|
Intriguing and different, Fred. Totally new to me. Wonderfully presented.
In answer to your question, why is there H-alpha and NII (identical to the H-alpha) but no OIII or SII, my guess would be:
(1) The NII image is actually H-alpha that has struggled through the NII filter. The bandpass of a 3nM NII filter overlaps that of a 3nM H-alpha filter.
(2) This is a youngish star-forming region, in which either (a) there are as yet no really hot young stars out and about nearby that can ionize oxygen and sulphur, or (b) there has been little supernova activity so no shock front energy to do the job, and/or there is not so very much oxygen and sulphur released from within, or (c) where there is oxygen and sulphur, the gas pressure is too high for the forbidden lines to form, or (d) most likely, all of the above.
You've captured much beautiful blue glow. Since you've shown it's not OIII, it is almost certainly reflection nebulosity.
Excellent!
Very best,
Mike
|