No abstract

No abstract

A study of the distribution of barred and nonbarred disk galaxies in the Virgo cluster is presented in an attempt to use the frequency and spatial distribution of galaxies with specific morphological features to study the efficiency of various environmental effects on the evolution of disk galaxies in clusters. The velocity distribution of the barred spirals in the Virgo region is clearly different than that of the nonbarred spirals, suggesting that barred spirals are more common in the main condensation of the cluster. A sample cleansed of galaxies not belonging to the main cluster condensation using the subcluster assignments of Binggeli et al. [A&AS, 98, 275 (1993)] bears this out, showing that the radial distribution of barred spirals is more centrally condensed than that of nonbarred spirals. In contrast to the spiral galaxies, the distribution of barred S0 galaxies is statistically indistinguishable from that of nonbarred S0's. Consideration of the level of tidal perturbation due to the cluster mass distribution as compared to that due to individual galaxies suggests that tidal triggering by the cluster mass distribution is the most likely source of the enhanced fraction of barred spirals in the cluster center.Comment: 16 pages, 5 figures included as encapsulated postscript, scheduled to appear in the May 1996 Astronomical Journa

No abstract

NGC 7421 is a barred spiral that is displaced from the centre of its optical envelope, and has a ‘bow-shock’-like western boundary, both suggestive of interaction with an intracluster medium. We have used five configurations of the ATCA to map the distribution and kinematics of HI in NGC 7421, and find supportive evidence for this scenario in the form of an HI ‘wake’. When compared with ROSAT PSPC observations of the diffuse hot gas in the surrounding group of galaxies, these new ATCA results will allow us to place new constraints on the density and dynamics of the intracluster medium.