Parallaxes & proper motions of OB stars from Gaia EDR3

The Gaia Early Data Release 3 (Gaia EDR3) provides the most precise parallaxes for many OB stars, which can be used to delineate the Galactic spiral structure. We investigate the local spiral structure with the largest sample of spectroscopically confirmed young OB stars available to date, and we compare it with what was traced by the parallax measurements of masers.

A sample consisting of three different groups of massive young stars, including O-B2 stars, O-B0 stars and O-type stars with parallax accuracies better than 10% was compiled and used in our analysis. The local spiral structures in all four Galactic quadrants within ~5kpc of the Sun are clearly delineated in detail. The revealed Galactic spiral pattern outlines a clear sketch of nearby spiral arms, especially in the third and fourth quadrants where the maser parallax data are still absent.