Gas and dust usually aggregate at the spiral arms, resulting in the formation of massive stars there.  Therefore, they are the primary tracers of the spiral arm structure. Here I present a spiral arm model developed by Reid et al. 2019, which is based on the maser source from young high massive star forming regions (green dots) , as studied in their work. The Galactic center (black asterisk) is located at ~ (0, 0) and the Sun (the Sun symbol) at ~ (0, 8) kpc. I also overplot some literature known OB stars (purple dots, Chen et al. 2019) and OB associations (orange dots, Wrignt 2020). 

In my future work, I aim to trace the structure of the spiral arms using massive stars and OB associations, as well as investigating the 'hole' structures shaped by OB stellar radiation, also known as 'superbubbles', as indicated by the dashed circle. Another goal is to study massive stars and OB associations in the direction of the Galactic anti-centre, as indicated by the dashed box.