No description available.

Simulations and observations of the microwave sky are of great importance for under- standing the Universe that we reside in. Specifically, knowledge of the Cosmic Microwave Background (CMB) and its foregrounds – including the Sunyaev-Zel’dovich (SZ) effect from clusters of galaxies and radio point sources – tell us about the Universe on its very largest scales, and also what the Universe is made of. We describe the creation of software to carry out large numbers of virtual sky simulations. The simulations include the CMB, SZ effect and point sources, and are designed to examine the effects of point sources and the SZ effect on present and recent observations of the CMB. Utilizing sets of 1,000 simulations, we find that the power spectrum resulting from the SZ effect is expected to have a larger standard deviation by a factor of 3 than would be expected from purely Gaussian realizations. It also has a distribution that is significantly skewed towards increased values for the power spectrum, especially when small map sizes are used. The effects of the clustering of galaxy clusters, residual point sources and uncertainties in the gas physics are also investigated, as are the implications for the excess power measured in the CMB power spectrum by the CBI and BIMA experiments. We also investigate the possibility of using the One Centimetre Receiver Array (OCRA) receivers to observe the CMB and measure this high-multipole excess. An automated data reduction package has been created for the OCRA receivers, which has been used in end-to-end simulations for OCRA-p observations of point sources. We find that these simulations are able to realistically simulate the noise present in real observations, and that the introduction of 1/ f noise into the simulations significantly reduces the predicted ability of the instruments to observe weak sources by measuring the sources for long periods of time. The OCRA-p receiver has been used to observe point sources in the Very Small Array fields so that they can be subtracted from observations of the CMB power spectrumWe find that these point sources are split between steep and flat spectrum sources. We have also observed 550 CRATES flat spectrum radio sources, which will be useful for comparison to Planck satellite observations. Finally, the assembly and commissioning of the OCRA-F receiver is outlined. This receiver is now installed on the Torun ́ 32-m telescope, and is currently being calibrated prior to starting observations in the next few months.

In this thesis I construct various models to interpret measurements of the clustering of dusty star-forming galaxies through the angular power spectrum statistic. The goals of this work are, firstly, to facilitate the separation of the dusty galaxy contribution from the cosmic microwave background background (CMB) power spectrum, and, secondly, to improve our understanding of the physical properties of these galaxies. I present analysis of the first cross-correlation of millimeter and submillimeter sky maps, using data from the Atacama Cosmology Telescope (ACT) and the Balloon-borne Large-Aperture Submillimeter Telescope (BLAST), which revealed that the dusty galaxies that dominate the submillimeter sky are, to a significant extent, those same sources that are a nuisance contaminant for CMB cosmology. I then perform a joint fit to the ACT and BLAST power spectra as well as early results from the Planck Surveyor to construct a simple phenomenological template for the frequency and angular scale dependence of the contribution from clustered dusty galaxies to the total power spectrum. This template may be used to assist in extracting the CMB signal from future ACT and other data sets. The correlation between dusty galaxies and the thermal Sunyaev Zel'dovich effect leads to an additional contribution to the measured angular power spectrum that further hampers constraining quantities of cosmological interest. I present the first physically-motivated model for this correlation, and make predictions for its frequency and scale dependence as a CMB foreground. Finally, I combine angular power spectrum measurements from ACT, Planck and other instruments with deep far-infrared and submillimeter source number counts and constrain a model for the emission properties of these dusty galaxies. I demonstrate that the power spectrum carries significant constraining power and can improve our understanding of dust emission and star formation from unresolved objects at high redshift.

The primary purpose of this investigation was to study the diurnal variation of cosmic-ray intensity.

