4.4. The Galactic Center The central parsec of the galaxy,
identified with the Sagittarius A nebula, contains ionized gas
powered by about 1040 ionizing photons sec-1 (Lacy el al. 1980).
A cluster of He I emission line stars has been observed and
spectroscopically analyzed (Tamblyn et al. 1996, Najarro et al.
1997). The complete spectrum of infrared fine structure lines
that has been observed, combined with the H Br and Br lines (see
Shields & Ferland 1994 for a compilation) should in principle
allow to perform an abundance analysis. From a two-component
photoionization model Shields & Ferland (1994) estimate that the
abundance of Ar should be about twice solar, but Ne seems rather
to have the solar value. The evidence for over solar metallicity
is thus mixed. The N/O ratio is estimated to about 3 - 4 times
solar. However, the derived abundances may be clouded by errors
in the reddening corrections (the extinction is as high as AV =
31, so, even at far infrared wavelengths, reddening become
important) and unc