Computer Science
Scientific paper
Nov 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000ign..confe..60v&link_type=abstract
Ionized Gaseous Nebulae. Mexico City November 21- 24, 2000, meeting abstract
Computer Science
Scientific paper
We have obtained the first high resolution spectra of individual stars in th e dwarf irregular galaxy, NGC6822. The spectra of the two A-type supergiants were obtained at the VLT and Keck Observatories, using UVES and HIRES, respectively. A detailed model atmospheres analysis has been used to determine their atmospheric parameters and elemental abundances. The mean iron abundance from these two stars is <[Fe/H]>=-0.49 ±0.22 (±0.21) [Note that the first uncertainty is the line-to-line scatter, and the second (in parentheses and italics) is an estimate of the systematic error due to uncertainties in the atmospheric parameters]. This confirms that NGC6822 has a metallicity that is slightly higher than that of the SMC, and is the first determination of the present-day iron-group abundances in NGC6822. The mean stellar oxygen abundance, 12+log(O/H)=8.36 ±0.19 (±0.21), is in good agreement with the nebular oxygen results. Oxygen has the same underabundance as iron, <[O/Fe]>=+0.02 ±0.20 (±0.21). This O/Fe ratio is very similar to that seen in the Magellanic Clouds, but is also within the errors of that observed in comparatively metal-poor stars in the Galactic disk. Combining all of the available abundance observations for NGC6822 shows that there is no trend in abundance with galactocentric distance. However, a subset of the highest quality data are consistent with a radial abundance gradient. More high quality stellar and nebular observations are needed to confirm this intriguing possibility.
Kaufer Andreas
Kudritzki Rolf Peter
Lemke Michael
Lennon Daniel J.
McCarthy James K.
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