Dust and Molecular gas properties of a large sample of Main-Sequence galaxies at z=3~4

In recent years, measurements of cold gas in galaxies have become an effective tool for investigating the nature and evolution of those stellar structures. The aim of this project is to constrain the gas content of 8 main-sequence galaxies for which we have ALMA data that target their CO(6-5) or CO(5-4) line (and the surrounding continuum). This project is the extension of a previous project (Cassata et al., 2020), that detected two CO transitions, and the surrounding continuum, in a similar sample of 5 galaxies. For the first part of this research, the CASA tool was used to handle the datacubes and identify the CO line and the surrounding continuum. However, since the project was never completed, the achieved rms is significantly worse than the requirement requested in the project, and 3× worse than for the Cassata et al., 2020 sample. As a consequence, the CO lines arenot detected, and for 5 out of 8 galaxies the continuum is detected at ∼ 500 with signal-to-noise ratio (S/N) > 2–7. We then converted these dust continuum fluxes into gas masses, obtaining values between 7.18 × 1010 ⊙ − 16.83 × 1010 ⊙. For the second part, we fitted the broad-band photometry for the 8 objects in the sample, from the UV to the FIR (including the new band4 ALMA data) with MAGPHYS. Our results show that there are no huge differences with the Cassata+2020 sample: 2 out of 8 galaxies lie close to the average star-forming main-sequence at ∼ 3, while the other 6 lie closer to the transition line between MS and Starbursts. In addition, the stellar mass range of these 8 MS galaxies is between log(∗ (10.15 - 11.58)). We found that the gas fraction of our eight galaxies cover a broad range of values, with gas fractions between 22% and 86%. Similarly, we also find that these galaxies have depletion times in the range 0.04 Gyr < < 0.51 Gyr.