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2. OBSERVATIONAL DATA

In the last decade there has been a considerable increase in the amount of near infrared [SIII] emission line data. We have compiled from the literature all the HII region like objects for which measurements of these lines, together with optical emission lines exist. The sample includes HII regions in our own Galaxy, HII regions in spirals and irregular galaxies and HII galaxies. The data are presented in Table 1, where the logarithmic intensities of the emission lines with respect to Hbeta are given, together with their corresponding observational errors when quoted in the original reference. These references are numbered in column 3 and listed at the bottom of the table. The observed intensities were corrected for reddening according to the derived logarithmic extinction at Hbeta listed in the last column of the table and a standard reddening law. The sample comprises a total of 196 objects.

Only 65 of these objects have electron temperatures derived directly. Table 2 lists for these objects their electron temperature, in units of 104 K, and their derived oxygen abundance expressed as 12 + log [O/H]. The electron temperature has been derived from the measured intensity of the [OIII] lambda4363 line except for the objects marked with an asterisk for which a measurement of the [OII] lambda7327 line has been used. The total oxygen abundance has been calculated as log[O/H] = log([(O+) / (H+)] + [(O++) / (H+)]). The errors in the abundances have been derived from those quoted for the emission lines whenever possible. For the HII regions in the Magellanic Clouds (Dennefeld & Stasiska 1983) we have adopted an abundance error of ± 0.10.

The oxygen abundance ranges from 2% solar for IZw18 to 70% solar for region VS24 in NGC 2403.

We have included in the table data for three regions of metallicity close to solar for which detailed modelling has been made: CC93 in M33 (Vílchez et al. 1988), S5 in M101 (Shields & Searle 1978; Díaz et al. 1990) and the nucleus of NGC 3310 (Pastoriza et al. 1993).

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