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Description
Imaging spectrophotometry in the nebular lines H{alpha}, H{beta}, [OIII]{lambda}5007 and [NII]{lambda}6584, using narrow-band interference filters, has been performed of 82, 55, and 79 H II regions in the barred spiral galaxies NGC 925, NGC 1073, and NGC 4303, respectively. The O/H abundance gradients were derived from the abundance indicators [O III]/H{beta} and [N II]/[O III], calibrated by Edmunds & Pagel (1984MNRAS.211..507E). The global O/H gradients in NGC 925 [{DELTA}log(O/H)/{DELTA}R=0.033dex/kpc] and NGC 1073 [{DELTA}log(O/H)/{DELTA}R=0.048dex/kpc] are flatter than the gradients observed in normal galaxies of the same morphological type. The abundance gradient in NGC 4303 is identical to that found in normal spiral galaxies. A comparison is made between the O/H gradients of normal galaxies and of a sample of galaxies showing a barred morphology it is concluded that the global abundance gradients of spiral galaxies with a barred structure are in general shallower than gradients of normal galaxies. The slopes of O/H gradients are analyzed as a function of two properties of bars: the relative length of the bar with respect to the size of the disk, and the bar ellipticity, defined by the axis ratio of the bar. It is found that gradients are flatter when the length or the ellipticity of the bar increases. This result is consistent with recent models of radial flows. These observations indicate that large-scale mixing of the interstellar gas occurs across the disks of barred spiral galaxies and affects the radial distribution of elements.
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