The integrated properties of the molecular clouds from the JCMT CO(3–2) High-Resolution Survey

Abstract

We define the molecular cloud properties of the Milky Way first quadrant\nusing data from the JCMT CO(3-2) High Resolution Survey. We apply the Spectral\nClustering for Interstellar Molecular Emission Segmentation (SCIMES) algorithm\nto extract objects from the full-resolution dataset, creating the first catalog\nof molecular clouds with a large dynamic range in spatial scale. We identify\n$>85\\,000$ clouds with two clear sub-samples: $\\sim35\\,500$ well-resolved\nobjects and $\\sim540$ clouds with well-defined distance estimations. Only 35%\nof the cataloged clouds (as well as the total flux encompassed by them) appear\nenclosed within the Milky Way spiral arms. The scaling relationships between\nclouds with known distances are comparable to the characteristics of the clouds\nidentified in previous surveys. However, these relations between integrated\nproperties, especially from the full catalog, show a large intrinsic scatter\n($\\sim0.5$ dex), comparable to other cloud catalogs of the Milky Way and nearby\ngalaxies. The mass distribution of molecular clouds follows a truncated-power\nlaw relationship over three orders of magnitude in mass with a form $dN/dM\n\\propto M^{-1.7}$ with a clearly defined truncation at an upper mass of $M_0\n\\sim 3 \\times 10^6~M_\\odot$, consistent with theoretical models of cloud\nformation controlled by stellar feedback and shear. Similarly, the cloud\npopulation shows a power-law distribution of size with $dN/dR \\propto R^{-2.8}$\nwith a truncation at $R_0 = 70$ pc.\n