Oxygen and Nitrogen in Leo a and Gr 8

We present elemental abundances for multiple HII regions in Leo A and GR 8 obtained from long slit optical spectroscopy of these two nearby low luminosity dwarf irregular galaxies. As expected from their luminosities, and in agreement with previous observations, the derived oxygen abundances are extremely low in both galaxies. High signal-to-noise ratio observations of a planetary nebula in Leo A yield 12 + log(O/H) = 7.30 ± 0.05; “semi-empirical” calculations of the oxygen abundance in four HII regions in Leo A indicate 12 + log(O/H) = 7.38 ± 0.10. These results confirm that Leo A has one of the lowest ISM metal abundances of known nearby galaxies. Based on results from two HII regions with high signal-to-noise measurements of the weak [O III] λ4363 line, the mean oxygen abundance of GR 8 is 12 + log(O/H) = 7.65 ± 0.06; using “empirical” and “semi-empirical” methods, similar abundances are derived for 6 other GR 8 HII regions. Similar to previous results in other low metallicity galaxies, the mean log(N/O) = −1.53 ± 0.09 for Leo A and −1.51 ± 0.07 for GR 8. There The National Astronomy and Ionosphere Center is operated by Cornell University under a cooperative agreement with the National Science Foundation.