Faint Emission Lines and Temperature Fluctuations in M8

Torres-Peimbert, S.; Peimbert, M.; Esteban, C.; Garcia Rojas, J.; Rodriguez, M.
Bibliographical reference

"IX Latin American Regional IAU Meeting, "Focal Points in Latin American Astronomy", held in Tonantzintla, Mexico, Nov 9-13, 1998, Eds: Aguilar, A.; Carraminana, A.; to be printed in Revista Mexicana de Astronomia y Astrofisica Serie de Conferencias."

Advertised on:
11
1998
Number of authors
5
IAC number of authors
2
Citations
0
Refereed citations
0
Description
We present echelle spectroscopy in the 3500 to 10300AA range of the Hourglass Nebula which is embedded in the galactic HII region M8. The data were obtained using the 2.1 m telescope at Observatorio Astronomico Nacional in San Pedro Martir, Baja California. We have measured the intensities of 274 emission lines, in particular 88 permitted lines of C+, N0, N+, O0, O+, Ne0, S0, S+, Si0, Si+ and Si++, some of them produced by recombination only and others mainly by fluorescence. We have determined electron temperatures and densities using different line intensity ratios. We derive the He^+, C++, O+ and O++ ionic abundances as well as --for the first time in a nebular object-- the total O abundance from recombination lines, these nebular values are independent of the temperature structure of the nebula. We have derived also abundances from collisionally excited lines for a large number of ions and elements, these abundances do depend on the temperature structure. Accurate t^2 values have been derived by comparing the C++, O+ and O++ ionic abundances obtained making use of both, collisionally excited lines and recombination lines. A comparison of the solar, Orion nebula and M8 chemical abundances is made.