A thesis submitted to the Department of Physics, University of the Witwatersrand in fulfilment of the academic requirements of the degree of Doctor of Philosophy. Johannesburg, June 17, 2016. / The nature of dark matter remains one of the most significant problems in modern physics. One candidate hypothesis with strong theoretical motivation is a WIMP (Weakly Interacting Massive Particle) in the form of the supersymmetric neutralino. Although this lacks experimental evidence, supersymmetry may manifest in collider experiments and also has observable consequences in the emission of annihilation products from cosmic structures which would play host to large neutralino densities. Historically, interest has been focussed upon the direct detection of WIMPs, as well as indirect observation through -rays produced by pair-annihilation processes. In this work we present a detailed argument for a multi-frequency observational strategy. We motivate this by studying the redshift evolution of radio synchrotron radiation emitted by WIMP annihilation-product electrons. In so doing, we demonstrate the potential power of the SKA to probe the neutralino parameter space, being able to produce constraints several orders of magnitude better than current limits and distinguish between differing neutralino masses and annihilation channels. Furthermore, we motivate the SKA as a machine to study dark matter by discussing its ability to characterise cosmic magnetic fields through rotation measures and polarimetry, as well as resolve between non-thermal emissions produced by dark matter and those resulting from strictly baryonic processes, like star formation. These technical capabilities obviate the central uncertainties in the study of synchrotron radiation. Additionally, we highlight optimal laboratories for neutralino detection via the SKA, based on structures that might produce dark matter emissions with lower background synchrotron radiation. In particular we highlight galaxies and galaxy clusters at redshifts z 1 and local dwarf spheroidal galaxies. Finally, we demonstrate the potential of X-rays, through the ASTRO-H mission, to compliment the SKA in a multi-frequency search. We then demonstrate our multi-frequency approach in the analysis of several prominent claims of signals compatible with dark matter-induced emissions. Showing that models designed to account for the AMS-2/Fermi/PAMELA antiparticle and galactic centre -ray excesses are incompatible with existing data as well as demonstrating that a dark matter interpretation of the Reticulum-2 -ray excess is untenable for a wide range of dark matter particle masses. / LG2017

In this thesis, I present my work related to the characterization of diffuse Galactic foregrounds for observing the polarization of the Cosmic Microwave Background (CMB) radiation, and the impact of these foregrounds on the measurement of cosmological parameters. One of the most important future challenges for cosmology is the potential detection of polarization B-modes of the CMB. Inflation is a theory that explains the extremely early Universe, and solves several problems that were present in classical cosmology. It describes the anisotropies observed in the current Universe as primordial quantum fluctuations stretched by rapid exponential expansion. A key prediction of inflation is the production of a background of primordial gravitational waves, which could be detected through the associated large-scale B-mode signal in the CMB polarization. The amplitude of the B-mode signal, which depends on the energy scale of inflation, is parametrized by the tensor-to-scalar ratio r. Diffuse emission from within our Galaxy, and other extra-Galactic sources, collectively referred to as CMB foregrounds, obscure a fraction of the cosmological signal from the CMB radiation. This is a huge problem, because they have to be cleaned using data analysis methods, called component separation. A significant challenge for the potential detection of the primordial B-mode signal is that it can be extremely small, to the extent that it can be dominated even by the residual foreground contamination after component separation. In this work, we characterize these foreground residuals and assess their impact on the cosmological parameters. We create a method to simulate observations of the microwave sky, including diffuse Galactic foregrounds, CMB realizations and instrumental noise. These simulations are used to propagate errors on the characterization of foregrounds through the analysis procedures employed in the observations of the CMB, including component separation, angular power spectra calculation and cosmological parameter estimation. We estimate the bias and the σ error for the tensor-to-scalar ratio, to quantify the impact of the foreground residuals in the cosmological signal. We also propose a novel method to model these residuals when determining cosmological parameters, in order to avoid a bias on the r parameter. We performed forecasts and optimization analyses for two proposed CMB polarization experiments: the Simon Observatory, a funded ground-based telescope that will observe the polarization of the CMB from the Atacama desert in Chile, and CORE, a proposed next-generation CMB satellite experiment. All of our work shows that the issue of foreground residuals must be considered very carefully in future studies. Foreground spectral parameters must be modelled very accurately, with errors < 0.5%, if we wish to measure a value r âˆ1⁄4 10^−3. These foreground residuals can easily be mistaken as primordial cosmological signals, so our work motivates further research into developing new data analysis techniques.

Chan Kit Hung. / "August 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (p. 132-152). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

The E and B EXperiment (EBEX) was a balloon-borne instrument designed to measure the polarization of the cosmic microwave background (CMB) while simultaneously characterizing Galactic dust emission. The instrument was based on a two-mirror ambient temperature Gregorian-Dragone telescope coupled with cooled refractive optics to a kilo-pixel array of transition edge sensor (TES) bolometeric detectors. To achieve sensitivity to both the CMB signal and Galactic foregrounds, EBEX observed in three signal bands centered on 150, 250, and 410 GHz. Polarimetry was achieved via a stationary wire-grid polarizer and a continuously rotating achromatic half-wave plate (HWP) based on a superconducting magnetic bearing (SMB). EBEX launched from McMurdo station, Antarctica on December 29, 2012 and collected ~ 1.3 TB of data during 11 days of observation. This thesis is presented in two Parts. Part I reviews the data analysis we performed to transform the raw EBEX data into maps of temperature and polarization sky signals, with a particular focus on post-flight pointing reconstruction; time stream cleaning and map making; the generation of model sky maps of the expected signal for each of the three EBEX signal bands; removal of the HWP-synchronous signal from the detector time streams; and our attempts to identify, characterize, and correct for non-linear detector responsivity. In Part II we present recent developments in instrumentation for the next generation of CMB polarimeters. The developments we describe, including advances in lumped-element kinetic inductance detector (LEKID) technology and the development of a hollow-shaft SMB-based motor for use in HWP polarimetry, were motivated in part by the design for a prospective ground-based CMB polarimeter based in Greenland.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / by David Hopkins Shoemaker. / M.S.

