[Ne III]/[O II] as an oxygen abundance indicator in the H II regions and H II galaxies
National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, PR China e-mail: firstname.lastname@example.org
Accepted: 20 August 2007
Aims.To calibrate the relationship between Ne3O2 (Ne3O2 = log ([Ne iii]/[O ii])) and oxygen abundances, we present a sample of ~3000 H ii galaxies from the Sloan Digital Sky Survey (SDSS) data release four. They are associated with a sample from the literature intended to enlarge the oxygen abundance region.
Methods.We calculated the electron temperatures (Te) of 210 galaxies in the SDSS sample with the direct method, and Te of the other 2960 galaxies in SDSS sample calculated with an empirical method. Then, we use a linear least-square fitting to calibrate the Ne3O2 oxygen abundance indicator.
Results.It is found that the Ne3O2 estimator follows a linear relation with 12 + log (O/H) that holds for the whole abundance range covered by the sample, from approximately 7.0 to 9.0. The best linear relationship between the Ne3O2 and the oxygen abundance is calibrated. The dispersion between oxygen abundance and Ne3O2 index in the metal rich galaxies may come partly from the moderate depletion of oxygen onto grains. The Ne3O2 method has the virtue of being single-valued and not affected by internal reddening. As a result, the Ne3O2 method can be a good metallicity indicator in the H ii regions and H ii galaxies, especially in high-redshift galaxies.
Key words: Galaxy: abundances / galaxies: ISM / H ii regions
© ESO, 2007