Calibrating Nebular Diagnostics of T_* and Abundance (Review)
M.S. Oey, J.C. Shields, M.A. Dopita, & R.C. Smith
We obtained nebular spectroscopy of LMC HII regions having
classified stellar populations, thereby strongly constraining the
ionization input parameters. Using photoionization models, we then
evaluate the performance of nebular diagnostics of T_* and abundance.
We introduce [Ne III]/H-beta as a nebular diagnostic of the ionizing
stellar T_*. In contrast to the widely-used \eta-prime parameter,
[Ne III]/H-beta has greater sensitivity to mid and early O-stars, and is
robust to nebular morphology and the presence of shocks. We present a
preliminary calibration of both T_* diagnostics for LMC
metallicity. We also introduce S234 = ([S II] + [S III] + [S
IV])/H-beta as a diagnostic of S abundance. S234 is much
less sensitive to the nebular ionization parameter than is
S23 or R23. The intensity of [S IV] 10.5 microns is
easily estimated from the optical and near-IR line ratios.
We present calibrations of S23 and S234 that are
reliable at metallicities Z < 0.5 Z_sol.
2001, Rev.Mex.A&A, Ser. de Conf., 12, 77
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