Hickson Compact Group
Encyclopedia
A Hickson Compact Group (abberviation: HCG) is a collection of galaxies designated as published by Paul Hickson in 1982.
The most famous group on Hickson’s list of 100 objects is HCG 92, Stephan's Quintet
.
According to Hickson: “Most compact groups contain a high fraction of galaxies having morphological or kinematical peculiarities, nuclear radio and infrared
emission, and starburst
or active galactic nuclei (AGN) activity. They contain large quantities of diffuse gas and are dynamically dominated by dark matter
. They most likely form as subsystems within looser associations and evolve by gravitational processes. Strong galaxy interactions result and merging is expected to lead to the ultimate demise of the group. Compact groups are surprisingly numerous, and may play a significant role in galaxy evolution.”
The most famous group on Hickson’s list of 100 objects is HCG 92, Stephan's Quintet
Stephan's Quintet
Stephan's Quintet in the constellation Pegasus is a visual grouping of five galaxies of which four form the first compact galaxy group ever discovered. The group was discovered by Édouard Stephan in 1877 at Marseilles Observatory....
.
According to Hickson: “Most compact groups contain a high fraction of galaxies having morphological or kinematical peculiarities, nuclear radio and infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
emission, and starburst
Starburst
Starburst may refer to:*Starburst region, a generic term to describe a region of space with a much higher than normal star formation*Starburst galaxy*Starburst , the breaking up of a large company...
or active galactic nuclei (AGN) activity. They contain large quantities of diffuse gas and are dynamically dominated by dark matter
Dark matter
In astronomy and cosmology, dark matter is matter that neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly detected via optical or radio astronomy...
. They most likely form as subsystems within looser associations and evolve by gravitational processes. Strong galaxy interactions result and merging is expected to lead to the ultimate demise of the group. Compact groups are surprisingly numerous, and may play a significant role in galaxy evolution.”
See also
- Abell catalogueAbell catalogueThe Abell catalog of rich clusters of galaxies is an all-sky catalog of 4,073 rich galaxy clusters of nominal redshift z 18.0*Galactic-Latitude: Areas of the sky in the neighbourhood of the Milky Way were excluded from the study because the density of stars in those fields—not to mention...
- Catalogue of Galaxies and Clusters of Galaxies
External links
- Astronomy Picture of the DayAstronomy Picture of the DayAstronomy Picture of the Day is a website provided by NASA and Michigan Technological University . According to the website, "Each day a different image or photograph of our universe is featured, along with a brief explanation written by a professional astronomer."The photograph is not necessarily...
- Galaxy Group Hickson 31 - 22 February 2010