Improved Measurements of Molecular Cloud Distances Based on Global
  Search
  The principle of the background-eliminated extinction-parallax (BEEP) method
is examining the extinction difference between on- and off-cloud regions to
reveal the extinction jump caused by molecular clouds, thereby revealing the
distance in complex dust environments. The BEEP method requires high-quality
images of molecular clouds and high-precision stellar parallaxes and extinction
data, which can be provided by the Milky Way Imaging Scroll Painting (MWISP) CO
survey and the Gaia DR2 catalog, as well as supplementary AV extinction data.
In this work, the BEEP method is further improved (BEEP-II) to measure
molecular cloud distances in a global search manner. Applying the BEEP-II
method to three regions mapped by the MWISP CO survey, we collectively measured
238 distances for 234 molecular clouds. Compared with previous BEEP results,
the BEEP-II method measures distances efficiently, particularly for those
molecular clouds with large angular size or in complicated environments, making
it suitable for distance measurements of molecular clouds in large samples.
