There are a wide range of distance estimates for this nebula.
Avedisova concludes that RCW 46 is ionised the O8 V class CP -56 2853
and 3 B-class stars at a distance of 1880 +/- 210 parsecs. She places it in star formation region SFR 282.32-1.33
along with the reflection nebula Bran 288
. (According to a 1989 paper by Stark and Brand, Bran 288 has a distance of 1970 +/- 400 parsecs so this is consistent with the Avedisova information.)
Grabelsky associates RCW 45, RCW 47 and possibly RCW 46 with the 225 thousand solar mass molecular cloud [GCB88] 3
at a distance of 3200 parsecs.
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.
RCW 46 is located just below a huge cavity visible in infrared as can be seen in this MSX image
, but little infrared emission is visible in the direction of RCW 46 itself. You can also see another infrared image of RCW 46
taken by 2MASS, which shows the infrared star group [DBS2003] 42
at its centre.
Bran 288 has a distance of 1970 +/- 400 parsecs.[1
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.[2
RCW 45 and RCW 46 lie at the eastern edge of the chimney GSH +277+0+036.[3
Contains the infrared group [DBS2003] 42
A 2011 paper mistakenly identifies RCW 46 with the giant HII region G282.0-1.2. [5
] However, G282.0-1.2 is visually obscured and RCW 46 is a distinct and smaller object located about a third of a degree away.
1. ^ Stark, Antony A. & Brand, Jan (1989). "Kinematics of molecular clouds. II
- New data on nearby giant molecular clouds", The Astrophysical Journal,
Vol. 339, 763-771. [1989ApJ...339..763S]
2. ^ 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]
3. ^ 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]
4. ^ Dutra, C. M., Bica, E., Soares, J., et al. (2003). "New infrared star
clusters in the southern Milky Way with 2MASS", Astronomy and Astrophysics,
Vol. 400, 533-539. [2003A&A...400..533D]
5. ^ Moisés, A. P., Damineli, A., Figuerêdo, E., et al. (2011).
"Spectrophotometric distances to Galactic H II regions", Monthly Notices of
the Royal Astronomical Society, Vol. 411, 705-760. [2011MNRAS.411..705M]