This enormous nebular region lies in the direction of the Car OB2
association and parts of it may be ionised by stars in that association. Gum splits this region into several distinct nebulae and the RCW catalog itself splits the region into four subnebulae, which are described separately as RCW 54a, 54b, 54c and 54d.
RCW 54b is the same as Gum 34a and Gum 34b, RCW 54d is the same as Gum 36. [1
This is actually several different objects at different distances, including RCW 54a, RCW 54b and RCW 54d. [2
1. ^ Georgelin, Y. M., Russeil, D., Amram, P., et al. (2000). "Deep Hα survey
of the Milky Way. V. The l=289o to 295o area", Astronomy and
Astrophysics, Vol. 357, 308-324. [2000A&A...357..308G]
2. ^ Rizzo, J. R. & Arnal, E. M. (1998). "A study of the interstellar gas
surrounding Carina OB2", Astronomy and Astrophysics, Vol. 332, 1025-1034.