Constraining the cosmic microwave background temperature evolution and the population and structure of galaxy clusters and groups from the South Pole Telescope and the Planck Surveyor

Liu, Jiayi (2014): Constraining the cosmic microwave background temperature evolution and the population and structure of galaxy clusters and groups from the South Pole Telescope and the Planck Surveyor. Dissertation, LMU München: Fakultät für Physik

Abstract

Galaxy clusters, the massive systems host hundreds of galaxies, are invaluable cosmological probes and astrophysical laboratories. Besides these fascinating galaxies, the concentration of dark matter creates a deep gravitational potential well, where even light passing by is bended and the background image is distorted. The baryonic gas falling into the potential well is heated up to more than 10^7 K that free electrons start to emitting in X-ray. Observing those phenomena leads to a throughout understanding of gravity, particle physics and hydrodynamics. In addition, residing on the top of the density perturbations, clusters are sensitive to the initial condition of the Universe, such that they are complimentary tools for cosmology studies. In this thesis we first introduce the basic framework of the Universe and supporting observational evidence. Following that, we sketch the principle to use clusters for cosmology study via their redshift and mass distribution. However cluster mass is not a direct observable, so we need to estimate it by other channels. We briefly exhibit cluster observations in optical, X-ray and microwave bands and discuss the challenges in estimating the underlying cluster mass with them. After this introduction, we present our results on three aspects of the cluster cosmology study. First, we present a study of Planck Sunyaev-Zel’dovich effect (SZE) selected galaxy cluster candidates using Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) imaging data. To fulfil the strength of SZE survey, the redshifts of clusters are required. In this work we examine 237 Planck cluster candidates that have no redshift in the Planck source catalogue. Among them, we confirmed 60 galaxy clusters and measure their redshifts. For the remaining sample, 83 candidates are so heavily contaminated by stars due to their location near the Galactic plane that we do not identify galaxy members and assign reliable redshifts. For the rest 94 candidates we find no optical counterparts. By examining with 150 Planck confirmed clusters with spectroscopy redshifts, our redshift estimations have an accuracy of σ_{z/(1+z)}~0.022. Scaling for the already published Planck sample, we expect the majority of the unconfirmed candidates to be noise fluctuations, except a few at high redshift that the Pan-STARRS1 (PS1) data are not sufficiently deep for confirmation. Thus we use the depth of the optical imaging for each candidate together with a model of the expected galaxy population for a massive cluster to estimate a redshift lower limit, beyond which we would not have expected to detect the optical counterpart. Second, we use 95GHz, 150GHz, and 220GHz observations from South Pole Telescope (SPT) to study the SZE signatures of a sample of 46 X-ray selected groups and clusters drawn from ~6 deg^2 of the XMM-Newton Blanco Cosmology Survey (XMM-BCS). The wide redshift range and low masses make this analysis complementary to previous studies. We develop an analysis tool that using X-ray luminosity as a mass proxy to extract selection-bias corrected constraints on the SZE significance- and Y_{SZ}-mass relations. The SZE significance- mass relation is in good agreement with an extrapolation of the relation obtained from high mass clusters. However, the fit to the Y_{SZ}-mass relation at low masses, while in agreement with the extrapolation from high mass SPT sample, is in tension at 2.8σ with the constraints from the Planck sample. We examine the tension with the Planck relation, discussing sample differences and biases that could contribute. We also analyse the radio galaxy point source population in this ensemble of X-ray selected systems. We find 18 of our systems have 1 GHz Sydney University Molonglo Sky Survey (SUMSS) sources within 2 arcmin of the X-ray centre, and three of these are also detected at significance >4 by SPT. Among these three, two are associated with the brightest cluster galaxies, and the third is a likely unassociated quasar candidate. We examined the impact of these point sources on our SZE scaling relation result and find no evidence of biases. We also examined the impact of dusty galaxies. By stacking the 220 GHz data, we found 2.8σ significant evidence of flux excess, which would correspond to an average underestimate of the SZE signal that is (17±9) % in this sample of low mass systems. Finally we predict a factor of four to five improvements on these SZE mass-observable relation constraints based on future data from SPTpol and XMM-XXL. In the end we present a study using clusters as tools to probe deviations from adiabatic evolution of the Cosmic Microwave Background (CMB) temperature. The expected adiabatic evolution is a key prediction of standard cosmology. We measure the deviation of the form T(z)=T_0(1+z)^{1-α} using measurements of the spectrum of the SZE with SPT. We present a method using the ratio of the SZE signal measured at 95 and 150 GHz in the SPT data to constrain the temperature of the CMB. We validate that this approach provides unbiased results using mock observations of cluster from a new set of hydrodynamical simulations. Applying this method to a sample of 158 SPT-selected clusters, we measure α=0.017^{+0.030}_{−0.028} consistent with the standard model prediction of α=0. Combining with other published results, we find α=0.005±0.012, an improvement of ~ 10% over published constraints. This measurement also provides a strong constraint on the effective equation of state, w_{eff}=−0.994±0.010, which is presented in models of decaying dark energy.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 530 Physik
• Fakultäten: Fakultät für Physik
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 29. Juli 2014
• 1. Bericht­erstatter:in: Mohr, Joseph