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2012MNRAS.422.3516W - Mon. Not. R. Astron. Soc., 422, 3516-3526 (2012/June-1)
Understanding and reducing statistical uncertainties in nebular abundance determinations.
WESSON R., STOCK D.J. and SCICLUNA P.
Abstract (from CDS):
Motivated by this issue, we have developed Nebular Empirical Analysis Tool (NEAT), a new code for calculating chemical abundances in photoionized nebulae. The code carries out a standard analysis of lists of emission lines using long-established techniques to estimate the amount of interstellar extinction, calculate representative temperatures and densities, compute ionic abundances from both collisionally excited lines and recombination lines, and finally to estimate total elemental abundances using an ionization correction scheme. NEATuses a Monte Carlo technique to robustly propagate uncertainties from line flux measurements through to the derived abundances.
We show that, for typical observational data, this approach is superior to analytic estimates of uncertainties. NEAT also accounts for the effect of upward biasing on measurements of lines with low signal-to-noise ratio, allowing us to accurately quantify the effect of this bias on abundance determinations. We find not only that the effect can result in significant overestimates of heavy element abundances derived from weak lines, but also that taking it into account reduces the uncertainty of these abundance determinations. Finally, we investigate the effect of possible uncertainties in R, the ratio of selective-to-total extinction, on abundance determinations. We find that the uncertainty due to this parameter is negligible compared to the statistical uncertainties due to typical line flux measurement uncertainties. Elemental abundances of intermediate-age open cluster NGC 3680
Abstract Copyright: 2012 The Authors Monthly Notices of the Royal Astronomical Society2012 RAS
Journal keyword(s): atomic processes - methods: statistical - ISM: abundances
Simbad objects: 13
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