There is a wide range of distance estimates given in the scientific literature for this nebula, but no information on ionising stars.
Avedisova places RCW 45 in the star formation region SFR 282.13-0.11
with the star cluster Loden 27
Grabelsky associates RCW 45, RCW 47 and possibly RCW 46 with the 225 thousand solar mass molecular cloud [GCB88] 3
According to a third source, RCW 45 and RCW 46 lie at the eastern edge of the chimney GSH 277+0+36
. The chimney is at a distance of about 6500 pc on the outer edge of the Carina arc, is more than 600 pc in diameter, and extends at least 1000 pc above and below the Galactic midplane.
One argument in favour of RCW 45 being a dimmer closer object rather than a brighter further object is its dimness in infrared as this MSX image shows
RCW 45, RCW 47 and possibly RCW 46 are associated the 225 thousand solar mass molecular cloud [GCB88] 3
at a distance of 3200 parsecs.[1
RCW 45 and RCW 46 lie at the eastern edge of the chimney GSH +277+0+036.[2
Kaltcheva and Golev question the association with the chimney and instead suggest that RCW 45 may be associated with the star CPD -55 3036
, which is located at a distance of about 1100 parsecs. [3
1. ^ Grabelsky, D. A., Cohen, R. S., Bronfman, L., et al. (1988). "Molecular
clouds in the Carina arm - The largest objects, associated regions of star
formation, and the Carina arm in the Galaxy", The Astrophysical Journal,
Vol. 331, 181-196. [1988ApJ...331..181G]
2. ^ McClure-Griffiths, N. M., Dickey, John M., Gaensler, B. M., et al. (2000).
"Two Large H I Shells in the Outer Galaxy near L=279°", The Astronomical
Journal, Vol. 119, 2828-2842. [2000AJ....119.2828M]
3. ^ Kaltcheva, N. T. & Golev, V. K. (2012). "Galactic Structure Toward the
Carina Tangent", Publications of the Astronomical Society of the Pacific,
Vol. 124, 128-139. [2012PASP..124..128K]