The effects of cluster environment on the chemical evolution of galaxies. III. NGC 753.

We have obtained spectra from 3600 to 9600 Å of 15 giant H II regions located in the massive spiral galaxy NGC 753, a member of the spiral-rich cluster Abell 262, in a continuing effort to carry out intensive abundance studies of cluster spirals. Using photoionization models to match the behaviour of emission lines as a function of galactocentric distance along the disc, we have derived gradients for O/H, N/O and S/O, along with information about excitation and ionization. The characteristic metallicity as well as the distribution of O/H with surface density in NGC 753 are similar to those found in field spirals of the same mass and morphological type, although we find O/H and N/O gradients in NGC 753 that resemble more closely the shallow gradients found in two Virgo cluster spirals that are deficient in H I. The behaviour of S/O in NGC 753 is indistinguishable from that seen in other field or cluster spirals. Thus in most respects NGC 753 resembles galaxies in the field of similar mass and morphology, suggesting that cluster membership alone does not necessarily result in altered chemical evolution of spiral galaxies.