Distance results for the Galactic Ring Survey

However, currently our insight about the fraction of CO in spiral arm and interarm regions is still limited by large uncertainties in assumed rotation curve models or distance determination techniques. In this work we use the Bayesian approach from Reid et al. (2016ApJ...823...77R) and Reid et al. (2019ApJ...885..131R) that is based on our presently most precise knowledge about the structure and kinematics of the Milky Way to obtain the current best assessment of the Galactic distribution of ^13^CO from the Galactic Ring Survey (GRS).

We performed two different distance estimates that either included (Run A) or excluded (Run B) a model for Galactic features, such as spiral arms or spurs. We also include a prior for the solution of kinematic distance ambiguity that was determined from a compilation of literature distances and an assumed size-linewidth relationship. Even though the two distance runs show strong differences due to the prior for Galactic features for Run A and larger uncertainties due to kinematic distances in Run B, the majority of their distance results are consistent with each other within the uncertainties.