We measured the oxygen abundances of the warm (T∼104K) phase of gas in seven early-type galaxies through long-slit observations. A template spectra was constructed from galaxies void of warm gas and subtracted from the emission-line galaxies, allowing for a clean measurement of the nebular lines. The ratios of the emission lines are consistent with photoionization, which likely originates from the UV flux of post-asymototic giant branch (PAGB) stars. We employ H II region photoionization models to determine a mean oxygen metallicity of 1.01±0.50 solar for the warm interstellar medium (ISM) in this sample. This warm ISM 0.5 to 1.5 solar metallicity is consistent with modern determinations of the metallicity in the hot (T∼106−107K) ISM and the upper range of this warm ISM metallicity is consistent with stellar population metallicity determinations. A solar metallicity of the warm ISM favors an internal origin for the warm ISM such as AGB mass loss within the galaxy.
@article{arxiv.0903.4197,
title = {Oxygen Metallicity Determinations from Optical Emission Lines in Early-type Galaxies},
author = {Alex E. Athey and Joel N. Bregman},
journal= {arXiv preprint arXiv:0903.4197},
year = {2011}
}