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Oxygen and nitrogen abundances of H ii regions in six spiral galaxies




Spectroscopic observations of 63 H ii regions in six spiral galaxies (NGC 628, NGC 783, NGC 2336, NGC 6217, NGC 7331 and NGC 7678) were carried out with the 6-m telescope (BTA) of Russian Special Astrophysical Observatory with the Spectral Camera attached to the focal reducer SCORPIO in multislit mode with a dispersion of 2.1 Å pixel−1 and a spectral resolution of 10 Å. These observations were used to estimate the oxygen and nitrogen abundances and the electron temperatures in H ii regions through the recent variant of the strong-line method (NS calibration). The parameters of the radial distribution (the extrapolated central intercept value and the gradient) of the oxygen and nitrogen abundances in the discs of spiral galaxies NGC 628, NGC 783, NGC 2336, NGC 7331 and NGC 7678 have been determined. The abundances in NGC 783, NGC 2336, NGC 6217 and NGC 7678 are measured for the first time. Galaxies from our sample follow well the general trend in the luminosity–central metallicity diagram for spiral and irregular galaxies.