Total molecular gas masses of Planck - Herschel selected strongly lensed hyper luminous infrared galaxies

Abstract

We report the detection of CO(1-0) line emission from seven Planck and Herschel selected hyper luminous ({L_{IR (8-1000{μ m})} > 10^{13} 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 {μ M_{H2} = (0.9-27.2) × 10^{11} (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.