On the Detection of the Nitrogen Molecule, N2, in the ISM

D. C. Knauth, B.-G. Andersson, S. R. McCandliss, and H. W. Moos
reported on
The Interstellar N2 Abundance Towards HD 124314 from Far-Ultraviolet Observations
Nature 429, 636–638 (2004).
The Far Ultraviolet Spectroscopic Explorer (Fuse) was used to identify N2 in the diffuse medium toward the slightly reddened star HD 124314, which is also known as IRAS 14111–6127, via its c'4 – X electronic transition at 95.86 nm and the c3 – X transition at 96.03 nm. The material is considered to be diffuse rather than translucent because of the slight reddening of the star. However, the derived fractional abundance of N2 with respect to H2 is about 3.3 × 10–7, two orders of magnitude higher than predictions from diffuse ISM models from that time. On the other hand, the column density is slightly less than that of CO on the same line of sight, and the deduced temperature is identical to that of the cold H2 component (about 38 K). Moreover, similar observations of NH also yielded relative abundances much higher than predicted by diffuse ISM models.
See also the news and views contribution by
T. P. Snow,
Molecular Nitrogen in Space
Nature 429, 615–616 (2004).

The same authors reported on the
Discovery of Interstellar N2
Proceedings of the "Astrophysics in the Far Ultraviolet: Five Years of Discovery with FUSE" Conference, 2–6 Aug, 2004, Victoria, BC, Canada; ASP Conference Series, Vol. 348, 421–423.
Besides their observations mentioned above, they report on N2 detection toward 20 Aql, aka HD 179406, however, with a fractional abundance wrt H2 almost one order of magnitude less than toward HD 124314.


Contributor(s): H. S. P. Müller; 11, 2016