Molecular clouds at the edge of the Galaxy. II. Physical properties and scaling relations

A total of 72 Galactic edge clouds were surveyed using the CO,(2--1) line with the IRAM,30,m telescope, leading to the identification of 112 CO clumps within molecular clouds with linear resolutions of 0.5--0.9,pc. The parameters such as size, mass, surface density, and velocity dispersion of these CO clumps, derived from CO,(2--1) observations, exhibit ranges of 0.6--3.4,pc, 34--8250,M_⊙, 12--1025,M_⊙,pc-2, and -1 , respectively.

Over the galactocentric distance range of 14--23,kpc, no systematic variations are found in these parameters. The velocity dispersion--size relationship of the Galactic edge clumps is modeled as σ_̊m v,=,0.69(±0.03)R_ ̊m eff ^ 0.36( , indicating that turbulence is present within the Galactic edge clumps, similarly to observations in the inner Galactic disk clouds. Furthermore, the luminous mass--size relation of the Galactic edge clumps is described by M_̊m lum,=,196(±17)R_ ̊m eff ^ ,2.18,( , suggesting the average column density remains almost constant for clouds of different sizes.