Signatures of Galaxy-Cluster Interactions: Spiral Galaxy Rotation Curve Asymmetry, Shape, and Extent

The environmental dependencies of the characteristics of spiral galaxyrotation curves are studied in this work. We use our large, homogeneouslycollected sample of 510 cluster spiral galaxy rotation curves to test the claimthat the shape of a galaxy's rotation curve strongly depends on its locationwithin the cluster, and thus presumably on the strength of the localintracluster medium and on the frequency and strength of tidal interactionswith the cluster and cluster galaxies. Our data do not corroborate such ascenario, consistent with the fact that Tully-Fisher residuals are independentof galaxy location within the cluster; while the average late-type spiralgalaxy shows more rise in the outer parts of its rotation curve than does thetypical early-type spiral galaxy, there is no apparent trend for either subsetwith cluster environment. We also investigate as a function of clusterenvironment rotation curve asymmetry and the radial distribution of H II regiontracers within galactic disks. Mild trends with projected cluster-centricdistance are observed: (i) the (normalized) radial extent of optical lineemission averaged over all spiral galaxy types shows a 4%+/-2% increase per Mpcof galaxy-cluster core separation, and (ii) rotation curve asymmetry falls by afactor of two between the inner and outer cluster for early-type spirals (anegligible decrease is found for late-type spirals). Such trends are consistentwith spiral disk perturbations or even the stripping of the diffuse, outermostgaseous regions within the disks as galaxies pass through the dense clustercores.Comment: 17 pages; to appear in the April 2001 Astronomical Journa