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Encyclopedia > Dwarf elliptical galaxy

Dwarf elliptical galaxies, or dE's, are elliptical galaxies that are much smaller than others, classified as dE. They are quite common in galaxy groups and clusters, and are usually companions to other galaxies. While the surface brightness profiles of giant elliptical galaxies are well described by de Vaucouleur's law, dE's have exponentially declining surface brightness profiles. Dwarf elliptical galaxies are, therefore, much more diffuse than giant elliptical galaxies. Dwarf elliptical galaxies have blue absolute magnitudes within the range -18 mag < M < -14 mag. Still fainter elliptical-like galaxies are called dwarf spheroidal galaxies. The giant elliptical galaxy ESO 325-G004. ... In astrophysics, de Vaucouleurs law describes the surface luminosity profile of an elliptical galaxy as a function of radius R By defining Re as the radius of the isophote containing half the luminosity (i. ... Wikipedia does not yet have an article with this exact name. ...


Dwarf ellipticals may be primordial objects. Within the currently favoured cosmological Lambda-CDM model, small objects (consisting of dark matter and gas) are the first to form. Because of their mutual gravitational attraction, some of these will coalesce and merge, forming more massive objects. Further mergers lead to ever more massive objects. This road to the present-day galaxies has been called "hierarchical merging". If this theory is correct, dwarf galaxies may be the building blocks of today's giant galaxies. Alternatively, Ben Moore of the University of Zurich, Switzerland, proposed in 1996 that dE's could also be the remnants of low-mass spiral galaxies that through the action of repeated gravitational interactions with giant galaxies within a cluster obtained a much rounder shape. This process of changing a galaxy's morphology by interactions has been called "galaxy harassment". Evidence for this latter theory has been found, in the form of stellar disks and spiral arms (all that is left of the original stellar disk of the transformed spiral galaxy) embedded within dE's. A pie chart indicating the proportional composition of different energy-density components of the universe. ...


One of the most nearby dE's is NGC205, a satellite of the Andromeda galaxy. It was discovered by the French comet hunter Charles Messier in 1773 and remained the only known dwarf galaxy untill, in 1944, Walter Baade confirmed NGC147 and NGC185 as members of the Local Group by resolving them into individual stars, a feat which was only possible because these dEs are very nearby galaxies. No other Local Group dE's other than these three satellites of the Andromeda galaxy have been discovered since then. In the 1950s, dE's were also discovered in the nearby Fornax and Virgo clusters. Messier 110 (also known as M110 and NGC 205) is a dwarf elliptical galaxy that is a satellite of the Andromeda Galaxy. ... The Andromeda Galaxy (IPA: , also known as Messier 31, M31, or NGC 224; older texts often called it the Great Andromeda Nebula) is a spiral galaxy approximately 2. ... Charles Messier Charles Messier (June 26, 1730 – April 12, 1817) was a French astronomer who in 1774 published a catalogue of 45 deep sky objects such as nebulae and star clusters. ... Wilhelm Heinrich Walter Baade (March 24, 1893 - June 25, 1960) was a German astronomer who emigrated to the USA in 1931. ... NGC147 NGC 147 aka ( DDO3) is a Dwarf spheroidal galaxy about 2. ... NGC 185 is a dwarf elliptical galaxy about 2. ... The Andromeda Galaxy (IPA: , also known as Messier 31, M31, or NGC 224; older texts often called it the Great Andromeda Nebula) is a spiral galaxy approximately 2. ...


See also


  Results from FactBites:
 
elliptical galaxy: Definition and Much More from Answers.com (694 words)
The giant elliptical galaxy NGC 4881 (the spherical glow at upper left) lies at the edge of the Coma Cluster of Galaxies.
Dwarf elliptical galaxies are probably not true ellipticals at all; they have properties that are similar to those of irregulars and late spiral-type galaxies.
Elliptical galaxies tend to lie in the cores of galaxy clusters and in compact groups of galaxies.
  More results at FactBites »

 
 

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