Whole-disk Sampling of Molecular Clouds in M83

We present a catalog of clouds identified from the 12CO (1–0) data of M83, which was observed using the Atacama Large Millimeter/submillimeter Array with a spatial resolution of ∼46 pc and a mass sensitivity of ∼104M⊙ (3σ). The almost full-disk coverage and high sensitivity of the data allowed us to sample 5724 molecular clouds with a median mass of ∼1.9 × 105M⊙, which is comparable to the most frequently sampled mass of giant molecular clouds by surveys in the Milky Way (MW). About 60% of the total CO luminosity in M83's disk arises from clouds more massive than 106M⊙. Such massive clouds comprise 16% of the total clouds in number and tend to concentrate toward the arm, bar, and center, while smaller clouds are more prevalent in interarm regions. Most >106M⊙ clouds have peak brightness temperatures Tpeak above 2 K with the current resolution. Comparing the observed cloud properties with the scaling relations determined by P. M. Solomon et al. (1987, hereafter S87), Tpeak > 2 K clouds follow the relations, but Tpeak < 2 K clouds, which are dominant in number, deviate significantly. Without considering the effect of beam dilution, the deviations would suggest modestly high virial parameters (median αvir ∼ 2.7) and low surface mass densities (median Σ ∼ 22 M⊙ pc−2) for the entire cloud samples, which are similar to values found for the MW clouds by T. S. Rice et al. (2016) and M.-A Miville-Deschênes et al. (2017). However, once beam dilution is taken into account, the observed αvir and Σ for a majority of the clouds (mostly Tpeak <2 K) can be potentially explained with intrinsic Σ of ∼100 M⊙ pc−2 and αvir of ∼1, which are similar to the clouds of S87.