Optical and near IR spectroscopy of low excitation HII regions with GTC
  The determination of chemical abundances in ionized gas nebulae is based on the detection of auroral emission lines, from which it is possible to deduce the line temperatures of several ions. These lines are weak in low excitation objects, so its measurement is only possible in great aperture telescopes. The GTC would allow to plan a comprehenssive study of chemical abundances in such objects from mid-high resolution spectra, what would give more accurate observational restrictions to models of chemical evolution. 
Enrique Perez-Montero, Marcelo Castellanos & Angeles I. Diaz   (Universikdad Autonoma de Madrid)