We present CO(J=1-0) and/or CO(J=2-1) spectroscopy for 31 galaxies selected from the ongoing Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, obtained with multiple telescopes. This sample is combined with CO observations from the literature to study the correlation of the CO luminosities (L CO(1−0) ) with the mid-infrared luminosities at 12 (L 12µm ) and 22 µm (L 22µm ), as well as the dependence of the residuals on a variety of galaxy properties. The correlation with L 12µm is tighter and more linear, but galaxies with relatively low stellar masses (M * 10 10 M ⊙ ) and blue colors (g − r 0.5 and/or NUV−r 3) fall significantly below the mean L CO(1−0) -L 12µm relation. We propose a new estimator of the CO(1-0) luminosity (and thus the total molecular gas mass M mol ) that is a linear combination of three parameters: L 12µm , M * and g −r. We show that, with a scatter of only 0.18 dex in log (L CO(1−0) ), this estimator provides unbiased estimates for galaxies of different properties and types. An immediate application of this estimator to a compiled sample of galaxies with only CO(J=2-1) observations yields a distribution of the CO(J=2-1) to CO(J=1-0) luminosity ratios (R21) that agrees well with the distribution of real observations, in terms of both the median and the shape. Application of our estimator to the current MaNGA sample reveals a gas-poor population of galaxies that are predominantly early-type and show no correlation between molecular gas-to-stellar mass ratio and star formation rate, in contrast to gas-rich galaxies. We also provide alternative estimators with similar scatters, based on r and/or z band luminosities instead of M * . These estimators serve as cheap and convenient M mol proxies to be potentially applied to large samples of galaxies, thus allowing statistical studies of gas-related processes of galaxies.

We present the data of an unbiased J = 1–0 12CO/13CO/C18O survey of molecular clouds in the Galactic plane over l = [129.°75, 140.°25] and b = [−5.°25, +5.°25]. For the full 10.°5 × 10.°5 region sampled at 30″, there are 1,590,120 spectra for each isotopologue. The high sensitivity and large spatial dynamic range of the maps provide valuable insights into the structure, physical properties, and kinematics of the molecular gas. The new data successfully trace the most distant spiral arm, as well as the internal subfeatures of the nearby spiral arms. The combined data set of 12CO, 13CO,  and C18O  allows us to make a more accurate inventory of gas column density and mass for molecular gas within this Galactic interval than hitherto attempted. A statistical analysis reveals that a large fraction of the observed molecular gas is emitted from regions with low excitation conditions. As expected, a considerable amount of H2 mass is found to be confined to the spiral arms. Moreover, we find that the C18O emission is exclusively seen along spiral arms at current detection limits. The physical properties of molecular gas vary considerably in different spiral arms and inter-arms. We find that the column density probability density functions and the amount of relatively denser gas (traced by 13CO or C18O) appear to be closely related to the level of massive star formation activity within the molecular gas. The high-quality data also reveal that the warp and flare of the Galactic plane become obvious beyond the Perseus arm in this Galactic longitude range.

No abstract