The integrated Sachs-Wolfe effect with Planck and the 2Mass Photometric Redshift Catalogue

This thesis presents a measurement of the Integrated Sachs-Wolfe (ISW) effect through cross-correlation of the Cosmic Microwave Background (CMB) and the galaxy distribution tracing the large scale structure of the Universe. The CMB data used are from the 2013 release from the Planck satellite, and the large-scale structure data are from the 2MASS Photometric Redshift Catalogue (2MPZ). The galaxy data were divided into redshift shells, and HEALPix was used to create pixelised maps of the CMB temperature anisotropies and the galaxy overdensity. The linear galaxy bias, relating the galaxy density distribution to the underlying matter density distribution, was measured through least squares fitting of the theoretical prediction of the galaxy auto-correlation function in each redshift shell.The bias values were then used to rescale the theoretical predictions for the matter-CMB crosscorrelation functions in each shell. The observed cross-correlation function between the Planck and 2MPZ data in each shell was computed, and the uncertainties associated with each measurement were calculated using cross-correlation of simulated CMB and galaxy overdensity maps. To quantify the possible detection of the ISW effect, hypothesis testing was performed through computation of the covariance matrix and χ 2 statistic in each shell. Detection of the ISW effect was found to be preferred over no detection in every case, with a total likelihood ratio of 3.4:1. While this is not quite strong evidence of detection of the ISW effect, this ratio is more than twice better than previous measurements using photometric redshift shells. While the photometric redshifts in the 2MPZ are more accurate than those that have been used before, a strong detection is out of reach with this data, as the redshifts in the 2MPZ are too shallow for more decisive ISW detection.

Grantor dc:publisher.institution

Department of Astronomy

Year dc:date.issued

2014

Author dc:creator

• Steward, Louise

Advisors dc:contributor.advisor

• Jarrett, Thomas
• Bilicki, M

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/13296

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/13296