de-Ville, Jordan
(2024)
Methods of Measuring and Simulating the Intracluster Light of Galaxy Clusters.
MPhil thesis, University of Nottingham.
Abstract
This thesis examines the Intracluster Light (ICL) of galaxy clusters, using both simulated and real observations. We, first, used data from the Millennium MAMBO lightcone to devise a method of simulating realistic images of the ICL for a given cluster. These simulated images may be used to infer the limiting capabilities of ICL detection codes, and to test whether reduction pipelines are suitable for ICL studies. They also allow users to further optimise their codes, as the input ICL variables are known.
We worked with the ICL science working group of the Euclid collaboration, using our method to simulate images compatible with the Euclid-VIS instrument, so that members could test their codes in preparation for the launch of Euclid. On inserting our images into a Euclid-VIS field mosaic image, which was processed with Euclid's pipeline, we discovered that the standard pipeline produced images with a background that was not sufficiently flat at the levels required, and would have removed any ICL present in the images prior to reduction. The need for an alternative background subtraction method was subsequently suggested, which should be optimised for studies of faint, extended sources.
We then measured the ICL radial profiles for clusters in HSC-SSP images, and investigated how the ICL fraction changes as a function of cluster redshift and mass, using a sample of 72 clusters in the redshift range 0.1 ≤ z ≤ 0.8. These clusters originate from two cluster catalogs: a sample of 18 XMM Cluster Survey (XCS) clusters, which are also included as part of a previous work (Furnell et al, 2021); and a sample of 54 clusters that are detected using the CAMIRA cluster-finding algorithm. Using HSC i-band data, we applied a surface brightness thresholding method to find an average ICL fraction of ∼ 0.24, which is typical of clusters in this redshift range. It was also found that there was no correlation between the ICL fraction and cluster redshift nor the ICL fraction and cluster mass. The former is in disagreement with the previous work, which used the same XCS sample of clusters and HSC i-band data to find a well-defined anti-correlation. We argue that the disagreement may be due to: this work using a more refined method that corrects for contaminant photometric cluster galaxies being included in calculations; this work masking the BCG using segmentation data versus the previous author using a fitting method; or this work using more recent data that has been processed in an optimal way for faint, extended sources - the previous work required `divot corrections' to account for an overly harsh background subtraction in the HSC pipeline at the time. The lack of correlation established between ICL fraction and cluster mass comes as no surprise, as this is commonly found in ICL studies and can be explained using ICL formation models.
We finish by outlining a new ICL detection algorithm: ficl. This automated code makes use of the best aspects of the three most common ICL detection methods in tandem: surface brightness thresholding, profile fitting and wavelet filtering. We use ficl in its current, incomplete form on a simple toy model image, as proof of concept, to show that it is already capable of recovering 60% of the ICL that was put in to the model.
| Item Type: |
Thesis (University of Nottingham only)
(MPhil)
|
| Supervisors: |
Bamford, Steven
Hatch, Nina
Aragon-Salamanca, Alfonso |
| Keywords: |
Galaxy clusters, intracluster light, parametric fitting, non-parametric fitting |
| Subjects: |
Q Science > QB Astronomy |
| Faculties/Schools: |
UK Campuses > Faculty of Science > School of Physics and Astronomy |
| Item ID: |
77445 |
| Depositing User: |
Deville, Jordan
|
| Date Deposited: |
23 Jul 2024 04:40 |
| Last Modified: |
23 Jul 2024 04:40 |
| URI: |
https://eprints.nottingham.ac.uk/id/eprint/77445 |
Actions (Archive Staff Only)
 |
Edit View |
Tools
Tools
