Erler, Jens: Spectro-spatial observations of galaxy clusters with Planck and CCAT-prime. - Bonn, 2020. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
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author = {{Jens Erler}},
title = {Spectro-spatial observations of galaxy clusters with Planck and CCAT-prime},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2020,
month = jul,

note = {The Sunyaev-Zeldovich (SZ) effect is a spectral distortion of the cosmic microwave background (CMB) caused by inverse Compton scattering of CMB photons by free electrons in the hot intracluster medium (ICM) of galaxy clusters. The last two decades have seen dramatic improvements in the quality of SZ data and the galaxy cluster sample size obtained through SZ observations. The obtained cluster samples are important probes for cosmological studies, which help to unravel the illusive nature of dark matter and dark energy, measure the masses of light relativistic particles, and more. The research presented in this work consists of three parts, focusing on observations of the thermal SZ (tSZ) effect of clusters with data from the Planck space telescope, the development of new techniques for the extraction of SZ images, and forecasts for the next-generation of SZ surveys.
The first part of this thesis is a detailed study of the average tSZ spectrum of 772 massive galaxy clusters observed with the Planck, IRAS, and Akari space telescopes. Of particular interest for this study are distortions of the tSZ spectrum caused by special-relativistic effects that allow to measure the ICM temperature. The tSZ effect spectra are extracted from multifrequency images of clusters using matched filters (MFs), which allow for an optimal removal of contaminating astrophysical emission while only making assumptions on the spatial signature of the observed clusters. The extracted average spectrum clearly traces the characteristic shape of the tSZ spectrum and reveals the presence of an additional far-infrared (FIR) excess due to thermal emission from warm dust grains in and around the clusters. Relativistic distortions of the tSZ effect are measured at a significance of 2.2σ, constraining the average SZ-measured ICM temperature of the cluster sample to kB Te = 4.4 +2.1 −2.0 keV. The analysis of a smaller sub-sample of clusters containing the hottest 100 objects delivered a measurement at a similar significance of 2.0σ and constrained the clusters’ mean ICM temperature to kB Te = 6.0 +3.8 −2.9 keV. The observed FIR excess was well modelled by a modified blackbody spectrum, implying an average dust grain temperature ≈ 18 K in the rest-frame of the clusters.
The second part of this work presents an extension of the MF technique used in the first part. It is shown that the matched filter algorithm can be generalised to allow for the extraction or suppression of multiple components at the same time if the corresponding sources can also be approximated by spatial templates. Using simulated microwave data, the unbiased tSZ-photometry of clusters with central radio sources is demonstrated and the dependence of the noise level of the obtained maps on the spatial resolution of the telescope is explored. The new method is further exemplified using Planck observations of the Perseus galaxy cluster, which harbours a bright central radio source. The new technique, called constrained MF (CMF), is also applicable to X-ray data of galaxy clusters and could offer improved separation of galaxy clusters and active galactic nuclei, which is investigated using mock data for the recently launched eROSITA X-ray space telescope.
The third and final part of this work presents detailed forecasts for the expected galaxy cluster sample size and SZ-spectral constrains for future microwave surveys with the upcoming CCAT-prime telescope, which will perform a submillimeter survey of a large fraction of the sky from the summit of the Cerro Chajnantor at 5600 m above sea level. Using a self-developed pipeline for the generation of mock observations of the microwave sky and the MF techniques developed before, it is found that CCAT-prime will detect and characterise between 2000 and 10 000 galaxy clusters, depending on the assumed survey area and potential synergies with other microwave observatories. Furthermore, it is shown that CCAT-prime data will allow to perform measurements of the spectrum of the SZ effect of clusters in much greater detail than the ones obtained from Planck-data presented in the first part of this work.},

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