On the accuracy in the derivation of elemental abundances of the emitting gas in HII galaxies

G.F. HÄGELE, A.I. DÍAZ, E. PÉREZ-MONTERO, E. TERLEVICH AND R. TERLEVICH

Barcelona, España

Congreso; VII Reunión Científica de la Sociedad Española de Astronomía; 2006

Universidad de Barcelona

We propose a methodology to perform a self-consistent analysis of the physical properties of the nebular material of HII galaxies adequate to the data that can be obtained with the XXI century technology. This methodology requires the production and calibration of empirical relations between the different line temperatures that should superseed the currently ones based on very simple, and poorly tested,  photo-ionization model sequences.As a first step to reach these goals we have obtained simultaneous blue to far red longslit spectra with the William Herschel Telescope (WHT) of three compact HII galaxies covering from 3200 to 10500,AA, including the Balmer jump, the  [O{sc ii}],$lambdalambda$,3727,29,AA lines, the [S{sc iii}],$lambdalambda$,9069,9532,AA doublet as well as various weakauroral lines such as [O{sc iii}],$lambda$,4363,AA and [S{sc iii}],$lambda$,6312,AA. For the three objects we have measured at least four line temperatures: T([O{sc iii}]), T([S{sc iii}]), T([O{sc ii}]) and T([S{sc ii}]) and the Balmer continuum temperature T(Bac). The analysis of these data along the lines described, allows a careful and realistic treatment of the observational errors and yields total oxygen abundances with accuracies between 5 and 9%. These accuracies are expected to improve as better calibrations based on more precise measurements, both on electron temperatures and  densities, are produced.