Finally I have finished the final thesis report of mu undergraduate project. Honestly, I am not satisfied with it myself. Because I could not do any real research I mean something innovative. But now I am trying to do some simulation using Java. This report can be considered as a theoretical database of 21-cm cosmology and observation which will be helpful for me in the coming years, at least I think so. Here I am presenting the report. Link of the pdf file is attached. Abstract and content is mentioned separately.
Undergraduate thesis report
– Review of constraining cosmological parameters using 21-cm signal from the era of Reionization.pdf
Supervisor
Mr. Shafiqur Rahman
Assistant professor, Dept. of EEE
Islamic University of Technology, OIC
Bangladesh
Co-supervisor
Mr. Syed Ashraf Uddin Shuvo
Teaching assistant and PhD student
University of Kentucky, USA.
Submitted By
Ahmed Raihan Abir (052470)
Khan Muhammad (Bin Asad) (052413)
Md. Emon Hossain Khan (052401)
Abstract
We were very ambitious regarding the outcome of our project. In fact we tried to improvise the necessity of a radio telescope on the far side of the Moon. But later we realized the importance of SKA (Square Kilometer Array) as a feasible tool for unveiling the mystery of the Universe. So we tried to calculate the precise error margins of the cosmological parameters that SKA will give us. As far as we know Fisher4Cast is an efficient tool to constrain the error margins in a astrophysical survey. But we didn’t get enough time to use this tool efficiently. So we studied a very important paper by Yi Mao, Max Tegmark et al. to understand the constraints. We learned that, for future experiments, marginalizing over nuisance parameters may provide almost as tight constraints on the cosmology as if 21 cm tomography measured the matter power spectrum directly. Before studying about the constraining process we studied the basic physics of Early Universe, Reionization era, Dark Ages and 21-cm signal. We have written a review on the physics and observational constraints promised by the future telescopes in this thesis report.
Contents
1 – Introduction
2 – Physics of the Early Universe
2.1 – Hubble’s law
2.2 – Cosmological principle
2.3 – Comoving co-ordinates
2.4 – Cosmic Microwave Background Radiation (CMBR)
2.4.1 – Source of CMB
2.5 – Friedmann models
2.6 – Simple cosmological solutions
2.6.1 – Empty de Sitter universe
2.6.2 – Vacuum energy dominated universe
2.6.3 – Radiation dominated universe
2.6.4 – Matter dominated universe
2.6.5 – General equation of state
2.7 – Effects of curvature and cosmological constant
2.7.1 – Open, flat space (k=0)
2.7.2 – Closed, spherical space (k=1)
2.7.3 – Open, hyperbolic space (k=-1)
2.7.4 – Effects of cosmological constant
2.8 – Matter density of the universe
3 – Physics of the Dark Ages
3.1 – Linear gravitational growth
3.2 – Post-linear evolution of density fluctuations
3.2.1 – Spherical top-hat collapse
3.2.2 – Coupled Dark Energy (cDE) models
3.2.3 – Spherical collapse model
3.3 – Nonlinear growth
4 – Physics of Reionization
4.1 – Radiative feedback from the first sources of light
4.2 – Propagation of ionization fronts in the IGM
4.3 – Reionization of Hydrogen
4.3.1 – Pre-overlap
4.3.2 – Overlap
4.4 – Characteristic observed size of ionized bubbles
4.5 – Reionization can give important information about Early Universe
5 – 21-cm Cosmology
5.1 – Fundamental physics of 21-cm line
5.1.1 – Brightness temperature
5.1.2 – Flux density
5.1.3 – Spin temperature
5.1.4 – Optical depth
5.1.5 – Contrast between high-redshift Hydrogen cloud and CMB
5.2 – Temperatures of Dark Ages
5.2.1 – Three temperatures
5.2.2 – Ménage a trios
5.3 – Global history of IGM
5.3.1 – Five critical points in 21-cm history
5.4 – Advantages of 21-cm tomography
6 – 21-cm Power spectrum
6.1 – Fractional perturbation to brightness temperature
6.2 – Fluctuations in 21-cm signal
6.2.1 – Isotropic fluctuations
6.2.2 – Anisotropy in 21cm signal
6.3 – Redshift space distortions
6.4 – Alcock-Paczynski effect
6.5 – Separating out the AP effect on 21-cm fluctuations
7 – Interferometer arrays and sensitivity
7.1 – Interferometric visibility
7.2 – Detector noise
7.3 – Average observing time
7.4 – Angular averaged sensitivity
7.5 – Foreground
7.6 – Sensitivity of future interferometers
7.7 – SKA specifications
8 – Constraining cosmological parameters
8.1 – Reference experiment for simulation
8.2 – Lambda-CDM model
8.3 – Optimistic reference model
8.4 – Simulation
8.4.1 – Varying redshift ranges
8.4.2 – Varying array layout
8.4.3 – Varying collecting area
8.4.4 – Varying observation time and system temperature
8.5 – Graphs of fractional error
8.5.1 – Fractional error at z = 8
8.5.2 – Fractional error at z = 12
8.6 – Significance of constraining cosmological parameters
9 – Conclusion
Appendices
References
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