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There is a significant amount of matter in the universe, which is not directly detectable. Fritz Zwicky observed using the Doppler shift and the virial theorem that the velocity spread within a cluster of galaxies implied that there was more mass than the luminous matter accounted for. Through further experimentation it was later concluded that our universe’s visible matter is set in a hallo matter which does not interact with light, but whose effects are observed through gravitational interactions. This non-luminous matter is called dark matter. The nature of dark matter is still unknown. (Galaxy formation and evolutions, Houjin Mo et al). Dark matter influences how galaxies form and even their rotation as it is the frame upon which the visible matter is embedded. The distribution of galaxies also depends on the distribution of dark matter in the universe. (B.F Burke and F Graham-Smith) states that dark matter may be hot or cold. The Hot Dark Matter (HDM) theory allows for a hierarchy in structure formation. The theory states that large scale structure such as the distribution of galaxies form first due to the presence of hot dark matter. Cold dark matter is theorized to be the seed for galaxy formation.  Galaxies are formed from the mergers of stellar material which result in the formation of systems of billions of stars, gas and dust, held together by gravitational attraction. (A Loeb) states that when an object above the Jeans mass collapses, the dark matter forms a halo inside of which the collapsed matter cools, condense to the centre of the dark matter halo, and eventually form stars. Dark matter is weakly interacting and is thus unable to cool. Consequently the emergent structure of a galaxy becomes one in which a central core that is occupied by stars and cold gas which is enclosed by dark matter. (A Loeb) further states that a centrifugal force associated with the rotation of the galaxy’s centre prevents the gas from collapsing into the centre and forming a black hole. The gas later forms stars and a galaxy is born. (A Loeb)  Radiative cooling, star formation and supernova explosions processes that are also integral to the formation of a galaxy while processes such as accretion of gas, and galaxy mergers, govern the galaxy’s structure. These sets of processes together drive the formation and evolution of galaxies. (D Ceverino at el)  Dark matter halos grow in hierarchy in the sense that larger halos are formed through the merging of smaller predecessors. Figure 2 illustrates the formation of a dark matter halo. In CDM models part of the growth of a massive halo is due to merging with a large number of much smaller halos, where mergers are thought as accretion (to a good approximation). (Mo et al, 2011)