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The 21-cm Power Spectrum Sensitivity of Current and Future Epoch of Reionization Arrays

Joseph, R.C. (2012) The 21-cm Power Spectrum Sensitivity of Current and Future Epoch of Reionization Arrays. Bachelor's Thesis, Astronomy.

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The Dark Ages of the Universe ended with the formation of the first structures. The formation of these first structures was accompanied by the heating and the subsequent reionization of the intergalactic medium. The Epoch of Reionization (EoR) is thought to hold the key to how and when the first galaxies formed. A promising probe to study this epoch is the redshifted 21-cm line of neutral hydrogen. In this thesis, we investigate the sensitivity of current and future low frequency radio telescopes to measure the redshifted 21-cm power spectrum during the Epoch of Reionization. In our comparison of current arrays we find for a bandwidth of 10 MHz, integration time of 1000 hr at redshift z=10 and scale size k = 0.1 Mpc^-1, that LOFAR outperforms MWA and PAPER by an order of magnitude in power spectrum sensitivity. This comes mostly from LOFAR's larger collecting area. MWA and PAPER compensate their lack of collecting area by increasing their field of view (FoV) and making their arrays compact. This however shifts their sensitivity to smaller k-values (i.e. larger scale modes), which are more relevant for cosmology than reionization studies. We also find that the LOFAR-AARTFAAC extension can increase the sensitivity of LOFAR by a factor ~ 5 for k<0.1 Mpc^-1, below redshift z=12. This comes from the combination of the FoV of a single tile and the total collecting area of the LOFAR-Superterp, which contains 288 antenna tiles in 12 stations. The LOFAR-Superstation in Nancy, which will consist of 96 stations each containing 19 LBA dipoles, has half an order of magnitude more sensitivity than even the LOFAR-AARTFAAC system in LBA mode, making it one of the most promising instruments for very high redshift 21-cm EoR observations (z >15) in the coming decade until the SKA comes online. We finally calculate the sensitivity of different SKA lay-outs, finding that compact arrays are the most sensitive, but that station size should be carefully considered since this constrains the range of measurable scale variations. Concentrating a large collecting area, e.g. 1 km^2, in only few stations could even lead to less power spectrum sensitivity than current arrays, due to the small field of view and increased sample variance. We also find that increasing the number of antennas increases the sensitivity on all scales, as expected. But the maximum number of antennas is constrained by computational power, hence we need to balance collecting area and stations size within the limits of the correlator.

Item Type: Thesis (Bachelor's Thesis)
Degree programme: Astronomy
Thesis type: Bachelor's Thesis
Language: English
Date Deposited: 15 Feb 2018 07:51
Last Modified: 15 Feb 2018 07:51

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