In English

Estimating masses of galaxy clusters - a first step in exploring dark matter

Elisabet Liljeblad
Göteborg : Chalmers tekniska högskola, 2012. 44 s.
[Examensarbete på avancerad nivå]

Masses of galaxy clusters and the cluster mass function (abundance of clusters as a function of cluster masses), have been estimated from the largest cluster catalog of SDSS galaxies using mainly three different interloper removal methods: the maximum velocity approach, the 2-3sigma-clipping approach and the maximum velocity gap approach. In these three approaches the virial mass estimator have been used. The maximum velocity approach sets a criteria on the circular velocity and the infalling velocity for every galaxy in a certain distance to the cluster center. The 2-3sigma-clipping approach cuts off interlopers by using the standard deviation on the velocities of the galaxies. Finally, the maximum velocity gap approach sets a constraint on the absolute velocity difference between neighboring galaxies. A set of 200 clusters provided by Wang et al. (2012) has been simulated on. The maximum velocity approach with a velocity constraint of 3000 km/s agrees best with the mass function derived analytically in Klypin et al. (2011). When using Hubble’s law, this constraint yields to a maximum cluster radii of around 40 Mpc (in the same range as the superclusters). The 2sigma-clipping approach also agrees well with the mass function in Klypin et al. (2011). However it is clear that when there is an excess of interlopers or too few member galaxies in the cluster, all three methods give a larger uncertainty and become less qualitative. The mass function derived is to be used as a forecasting tool for the European Space Agency mission Euclid.

Nyckelord: galaxy cluster, mass function



Publikationen registrerades 2012-06-18. Den ändrades senast 2013-04-04

CPL ID: 159140

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