Far-Infrared [N\II.] Emission from Sgr A West

Previous abstract Next abstract

Session 44 -- Interstellar Medium
Display presentation, Thursday, January 13, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[44.04] Far-Infrared [N\II.] Emission from Sgr A West

E.F.Erickson, M.R.Haas, S.W.J.Colgan, J.P.Simpson (NASA/Ames Research Center)

NASA's Kuiper Airborne Observatory was used in May 1993 to measure the 122 and 205 \mm. lines of [N\II.] in a $\sim 1'$ beam centered on Sgr A$^*$ and encompassing the unusual H\II. region Sgr A West. The ratio of the measured line intensities, when compared with the electron-density dependence of the theoretical volume emissivity ratio, determines the density of the N$^+$ emitting gas. The resulting value is $1400^{+\infty}_{-400}$ cm$^{-3}$, which is very close to the high density limit. This value is comparable to that which we obtain for S$^{++}$, and about twice that for O$^{++}$. The low critical density of the [N\II.] lines and the relatively high value of the density implied by their ratio suggests that there is little low-density N$^+$ gas in our beam. It is possible that most of the [N\II.] emission arises in the compact, high-density ($\sim 10^4$ cm$^{-3}$) ionized spiral streamers unresolved in our beam, whereas the [S\III.] and [O\III.] lines probably originate in the lower density gas of the surrounding cavity.

Thursday program listing