A New Search for Star Forming Regions in the Southern Outer Galaxy
  Star-formation in the outer Galaxy is thought to be different from the inner
Galaxy, as it is subject to different environmental parameters such as
metallicity, interstellar radiation field, or mass surface density that all
change with Galactocentric radius. We therefore aimed at getting a more
detailed view on the structure of the outer Galaxy, determining physical
properties for a large number of star forming clumps and understanding
star-formation outside the Solar circle. We use pointed $^{12}$CO(2-1)
observations conducted with the APEX telescope to determine the velocity
components towards 830 dust clumps identified from 250 $\mu$m Herschel/Hi-GAL
SPIRE emission maps in the outer Galaxy between $225\deg<\ell<260\deg$. We
determined kinematic distances from the velocity components, in order to
analyze the structure of the outer Galaxy and to estimate physical properties
such as dust temperatures, bolometric luminosities, clump masses, and H2 column
densities for 611 clumps. We find the CO clouds to be strongly correlated with
the highest column density parts of the Hi emission distribution, spanning a
web of bridges, spurs and blobs of star forming regions between the larger
complexes, unveiling the complex three-dimensional structure of the outer
Galaxy in unprecedented detail. Using the physical properties of the clumps, we
find an upper limit of 6% (40 sources) to be able to form high-mass stars. This
is supported by the fact that only 2 methanol Class II masers or 34 known or
candidate Hii regions are found in the whole survey area, indicating an even
lower fraction to be able to form high-mass stars in the outer Galaxy. We fail
to find any correlation of the physical parameters of the identified
(potential) star forming regions with the expanding supershell, indicating that
although the shell organizes the interstellar material into clumps, their
properties are unaffected.
