PHYSICAL-PROPERTIES OF MOLECULAR CLOUDS IN THE SOUTHERN OUTER GALAXY

We have used a deep CO survey of the third galactic quadrant (May et a l. 1993) to derive the physical properties of molecular clouds in the outer Galaxy. Within the range of this survey, from 194 degrees to 270 degrees in galactic longitude, 177 molecular clouds have been identif ied beyond 2 kpc from the Sun. Distances have been determined kinemati cally using the rotation curve of Brand (1986) with R. = 8.5 kpc and T heta. = 220 km s(-1). Power-law relations between line widths and size s of the clouds, and between their densities and sizes have been found , although they do not fulfill exactly the requirements to be in viria l equilibrium. Adopting a CO luminosity-to-Hz conversion factor X = 3. 8 10(20) molecules cm(-2) (K km s(-1))(-1), the derived M-CO masses st atistically agree with the virial masses. The derived size and mass di stributions show that the clouds are smaller, less massive and with na rrower lines than those in the inner Galaxy. However, the mass spectru m for the clouds in our Sample with masses greater than or equal to 2. 5 10(4) M. has a slope -1.45 which is similar to that found for inner Galaxy clouds. The warping and flaring of the outer molecular disk is clearly delineated.