Chan, Wing Hang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 76-78). / Abstracts in English and Chinese. / Chan, Wing Hang. / Chapter 1 --- Review of Cosmology --- p.1 / Chapter 1.1 --- Background Evolution of Universe --- p.1 / Chapter 1.1.1 --- The Cosmological Principle --- p.1 / Chapter 1.1.2 --- The Non-static Universe --- p.3 / Chapter 1.1.3 --- Robertson-Walker metric --- p.3 / Chapter 1.1.4 --- Scale Factor and Cosmological Redshift --- p.3 / Chapter 1.1.5 --- Hubble Constant --- p.4 / Chapter 1.1.6 --- The Einstein Field Equations --- p.4 / Chapter 1.1.7 --- The Cosmological Constant --- p.6 / Chapter 1.1.8 --- Time Evolution --- p.6 / Chapter 1.1.9 --- Continuity Equation --- p.7 / Chapter 1.1.10 --- Conformal Distance --- p.8 / Chapter 1.2 --- Observational Data --- p.8 / Chapter 1.2.1 --- Type Ia Supernovae --- p.9 / Chapter 1.2.2 --- Cosmic Microwave Background --- p.9 / Chapter 2 --- Review of Dark Energy Models --- p.11 / Chapter 2.1 --- The Cosmological Constant --- p.11 / Chapter 2.2 --- Quintessence --- p.11 / Chapter 2.3 --- Extra Dimension Models --- p.12 / Chapter 2.3.1 --- Kaluza-Klein --- p.12 / Chapter 2.3.2 --- Generalized Homogeneous and Isotropic Extra Dimensions --- p.12 / Chapter 3 --- Review of CMB and Type Ia Supernovae --- p.17 / Chapter 3.1 --- Type Ia Supernovae --- p.17 / Chapter 3.1.1 --- Comparison of cosmological models with recent SNIa data --- p.18 / Chapter 3.2 --- Cosmic Microwave Background Radiation --- p.18 / Chapter 3.2.1 --- Power Spectrum of CMBA --- p.18 / Chapter 3.2.2 --- Photon Baryon Oscillation --- p.21 / Chapter 3.2.3 --- Acoustic Peaks --- p.23 / Chapter 3.2.4 --- Matter Perturbation --- p.24 / Chapter 3.2.5 --- Baryon Loading --- p.24 / Chapter 3.2.6 --- Photons Driving --- p.25 / Chapter 3.2.7 --- Initial Conditions --- p.25 / Chapter 3.2.8 --- Reionization --- p.26 / Chapter 3.2.9 --- The Vanilla ACDM Model --- p.26 / Chapter 3.2.10 --- Summary of CMBA --- p.26 / Chapter 4 --- Constraining Dark Energy Models --- p.27 / Chapter 4.1 --- Constraining Dark Energy Density Using SN Ia data --- p.27 / Chapter 4.1.1 --- Direct Calculation of Dark Energy Density --- p.27 / Chapter 4.2 --- Constraining Dark Energy Density Using CMB data --- p.31 / Chapter 4.2.1 --- Dark Energy Evolution for time varying EOS --- p.31 / Chapter 4.2.2 --- Dark Energy Density Perturbation --- p.32 / Chapter 4.2.3 --- Parameterization of Time Varying Dark Energy --- p.32 / Chapter 4.2.4 --- Effect of Dark Energy Density on CMBA power spectrum --- p.33 / Chapter 4.2.5 --- Limitations and Difficulties Constraining Dark Energy Equation of State --- p.41 / Chapter 4.2.6 --- Constraining the Evolution of Dark Energy Density with a polynomial model --- p.54 / Chapter 4.2.7 --- Constraining Evolution of Dark Energy Density with Gaussian-type EOS --- p.59 / Chapter 4.2.8 --- Constraining Evolution of Dark Energy Step Function EOS with CMB Acoustic Peaks --- p.66 / Chapter 5 --- Summary --- p.73 / Bibliography --- p.76