In this dissertation we aim to perform a multi-wavelength analysis of galaxy clusters. We discuss
various methods for clustering in order to determine physical parameters of galaxy clusters
required for this type of study. A selection of galaxy clusters was chosen from 4 papers, (Popesso
et al. 2007b, Yoon et al. 2008, Loubser et al. 2008, Brownstein & Mo at 2006) and restricted
by redshift and galactic latitude to reveal a sample of 40 galaxy clusters with 0.0 < z < 0.15.
Data mining using Virtual Observatory (VO) and a literature survey provided some background
information about each of the galaxy clusters in our sample with respect to optical, radio and
X-ray data. Using the Kayes Mixture Model (KMM) and the Gaussian Mixing Model (GMM),
we determine the most likely cluster member candidates for each source in our sample. We compare
the results obtained to SIMBADs method of hierarchy. We show that the GMM provides
a very robust method to determine member candidates but in order to ensure that the right
candidates are chosen we apply a select choice of outlier tests to our sources. We determine
a method based on a combination of GMM, the QQ Plot and the Rosner test that provides a
robust and consistent method for determining galaxy cluster members. Comparison between
calculated physical parameters; velocity dispersion, radius, mass and temperature, and values
obtained from literature show that for the majority of our galaxy clusters agree within 3 range.
Inconsistencies are thought to be due to dynamically active clusters that have substructure or
are undergoing mergers, making galaxy member identi cation di cult. Six correlations between
di erent physical parameters in the optical and X-ray wavelength were consistent with
published results. Comparing the velocity dispersion with the X-ray temperature, we found a
relation of T0:43 as compared to T0:5 obtained from Bird et al. (1995). X-ray luminosity
temperature and X-ray luminosity velocity dispersion relations gave the results LX T2:44
and LX 2:40 which lie within the uncertainty of results given by Rozgacheva & Kuvshinova
(2010). These results all suggest that our method for determining galaxy cluster members is
e cient and application to higher redshift sources can be considered. Further studies on galaxy
clusters with substructure must be performed in order to improve this method. In future work,
the physical parameters obtained here will be further compared to X-ray and radio properties
in order to determine a link between bent radio sources and the galaxy cluster environment. / MSc (Space Physics), North-West University, Potchefstroom Campus, 2013
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/15822 |
| Date | January 2012 |
| Creators | Wilson, Susan |
| Source Sets | North-West University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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