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:
Simulations of Galaxy Harassment
- with bright galaxies within the cluster
- once per Gyr
- several times from z=0.4 to z=0
- 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
- simulations of galaxy harassment reproduce observations
- morphological transformation from disturbed spirals to dwarf ellipticals
- multiple starbursts