Galaxy Cluster Science with Chandra

  • Crispin H A Logan

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)


Galaxy clusters are the largest gravitationally bound structures in our Universe, and hence can
be used to constrain the physical laws that govern cosmic evolution. In order to use clusters as
cosmological probes, large samples of bona-fide clusters are needed, in addition to a method with
which to estimate cluster masses accurately. Additionally, clusters can be studied to understand
the physical processes within the clusters themselves. As clusters form via hierarchical growth,
growing ever larger through mergers with smaller systems and accretion of matter from the
surrounding environment, understanding the physical processes in the outer regions of a cluster
can tell us more about how they grow.

The first project in my PhD tackled the issue of constructing reliable samples of clusters
for cosmology, specifically analysing Chandra observations of high redshift cluster candidates
detected in the XXL survey, to probe not only their AGN contamination, but also to ensure that
they were indeed genuine clusters.

The second project in my PhD focussed on the calibration of the X-ray hydrostatic cluster
mass estimation method, by comparing the X-ray hydrostatic masses of a sample of 44 clusters
with masses for the same sample of clusters measured with an entirely independent method
based on information on galaxy dynamics obtained from optical observations.

The final project in my PhD used the same sample of clusters as the mass calibration work to
study the outer regions of clusters, specifically calculating the gas fraction at large radii of these
clusters, to gain insight into the state of the cluster gas in the cluster outskirts.
Date of Award12 May 2020
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorMalcolm N Bremer (Supervisor) & Ben J Maughan (Supervisor)


  • galaxy clusters

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