There are at least two conflicting distance estimates - one is based on the assumption that this HII region is associated with the star cluster Trumpler 10
at about 400 pc, and the other that it is associated with HD 75759
at about 1000 pc.
You can see a good colour image of RCW 32 and RCW 33 together here
, which is linked from Steven Lee's webpage
Avedisova concludes that RCW 33 is ionised by the O9 V star HD 75759 (which she also lists as an ionising star for RCW 32) as well as the B0.5 V star HD 75724
] She places RCW 27, RCW 32, and RCW 33 together in the star formation region SFR 265.00-2.00
along with the Vela dark cloud complex described in this 1976 paper
Kharchenko, on the other hand, places HD 75724 in Trumpler 10, for which she gives a distance estimate of 417 parsecs. She places HD 75759 in a more distant star cluster, Alessi 43 = [KPR2005] 50
, at 850 parsecs.
You can see this large nebula in this SuperCOSMOS hydrogen-alpha image
, which also shows the boundaries of Trumpler 10 and Alessi 43.
Probably ionised by the O9V star HD 75759 at a distance of about 1000 pc.[2
1. ^ Avedisova, V. S. & Kondratenko, G. I. (1984). "Exciting stars and the
distances of the diffuse nebulae", Nauchnye Informatsii, Vol. 56, 59.
2. ^ Pettersson, B. & Reipurth, B. (1994). "Young stars associated with the
VELA Molecular Ridge. I. VMR clouds C and D, Collinder 197 and VELA R2",
Astronomy and Astrophysics Supplement Series, Vol. 104, 233-258.