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Dwarf galaxies, seven groups discovered. The observation of groups of dwarf galaxies that interact with each other through the force of gravity shows that large galaxies are the result of the merger of many smaller galaxies. The discovery is also an indirect confirmation of the current models that predict the existence of dark matter. Seven groups of small galaxies gravitationally bound to each other confirm the theories on the formation of large galaxies like our Milky Way, and indirectly corroborate the current model of a universe dominated by dark matter.
Currently it is believed that most of the galaxies was formed through the collision and merging of smaller galaxies. However, only five per cent of dwarf galaxies surveyed – ie galaxies from 10 to 1000 times smaller than the Milky Way – has some other dwarf companion galaxy. The others are satellites of giant galaxies or wander scattered in space. Demonstrating the existence of dwarf galaxies groups was therefore a primary objective to validate the theory on the evolution of galaxies.
Through a close examination of images from the Sloan Digital Sky Survey – which has mapped a quarter of the sky to a depth of 1.5 billion light years, cataloging over a million galaxies – Astronomers have identified 60 potential groups of related small galaxies Between them.
These galaxies were subsequently observed with Walter Baade Telescope from 6.5 meters (one of the two Magellan telescopes in Las Campanas Observatory in Chile) with the 8-meter Gemini North telescope on Mauna Kea, Hawaii, and the telescope 3.5 meters of Apache Point Observatory in Sunspot, New Mexico.
Most of the candidate proved in fact constituted from very distant galaxies from each other, but which are simply on lines very close view. However for seven of them researchers have had confirmation that it was indeed groups of galaxies between their bound by the gravitational point of view. These groups are formed from 3:00 to 5:00 galaxies, each of which has a total mass of between 4 and 20 billion solar masses. For comparison, it is estimated that the Milky Way exceed 200 billion solar masses. Subsequent simulations have shown that the reciprocal movements of galaxies in each group are not explainable on the basis of gravitational interactions due to their observable mass. These movements require the presence of an additional mass, of entities roughly corresponding to that assumed by the cosmological models of Dark Matter.
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