The rotation curve of the cluster galaxy DC 1842-62 No. 24 does not decrease.

Whitmore, Forbes & Rubin (1988) claimed a good correlation between slope of rotation curves and location within a cluster, in the sense that inner galaxies tend to have falling rotation curves, while outer and field galaxies tend to have flat or rising rotation curves. Amram et al (1993, 1995b) did not confirm these correlations. Nevertheless, the lack of very inner galaxies in our sample did not allow us to conclude if environmental effects are important within a very small distance from the cluster center. The galaxy DC 1842-62 #24 presented both the most decreasing rotation curve and the closest location to the cluster center in Whitmore et al.'s sample (1988), and thus was a crucial case in the study of rotation curve behaviour in the very inner part of a cluster. From Perot-Fabry observations, we definitively find a non-decreasing rotation curve for this galaxy. A two-component mass model (disk plus halo) rules out any decrease of the rotation curve and indicates that luminous matter is dominant.