Knowra Galaxy harassment Galaxy harassment Galaxy harassment is the cumulative transformation of galaxies through repeated high-speed encounters and tidal forces, especially in dense environments such as galaxy clusters.
Galaxy cluster : A gravitationally bound structure containing hundreds to thousands of galaxies, hot gas, and dark matter. Its dense population and deep gravitational potential make repeated fast encounters common.
Virgo Cluster : The nearest massive galaxy cluster, located about 16.5 megaparsecs from the Milky Way. Its dense core contains galaxies exposed to strong tides and frequent high-speed passages.
Galaxy morphology-density relation : The observed trend for dense regions to contain more elliptical and lenticular galaxies than low-density regions. This environmental pattern motivated explanations involving repeated encounters in clusters.
Morphological transformation : A change in a galaxy’s large-scale structural type, such as from a disk to a spheroidal form. Harassment can weaken or disrupt disks and leave more spheroidal remnants.
Tidal interaction : A gravitational encounter in which one object distorts another through spatial differences in gravitational force. Repeated tidal perturbations heat stellar orbits and remove loosely bound material.
Coma Cluster : A rich galaxy cluster in the constellation Coma Berenices, roughly 100 megaparsecs from Earth. Its dense population provides a setting where cumulative galaxy encounters can be significant.
Galaxy cluster environment : The conditions inside a galaxy cluster, including its gravitational potential, hot gas, and galaxy population. Harassment is an environmental transformation, not an isolated-galaxy process.
Star formation quenching : The decline or cessation of a galaxy’s production of new stars. Tidal damage and gas loss can contribute to reduced star formation, though they are not the only causes.
Dynamical heating : An increase in the random motions of stars or other particles caused by changing gravitational forces. Rapid encounters can puff up stellar disks by increasing their random motions.
Dwarf spheroidal galaxy : A small, faint galaxy dominated by old stars and containing little detectable cold gas. Cluster encounters can help transform disk galaxies into diffuse, gas-poor systems of this kind.
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