Galaxy Harassment
Galaxy Harassment is defined as frequent high speed galaxy encounters within clusters. This is a mechanism for transforming low luminosity cluster galaxies from the disturbed spirals that are seen at z=0.4 to the dwarf ellipticals that are seen today.

A close encounter is described as a low luminosity galaxy interaction with a bright cluster galaxy within a radius of 50kpc.

Close encounters occur:

• with bright galaxies within the cluster
• once per Gyr
• several times from z=0.4 to z=0

Simulations of Galaxy Harassment

• first encounters create disturbed barred spirals
• further encounters produce multiple starbursts
• loss of angular momentum and gas heating cause the formation of a prolate morphology
• further encounters do not disturb the galaxy further

Conclusions

• simulations of galaxy harassment reproduce observations
• morphological transformation from disturbed spirals to dwarf ellipticals
• multiple starbursts