vital tool to trace the bulk molecular gas mass across all redshifts. Our results place tight constraints on the total gas content of these most apparently luminous high-z star-forming galaxies (apparent IR luminosities of L_IR > 10^13 - 14^ L_☉), while we confirm their predetermined redshifts measured using the Large Millimeter Telescope, LMT (z_CO = 1.33-3.26). The CO(1-0) lines show similar profiles as compared to J_up = 2-4 transitions previously observed with the LMT. We report enhanced infrared to CO line luminosity ratios of <L_ IR_/ L^′^_ CO(1 -0)_ > = 110 ±22 L_☉ (K km s^–1 pc^–2)^–1 compared to normal star-forming galaxies, yet similar to those of well-studied IR-luminous galaxies at high-z. We find average brightness temperature ratios of < r₂₁> = 0.93 (2 sources), < r₃₁> = 0.34 (5 sources), and < r₄₁> = 0.18 (1 source). The r₃₁ and r₄₁ values are roughly half the average values for SMGs. We estimate the total gas mass content as µM_H2 = (0.9 -27.2) ×10¹¹ (α_ CO_/0.8) M_☉, where µ is the magnification factor and α_CO is the CO line luminosity to molecular hydrogen gas mass conversion factor. The rapid gas depletion times, <τ_ depl_ >= 80 Myr, reveal vigorous starburst activity, and contrast the Gyr depletion time-scales observed in local, normal star-forming galaxies.